MAX16129AUAEBD+T - Maxim Integrated

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General Description

The MAX16128/MAX16129 load-dump/reverse-voltage

protection circuits protect power supplies from damaging

input-voltage conditions, including overvoltage, reverse-

voltage, and high-voltage transient pulses. Using a

built-in charge pump, the devices control two external

back-to-back n-channel MOSFETs that turn off and isolate

downstream power supplies during damaging input

conditions, such as an automotive load-dump pulse or a

reverse-battery condition. Operation is guaranteed down

to 3V that ensures proper operation during automotive

cold-crank conditions. These devices feature a flag output

(FLAG) that asserts during fault conditions.

For reverse-voltage protection, external back-to-back

MOSFETs outperform the traditional reverse-battery

diode, minimizing the voltage drop and power dissipation

during normal operation.

The devices use fixed overvoltage and undervoltage

thresholds, minimizing the external component count.

The MAX16129 provides limiter-mode fault management

for overvoltage and thermal-shutdown conditions; whereas

the MAX16128 provides switch-mode fault management

for overvoltage and thermal shutdown conditions. In the

limiter mode, the output voltage is limited and FLAG is

asserted low during a fault. In the switch mode, the

external MOSFETs are switched off and FLAG is asserted

low after a fault. The switch mode is available in four

options—Latch mode, 1 Autoretry mode, 3 Autoretry

mode, and Always autoretry mode.

The MAX16128/MAX16129 are available in an 8-pin

µMAX® package and operate over the automotive

temperature range (-40°C to +125°C).

Applications

●Automotive

●Industrial

●Avionics

●Telecom/Server/Networking

Benets and Features

●Increases Protection of Sensitive Electronic

Components in Harsh Environments

• -36V to +90V Wide Input-Voltage Protection Range

• Fast Gate Shutoff During Fault Conditions with

Complete Load Isolation

• Thermal Shutdown Protection

• FLAG Output Identies Fault Condition

●Automotive Qualified

• Operates Down to +3V, Riding Out Cold-Crank

Conditions

• -40°C to +125°C Operating Temperature Range

●Integration Reduces Solution Size

• Internal Charge-Pump Circuit Enhances External

n-Channel MOSFET

• Fixed Undervoltage/Overvoltage Thresholds

• 3mm × 3mm, 8-Pin µMAX Package

●Reduced Power Dissipation Compared to Discrete

Solutions

• Minimal Operating Voltage Drop for Reverse-

Voltage Protection

• 380µA Supply Current and 100µA Shutdown

Current at 30V Input

Ordering Information appears at end of data sheet.

19-6146; Rev 5; 2/17

MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits

µMAX

Junction-to-Ambient Thermal Resistance (θJA) .......77.6°C/W

Junction-to-Case Thermal Resistance (θJC) .................5°C/W

(All pins referenced to GND.)

IN ............................................................................ -36V to +90V

SHDN ...........................................-0.3V to max (0V, VIN + 0.3V)

SRC, GATE ............................................................-36V to +45V

SRC to GATE .........................................................-36V to +30V

OUT .......................................................................-0.3V to +45V

FLAG .....................................................................-0.3V to +45V

Continuous Sink/Source (All Pins) .................................±100mA

Continuous Power Dissipation (TA = +70°C) (multilayer board)

µMAX (derate 12.9mW/°C above +70°C) ..............1030.9mW

Operating Temperature Range ......................... -40°C to +125°C

Junction Temperature ...................................................... +150°C

Storage Temperature Range ............................ -60°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Soldering Temperature (reflow) ....................................... +260°C

(Note 1)

(VIN = 12V, CGATE-SOURCE = 1nF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Input Voltage Range VIN

