MIC2587,87R Datasheet by Microchip Technology

Enlllilil: www.micrel.com

MIC2587/MIC2587R

Single-Channel, Positive High-Voltage

Hot Swap Controller

Revision 2.0

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

January 24, 2013

Revision 2.0

General Description

The MIC2587 and MIC2587R are single-channel positive

voltage hot swap controllers designed to provide safe

insertion and removal of boards for systems that require

live (always-powered) backplanes. These devices use few

external components and act as controllers for external N-

channel power MOSFET devices to provide inrush current

control and output voltage slew rate control. Overcurrent

fault protection is provided via programmable analog fold-

back current-limit circuitry equipped with a programmable

overcurrent filter. These protection circuits combine to limit

the power dissipation of the external MOSFET to ensure

that the MOSFET is in its SOA during fault conditions. The

MIC2587 provides a circuit breaker function that latches

the output MOSFET off if the load current exceeds the

current limit threshold for the duration of the programmable

timer. The MIC2587R provides a circuit breaker function

that automatically attempts to restart power after a load

current fault at a low duty cycle to prevent the MOSFET

from overheating. Each device provides either an active-

HIGH (−1YM) or an active-LOW (−2YM) “Power-is-Good”

signal to indicate that the output load voltage is within

tolerance of the application circuit’s design objective.

Datasheets and support documentation are available on

Micrel’s web site at: www.micrel.com.

Features

• MIC2587: Pin-for-pin functional equivalent to the

LT1641

• Operates from +10V to +80V with 100V ABS MAX

operation

• Programmable current limit with analog foldback

• Active current regulation minimizes inrush current

• Electronic circuit breaker for overcurrent fault protection:

− Output latch off (MIC2587)

− Output auto-retry (MIC2587R)

• Fast responding circuit breaker (< 1 s) to short circuit

loads

• Programmable input undervoltage lockout

• Open-drain “Power-is-Good” output for enabling DC/DC

converter(s):

− Active-HIGH: MIC2587-1/MIC2587R-1

− Active-LOW: MIC2587-2/MIC2587R-2

• Fault Reporting

Applications

• General-purpose hot board insertion

• High-voltage, high-side electronic circuit breaker

• +12V/+24V/+48V distributed power systems

• +24V/+48V industrial/alarm systems

• Telecom systems

• Medical systems

BACKPLANE PCB EDGE \N. DC-DC owe? CONVERTER \N- MODULE' 45V " om .5v RTN CONNECTOR CONNECTOR R35“: M1 — — D I summmo-ug .24v: 1.11 ' ' ¢Z4V\NFUT * (LONG PIN) R3 12 10;) MMSZszAaB 4' + ca 02 ouvwqu R5 01 F mu r (SHORT FIN) 59%;) ” ” cm ' ' Cl :74 mnF om: 1. mm PAL 5mm , , s 49 9:22 we sense GATE w. FB 1 357556 ‘ 1 0” MICZSN-WM Wi R2 MlczsnR-WM 34m FWRGD ’ 1% GND YIMER . 5 i333“; l— GNDI: T I“ L— —.24va (LONG PIN) OVERCURRENT RESPONSE T‘ME = 6 6m: INPLIT UNDERVOLTAGE THRESHOLDS VUMEX) 0 W mm 19 7v POWERVISVGOOD OUTPUT THRESHOLDS mesoum = 22 ‘V mmNoY :3wa = 22 0V ‘INPUT P‘N WITH \NTERNAL ONIOFFPULLUF

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

2 Revision 2.0

Typical Application

ON I: FE E PWHGD E GND [2 E vac 2| SENSE El GATE El TIMER ON E FB IE /PWFlGD IE GND E E vcc ZI SENSE El GATE E TIMER

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

3 Revision 2.0

Ordering Information

Part Number PWRGD Polarity Circuit Breaker Function Package Finish

MIC2587-1YM Active-HIGH Latched 8-Pin SOIC Pb-Free

MIC2587-2YM Active-LOW Latched 8-Pin SOIC Pb-Free

MIC2587R-1YM Active- HIGH Auto-retry 8-Pin SOIC Pb-Free

MIC2587R-2YM Active-LOW Auto-retry 8-Pin SOIC Pb-Free

Pin Configuration

8-pin SOIC (M)

MIC2587-1YM

MIC2587R-1YM

(Top View)

8-pin SOIC (M)

MIC2587-2YM

MIC2587R-2YM

(Top View)

Pin Description

Pin Number

Pin Name

Pin Function

1 ON

Enable Input: When the voltage at the ON pin is higher than the VONH threshold, a start cycle is

initiated. An internal current source (IGATEON) is activated which charges the GATE pin, ramping

up the voltage at this pin to turn on an external MOSFET. Whenever the voltage at the ON pin is

lower than the VONL threshold, an undervoltage lockout condition is detected and the IGATEON

current source is disabled while the GATE pin is pulled low by IGATEOFF. After a load current fault,

toggling the ON pin LOW then back HIGH will reset the circuit breaker and initiate another start

cycle.

2 FB

Output Voltage Feedback Input: This pin is connected to an external resistor divider that is used

to sample the output load voltage. The voltage at this pin is measured against an internal

comparator whose output controls the PWRGD (or /PWRGD) signal. PWRGD (or /PWRGD)

asserts when the FB pin voltage crosses the VFBH threshold. When the FB pin voltage is lower

than its VFBL threshold, PWRGD (or /PWRGD) is de-asserted. The FB comparator exhibits a

typical hysteresis of 80mV.

The FB pin voltage also affects the MIC2587/MIC2587R’s foldback current limit operation (see

the “Functional Description” section for further information).

y belore

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

4 Revision 2.0

Pin Description (Continued)

Pin Number Pin Name Pin Function

PWRGD

(MIC2587-1)

(MIC2587R-1)

Active-HIGH

/PWRGD

(MIC2587-2)

(MIC2587R-2)

Active-LOW

Power-is-Good (PWRGD or /PWRGD), Open-Drain Output: This pin remains de-asserted during

start up while the FB pin voltage is below the VFBH threshold. Once the voltage at the FB pin

rises above the VFBH threshold, the Power-is-Good output asserts with minimal delay

(typically ≤ 5µs).

