General Description
The MAX16126/MAX16127 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 to ensure 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 MAX16126/MAX16127 use external resistors to
adjust the overvoltage and undervoltage comparator
thresholds for maximum flexibility.
The MAX16127 provides limiter-mode fault management
for overvoltage and thermal shutdown conditions; whereas
the MAX16126 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 MAX16126/MAX16127 are available in 12-pin TQFN
packages. These devices operate over the automotive
temperature range (-40°C to +125°C).
Benets 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
• Active-Low FLAG Output Identies Fault Condition
●AEC-Q100 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
• Adjustable Undervoltage/Overvoltage Thresholds
• 3mm x 3mm, 12-Pin TQFN Package
●Reduced Power Dissipation Compared to Discrete
Solutions
• Minimal Operating Voltage Drop for Reverse-
Voltage Protection
• 350μA (max) Supply Current and 100μA (max)
Shutdown Current at 30V Input
Applications
●Automotive
●Industrial
●Avionics
●Telecom/Server/Networking
Ordering Information appears at end of data sheet.
19-6053; Rev 7; 8/17
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
EVALUATION KIT AVAILABLE
(All pins referenced to GND.)
IN ............................................................................ -36V to +90V
SHDN ...........................................-0.3V to max (0V, VIN + 0.3V)
TERM ...........................................-0.3V to max (0V, VIN + 0.3V)
SRC, GATE ............................................................-36V to +45V
SRC to GATE .........................................................-36V to +36V
OUT .......................................................................-0.3V to +45V
FLAG .....................................................................-0.3V to +45V
OVSET, UVSET ....................................................... -0.3V to +6V
Continuous Sink/Source (all pins) ..................................±100mA
Continuous Power Dissipation (TA = +70°C) (multilayer board)
TQFN (derate 14.7mW/°C above +70°C)...............1176.5mW
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)
TQFN
Junction-to-Ambient Thermal Resistance (θJA) ..........68°C/W
Junction-to-Case Thermal Resistance (θJC) ............... 11°C/W
(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 224 320
µA
VIN = VSRC =
VOUT = 30V 260 350
SHDN = low VIN = 12V 34 50
VIN = 30V 64 100
SRC Input Current ISRC
VSRC = VIN = 12V, SHDN = high 136 200 µA
VSRC = VIN = 30V, SHDN = high 240 350
IN Undervoltage Lockout VUVLO VIN rising 2.92 V
OVSET/UVSET Input Current IUVSET/OVSET 100 nA
OVSET/UVSET Threshold (Rising) VTH VIN rising 1.2 1.225 1.25 V
OVSET/UVSET Threshold Hysteresis VTH-HYS
0.05 x
VTH
V
POK Threshold Rising VPOK+
0.9 x
VIN
V
POK Threshold Falling VPOK-
0.87 x
VIN
V
TERM On-Resistance RTERM 0.7 1.2 kΩ
Absolute Maximum Ratings
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.
Package Thermal 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.
Electrical Characteristics
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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(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.