Operating range 3 30 V

Protection range -36 +90

Input Supply Current IIN

SHDN = high

VIN = VSRC =

VOUT = 12V 260 360

µA

VIN = VSRC =

VOUT = 30V 290 400

SHDN = low VIN = 12V 44 60

VIN = 30V 64 100

SRC Input Current ISRC

VIN = VSRC = 12V, SHDN = high 36 200 µA

VIN = VSRC = 30V, SHDN = high 240 350

Internal Undervoltage Threshold VUV_TH VIN rising 0.97 ×

VUV

1.03 ×

VUV

Internal Undervoltage-Threshold

Hysteresis VUV_HYS

0.05 ×

VUV

Internal Overvoltage Threshold VOV_TH VIN rising 0.97 ×

VOV

1.03 ×

VOV

Internal Overvoltage-Threshold

Hysteresis VOV_HYS

0.05 ×

VOV

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Electrical Characteristics

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer

board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.

Package Thermal Characteristics

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these

or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect

device reliability.

Absolute Maximum Ratings

(VIN = 12V, CGATE-SOURCE = 1nF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Internal Cold-Crank Threshold VCCK VIN falling 0.97 ×

VCCK

1.03 ×

VCCK

Internal Cold-Crank Threshold Hysteresis VCCK_HYS

0.05 ×

VCCK

OUT Input Resistance to Ground ROUT

MAX16128 4 MW

MAX16129 2

POK Threshold Rising VPOK+ 0.9 x VIN V

POK Threshold Falling VPOK-

0.87 ×

VIN

Startup Response Time tSTART (Note 3) 150 µs

Autoretry Timeout tRETRY 150 ms

GATE Rise Time tRISE VGATE rising (GND to VSRC + 8V) 1 ms

Overvoltage-to-GATE Propagation Delay tOVG

VIN rising (MAX16128) from

(0.9 × VOV_TH) to (1.1 × VOV_TH),

VOUT rising (MAX16129) from

(0.9 × VOV_TH) to (1.1 × VOV_TH)

1 µs

Undervoltage-to-GATE Propagation Delay tUVG

VIN falling from (1.1 × VUV_TH) to

(0.9 × VUV_TH)21 µs

Overvoltage to FLAG Propagation Delay tOV

VIN rising (MAX16128) from

(0.9 × VOV_TH) to (1.1 × VOV_TH)

VOUT rising (MAX16129) from

(0.9 × VOV_TH) to (1.1 × VOV_TH)

1 µs

GATE Output Voltage High Above VSRC VGS

VIN = VSRC = VOUT = 3V,

IGATE = -1µA 4.25 5 5.5

VIN = VSRC = VOUT = 12V,

IGATE = -1µA 8 9 10

VIN = VSRC = VOUT = 24V,

IGATE = -1µA 7 8.5 10

VIN = VSRC = VOUT = 30V,

IGATE = -1µA 6.25 8 9.5

GATE Pulldown Current IPD VGATE = 12V 8.8 mA

GATE Charge-Pump Current IGATE VIN = VGATE = VSRC = 12V 180 µA

Thermal Shutdown T++145 °C

Thermal-Shutdown Hysteresis ∆T 15 °C

SHDN Logic-High Input Voltage VIH 1.4 V

SHDN Logic-Low Input Voltage VIL 0.4 V

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Electrical Characteristics (continued)

(VIN = 12V, TA = +25°C, unless otherwise noted.)

(VIN = 12V, CGATE-SOURCE = 1nF, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)

Note 2: All parameters are production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design

and characterization.

Note 3: The MAX16128/MAX16129 power up with the external MOSFETs in off mode (VGATE = VSRC). The external MOSFETs turn

on tSTART after the devices are powered up and all input conditions are valid.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

SHDN Input Pulse Width tPW 6 µs

SHDN Input Pulldown Current ISPD 0.8 1.2 µA

FLAG Output Voltage Low VOL FLAG sinking 1mA 0.4 V

FLAG Leakage Current IIL VFLAG = 12V 0.5 µA

0.1

0.2

0.3

0.4

0.6

0.7

0.8

0.9

0.5

SHDN PULLDOWN CURRENT

vs. TEMPERATURE

MAX16128/ 29 toc05

TEMPERATURE (°C)

SHDN PULLDOWN CURRENT (µA)

