µMAX is a registered trademark of Maxim Integrated Products, Inc.
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 JA) .......77.6°C/W
Junction-to-Case Thermal Resistance JC) .................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
VUV
1.03 ×
VUV
V
Internal Undervoltage-Threshold
Hysteresis VUV_HYS
0.05 ×
VUV
V
Internal Overvoltage Threshold VOV_TH VIN rising 0.97 ×
VOV
VOV
1.03 ×
VOV
V
Internal Overvoltage-Threshold
Hysteresis VOV_HYS
0.05 ×
VOV
V
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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
VCCK
1.03 ×
VCCK
V
Internal Cold-Crank Threshold Hysteresis VCCK_HYS
0.05 ×
VCCK
V
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
V
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
V
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
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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
0
-40 125
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX16128/ 29 toc04
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
1109565 80-10 5 20 35 50-25
15
20
25
30
35
40
45
50
10
-40 125
SHDN = LOW
SHUTDOWN SUPPLY CURENT
vs. SUPPLY VOLTAGE
MAX16128/29 toc03
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
2721159
20
30
40
50
60
70
80
90
100
10
3
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
50
3
SHDN = HIGH
GATE ENHANCED
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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
0 2.0
INTERNAL UNDERVOLTAGE THRESHOLD
vs. TEMPERATURE
MAX16128/ 29 toc10B
TEMPERATURE (°C)
INTERNAL UNDERVOLTAGE THRESHOLD (%V
UV
)
1109565 80-10 5 20 35 50-25
102
104
90
-40 125
92
94
96
98
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
90
-40 125
92
94
96
98
100
RISING
FALLING
GATE PULLUP CURRENT vs. VIN
MAX16128/ 29 toc09
GATE PULL-UP CURRENT (µA)
20
40
60
100
80
140
120
160
180
200
0
VIN (V)
3020 25151050
VIN = VGATE = VSRC
GATE ENHANCED
8
11
14
17
GATE PULLDOWN CURRENT
vs. TEMPERATURE
MAX16128/ 29 toc08
TEMPERATURE (°C)
GATE PULLDOWN CURRENT (mA)
1109565 80-10 5 20 35 50-25
20
5
-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
1
2
3
4
5
6
7
8
9
10
0
0 35
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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 = 100, 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 = 100,
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
5
10
15
20
25
30
0
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 (
µ
s)
1109565 80-10 5 20 35 50-25
2.0
1.0
-40 125
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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
+
1
2
3
4
8
7
6
5
FLAG
I.C.
GND
IN
GATE
SRC
OUT
MAX16128
MAX16129
µMAX
SHDN
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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.
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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
MAX16128/MAX16129 Load-Dump/Reverse-Voltage Protection Circuits
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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
100
100k
100nF
GATE
VBATT
SRC OUT
IN OUT
DC-DC
CONVERTER
SHDN
FLAG
IN
GND
D1
D2
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
IN
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
1.225V
POWER-
OK
CHARGE
PUMP
OUTSRCGATE
CONTROL LOGIC
CCK
1.225V
UV
OV
SHDN
FLAG
IN
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
© 2017 Maxim Integrated Products, Inc.
15
Revision History
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