General Description
The MAX6791–MAX6796 ultra-low-quiescent-current,
single-/dual-output linear regulators are ideal for auto-
motive applications. The devices offer a wide 5V to 72V
operating input range, allowing them to withstand auto-
motive load-dump conditions while consuming only
68µA. The MAX6791–MAX6794 are dual-output regula-
tors capable of supplying up to 150mA per output. The
MAX6795/MAX6796 offer a single output capable of
delivering up to 300mA. These devices offer standard
output-voltage options (5V, 3.3V, 2.5V, or 1.8V) and can
be adjusted to any voltage from 1.8V to 11V. The
MAX6791–MAX6794 also offer a fixed 5V output.
All devices feature a push-pull or open-drain, active-low
RESET output with a fixed output reset threshold that is
92.5%/87.5% of the regulator output OUT/OUT1. The
reset output asserts low when OUT/OUT1 drops below
the reset threshold and remains low for the fixed or
capacitor-adjustable reset timeout period after
OUT/OUT1 exceeds the reset threshold.
The MAX6791–MAX6796 provide a watchdog input that
monitors a pulse train from the microprocessor (µP) and
generates reset pulses if the watchdog input remains
high or low for a duration longer than the watchdog
timeout period. All devices are available with either a
fixed watchdog timeout period of 280ms (min) or a peri-
od adjustable with an external capacitor. The
MAX6791/MAX6792 feature a windowed watchdog
timeout period with selectable window ratio. The watch-
dog feature can be disabled.
The MAX6791–MAX6794 provide dual enable inputs
(ENABLE1 and ENABLE2) that control each regulator
independently. The single-output MAX6795/MAX6796
feature one enable input (ENABLE).
All devices include a hold input (HOLD) that aids the
implementation of a self-holding circuit without requir-
ing external components. Once the regulator is
enabled, setting HOLD low forces the regulator to
remain on even if ENABLE/ENABLE1 is subsequently
set low. Releasing HOLD shuts down the regulator.
The MAX6791–MAX6796 are available in a small, ther-
mally enhanced TQFN package. The 5mm x 5mm
package dissipates up to 2.7W, supporting continuous
regulator operation during high ambient temperatures,
high battery voltage, and high load-current conditions.
The MAX6791–MAX6796 are specified for a -40°C to
+125°C operating temperature range.
Applications
Automotive
Features
oLow 68µA Quiescent Current
oWide 5V to 72V Supply Voltage Range
oOutput Current
Single Output Up to 300mA
Dual Outputs Up to 150mA per Output
oLow Dropout Voltage
420mV (typ) at 100mA (Single)
840mV (typ) at 100mA (Dual)
oFixed Output-Voltage Options: 5V, 3.3V, 2.5V,
1.8V, or Adjustable Output (from 1.8V to 11V)
oENABLE and HOLD Functionality
oRESET Output: Open Drain or Push-Pull
oInternally Fixed (35µs, 3.125ms, 12.5ms, 50ms, or
200ms) or Capacitor-Adjustable Reset Timeout
Periods
oInternally Fixed or Capacitor-Adjustable
Watchdog Timeout Periods
oWindowed (Minimum/Maximum) Watchdog Timer
Options (MAX6791/MAX6792)
oWatchdog Disable Feature
oThermal, Short-Circuit, and Output Overvoltage
Protection
oFully Specified from -40°C to +125°C
oSmall, Thermally Enhanced, 5mm x 5mm TQFN
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual
Linear Regulators with Supervisory Functions
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-3875; Rev 2; 10/11
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
+
Denotes lead-free package.
For tape-and-reel, add a T after the “+.” Tape-and-reel are
offered in 2.5k increments. The first placeholder “_” designates
preset output-voltage option and preset reset threshold level;
see Table 1. The second placeholder “_ ” designates the reset
timeout period; see Table 2. For example, the MAX6791TPSD3+
indicates a 3.3V output voltage with a reset threshold of 87.5%
at nominal voltage and a 50ms reset timeout period. Samples
are generally held in stock. Nonstandard versions require a 2.5k
minimum order quantity.
/V
Denotes an automotive-qualified part.