1109565 80-10 5 20 35 50-25

1.0

-40 125

SHUTDOWN SUPPLY CURRENT

vs. TEMPERATURE

MAX16128/ 29 toc04

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

1109565 80-10 5 20 35 50-25

-40 125

SHDN = LOW

SHUTDOWN SUPPLY CURENT

vs. SUPPLY VOLTAGE

MAX16128/29 toc03

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

2721159

100

SHDN = LOW

SUPPLY CURRENT

vs. TEMPERATURE

MAX16128/29 toc02

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

120100-20 0 20 6040 80

170

190

210

230

250

270

290

310

150

-40

SHDN = HIGH

GATE ENHANCED

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX16128/ 29 toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

332313

100

150

200

250

300

SHDN = HIGH

GATE ENHANCED

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Typical Operating Characteristics

Electrical Characteristics (continued)

(VIN = 12V, TA = +25°C, unless otherwise noted.)

FLAG OUTPUT LOW VOLTAGE

vs. CURRENT

MAX16128/ 29 toc11

FLAG CURRENT (mA)

FLAG VOLTAGE (V)

1.51.00.5

0.1

0.2

0.3

0.4

0.5

0 2.0

INTERNAL UNDERVOLTAGE THRESHOLD

vs. TEMPERATURE

MAX16128/ 29 toc10B

TEMPERATURE (°C)

INTERNAL UNDERVOLTAGE THRESHOLD (%V

)

1109565 80-10 5 20 35 50-25

102

104

-40 125

100

RISING

FALLING

INTERNAL OVERVOLTAGE THRESHOLD

vs. TEMPERATURE

MAX16128/ 29 toc10A

TEMPERATURE (°C)

INTERNAL OVERVOLTAGE THRESHOLD (%VOV)

1109565 80-10 5 20 35 50-25

102

-40 125

100

RISING

FALLING

GATE PULLUP CURRENT vs. VIN

MAX16128/ 29 toc09

GATE PULL-UP CURRENT (µA)

100

140

120

160

180

200

VIN (V)

3020 25151050

VIN = VGATE = VSRC

GATE ENHANCED

GATE PULLDOWN CURRENT

vs. TEMPERATURE

MAX16128/ 29 toc08

TEMPERATURE (°C)

GATE PULLDOWN CURRENT (mA)

1109565 80-10 5 20 35 50-25

-40 125

VGATE = 12V

GATE-TO-SRC VOLTAGE

vs. TEMPERATURE

MAX16128/ 29 toc07

TEMPERATURE (°C)

GATE-TO-SRC VOLTAGE (V)

1109565 80-10 5 20 35 50-25

10.0

6.0

-40 125

6.8

6.4

7.2

7.6

8.0

8.4

9.2

8.8

9.6

VIN = VSRC = VOUT = 12V

GATE ENHANCED

GATE-TO-SRC VOLTAGE vs. VIN

MAX16128/ 29 toc06

VIN (V)

GATE-TO-SRC VOLTAGE (V)

302515 20105

0 35

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Typical Operating Characteristics (continued)

(VIN = 12V, TA = +25°C, unless otherwise noted.)

OVERVOLTAGE LIMITER

(VOV = 21V, CIN = 0.1µF, COUT = 10µF)

MAX16128/ 29 toc17

20ms/div

VIN

20V/div

VGATE

20V/div

VOUT

10V/div

OVERVOLTAGE SWITCH FAULT

(VOV = 21V, CIN = 0.1µF, COUT = 10µF)

MAX16128/ 29 toc16

20ms/div

VIN

20V/div

VGATE

10V/div

VOUT

10V/div

STARTUP FROM SHUTDOWN (SHDN)

RISING FROM O TO 2V, VIN = 12V,

RLOAD = 100Ω, CIN = 0.1µF

MAX16128/ 29 toc15

400µs/div

VSHDN

2V/div

VGATE

10V/div

VOUT

10V/div

STARTUP WAVEFORM

(VIN PULSED O TO 12V, RLOAD = 100Ω,

CIN = 0.1µF, COUT = 10µF)