For the (−1) options, the PWRGD output pin will be high-impedance when the FB pin voltage is

higher than VFBH and will pull down to GND when the FB pin voltage is less than VFBL.

For the (−2) options, the /PWRGD output pin will be high-impedance when the FB pin voltage is

lower than VFBL and will pull down to GND when the FB pin voltage is higher than VFBH.

The Power-is-Good output pin is connected to an open-drain, N-channel transistor implemented

with high-voltage structures. These transistors are capable of operating with pull-up resistors to

supply voltages as high as 100V.

To use this signal as a logic control in low-voltage DC/DC conversion applications, an external

pull-up resistor between this pin and the logic supply voltage is recommended unless the DC/DC

module or other load is equipped with a internal pull-up impedance.

4 GND Tie this pin directly to the system’s analog GND plane.

5 TIMER

Current-Limit Response Timer: A capacitor connected from this pin to GND sets the time (tFLT)

for which the controller is allowed to remain in current limit before “tripping” the circuit breaker.

The overcurrent filter is designed to prevent nuisance “tripping” of the circuit breaker that can be

caused by transient current spikes or other undesired “noise”. Once the MIC2587 circuit breaker

trips, the output latches off. Under normal (steady-state) operation, the TIMER pin is held to

GND by an internal 3.5µA current source (ITIMERDN). When the voltage across the external sense

resistor exceeds the VTRIP threshold, an internal 65µA current source (ITIMERUP) is activated to

charge the capacitor connected to the TIMER pin. When the TIMER pin voltage reaches the

VTIMERH threshold, the circuit breaker is tripped pulling the GATE pin low, the ITIMERUP current

source is disabled, and the TIMER pin capacitor is discharged by the ITIMERDN current source.

When the voltage at the TIMER pin is less than 0.5V, the MIC2587 can be restarted by toggling

the ON pin LOW then HIGH.

For the MIC2587R, the GATE output attempts another start cycle to re-establish the output

voltage when the circuit breaker is tripped upon an overcurrent fault. The capacitor connected to

the TIMER pin sets the period of auto-retry with a fixed, nominal duty cycle of 5%.

6 GATE

Gate Drive Output: This pin is the output of an internal charge pump connected to the gate of an

external, N-channel power MOSFET. The charge pump has been designed to provide a

minimum gate drive (∆VGATE = VGATE − VCC) of +7.5V over the input supply’s full operating range.

When the ON pin voltage is higher than the VONH threshold, a 16µA current source (IGATEON)

charges the GATE pin.

When in current limit, the output voltage at the GATE pin is adjusted so that the voltage across

the external sense resistor is held equal to VTRIP while the capacitor connected to the TIMER pin

charges. If the current limit condition goes away before the TIMER pin voltage rises above the

VTIMERH threshold, then steady-state operation resumes.

The GATE output pin is shut down whenever: (1) the input supply voltage is lower than the VUVL

threshold, (2) the ON pin voltage is lower than the VONL threshold, (3) the TIMER pin voltage is

higher than the VTIMERH threshold, or (4) the difference between the VCC and SENSE pins is

greater than VTRIP while the TIMER pin is grounded. For cases (3) and (4) – overcurrent fault

conditions – the GATE is immediately pulled to ground by IGATEFLT, an 80mA pull-down current

source.

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

5 Revision 2.0

Pin Description (Continued)

Pin Number Pin Name Pin Function

7 SENSE

Circuit Breaker Sense Input: This pin is the (−) Kelvin sense connection for the output supply rail.

A low-valued resistor (RSENSE) between this pin and the VCC pin sets the circuit breaker’s

current-limit trip point. When the current-limit detector circuit is enabled (as well as the current

limit0020timer), while the FB pin voltage remains higher than 1V, the voltage across the sense

resistor (VCC − VSENSE) will be regulated to VTRIP (47mV, typically) to maintain a constant current

into the load. When the FB pin voltage is less than ≅ 0.5V, the circuit breaker trip voltage

decreases linearly to 12mV (typical) when the FB pin voltage is at 0V.

To disable the circuit breaker (and defeat all current-limit protections), the SENSE pin and the

VCC pin can be tied together.

8 VCC

Positive Supply Voltage Input: This pin is the positive supply input to the controller and the (+)

Kelvin sense connection for the output supply rail. The nominal operating voltage range for the

MIC2587 and the MIC2587R is +10V to +80V, and VCC can withstand input transients up to

+100V. An undervoltage lockout circuit holds the GATE pin low whenever the supply voltage to

the MIC2587 and the MIC2587R is less than the VUVH threshold.

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

6 Revision 2.0

Absolute Maximum Ratings(1)

(All voltages are referred to GND)

Supply Voltage (VCC) pin ............................. −0.3V to +100V

GATE pin ..................................................... −0.3V to +100V

ON, SENSE pins ......................................... −0.3V to +100V

PWRGD, /PWRGD pins .............................. −0.3V to +100V

FB pin .......................................................... −0.3V to +100V

TIMER pin ....................................................... −0.3V to +6V

Junction Temperature (TJ) ....................................... +125°C

Lead Temperature (Soldering, 10s) ......................... +260°C

Storage Temperature .........................–65°C ≤ TA ≤ +150°C

ESD Rating(3)

Human Body Model ................................................. 2kV

Machine Model ............................................................. 200V

Operating Ratings(2)

Supply Voltage (VCC) ...................................... +10V to +80V

ON, PWRGD, /PWRGD ........................................ 0V to VCC

FB ...................................................................... 0V to VOUT

GATE .................................................. 0V to (VCC + ∆VGATE)

Ambient Temperature Range (TA) .............. −40°C to +85°C

Package Thermal Resistance (θJA)

8-pin SOIC .................................................... +160 °C/W

DC Electrical Characteristics(4)

VCC = +24V and +48V, TA = +25°C, unless otherwise noted. Bold indicates specifications apply over the full operating temperature

range of TA = −40°C to +85°C.