Note 3: The MAX16126/MAX16127 power up with the external MOSFETs in off mode (VGATE = VSRC). The external MOSFETs turn
on tSTART after the IC is powered up and all input conditions are valid.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
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
OVSET-to-GATE Propagation Delay tOVG
VOVSET rising (VTH - 100mV to
VTH + 100mV) 0.55 µs
UVSET-to-GATE Propagation Delay tUVG
VUVSET falling (VTH + 100mV to
VTH - 100mV) 20 µs
Output Input Resistance to GND ROUT
MAX16126 4 MΩ
MAX16127 2
OVSET-to-FLAG Propagation Delay tOV
VOVSET rising (VTH - 100mV to
VTH + 100mV) 0.3 µs
GATE Output Voltage High Above
VSRC
VGS
VIN = VSRC = VOUT = 3V,
IGATE = -1FA 5 5 5.5
V
VIN = VSRC = VOUT = 12V,
IGATE = -1FA 8 9 10
VIN = VSRC = VOUT = 24V,
IGATE = -1FA 7 8.5 10
VIN = VSRC = VOUT = 30V,
IGATE = -1FA 6.25 8 9.5
GATE Pulldown Current IPD VGATE = 12V 8.8 mA
GATE Charge-Pump Current IGATEVIN = VGATE = VSRC = 12V 180 µA
Thermal Shutdown T++145 °C
Thermal-Shutdown Hysteresis δT 15 °C
SHDN Logic-High Input Voltage VIH 1.4 V
SHDN Logic-Low Input Voltage VIL 0.4 V
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
Electrical Characteristics (continued)
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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(VIN = 12V, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX16126 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
302010
100
150
200
250
300
50
04
0
SHDN = HIGH
GATE ENHANCED
SUPPLY CURRENT vs. TEMPERATURE
MAX16126 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
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX16126 toc03
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
2418126
20
30
40
50
60
70
80
90
100
10
03
0
SHDN = LOW
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX16126 toc04
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
11095-25 -10 5 35 50 6520 80
15
20
25
30
35
40
45
50
10
-40 125
SHDN = LOW
SHDN PULLDOWN CURRENT
vs. TEMPERATURE
MAX16126 toc05
TEMPERATURE (°C)
SHDN PULLDOWN CURRENT (µA)
1109565 80-10 5 20 35 50-25
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
-40 125
GATE-TO-SOURCE VOLTAGE
vs. SUPPLY VOLTAGE
MAX16126 toc06
VIN (V)
GATE-TO-SOURCE VOLTAGE (V)
302515 20105
1
2
3
4
5
6
7
8
9
10
0
03
5
GATE-TO-SOURCE VOLTAGE
vs. TEMPERATURE
MAX16126 toc07
TEMPERATURE (°C )
GATE-TO-SOURCE VOLTAGE (V)
1109565 80-10 5 20 35 50-25
6.4
6.8
7.2
7.6
8.0
8.4
8.8
9.2
9.6
10.0
6.0
-40 125
VIN = VSRC = VOUT = 12V
GATE ENHANCED
GATE PULLDOWN CURRENT
vs. TEMPERATURE
MAX16126 toc08
TEMPERATURE (°C)
GATE PULLDOWN CURRENT (mA)
8
11
14
17
20
5
11095-25 -10 535506520 80-40 125
VGATE = 12V
VSRC = GND
GATE-PULLUP CURRENT
vs. SUPPLY VOLTAGE
MAX16126 toc09
VIN (V)
GATE PULL-UP CURRENT(µA)
252015105
20
40
60
80
100
120
140
160
180
200
0
03
0
VIN = VGATE = VSRC
GATE ENHANCED
Typical Operating Characteristics
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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(VIN = 12V, TA = +25°C, unless otherwise noted.)
OVSET THRESHOLD vs. TEMPERATURE
MAX16126 toc10a
TEMPERATURE (°C)
OVSET THRESHOLD (V)
0.7
0.9
1.1
1.3
1.5
0.5
11095-25 -10 535506520 80-40 125
FALLING
RISING
UVSET THRESHOLD vs. TEMPERATURE
MAX16126 toc10b
TEMPERATURE (°C)
UVSET THRESHOLD (V)
0.7
0.9
1.1
1.3
1.5
0.5
11095-25 -10 535506520 80-40 125
FALLING
RISING
FLAG OUTPUT LOW VOLTAGE
vs. CURRENT
MAX16126 toc11
FLAG CURRENT (mA)
FLAG VOLTAGE (V)
1.51.00.5
0.1
0.2
0.3
0.4
0.5
0
02
.0
OVERVOLTAGE FAULT TO GATE
PROPAGATION DELAY vs. TEMPERATURE
MAX16126 toc12
TEMPERATURE (°C)
PROPAGATION DELAY (µs)
0.25
0.50
0.75
1.00
0
11095-25 -10 535506520 80-40 125
VOVSET PULSED FROM
(VTH - 100mV) TO (VTH + 100mV)
REVERSE CURRENT
vs. REVERSE VOLTAGE
MAX16126 toc13
REVERSE VOLTAGE (V)
REVERSE CURRENT (µA)
252015105
5
10
15
20
25
30
0
03
0
Typical Operating Characteristics (continued)
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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(VIN = 12V, TA = +25°C, unless otherwise noted.)