*EP = Exposed pad.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
M A X6 7 9 1 TP _D _+ -40°C to +125°C 20 TQFN-EP*
M A X6 7 9 2 TP _D _+ -40°C to +125°C 20 TQFN-EP*
M A X6 7 9 3 TP _ D _+ -40°C to +125°C 20 TQFN-EP*
M A X6 7 9 4 TP _ D _+ -40°C to +125°C 20 TQFN-EP*
M A X6 7 9 5 TP _ D _+ -40°C to +125°C 20 TQFN-EP*
M AX 6795TP _D _/V + -40°C to +125°C 20 TQFN-EP*
M AX 6795TP S D 2/V + -40°C to +125°C 20 TQFN-EP*
M A X6 7 9 6 TP _D _+ -40°C to +125°C 20 TQFN-EP*
Typical Application Circuit, Pin Configurations, and Selector
Guide appear at end of data sheet.
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = 14V, CIN = 1µF, COUT = 10µF, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= TJ= +25°C.)
(Note 1)
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.
(All pins referenced to GND, unless otherwise noted.)
IN to GND ...............................................................-0.3V to +80V
ENABLE, ENABLE1, ENABLE2, PFI,
GATEP to GND .........................................-0.3V to (VIN + 0.3V)
GATEP to IN ...........................................................-12V to +0.3V
OUT, OUT1, OUT2, PFO, RESET (open-drain versions),
CSRT, CSWT .......................................................-0.3V to +12V
HOLD, RESET (push-pull versions), WDI, WDS0, WDS1,
WD-DIS, SET, SET1 ......................-0.3V to (VOUT/OUT1 + 0.3V)
OUT, OUT1, OUT2 Short Circuit to GND.....................Continuous
Maximum Current (all pins except IN and OUT_)...............50mA
Continuous Power Dissipation (TA= +70°C)
20-Pin TQFN (derate 33.3mW/°C above +70°C) .....2666.7mW
Operating Temperature Range (TA) ..................-40°C to +125°C
Junction Temperature (TJ) .................................................150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range VIN 5 72 V
Regulators on (ILOAD = 0mA), VIN = 8V 68 85
VIN = 8V, ILOAD = 300mA
(MAX6795/MAX6796) 130 220
VIN = 14V, ILOAD = 100mA
(MAX6795/MAX6796) 100 160
VIN = 8V, ILOAD1 = ILOAD2
= 150mA
(MAX6791–MAX6794)
130 220
Regulators on,
VOUT/OUT1 =
VOUT2 = 5V
VIN = 14V, ILOAD1 =
ILOAD2 = 50mA
(MAX6791–MAX6794)
100 160
Regulators on (ILOAD = 0mA), VIN = 42V 74 95
Supply Current IIN
Regulators on (ILOAD = 20mA, total)
OUT1/OUT2/OUT = 5V, VIN = 42V 100 170
µA
Shutdown Supply Current ISHDN Regulators off, VIN = 14V 27 45 µA
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 14V, CIN = 1µF, COUT = 10µF, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= TJ= +25°C.)
(Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
L/M, ILOAD = ILOAD1 = 1mA 4.858 4.974 5.090
L/M, ILOAD = 150mA (MAX6791–MAX6794),
VIN = 8V 4.811 4.945 5.078
L/M, ILOAD = 300mA (MAX6795/MAX6796),
VIN = 8V 4.850 5 5.150
T/S, ILOAD = ILOAD1 = 1mA 3.206 3.282 3.360
T/S, ILOAD = 150mA (MAX6791–MAX6794),
VIN = 6V 3.175 3.263 3.351
T/S, ILOAD = 300mA (MAX6795/MAX6796),
VIN = 6V 3.201 3.3 3.399
Z/Y, ILOAD = ILOAD1 = 1mA 2.429 2.487 2.546
Z/Y, ILOAD = 150mA (MAX6791–MAX6794),
VIN = 5.5V 2.405 2.472 2.539
Z/Y, ILOAD = 300mA (MAX6795/MAX6796),
VIN = 5.5V 2.425 2.5 2.575