Symbol Parameter Condition Min. Typ. Max. Units

VCC Supply Voltage 10 80 V

ICC Supply Current VON = VFB = 1.5V 2 5 mA

VUVH

VUVL Supply Voltage Undervoltage Lockout VCC rising

VCC falling

7.5

7.0

8.0

7.5

8.5

8.0 V

VHYSLO VCC Undervoltage Lockout Hysteresis 500 mV

VFBH Feedback Pin Voltage High Threshold FB Low-to-High transition 1.280 1.313 1.345 V

VFBL Feedback Pin Voltage Low Threshold FB High-to-Low transition

1.208

1.233

1.258

VHYSFB Feedback Voltage Hysteresis 80 mV

∆VFB FB Pin Threshold Line Regulation 10V ≤ VCC ≤ 80V

−

0.05 0.05 mV/V

IFB FB Pin Input Current 0V ≤ VFB ≤ 3V

−

1 1 µA

VTRIP Circuit Breaker Trip Voltage,

VCC - VSENSE(5)

VFB = 0V (see Figure 1)

VFB = 1V (see Figure 1)

55 mV

∆VGATE MOSFET Gate Drive, VGATE - VCC +10V ≤ VCC ≤ +80V 7.5 18 V

IGATEON GATE Pin Pull-Up Current Start cycle, VGATE = 7V

−

10 −16 -22 µA

IGATEFLT

GATE Pin rapid pull-down current

during a fault condition, until

VGATE = VGATE[TH]

(VGATE[TH] is the MOSFET threshold)

(VCC − VSENSE) = (VTRIP + 10mV)

VGATE = 5V

200

Notes:

1. Exceeding the absolute maximum rating may damage the device.

2. The device is not guaranteed to function outside its operating rating.

3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.

4. Specification for packaged product only.

5. Circuit breaker trip threshold is verified by monitoring the TIMER pin as it switches from discharging to charging (current), and by the GATE output

voltage going low.

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

7 Revision 2.0

DC Electrical Characteristics(4) (Continued)

VCC = +24V and +48V, TA = +25°C, unless otherwise noted. Bold indicates specifications apply over the full operating temperature

range of TA = −40°C to +85°C.

Symbol Parameter Condition Min. Typ. Max. Units

IGATEOFF GATE Pin Turn-off Current Normal turn-off, or from VGATE[TH]

(MOSFET) to 0V after a fault condition 1.8 mA

ITIMERUP Timer Pin Charging Current (VCC – VSENSE) > VTRIP

VTIMER = 0V

−

24 -65

−

120 µA

ITIMERDN Timer Pin Pull-Down Current (VCC – VSENSE) < VTRIP

VTIMER = 0.6V 1.5 3.5 5 µA

VTIMERH TIMER Pin High Threshold Voltage 1.280 1.313 1.345 V

VTIMERL TIMER Pin Low Threshold Voltage 0.4 0.49 0.6 V

VONH ON Pin High Threshold Voltage ON Low-to-High transition 1.280 1.313 1.355 V

VONL ON Pin Low Threshold Voltage ON High-to-Low transition 1.208 1.233 1.258 V

VHYSON ON Pin Hysteresis 80 mV

ION ON Pin Input Current 0V ≤ VON ≤ 80V 2 µA

VOL Power-Good Output Voltage

PWRGD or /PWRGD = LOW

IOL = 1.6mA

IOL = 4mA

0.4

0.8

IOFF Power-Good Leakage Current PWRGD or /PWRGD = Open-Drain

VPG = VCC, VON = 1.5V 10 µA

AC Electrical Characteristics

VCC = +24V and +48V, TA = 25°C, unless otherwise noted. Bold indicates specifications apply over the full operating temperature range

of TA = −40°C to +85°C.

Symbol Parameter Condition Min. Typ. Max. Units

tPONLH ON High to GATE High CGATE = 10nF 3 ms

tPONHL ON Low to GATE Low VIN = 48V, CGATE = 10nF 1 ms

tPFBLH FB Valid to PWRGD High

(MIC2587/MIC2587R-1)

RPG = 50kΩ pull-up to 48V

CL=100pF 2 µs

tPFBHL FB Invalid to PWRGD Low

(MIC2587/MIC2587R-1)

RPG = 50kΩ pull-up to 48V

CL=100pF 4 µs

tPFBHL FB Valid to /PWRGD Low

(MIC2587/MIC2587R-2)

RPG = 50kΩ pull-up to 48V

CL=100pF 4 µs

tPFBLH FB Invalid to /PWRGD High

(MIC2587/MIC2587R-2)

RPG = 50kΩ pull-up to 48V

CL=100pF 2 µs

tOCSENSE

Overcurrent Sense to GATE Low

Trip Time

(VCC - VSENSE) = (VTRIP + 10mV)

Figure 7 1 2 µs

47mV ‘ 3‘3" 1 233v ON kw 12mV 5v GATE w 0v 0 5v v“, ‘ 3“" 1,233v ‘ 3”" 123w F5 F5 um ‘xw ‘—* ‘vrm ‘pram <—. meo="" w="" w="" ipwrgd="" w="" w="" 5—="" «mm="" v"="" *="" vwner="" ‘mms="" v="" gate="" ‘c="">