STARTUP WAVEFORM
(VIN = 0 TO 12V, RL = 100I,
CIN = 0.1µF, COUT = 100µF)
MAX16126 toc14
VIN
10V/div
VGATE
10V/div
VOUT
10V/div
400µs/div
STARTUP FROM SHUTDOWN
(SHDN RISING 0 TO 2V, VIN = 12V,
RLOAD = 100I, CIN = 0.1µF)
MAX16126 toc15
VSHDN
2V/div
VGATE
10V/div
VOUT
10V/div
400µs/div
OVERVOLTAGE SWITCH FAULT
(VOV = 20V, CIN = 0.1µF, COUT = 100µF)
MAX16126 toc16
VIN
20V/div
VGATE
10V/div
VOUT
20V/div
100ms/div
OVERVOLTAGE LIMITER
(VUV = 4V, VOV = 20V,
CIN = 0.1µF, COUT = 100µF)
MAX16126 toc17
VIN
20V/div
VGATE
20V/div
VOUT
10V/div
20ms/div
Typical Operating Characteristics (continued)
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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12
11
10
4
5
TERM
N.C.
6
I.C.
OUT
12
GATE
3
987
IN
GND
OVSET
UVSET
EP
SRC
TQFN
MAX16126
MAX16127
TOP VIEW
+
FLAG
SHDN
Pin Conguration
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PIN NAME FUNCTION
1SHDN Shutdown Input. Drive SHDN low to force GATE and FLAG low and turn off the external n-channel
MOSFETs. Connect a 100kΩ resistor from SHDN to IN for normal operation.
2 TERM Voltage-Divider Termination Output. TERM is internally connected to IN. TERM is high impedance when
SHDN is low, forcing the current to zero in the resistive-divider connected to TERM.
3 N.C. No Connection. Not internally connected.
4 UVSET Undervoltage Threshold Adjustment Input. Connect UVSET to the external resistive voltage-divider
network to adjust the desired input undervoltage threshold. Connect the resistive divider to TERM.
5 OVSET
Overvoltage Threshold Adjustment Input. Connect OVSET to an external resistive voltage-divider network
to adjust the desired overvoltage disable or overvoltage limit threshold. Connect the resistive divider to
TERM for overvoltage switch-mode applications or to OUT for overvoltage limiting applications.
6 GND Ground
7 I.C. Internally Connected. Connect 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.
9 OUT Output Voltage-Sense Input. Connect OUT to the load with a 100Ω series resistor. Bypass with a
minimum 10µF capacitor to GND.
10 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.
11 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.
12 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.
— EP Exposed Pad. Can be connected to GND or left unconnected.
Pin Description
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Detailed Description
The MAX16126/MAX16127 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 voltage and
control two external common-source n-channel MOSFETs
to protect downstream voltage regulators during load-dump
events or other automotive pulse conditions.
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 cur-
rent during a fault condition. Compared to a traditional
reverse-battery diode, this approach minimizes power
dissipation and voltage drop, and allows the circuit to
operate at very low cold-crank voltages (3V minimum).
The MAX16127 provides a limiter-mode fault manage-
ment for overvoltage and thermal shutdown conditions,
whereas the MAX16126 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 MAX16126/MAX16127 use a charge pump to gener-
ate the GATE to SRC voltage and enhance the external
MOSFETs. After the input voltage exceeds the input
undervoltage threshold, the charge pump turns on after
a 150Fs delay.
During a fault condition, GATE is pulled to ground with a
8.8mA (min) pulldown current. Note that an external zener
diode is required to be connected between the gate and
source of the external MOSFETs. See the Applications
Information section.
Overvoltage Protection
The MAX16126/MAX16127 detect overvoltage conditions
using a comparator that is connected through an external
resistive divider to the input or output voltage. An overvolt-
age condition causes the GATE output to go low, turning
off the external MOSFETs. FLAG also asserts to indicate
the fault condition.
Overvoltage Limiter (MAX16127)
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 a resis-
tive divider between OUT and OVSET. 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 overvolt-
age 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
MAX16127 in voltage-limiting mode for long durations.