MAX16128/ 29 toc14

200µs/div

VIN

10V/div

VGATE

10V/div

VOUT

10V/div

REVERSE CURRENT

vs. REVERSE VOLTAGE

MAX16128/ 29 toc13

REVERSE VOLTAGE (V)

REVERSE CURRENT (µA)

252015105

0 30

1.2

1.4

1.6

1.8

OVERVOLTAGE FAULT-TO-GATE

PROPAGATION DELAY vs. TEMPERATURE

MAX16128/ 29 toc12

TEMPERATURE (°C)

PROPAGATION DELAY (

1109565 80-10 5 20 35 50-25

2.0

1.0

-40 125

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Typical Operating Characteristics (continued)

PIN NAME FUNCTION

1 OUT Output Voltage-Sense Input. Connect OUT to the load with a 100W series resistor. Bypass with a minimum

10µF capacitor to GND.

2 SRC

Source Input. Connect SRC to the common source connection of the external MOSFETs. When the

MOSFETs are turned off, this connection is clamped to GND. An external zener diode between SRC and

GATE protects the gates of the external MOSFETs.

3 GATE

Gate-Driver Output. Connect GATE to the gates of the external n-channel MOSFETs. GATE is the charge-

pump output during normal operation. GATE is quickly pulled low during a fault condition or when SHDN

is pulled low.

4 IN Positive Supply Input Voltage. Connect IN to the positive side of the input voltage. Bypass IN with a 0.1µF

ceramic capacitor to GND.

5SHDN Shutdown Input. Drive SHDN low to force GATE and FLAG low and turn off the external n-channel

MOSFETs. Connect a 100kW resistor from SHDN to IN for normal operation.

6 GND Ground

7 I.C. Internally connected to GND

8FLAG

FLAG Output. During startup, FLAG is low as long as VOUT is lower than 90% of VIN and after that

it is high impedance. It asserts low during shutdown mode, an overvoltage, thermal shutdown, or

undervoltage fault or when VOUT falls below 90% of VIN. FLAG asserts low during a cold-crank fault to

signal reverse-current protection.

TOP VIEW

FLAG

I.C.

GND

GATE

SRC

OUT

MAX16128

MAX16129

µMAX

SHDN

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Pin Description

Pin Conguration

Detailed Description

The MAX16128/MAX16129 transient protection circuits

are suitable for automotive and industrial applications

where high-voltage transients are commonly present on

supply voltage inputs. The devices monitor the input volt-

age and control two external common-source n-channel

MOSFETs to protect downstream voltage regulators dur-

ing load-dump events or other automotive pulse condi-

tions.

The devices feature an overvoltage and an undervoltage

comparator for voltage window detection. A flag output

(FLAG) asserts when a fault event occurs.

Two external back-to-back n-channel MOSFETs provide

reverse-voltage protection and also prevent reverse

current during a fault condition. Compared to a traditional

reverse-battery diode, this approach minimizes power dis-

sipation and voltage drop.

The MAX16129 provides a limiter-mode fault manage-

ment for overvoltage and thermal-shutdown conditions,

whereas the MAX16128 provides switch-mode fault

management for overvoltage and thermal-shutdown con-

ditions. In the limiter mode, the MOSFETs cycle on and

off so the output voltage is limited. In the switch mode,

the external MOSFETs are switched off, disconnecting

the load from the input. In both cases, FLAG asserts to

indicate a fault.

Gate Charge Pump

The devices use a charge pump to generate the GATE to

SRC voltage and enhance the external MOSFETs. After

the input voltage exceeds the input undervoltage thresh-

old, the charge pump turns on after a 150µs delay.

During a fault condition, GATE is pulled to ground with

an 8.8mA (min) pulldown current. Note that an exter-

nal zener diode is required to be connected between

the gate and source of the external MOSFETs (see the

Applications Information section).