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

8 Revision 2.0

Timing Diagrams

Figure 1. Foldback Current-Limit Transfer Characteristic

Figure 2. ON-to-GATE Timing

Figure 3. MIC2587/87R-1 FB to PWRGD Timing

Figure 4. MIC2587/87R-2 FB to /PWRGD Timing

Figure 5. Overcurrent Sense-to-GATE Timing

Sn pply Current vs. Supply Voltage 5. "a < 5="" 4="" e="" e="" 3.="" pr="" 2="" 2="" o="" 2="" ,="" §="" 1,="" 3="" l.="" "'="" o.="" uzoanwsusnman="" supply="" voltage="" (v)="" crrcurtbreakertrip="" 2°="" (foldback)="" vs.="" temperature="" 13="" vre="°V" 16="" 14="" vm="Aav" e12="" .="" -="" .="" ‘="" .="" e="" 10.="" e=""> a. a 4. 2. 40-20 0 2U 40 so an TEMPERATURE (Tc) FE Hystere 1 vs. Temperalule 9 E 9 r» .u E I» 1/) > I n u 40-20 0 20 4o 60 an TEMPERATURE ("0) Supply Current vs. Temperauue 5(‘2 5 g 20 g _ _ _ - . pr 15 2 o 5 1n n. u : u5 ur 740 720 o 20 40 so an TEMPERATURE(”C) UVLO Thlesllold 12 vs. Temperauue In a S . A _ e e _ 3 an 3 An 20 740 720 o 20 40 so an TEMPERATURE(”C) Timer Pin Charge Currenl vs.Teruperalure i ‘3 r E 740 720 o 20 40 so an TEMPERATURE(”C) Vlm P ""V) 60 Tllleshold vs. Temperature N s» m :7 Fa THRESHOLD (V) :1 m ‘Y‘MERDN (W N Cimuil Stalker Trip TEMPERATURE (”(2) FE Threshold vs Temperalure ul .n m , = 'n Timer Pin Discharge Curlen! 720 o 20 40 so an TEMPERATURE(”C) vs. Tempelalu re a .40 -20 0 20 A0 60 80 TEMPERATURE 1°C)

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

9 Revision 2.0

Typical Characteristics

GATE antaue vs. Temperalure vcc:43v vcc=wv GATE VOLTAGE (V) 740 720 o 20 40 so an TEMPERATURE("C) GATE(OFF] Current vs. Temperaluve e. u GATEloEE) CURRENT (mA) o lo 40-20 0 20 4o 60 an TEMPERATURE ('0) ON Pin Current vs. Temperature 0N FIN CURRENT (pA) o o o o - A A — - N -20 a 2n an 60 an TEMPERATURE ('c) GATE antaue vs. Supply Vollage 1 El 3 5 l 6 l > E < w="" uzoanwsnsnman="" supply="" voltage="" (v)="" gate(fault)="" cur-em="" 1="" vs.1emperalure="" 31="" f="" e="" 1100="" 5="" u="" 7="" \\="" e="" \~="" 3="" so="" e="" e="" z="" o="" 40="" -20="" o="" 20="" «a="" 60="" an="" temperature="" ('0)="" gate="" cullen!="" vs.="" tempemure="" §="" ’2="" m="" 1="" l:="" m="" b="" 1="" n1="" 5="" aﬂ-zd="" 0="" 20="" ad="" 6d="" ed="" temperature="" vc)="" 0n="" pln="" threshold="" 2="" vs.="" temperature="" a="" r="" z="" 1="" .="" .="" g="" 1="" vmlrlslngj="" i="" 1="" ,,="" ,="" u;="" m(f="" g="" 1.="" e="" o.="" z="" a="" 0.="" z="" 0="" °="" 0="" «10-20="" 0="" 20="" a0="" 60="" 80="" temperature="" 1’0)="">

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

10 Revision 2.0

Typical Characteristics (Continued)

(500mV/dlv) TIMER._/ . GATE . > f Auto-Retry Response win “whim” 444 (swam E . i. ....... INRUSH . : (SODmA/div) i Time (25msldiv) Hot-Plug Turn-0n Response TIMER 1 (500mV/div) v_cc . W (ZOVIdw)>M GATE» “mi.“i .mwﬂ-Hmiikii.‘ (zowmv) W iqu.——¢¢< ww)="" mw="" sense="" ,="" (somwd="" iv)="" fe="" timer="" (1mm="" -m="" iou!="" (5mm="" (20v/div)="" sense="" (50mv/div)="" gate=""><: time="" (10ms/div)="" tum-on="" into="" fault="" time="" (ems/div)="" foldback="" current="" limit="" response="" sense=""> (SOmV/div) M (1V/div) TIMER~--——~/ (1wuw) lLOAD’ (1Ndiv) SENSE» (50mV/d iv) TIMER» (1Vldiv) Tlme (Ems/div) Short Circuit Response i DC=1DmA. . x , M -- jm =1mA has,» M: 3m IOUT (2Ndiv)> PWRGD’ i (50V/div) Time (Ems/div) Turn-On Response l ONNMJ‘ , “ (5m w) (20Vldiv) VOUT (ZOV/div) INRUSH > (1A/div) FB (500mV/dlv) , . GATE..../.. ; 3. Wm. PWRGD (ZOV/dlv) Time (10ms/div)

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

11 Revision 2.0

Functional Characteristics

SENSE 7 vcc ON‘ INTE RNAL REFERENCE VOLTAGE —chc. 12mV747mV \ CHARGE PUMP & [ GATE DRIVER UVLO cci mm = a 49V \ (8V) .— REFERENCE GENERATO LOGIC V001 em 35W 6 GATE FB 3 PWRGD or [FWRGD 5 TIMER

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

12 Revision 2.0

Functional Diagram

MIC2587/MIC2587R Block Diagram

‘GATEON GATE

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

13 Revision 2.0

Functional Description

Hot Swap Insertion

When circuit boards are inserted into systems carrying

live supply voltages ("hot swapped"), high inrush currents

often result due to the charging of bulk capacitance that

resides across the circuit board's supply pins. These

current spikes can cause the system's supply voltages to

temporarily go out of regulation causing data loss or

system lock-up. In more extreme cases, the transients

occurring during a hot swap event may cause permanent

damage to connectors or other on-board components.

The MIC2587/MIC2587R was designed to address these

issues by limiting the maximum current that is allowed to

flow during hot swap events. This is achieved by

implementing a constant-current control loop at turn-on.

In addition to inrush current control, the MIC2587 and

MIC2587R incorporate input voltage supervisory

functions and user-programmable overcurrent protection,

thereby providing robust protection for both the system

and the circuit board.

Input Supply Transient Suppression and Filtering

The MIC2587/MIC2587R is guaranteed to withstand

transient voltage spikes up to 100V. However, voltage

spikes in excess of 100V may cause damage to the

controller. In order to suppress transients caused by

parasitic inductances, wide (and short) power traces

should be utilized. Alternatively, heavier trace plating will

help minimize inductive spikes that may arise during

events that cause a large di/dt to occur (e.g., short circuit

loads). External surge protection, such as a clamping

diode, is also recommended as an added safeguard for

device, and system protection. And lastly, a 0.1µF

decoupling capacitor from the VCC pin to ground is

recommended to assist in noise rejection. Place this filter

capacitor as close as possible to the VCC pin of the

controller.