Since MOSFETs can dissipate power continuously during
this interval, proper heat sinking should be implemented
to prevent damage to them.
Overvoltage Switch (MAX16126)
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 MAX16126 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:
U One time, then latch off (suffix B)
U Three times, then latch off (suffix C)
U Always retry and never latch off (suffix 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 MAX16126/MAX16127 monitor the input voltage
for undervoltage conditions. If the input voltage is below
the undervoltage threshold (VIN < VTH - VTH-HYS),
GATE goes low, turning off the external MOSFETs and
FLAG asserts. When the input voltage exceeds the
undervoltage threshold (VIN > VTH), GATE goes high
after a 150Fs delay (typ).
For the MAX16126/MAX16127, an external resistive
divider connected between TERM, UVSET, and GND
sets the undervoltage threshold (TERM is connected to
IN when SHDN is high).
Thermal Shutdown
The MAX16126/MAX16127 thermal shutdown feature
turns off the MOSFETs if the internal die tempera-
ture exceeds +145°C (TJ). By ensuring good thermal
coupling between the MOSFETs and the MAX16126/
MAX16127, 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 = +150°C.
Flag Output (FLAG)
An open-drain FLAG output indicates fault conditions.
During startup, FLAG is initially low and goes high
impedance when VOUT is greater than 90% of VIN if no
fault conditions are present. FLAG asserts low during
shutdown mode, an overvoltage, thermal shutdown, or
undervoltage fault, or when VOUT falls below 90% of VIN.
TERM Connection
The TERM connection has an internal switch to IN. In
shutdown (SHDN = GND), this switch is open. By con-
necting the voltage threshold resistive divider to TERM
instead of directly to IN, power dissipation in the resistive
divider can be eliminated and the shutdown supply cur-
rent reduced.
Reverse-Voltage Protection
The MAX16126/MAX16127 integrate reverse-voltage
protection, preventing damage to the downstream cir-
cuitry 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 condition, 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
10µF from OUTPUT to GND, and minimize the parasitic
capacitance from GATE to GND to have a fast reserve-
battery voltage-transient protection. During normal
operation, both MOSFETs are turned on and have a mini-
mal forward voltage drop, providing lower power dissipa-
tion 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 define various
pulses that can occur. Table 1 summarizes the pulses
from the ISO 7637-2 specification.
Most of the pulses can be mitigated with capaci-
tors and zener clamp diodes (see the Typical
Operating Characteristics and also the Increasing the
Input Voltage Protection 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 sudden 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 char-
acteristics of the charging system. The magnitude of the
pulse 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 MAX16126/MAX16127 can operate down
to 3V, the downstream circuitry can continue to operate
through a cold-crank condition. If desired, the undervolt-
age threshold 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.
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Setting Overvoltage and Undervoltage
Thresholds (MAX16126)
The MAX16126 uses an external resistive divider to set the
overvoltage and undervoltage thresholds. The MAX16126
operates in switch mode in which the internal overvoltage
comparator monitors the input voltage. It uses three resis-
tors in a single resistive divider to set the undervoltage
and overvoltage thresholds. The top of the resistive divider
connects to TERM (see Figure 1).
The MAX16126 includes internal undervoltage and over-
voltage comparators for window detection. GATE is
enhanced and the n-channel MOSFETs are on when
the IN voltage is within the selected window. When the
monitored voltage falls below the lower limit (VTRIPLOW)
or exceeds the upper limit (VTRIPHIGH) of the window, the
GATE voltage goes to GND, turning off the MOSFETs.
The circuit in Figure 1 shows the MAX16126 enabling the
DC-DC converter when the monitored voltage is in the
selected window.
The resistor values R1, R2, and R3 can be calculated as
follows:
TOTAL
TRIPLOW TH TH-HYS
R
V (V - V ) R2 R3
=
+
TOTAL
TRIPHIGH TH
R
VV
R3
=
where RTOTAL = R1 + R2 + R3, VTH is the 1.225V
OVSET/UVSET threshold, and VTH-HYS is the hysteresis.