Overvoltage Protection

The devices detect overvoltage conditions using a com-

parator that is connected through an internal resistive

divider to the input or output voltage. An overvoltage

condition causes the GATE output to go low, turning off

the external MOSFETs. FLAG also asserts to indicate the

fault condition.

Overvoltage Limiter (MAX16129)

In overvoltage-limiter mode, the output voltage is regu-

lated at the overvoltage-threshold voltage and continues

to supply power to downstream devices. In this mode, the

device operates like a voltage regulator.

During normal operation, GATE is enhanced 9V above

SRC. The output voltage is monitored through an internal

resistive divider. When OUT rises above the overvoltage

threshold, GATE goes low and the MOSFETs turn off. As

the voltage on OUT falls below the overvoltage threshold

minus the threshold hysteresis, GATE goes high and

the MOSFETs turn back on again, regulating OUT in a

switched-linear mode at the overvoltage threshold.

The switching frequency depends on the gate charge of

the MOSFETs, the charge-pump current, the output load

current, and the output capacitance.

Caution must be exercised when operating the

MAX16129 in voltage-limiting mode for long durations.

Since MOSFETs can dissipate power continuously during

this interval, proper heatsinking should be implemented to

prevent damage to them.

Overvoltage Switch (MAX16128)

In the overvoltage switch mode, the internal overvolt-

age comparator monitors the input voltage and the load

is completely disconnected from the input during an

overvoltage event. When the input voltage exceeds the

overvoltage threshold, GATE goes low and the MOSFETs

turn off, disconnecting the input from the load. After that,

for the autoretry-mode version, the autoretry timer starts,

while for the latched-mode version a power cycle to IN or

a cycle on SHDN is needed to turn the external MOSFETs

back on.

The MAX16128 can be configured to latch off (suffix D)

even after the overvoltage condition ends. The latch is

cleared by cycling IN below the undervoltage threshold or

by toggling SHDN.

The devices can also be configured to retry:

● One time, then latch off (sufx B)

● Three times, then latch off (sufx C)

● Always retry and never latch off (sufx A)

There is a fixed 150ms (typ) delay between each retry

attempt. If the overvoltage-fault condition is gone when

a retry is attempted, GATE goes high and power is

restored to the downstream circuitry.

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Undervoltage Protection

The devices monitor the input voltage for undervoltage

conditions. If the input voltage is below the undervoltage

threshold (VIN < VUV_TH - VUV_HYS), GATE goes low,

turning off the external MOSFETs and FLAG asserts.

When the input voltage exceeds the undervoltage thresh-

old (VIN > VUV_TH), GATE goes high after a 150µs delay

(typ). A resistance in series with the supply input and IN

must not exceed 50W.

For the MAX16128/MAX16129, the undervoltage threshold

is determined by the part number suffix option (see Table 2).

Cold-Crank Monitoring

Cold-crank faults occur when the input voltage decreases

from its steady-state condition. A cold-crank compara-

tor monitors IN through an internal resistive divider. The

MAX16128/MAX16129 offer two ways to handle this

kind of fault depending on a part number suffix (see the

Selector Guide):

●The cold-crank comparator is disabled and external

MOSFETs stay on during the falling input-voltage

transient unless the input voltage falls below the un-

dervoltage threshold (see Table 2).

●The cold-crank comparator is enabled and external

MOSFETs are switched off by pulling down GATE if

the input voltage falls below the cold-crank threshold

to avoid load discharge due to reverse current from

OUT to IN (see Table 4).

In the last case, cold-crank protection is enabled as long

as VOUT is higher than 90% of VIN (with a 3% hysteresis)

and VIN is higher than the undervoltage threshold. When

the monitored input voltage falls below the falling cold-

crank fault threshold (VIN < VCCK), the GATE is pulled

down and FLAG is asserted low. When the input voltage

rises back above the rising cold-crank fault threshold

(VIN > VCCK + VCLK_HYS), FLAG is released and the

charge pump enhances GATE above SRC, reconnecting

the load to the input.