Start-Up Cycle

When the power supply voltage to the

MIC2587/MIC2587R is higher than the VUVH and the VONH

threshold voltages, a start cycle is initiated. When the

controller is enabled, an internal 16µA current source

(IGATEON) is turned on and the GATE pin voltage rises

from 0V with respect to ground at a rate equal to

Equation 1:

dVGATE

dt =IGATEON

CGATE

Eq. 1

where CGATE is the total capacitance seen at the GATE

output of the controller (external capacitor from GATE to

ground plus CGS of the external MOSFET). The internal

charge pump has sufficient output drive to fully enhance

commonly available power MOSFETs for the lowest

possible DC losses. The gate drive is guaranteed to be

between 7.5V and 18V over the entire supply voltage

operating range (10V to 80V), so 60V BVDSS and 30V

BVDSS N-channel power MOSFETs with a maximum gate-

source voltage of 20V can be used for +48V and +24V

applications, respectively. However, due to the harsh

electrical environments of most backplanes and other

“live” power supplies, the use of 100V and 60V power

MOSFETs, respectively, is recommended to withstand

transient spikes caused by stray inductances.

Additionally, an external Zener diode (18-V) connected

from the source to the gate as shown in the typical

applications circuit is also recommended. A good choice

for an 18-V Zener diode in this application is the

MMSZ5248B, available in a small SOD123 package.

C4 is used to adjust the GATE voltage slew rate while R3

minimizes the potential for high-frequency parasitic

oscillations from occurring in M1. However, note that

resistance in this part of the circuit has a slight

destabilizing effect upon the MIC2587/MIC2587R's

current regulation loop. Compensation resistor R4 is

necessary for stabilization of the current regulation loop.

The current through the power transistor during initial

inrush is given by:

IINRUSH =CLOAD ×IGATEON

CGATE

Eq. 2

The drain current of the MOSFET is monitored via an

external current sense resistor to ensure that it never

exceeds the programmed threshold, as described in the

"Circuit Breaker Operation" section.

A capacitor connected to the controller’s TIMER pin sets

the value of overcurrent detector delay, tFLT, which is the

time for which an overcurrent event must last to signal a

fault condition and to cause the output to latch-off. The

MIC2587/MIC2587R controller is most often utilized in

applications with large capacitive loads, so a properly

chosen value of CTIMER prevents false-, or nuisance-,

tripping at turn-on as well as providing immunity to noise

spikes after the start-up cycle is complete. The procedure

for selecting a value for CTIMER is given in the "Circuit

Breaker Operation" section.

2 x before

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

14 Revision 2.0

Overcurrent Protection

The MIC2587 and the MIC2587R use an external, low-

value resistor in series with the drain of the external

MOSFET to measure the current flowing into the load.

The VCC connection (Pin 8) and the SENSE connection

(Pin 7) are the (+) and (−) inputs, respectively, of the

device's internal current sensing circuits. Kelvin sense

connections are strongly recommended for sensing the

voltage across these pins. See the Applications

Information section for further details.

The nominal current limit is determined by Equation 3:

SENSE

TRIP(TYP)

LIM

Eq. 3

where VTRIP(TYP) is the typical current-limit threshold

specified in the datasheet and RSENSE is the value of the

selected sense resistor. The controllers employ a

constant-current regulation scheme while in current limit.

The internal charge pump’s output voltage, seen at the

GATE pin, is adjusted so that the voltage across the

external sense resistor is held equal to VTRIP while the

capacitor connected to the TIMER pin is being charged. If

the current-limit condition goes away before the TIMER

pin voltage rises above the VTIMERH threshold, then

steady-state operation resumes. To prevent excessive

power dissipation in the external MOSFET under load

current fault conditions, the FB pin voltage is used as an

input to a circuit that lowers the current limit as a function

of the FB pin voltage. When the load current increases to

the point where the output voltage at the load approaches

0V (likewise, the MIC2587/MIC2587R’s FB pin voltage

also approaches 0V), the result is a proportionate

decrease in the maximum current allowed into the load.

The transfer characteristic of this foldback current limit

subcircuit is shown in Figure 1. When VOUT = VFB = 0V,

the foldback current-limiting circuit controls the

MIC2587/MIC2587R’s GATE drive to force a constant

12mV (typical) voltage drop across the external sense

resistor.

Circuit Breaker Operation

The MIC2587/MIC2587R is equipped with an electronic

circuit breaker that protects the external N-channel power

MOSFET and other system components against large-

scale output current faults, both during initial card

insertion or during steady-state operation. The current

limit threshold is set via an external resistor, RSENSE,

connected between the controller’s VCC (Pin 8) and

SENSE (Pin 7) pins. For the MIC2587/MIC2587R, a fault

current timing circuit is set via an external capacitor

CTIMER that determines the length of the time delay for

which the controller remains in current limit before the

circuit breaker is tripped.

Programming the response time of the overcurrent

detector helps to prevent nuisance tripping of the circuit

breaker attributed to transient current surges (e.g., inrush

current charging bulk load capacitance). The nominal

overcurrent response time (tFLT) is approximated by

Figure 4:

TIMERUP

TIMERHTIMER

FLT I

t×

×≅ 20(ms)tFLT

TIMER

(µF) Eq. 4

The typical overcurrent filter delay time for several

standard value capacitors is listed in Table 1.

Table 1. Overcurrent Filter Delay Time for Several Standard

Capacitor Values

TIMER

(µF)

FLT

(ms)

0.1

0.22

4.4

0.33

6.6

0.47

9.4

1.0

2.2

3.3

Whenever the voltage across RSENSE exceeds the

MIC2587/MIC2587R’s circuit-breaker threshold voltage

(47mV typical) during steady-state operation, the

following two events occur:

A constant-current regulation loop engages within 1µs

after an overcurrent condition is detected by the input

sense pins monitoring the voltage across RSENSE.