Use the following steps to determine the values for R1,
R2, and R3:
1) Choose a value for RTOTAL, the sum of R1, R2, and
R3.
2) Calculate R3 based on RTOTAL and the desired upper
trip point:
TH TOTAL
TRIPHIGH
VR
R3 V
×
=
3) Calculate R2 based on RTOTAL, R3, and the desired
lower trip point:
TH TH-HYS TOTAL
TRIPLOW
(V - V ) R
R2 - R3
V
×
=
4) Calculate R1 based on RTOTAL, R2, and R3:
TOTAL
R1 R - R2 - R3=
Table 1. Summary of ISO 7637 Pulses
*Relative to system voltage.
NAME DESCRIPTION PEAK VOLTAGE (V) (max)*
DURATION
12V SYSTEM
Pulse 1 Inductive load disconnection -100 1ms 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)
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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Setting Overvoltage and Undervoltage
Thresholds (MAX16127)
The MAX16127 operates in limiter mode and uses
separate resistive dividers to set the undervoltage and
overvoltage thresholds. The top of the overvoltage divider
connects to OUT and the top of the undervoltage divider
connects to TERM (see Figure 2).
Use the following formula to calculate R4:
TOTAL_OV
TH OV
R
R4 V V
= ×
where RTOTAL_OV = R3 + R4, VTH is the 1.225V OVSET
rising threshold, and VOV is the desired overvoltage
threshold. The falling threshold of VTH is 5% below the
rising threshold.
Similarly, to calculate the values of R1 and R2:
TOTAL_UV
TH TH-HYS UV
R
R2 (V - V ) V
= ×
where RTOTAL_UV = R1 + R2, VTH is the 1.225V UVSET
rising threshold, VTH-HYS is the hysteresis, and VUV is
the desired undervoltage threshold.
Use the nearest standard-value resistor that is less
than the calculated value. A lower value for total resis-
tance dissipates more power, but provides slightly better
accuracy.
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.
Figure 1. Overvoltage and Undervoltage Window Detector Circuit (MAX16126)
GND
GATE
VIN
100kI
10nF
SRC OUT
IN OUT
DC-DC
CONVERTER
SHDN
TERM
IN
UVSET
OVSET
GND
R1
R2
R3
MAX16126
0.1µF
FLAG
10µF
100I
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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 x 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 x (VIN - VOUT)
where P is the average power dissipated in both
MOSFETs, ILOAD is the average load current, VIN is the
input voltage, 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 capacitance, 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.
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
Input Voltage Protection Range
The MAX16126/MAX16127 can tolerate -36V to +90V.
To increase the positive input voltage range protection,
connect two back-to-back zener diodes from IN to system
ground, and connect a resistor in series with IN and the
power-supply input to limit the current drawn by the zener
diodes (see Figure 3).
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.
Figure 2. Overvoltage and Undervoltage Limiter Protection Configuration (MAX16127)
GND
GATE
VIN
100kI
SRC
IN OUT
DC-DC
CONVERTER
100I
SHDN
IN OUT
TERM
OVSET
UVSET
GND
R3
R4
R1
R2
MAX16127
10nF
0.1µF
FLAG
10µF
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It is important to compute the peak power dissipation
in the series resistor. Most standard surface-mount
resistors cannot withstand the peak power dissipation
during certain pulse events. Check the resistor data
sheets for pulse power derating curves. If necessary, con-
nect 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 100kI
Increasing the
Input Voltage Operating Range
With proper external component selection, the MAX16126/
MAX16127’s input voltage operating range can be extend-
ed beyond 30V. Normally the input voltage can swing up
to 90V in protection mode, but normal operation is listed in
the electrical characteristics table to 30V. Higher voltage
operation is permissible so long as the resulting GATE
bias voltage does not exceed 45V with respect to GND.
To enable operating voltages above 30V, a 6.8V
Zener diode clamp can be added GATE-to-SRC to the
external switches to limit the maximum GATE voltage.
The circuit in Figure 4 shows the recommended arrange-
ment. When VIN = 35V, VGATE = 35V + 6.8V or 41.8V.