Thermal Shutdown

The devices’ thermal-shutdown feature turns off the

MOSFETs if the internal die temperature exceeds 145°C

(TJ). By ensuring good thermal coupling between the

MOSFETs and the devices, the thermal shutdown can

turn off the MOSFETs if they overheat.

When the junction temperature exceeds TJ = +145°C

(typ), the internal thermal sensor signals the shutdown

logic, pulling the GATE voltage low and allowing the

device to cool. When TJ drops by 15°C (typ), GATE goes

high and the MOSFETs turn back on. Do not exceed the

absolute maximum junction-temperature rating of TJ =

+150NC.

Flag Output (FLAG)

An open-drain FLAG output indicates fault conditions.

During startup, FLAG is initially low and goes high imped-

ance when VOUT is greater than 90% of VIN if no fault

conditions are present. FLAG asserts low during shut-

down mode, an overvoltage, thermal shutdown, or under-

voltage fault, or when VOUT falls below 90% of VIN. In

the versions where the cold-crank comparator is enabled,

FLAG asserts low during a cold-crank fault.

Reverse-Voltage Protection

The devices integrate reverse-voltage protection, pre-

venting damage to the downstream circuitry caused by

battery reversal or negative transients. The devices can

withstand reverse voltage to -36V without damage to

themselves or the load. During a reverse-voltage condi-

tion, the two external n-channel MOSFETs are turned off,

protecting the load. Connect a 0.1µF ceramic capacitor

from IN to GND, connect a 10nF ceramic capacitor from

GATE to SRC, connect a 10µF capacitor from OUT to

GND, and minimize the parasitic capacitance from GATE

to GND to have fast reverse-battery voltage-transient

protection. During normal operation, both MOSFETs are

turned on and have a minimal forward-voltage drop, pro-

viding lower power dissipation and a much lower voltage

drop than a reverse-battery protection diode.

Applications Information

Automotive Electrical Transients

(Load Dump)

●Automotive circuits generally require supply voltage

protection from various transient conditions that occur

in automotive systems. Several standards dene vari-

ous pulses that can occur. Table 1 summarizes the

pulses from the ISO 7637-2 specication:

Most of the pulses can be mitigated with capacitors

and zener clamp diodes (see the Typical Operating

Characteristics and also the Increasing the Operating

Voltage Range section). The load dump (pulse 5a and

5b) occurs when the alternator is charging the battery

and a battery terminal gets disconnected. Due to the sud-

den change in load, the alternator goes out of regulation

and the bus voltage spikes. The pulse has a rise time

of about 10ms and a fall time of about 400ms but can

extend out to 1s or more depending on the characteris-

tics of the charging system. The magnitude of the pulse

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depends on the bus voltage and whether the system is

unsuppressed or uses central load-dump suppression

(generally implemented using very large clamp diodes

built into the alternator). Table 1 lists the worst-case

values from the ISO 7637-2 specification.

Cold crank (pulse 4) occurs when activating the starter

motor in cold weather with a marginal battery. Due to the

large load imposed by the starter motor, the bus voltage

sags. Since the devices can operate down to 3V, the

downstream circuitry can continue to operate through a

cold-crank condition. If desired, the undervoltage thresh-

old can be increased so that the MOSFETs turn off during

a cold crank, disconnecting the downstream circuitry. An

output reservoir capacitor can be connected from OUT to

GND to provide energy to the circuit during the cold-crank

condition.

Refer to the ISO 7637-2 specification for details on pulse

waveforms, test conditions, and test fixtures.

MOSFET Selection

MOSFET selection is critical to design a proper protec-

tion circuit. Several factors must be taken into account:

the gate capacitance, the drain-to-source voltage rating,

the on-resistance (RDS(ON)), the peak power-dissipation

capability, and the average power-dissipation limit. In gen-

eral, both MOSFETs should have the same part number.

For size-constrained applications, a dual MOSFET can

save board area. Select the drain-to-source voltage so

that the MOSFETs can handle the highest voltage that

might be applied to the circuit. Gate capacitance is not

as critical but it does determine the maximum turn-on

and turn-off time. MOSFETs with more gate capacitance

tend to respond more slowly.