An internal 65µA current source (ITIMERUP) begins to

charge CTIMER. If the excessive current persists such that

the voltage across CTIMER crosses the VTIMERH threshold

(1.313V, typically), the circuit breaker trips and the GATE

pin is immediately pulled low by a 80mA (typical) internal

current sink while the TIMER pin is discharged to ground

by a 3.5µA current sink (ITIMERDN).

An initial value for CTIMER is found by calculating the time

it will take for the MIC2587/MIC2587R to completely

charge the output capacitive load during startup. The

turn-on delay time is derived from the expression, I = C ×

(dV/dt):

LIMIT

CC(MAX)LOAD

ON-TURN I

t×

Eq. 5

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

15 Revision 2.0

Using parametric values for the MIC2587/MIC2587R, an

expression relating a worst-case design value for CTIMER,

using the MIC2587/MIC2587R specification limits, to the

circuit's turn-on delay time is:

























−

××

sec.

μF

1094t

1.280V

120μ2

ONTURN

TIMER(MIN)

TURN

TIMER(MIN)

)

TIMERH(MIN

)

TIMERH(MAXONTURN

TIMER(MIN)

Eq. 6

For example, in a system with a CLOAD = 1000µF, a

maximum VCC = +72V, and a maximum load current on a

nominal +48V buss of 1.65A, the initial steps for the

circuit design are:

• Choose ILIMIT = IHOT_SWAP(nom) = 2A (1.65A + 20%)

• Select an RSENSE (Closest 1% standard value is

19.6mΩ)

• Using ICHARGE = ILIMIT = 2A, the application circuit turn-

on time is calculated using Equation 5:

( )

36ms

72V1000µF

tON-TURN =

• Allowing for capacitor tolerances and a maximum

36ms turn-on time, an initial worst-case value for

CTIMER is:













−××= sec.

μF

610940.036s

TIMER(MIN)

= 3.3µF

A standard 3.3µF ±5% tolerance capacitor would be a

good initial starting value for prototyping since this value

would allow the controller to start up without nuisance

tripping over the entire voltage range given in the

example application.

Auto-Retry Period

For the MIC2587R, once the overcurrent timer “times out”

and the circuit breaker “trips”, the TIMER pin begins to

discharge. Once the timer pin voltage discharges below

the VTIMERL threshold, the circuit breaker resets to initiate

another start-up cycle. If the overcurrent fault condition is

still present, then the auto-retry cycle will continue until

either of the following occurs: a) the fault condition is

removed, b) the input supply voltage power is

removed/recycled, or c) the ON pin is toggled LOW then

HIGH. The duty cycle of the auto-restart function is

therefore fixed at 5% and the nominal period of the auto-

restart cycle is given by:

( ) ( )

TIMERH

TIMERLTIMERHTIMER

RETRY-AUTO I

VVC

20t −×

×=

tAUTO-RETRY(ms) = 250 × CTIMER (µF)

Eq. 7

The auto-restart period for the example above where the

worst-case CTIMER was calculated to be 3.3µF is:

tAUTO-RETRY = 825ms

The typical auto-restart period for several standard value

capacitors is listed in Table 2.

Table 2. Auto-Restart Period for Several Standard

Capacitor Values

TIMER

(µF)

AUTO-RETRY

(ms)

0.1

0.22

0.33

82.5

0.47

117.5

1.0

250

2.2

550

3.3

825

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

16 Revision 2.0

Input Undervoltage Lockout

The MIC2587/MIC2587R have an internal undervoltage

lockout circuit that inhibits operation of the controller’s

internal circuitry unless the power supply voltage is stable

and within an acceptable tolerance. If the supply voltage

to the controller with respect to ground is greater than the

VUVH threshold voltage (8V typical), the controller’s

internal circuits are enabled and the controller is then

ready for normal operation pending the state of the ON

pin voltage. Once in steady-state operation, the

controller’s internal circuits remain active so long as the

supply voltage with respect to ground is higher than the

controller’s internal VUVL threshold voltage (7.5V typical).

Power-is-Good Output Signals

For the MIC2587-1 and MIC2587R-1, the power-good

output signal (PWRGD) will be high impedance when the

FB pin voltage is higher than the VFBH threshold and will

pull-down to GND when the FB pin voltage is lower than

the VFBL threshold. For the MIC2587-2 and MIC2587R-2,

the power-good output signal (/PWRGD) will pull down to

GND when the FB pin voltage is higher than the VFBH

threshold and will be high impedance when the FB pin

voltage is lower than the VFBL threshold. Hence, the (−1)

parts have an Active-HIGH PWRGD signal and the (−2)

parts have an Active-LOW /PWRGD output. PWRGD (or

/PWRGD) may be used as an enable signal for one or

more following DC/DC converter modules or for other

system uses as desired. When used as an enable signal,

the time necessary for the PWRGD (or /PWRGD) signal

to pull-up (when in high impedance state) will depend

upon the (RC) load at the Power-is-Good pin.

The Power-is-Good output pin is connected to an open-

drain, N-channel transistor implemented with high-voltage

structures. These transistors are capable of operating

with pull-up resistors to supply voltages as high as 100V.

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

17 Revision 2.0

Application Information

External ON/OFF Control

The MIC2587/MIC2587R have an ON pin input that is

used to enable the controller to commence a start-up

sequence upon card insertion or to disable controller

operation upon card removal. In addition, the ON pin can

be used to reset the MIC2587/MIC2587R’s internal

electronic circuit breaker in the event of a load current

fault. To reset the electronic circuit breaker, the ON pin is

toggled LOW then HIGH. The ON pin is internally

connected to an analog comparator with 80mV of

hysteresis. When the ON pin voltage falls below its

internal VONL threshold, the GATE pin is immediately

pulled low. The GATE pin will be held low until the ON pin

voltage is above its internal VONH threshold. The external

circuit's ON threshold voltage level is programmed using

a resistor divider (R1 & R2) as shown in the "Typical

Application” circuit. The equations to set the trip points

are shown below. For the example illustrated in Equation

8, the supply voltage needed to turn on the controller is

set to +37V, a value commonly used in +48V Central

Office power distribution applications.