When VIN > 35V, the MAX16126/MAX16127 detects
the input over voltage condition by sensing the voltage
at the OVSET pin and turns off the charge pump. The
resistive voltage divider on OVSET must be selected to
disable the circuit before the gate voltage reaches 45V.
The MAX16126TCA/MAX16127TCA automatically reen-
able GATE drive when the input voltage drops 5% below
the overvoltage threshold. For the MAX16126TCD, the
latch-mode option, GATE drive is enabled by either power
cycling the IN voltage below UVLO threshold or by tog-
gling SHDN. See the Ordering Information section for
other available options.
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 3. Circuit to Increase Input Voltage Protection Range
GND
GATE
VBATT
SRC OUT
IN OUT
DC-DC
CONVERTER
SHDN
IN
GND
D1
D2
*SYSTEM GROUND
*
* *
MAX16126
MAX16127
100kI
FLAG
100I
10µF
10nF
100I
RS
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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Figure 5. MAX16126 Typical Operating Circuit
Figure 4. Use of a 6.8V Zener Clamp to Enable Operation with VIN Up to 35V
IN
GATE
SRC
OUT
GND
OVSET
TERM
SHDN
37.9kI
1.37kI
MAX16127
0.1µF
100I10µF
6.8V
10nF
VIN
100kI
VOUT
GATE
VIN
R1
R2
R3
100kI
SRC OUT
VOUT
COUT
10µF
SHDN
TERM
IN
UVSET
OVSET
GND
MAX16126 FLAG
100I
0.1µF
10nF
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Figure 6. MAX16127 Typical Operating Circuit
GATE
VIN
100kI
SRC OUT
VOUT
SHDN
OVSET
R1
R3
R4
R2
TERM
IN
UVSET
GND
MAX16127
FLAG
100I
0.1µF
10nF 10µF
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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Figure 7. MAX16126/MAX16127 Functional Diagram
1.225V
SHDN
POWER-OK
CHARGE
PUMP
OUT
SRCGATE
CONTROL LOGIC
UVLO
1.225V
FLAG
UVSET
OVSET
TERM
IN
THERMAL
PROTECTION
GND
MAX16126
MAX16127
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
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+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
*Future product—contact factory for availability.
**EP = Exposed pad.
Note: All devices are specified over the -40°C to +125°C temperature range.
PART PIN-PACKAGE TOP MARK FUNCTION
MAX16126TCA+ 12 TQFN-EP** +ABV
Switch mode
Always autoretry
MAX16126TCA/V+ 12 TQFN-EP** +ACR
MAX16126TCB+ 12 TQFN-EP** +ABX One retry, then latch
MAX16126TCB/V+ 12 TQFN-EP** +ADT
MAX16126TCC+ 12 TQFN-EP** +ABY Three retries, then latch
MAX16126TCC/V+ 12 TQFN-EP** +ADU
MAX16126TCD+ 12 TQFN-EP** +ABZ Latch mode
MAX16126TCD/V+* 12 TQFN-EP** +ADH
MAX16127TC+ 12 TQFN-EP** +ABW Limiter mode
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
12 TQFN-EP T1233+4 21-0136 90-0019
Ordering Information
Package Information
For the latest package outline information and land patterns (foot-
prints), 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
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REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
011/11 Initial release —
1 6/12
Revised the Electrical Characteristics, Typical Operating Characteristics, the
Overvoltage Limiter (MAX16127), Reverse-Voltage Protection, and the Increasing the
Input Voltage Protection Range sections and Figure 3.
1–3, 4, 9, 10,
14
2 12/12 Updated Input Supply Current, SRC Input Current, and GATE Output Voltage High
Above VSRC conditions in the Electrical Characteristics and updated Figure 3 2, 3, 14
3 12/13 Updated Figure 3 12
4 1/14 Added /V automotive OPNs to Ordering Information 18
5 10/14 Added Increasing the Input Voltage Operating Range section and new Figure 4 14–17
6 3/15 Updated Benets and Features section 1
7 8/17 Corrected Ordering Information table 18
Revision History
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 specications 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.
MAX16126/MAX16127 Load-Dump/Reverse-Voltage Protection Circuits
© 2017 Maxim Integrated Products, Inc.
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For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