MOSFET Power Dissipation

The RDS(ON) must be low enough to limit the MOSFET

power dissipation during normal operation. Power

dissipation (per MOSFET) during normal operation can be

calculated using this formula:

P = ILOAD2 × RDS(ON)

where P is the power dissipated in each MOSFET and

ILOAD is the average load current.

During a fault condition in switch mode, the MOSFETs

turn off and do not dissipate power. Limiter mode imposes

the worst-case power dissipation. The average power can

be computed using the following formula:

P = ILOAD × (VIN - VOUT)

where P is the average power dissipated in both MOSFETs,

ILOAD is the average load current, VIN is the input volt-

age, and VOUT is the average limited voltage on the

output. In limiter mode, the output voltage is a sawtooth

wave with characteristics determined by the RDS(ON) of

the MOSFETs, the output load current, the output capaci-

tance, the gate charge of the MOSFETs, and the GATE

charge-pump current.

Since limiter mode can involve high switching currents

when the GATE is turning on at the start of a limiting

cycle (especially when the output capacitance is high), it

is important to ensure the circuit does not violate the peak

power rating of the MOSFETs. Check the pulse power rat-

ings in the MOSFET data sheet.

*Relative to system voltage.

Table 1. Summary of ISO 7637-2 Pulses

NAME DESCRIPTION PEAK VOLTAGE (V) (max)*

DURATION

12V SYSTEM

Pulse 1 Inductive load disconnection -100 1 to 2ms

Pulse 2a Inductive wiring disconnection 50 0.05ms

Pulse 3a Switching transients -150 0.2µs

Pulse 3b 100

Pulse 4 Cold crank -7 100ms (initial)

-6 Up to 20s

Pulse 5a Load dump (unsuppressed) 87 400ms (single)

Pulse 5b Load dump (suppressed) (Varies, but less than pulse 5a)

MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits

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MOSFET Gate Protection

To protect the gate of the MOSFETs, connect a zener

clamp diode from the gate to the source. The cathode

connects to the gate, and the anode connects to the

source. Choose the zener clamp voltage to be above 10V

and below the MOSFET VGS maximum rating.

Increasing the Operating Voltage Range

The devices can tolerate -36V to +90V. To increase the

positive input-voltage protection range, connect two

back-to-back zener diodes from IN to GND, and connect

a resistor in series with IN and the power-supply input to

limit the current drawn by the zener diodes (see Figure 1).

Zener diode D1 clamps positive voltage excursions and

D2 clamps negative voltage excursions. Set the zener

voltages so the worst-case voltages do not exceed the

ratings of the part. Also ensure that the zener diode

power ratings are not exceeded. The combination of

the series resistor and the zener diodes also help snub

pulses on the supply voltage input and can aid in clamping

the low-energy ISO 7637-2 pulses.

It is important to compute the peak power dissipation in

the series resistor. Most standard surface-mount resistors

are not able to withstand the peak power dissipation during

certain pulse events. Check the resistor data sheets for

pulse-power derating curves. If necessary, connect

multiple resistors in parallel or use automotive-rated resistors.

The shutdown input needs a series resistor to limit the

current if VIN exceeds the clamped voltage on IN. A good

starting point is 100kW.

Output Reservoir Capacitor

The output capacitor can be used as a reservoir capaci-

tor to allow downstream circuitry to “ride out” fault

transient conditions. Since the voltage at the output is

protected from input-voltage transients, the capacitor

voltage rating can be less than the expected maximum

input voltage.