+

×= R2

R2R1

ONHIN(ON)

Eq. 8

Given VONH and R2, a value for R1 can be determined. A

suggested value for R2 is that which will provide at least

100µA of current through the voltage divider chain at VCC

= VONH. This yields the following as a starting point:

Ω==

=13.13k

A100μ

1.313V

A100μ

ONH(TYP)

The closest standard 1% value for R2 is 13kΩ. Now,

solving for R1 yields:

Ω=











−













×Ω











−













=k 353.3

1.313V

37V

13k1

R2R1

ONH(TYP)

IN(ON)

The closest standard 1% value for R1 is 357kΩ.

Using standard 1% resistor values, the external circuit's

nominal ON and OFF thresholds are VIN(ON) = +36V and

VIN(OFF) = +34V. In solving for VIN(OFF), replace VONH with

VONL in Equation 8.

Output Voltage Power-is-Good Detection

The MIC2587/MIC2587R includes an analog comparator

used to monitor the output voltage of the controller

through an external resistor divider as shown in the

“Typical Application” circuit. The FB input pin is

connected to the non-inverting input and is compared

against an internal reference voltage. The analog

comparator exhibits a hysteresis of 80mV.

Setting the “Power-is-Good” threshold for the circuit

follows a similar approach as setting the circuit’s ON/OFF

input voltage. The equations to set the trip points are

shown below. For the +48V telecom application shown in

Equation 9, power-is-good output signal PWRGD (or

/PWRGD) is to be de-asserted when the output supply

voltage is lower than +48V-10% (+43.2V):











+

×= R6

R6R5

FBLGOOD) OUT(NOT

Eq. 9

Given VFBL and R6, a value for R5 can be determined. A

suggested value for R6 is that which will provide

approximately 100µA of current through the voltage

divider chain at VOUT(NOT GOOD) = VFBL. This yields the

following equation as a starting point:

kΩ 12.33

100μ0

1.233V

100μ0

FBL(TYP)

===

Eq. 10

The closest standard 1% value for R6 is 12.4kΩ. Now,

solving for R5 yields:

Ω=











−













×Ω=











−













×= k 4221

1.233V

43.2V

12.4k1

R6R5

FBL(TYP)

GOOD) OUT(NOT

The closest standard 1% value for R5 is 422kΩ.

Using standard 1% resistor values, the external circuit's

nominal “power-is-good” and “power-is-not-good” output

voltages are VOUT(GOOD) = +46V and VOUT(NOT GOOD) =

+43.2V. In solving for VOUT(GOOD), substitute VFBH for VFBL

in Equation 9.

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

18 Revision 2.0

Sense Resistor Selection

The sense resistor is nominally valued at:

OM)HOT_SWAP(N

TRIP(TYP)

SENSE(NOM) I

Eq. 11

where:

VTRIP(TYP) is the typical (or nominal) circuit breaker

threshold voltage (47mV) and IHOT_SWAP(NOM) is the

nominal inrush load current level to trip the internal circuit

breaker.

To accommodate worst-case tolerances in the sense

resistor (for a ±1% initial tolerance, allow ±3% tolerance

for variations over time and temperature) and circuit

breaker threshold voltages, a slightly more detailed

calculation must be used to determine the minimum and

maximum hot swap load currents.

As the MIC2587/MIC2587R's minimum current-limit

threshold voltage is 39mV, the minimum hot swap load

current is determined where the sense resistor is 3%

high:

( )

SENSE(NOM)SENSE(NOM)

IN)HOT_SWAP(M R

37.9mV

R1.03

39mV

Keep in mind that the minimum hot swap load current

should be greater than the application circuit's upper

steady-state load current boundary. Once the lower value

of RSENSE has been calculated, it is good practice to check

the maximum hot swap load current (IHOT_SWAP(MAX)) which

the circuit may let pass in the case of tolerance build-up

in the opposite direction. Here, the worst-case maximum

is found using a VTRIP(MAX) threshold of 55mV and a sense

resistor 3% low in value:

( )

SENSE(NOM)SENSE(NOM)

AX)HOT_SWAP(M

56.7mV

R0.97

55mV

In this case, the application circuit must be sturdy enough

to operate over a ~1.5-to-1 range in hot swap load

currents. For example, if an MIC2587 circuit must pass a

minimum hot swap load current of 4A without nuisance

trips, RSENSE should be set to:

Ω=

=9.75m

39mV

RSENSE(NOM)

where the nearest 1% standard value is 9.76mΩ. At the

other tolerance extremes, IHOT_SWAP(MAX) for the circuit in

question is then simply:

5.8A

9.76m

56.7mV

AX)HOT_SWAP(M

Ω

With a knowledge of the application circuit's maximum

hot swap load current, the power dissipation rating of the

sense resistor can be determined using P = I2 × R. Here,

The current is IHOT_SWAP(MAX) = 5.8A and the resistance

RSENSE(MIN) = (0.97)(RSENSE(NOM)) = 9.47mΩ. Thus, the

sense resistor's maximum power dissipation is:

PMAX = (5.8A)2 × (9.47mΩ) = 0.319W

A 0.5W sense resistor is a good choice in this application.

When the MIC2587/MIC2587R’s foldback current limiting

circuit is engaged in the above example, the current limit

would nominally fold back to 1.23A when the output is

shorted to ground.

vows»: mas Powzw mas mom vi: '0 MOSFEY mum ma mm mm a 03' p52 AMPERE um; m w sum was mm me; vs wozssnm vu Pm to mczsmm ssts pm TO THE \NPUT POWER SUPPLV .— HIGHVCURRENT POWER TRACES TO THE EXTERNAL \ MOSFETANDLOAD —> / Rama: \ 1K 10on vac sms; Mlczss'l/MICZSB'IR cannon.“

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

19 Revision 2.0

PCB Layout Recommendations

4-Wire Kelvin Sensing

Because of the low value typically required for the sense

resistor, special care must be used to accurately

measure the voltage drop across it. Specifically, the

measurement technique across RSENSE must employ 4-

wire Kelvin sensing. This is simply a means of ensuring

that any voltage drops in the power traces connected to

the resistors are not picked up by the signal conductors

measuring the voltages across the sense resistors.

Figure 6 illustrates how to implement 4-wire Kelvin

sensing. As the figure shows, all the high current in the

circuit (from VCC through RSENSE and then to the drain of

the N-channel power MOSFET) flows directly through the

power PCB traces and through RSENSE.

Figure 6. 4-Wire Kelvin Sense Connections for RSENSE

The voltage drop across RSENSE is sampled in such a way

that the high currents through the power traces will not

introduce significant parasitic voltage drops in the sense

leads. It is recommended to connect the hot swap

controller's sense leads directly to the sense resistor's

metalized contact pads. The Kelvin sense signal traces

should be symmetrical with equal length and width, kept

as short as possible and isolated from any noisy signals

and planes.

In most applications, the use of a capacitor from the

TIMER pin to ground will effectively eliminate nuisance

tripping due to noise and/or transient overcurrent spikes.

If the circuit breaker trips regularly due to a system

environment that is vulnerable to noise being injected

onto the Kelvin sense connections, the example circuit

shown in Figure 7 can be implemented to combat such

noisy environments. This circuit implements a 1.6 MHz

low-pass filter to attenuate higher frequency disturbances

on the current sensing circuitry. However, individual

system analysis should be used to determine if filtering is

necessary and to select the appropriate cutoff frequency

for each specific application.

Other Layout Considerations

Figure 8 is a recommended PCB layout diagram for the

MIC2587-2YM. Many hot swap applications will require

load currents of several amperes. Therefore, the power

(VCC and Return) trace widths (W) need to be wide

enough to allow the current to flow while the rise in

temperature for a given copper plate (e.g., 1oz. or 2oz.) is

kept to a maximum of 10°C to 25°C. Also, these traces

should be as short as possible in order to minimize the IR

drops between the input and the load. The feedback

network resistor values in Figure 8 are selected for a

+24V application. The resistors for the feedback (FB) and

ON pin networks should be placed close to the controller

and the associated traces should be as short as possible

to improve the circuit’s noise immunity. The input

“clamping diode” (D1) is referenced in the “Typical

Application Circuit” on Page 1. If possible, use high-

frequency PCB layout techniques around the GATE

circuitry (shown in the typical application circuit) and use

a dummy resistor (e.g., R3 = 0Ω) during the prototype

phase. If R3 is needed to eliminate high-frequency

oscillations, common values for R3 range between 4.7Ω

to 20Ω for various power MOSFETs. Finally, the use of

plated-through vias will be needed to make circuit

connection to the power and ground planes when utilizing

multi-layer PCBs.

Figure 7. Current-Limit Sense Filter for Noisy Systems

CURRENT FLOW CURRENT FLOW FROM THE LOAD FROM rHE LOAD ‘ —. ‘SENSE RESISTOR Fowfgiggﬁﬁ —. (WSR-z ur WSLZSI 2) — a w w l “ l VIA TO THE POWER(OUTF'UT) PLANE - -. m m m m \ / (O a E V‘A TO THE srl’éﬂiglﬁng ° "“ g 3 . GROUND PLANE MlCZ5B7-ZVM A E = 5 C E 5 m m m m '5! I M CURRENT FLOW - I V‘ATO THE FROM THE LOAD '3 57" POWER(OUTFUT) <— “*="" plane="" drawng="" ‘5="" n01="" to="" 5m:="" ;;="" wu="" f="">< ma="" my="" mmmsmwnms="" oononems="" wzcomswso="" row="" an:="" snaluzmm="" ‘opmnalcochenys="" mums="" 010594="" for="" a24vappucmon="" mm="" mum="" (w)="" guimlm:x="" 'puu="" mum="" htuomvmmuona="" cr="" m:="" mum“="">

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

20 Revision 2.0

Figure 8. Recommended PCB Layout for Sense Resistor,

Power MOSFET, Timer and Feedback Network

www si Iconix cum www silucomx cum www irf cum www renesas om www vxshay com/docswsl 30100 gdf

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

21 Revision 2.0

MOSFET and Sense Resistor Vendors

Device types, part numbers, and manufacturer contacts

for power MOSFETs and sense resistors are provided in

Tables 3 and 4.

Table 3. MOSFET Vendors

MOSFET Vendors Key MOSFET Type(s) Breakdown Voltage (VDSS) Contact Information

Vishay - Siliconix

SUM75N06-09L (TO-263)

SUM70N06-11 (TO-263)

SUM50N06-16L (TO-263)

60V

www.siliconix.com

(203) 452-5664

SUP85N10-10 (TO-220AB)

SUB85N10-10 (TO-263)

SUM110N10-09 (TO-263)

SUM60N10-17 (TO-263)

100V

www.siliconix.com

(203) 452-5664

International

Rectifier IRF530 (TO-220AB)

IRF540N (TO-220AB) 100V

100V www.irf.com

(310) 322-3331

Renesas 2SK1298 (TO-3PFM)

2SK1302 (TO-220AB)

2SK1304 (TO-3P)

60V

100V

www.renesas.com

(408) 433-1990

Table 4. Resistor Vendors

Resistor Vendors Sense Resistors Contact Information

Vishay - Dale “WSL” and “WSR” Series www.vishay.com/docswsl_30100.pdf

mp lew name: (599%!) . 34:35: *D J 2— unes :mg . ’3‘ 5 _5. BEAM any i" “9‘ ® [15:12 mm .n m (mam: END vIEw EDTTEIM VIEV SEE nETAIL A um $35“: [n 3: m: n ms .u a 4L ”wading" m“ (a an _,..,, J NEITEX‘ I DIMENSIEINS An: [N JNCHESLMMI CEINTREILLJNG DEFENSIUNl INCHES. mmmxmu nut: um mum: MDLD FLﬂXH Eli PRUIRUXHZINS, EIETRNEXRIDEF VHICH SHALL NEIT EXCEED magmas] hug' lwww mlcre com ant

Micrel, Inc.

MIC2587/MIC2587R

January 24, 2013

22 Revision 2.0

Package Information(1)

8-Pin SOIC (M)

Note:

1. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com.

MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com

Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This

information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,

specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual

property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability

whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties

relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product

can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant

into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A

Purchaser’s use or sale of Micrel Products for use in life suppor

t appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully

indemnify Micrel for any damages resulting from such use or sale.