Figure 1. Circuit to Increase Input-Voltage Protection Range

GND

100Ω

100kΩ

100nF

GATE

VBATT

SRC OUT

IN OUT

DC-DC

CONVERTER

SHDN

FLAG

GND

R3 R3

MAX16128

MAX16129

10nF 10µF

MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits

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Figure 2. MAX16128/MAX16129 Typical Operating Circuit

GATE

VIN

100kΙ

100nF

10nF

SRC OUT

VOUT

COUT

10µF

SHDN

GND

MAX16128

MAX16129

FLAG

100Ι

MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits

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│

Typical Operating Circuit

Figure 3. MAX16128/MAX16129 Functional Diagram

1.225V

POWER-

CHARGE

PUMP

OUTSRCGATE

CONTROL LOGIC

CCK

1.225V

SHDN

FLAG

THERMAL

PROTECTION

GND

MAX16128

MAX16129

MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits

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│

Functional Diagram

Note: The first “_” is a placeholder for the undervoltage threshold. A desired undervoltage threshold is set by the letter suffix found

in Table 2. The second “_” is a placeholder for the overvoltage threshold. A desired overvoltage threshold is set by the letter suffix

found in Table 3. The third “_” is a placeholder for the CCK threshold set by the letter suffix found in Table 4. For MAX16128 options,

the fourth “_” is a placeholder for the switch-mode option. A desired switch mode is set by the letter suffix found in Table 5.

+Denotes a lead(Pb)-free/RoHS-compliant package.

Table 5. Switch Mode Option

(MAX16128 Only)

Table 4. CCK Threshold (Third Suffix)

Table 3. OV Threshold (V) (Second Suffix)

Table 2. UV Threshold (V) (First Suffix)

PACKAGE

TYPE

PACKAGE

CODE

OUTLINE

NO.

LAND

PATTERN NO.

8 µMAX U8+1 21-0036 90-0092

PART TEMP RANGE PIN-PACKAGE FUNCTION

MAX16128UA_ _ _ _+ -40°C to +125°C 8 µMAX Switch Mode

MAX16129UA_ _ _+ -40°C to +125°C 8 µMAX Limiter Mode

PART PIN-

PACKAGE

TOP

MARK FUNCTION

MAX16128UAACAC+ 8 µMAX +AACE Switch Mode

MAX16129UAEBD+ 8 µMAX +AACG Limiter Mode

PART SUFFIX SWITCH MODE

A Always autoretry

B One retry, then latch

C Three retries, then latch

D Latch mode

PART SUFFIX CCK THRESHOLD (TYP) (V)

ANo CCK

B 5.64

C 7.65

D 9.67

PART SUFFIX OV THRESHOLD (TYP) (V)

A 13.64

B 15

C 18.6

D 20.93

E 24.16

F 28.66

G 31.62

PART SUFFIX UV THRESHOLD (TYP) (V)

A 3

B 5

C 5.98

D 7.03

E 8.13

F 9.09

G 10.3

MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits

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│

Package Information

For the latest package outline information and land patterns

(footprints), go to www.maximintegrated.com/packages. Note

that a “+”, “#”, or “-” in the package code indicates RoHS status

only. Package drawings may show a different suffix character, but

the drawing pertains to the package regardless of RoHS status.

Chip Information

PROCESS: BiCMOS

Ordering Information

Selector Guide

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

0 12/11 Initial release —

1 9/12

Updated the Features, Electrical Characteristics, Typical Operating Characteristics,

Cold-Crank Monitoring, Increasing the Operating Voltage Range sections, and

Tables 3 and 4

1–5, 9, 11, 14

2 12/12 Updated Input Supply Current spec in Electrical Characteristics and updated part

numbers in Ordering Information and Selector Guide 2, 14

3 12/13

Changed unit in Electrical Characteristics for OUT Input Resistance to Ground from

mW to MW and changed voltage from -6V to -36V in the Reverse-Voltage Protection

section

3, 9

4 5/15 Added the Benets and Features section 1

5 2/17 Updated to reect IC’s xes 2, 3, 9

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses

are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)

shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.

MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits

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Revision History

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MAX16128AUAACAC+ MAX16129UAEBD+ MAX16128UAADAA+T MAX16129UAAGA+T MAX16128UAACAC+

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MAX16128UAACAC+T MAX16129UAABA+T MAX16129UADFD+ MAX16129UAABA+ MAX16129UADFD+T