W/V, ILOAD = ILOAD1 = 1mA 1.748 1.791 1.832
W/V, ILOAD = 150mA (MAX6791–MAX6794),
VIN = 5V 1.731 1.780 1.828
Output Voltage VOUT/
VOUT1
W/V, ILOAD = 300mA (MAX6795/MAX6796),
VIN = 5V 1.746 1.8 1.854
V
ILOAD2 = 1mA 4.858 4.974 5.090
Output Voltage
(MAX6791–MAX6794) VOUT2 ILOAD2 = 150mA 4.811 4.945 5.079 V
SET/SET1 Threshold Voltage VSET I
LOAD = ILOAD1 = 1mA, VOUT/OUT1 = 5V 1.207 1.2315 1.256 V
Adjustable Output Voltage VOUT 1.8 11.0 V
SET/SET1 rising 124
Dual-Mode™ SET Threshold SET/SET1 falling 62 mV
SET/SET1 Input Current SET/SET1 = 1V, VIN = 11V -100 +100 nA
L/M, ILOAD = 20mA (Note 2) 84 130
L/M, ILOAD = 300mA (Note 2) 1200 1800
(MAX6795/
MAX6796)
T/S, ILOAD = 300mA (Note 3) 1700 2400
L/M, ILOAD = 150mA (Note 2) 1000 1800
L/M, ILOAD = 10mA (Note 2) 84 130
Dropout Voltage VDO
(MAX6791–
MAX6794)
T/S, ILOAD = 150mA (Note 3) 1700 2400
mV
MAX6795/MAX6796, inferred from dropout test 300
Guaranteed Output Current
(Note 4) MAX6791–MAX6794, inferred from dropout test 150 mA
Dual Mode is a trademark of Maxim Integrated Products, Inc.
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 14V, CIN = 1µF, COUT = 10µF, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= TJ= +25°C.)
(Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX6795/MAX6796, output shorted,
VIN = 6V 400 480
Short-Circuit Output Current Limit
(Note 4) MAX6791–MAX6794, output shorted,
VIN = 6V 200 240
mA
Thermal-Shutdown Temperature +165 °C
Thermal-Shutdown Hysteresis 20 °C
8V VIN 72V, ILOAD = 1mA 1
Line Regulation 8V VIN 72V, ILOAD = 10mA 1
% of
VOUT
IOUT = 1mA to 300mA
(MAX6795/MAX6796) 2
Load Regulation (Note 5)
IOUT = 1mA to 150mA
(MAX6791–MAX6794) 1.5
%
Power-Supply Rejection Ratio PSRR ILOAD = 10mA, f = 100Hz, VIN = 500mVP-P 69 dB
ILOAD = 300mA, VOUT = 5V,
VOUT = 90% of its nominal value 180
Startup Response Time tSTART ILOAD = 150mA, VOUT = 5V,
VOUT1/OUT2 = 90% of its nominal value 360
µs
Output Overvoltage Protection
Threshold OVTH I
SINK = 1mA from OUT/OUT1/OUT2 1.05 x
VOUT
1.1 x
VOUT V
Output Overvoltage Protection
Sink Current V
OUT = VOUT (nominal) x 1.15 5 10 mA
IN to GATEP Clamp Voltage IGATEP = -100µA, VIN = 20V 13.8 16.3 18.8 V
IN to GATEP Drive Voltage IGATEP = 0A, VIN = 20V 8 10 12 V
ENABLE/ENABLE1/ENABLE2/
HOLD Input-Voltage Low VIL 0.4 V
ENABLE/ENABLE1/ENABLE2/
HOLD Input-Voltage High VIH 1.4 V
ENABLE/ENABLE1/ENABLE2
Input Pulldown Current Enable is internally pulled down to GND 0.5 µA
HOLD Input Pullup Current HOLD is internally pulled to OUT/OUT1 2 µA
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 14V, CIN = 1µF, COUT = 10µF, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= TJ= +25°C.)
(Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
RESET OUTPUT
L 4.500 4.625 4.750
M 4.250 4.375 4.500
T 2.970 3.053 3.135
S 2.805 2.888 2.970
Z 2.250 2.313 2.375
Y 2.125 2.188 2.250
W 1.620 1.665 1.710
Reset Threshold (Preset Output
Voltage) SET/SET1 = GND
V 1.530 1.575 1.620
V
L/T/Z/W 0.90 x
VOUT
0.925 x
VOUT
0.95 x
VOUT
Reset Threshold (Adjustable
Output Voltage)
M/S/Y/V 0.85 x
VOUT
0.875 x
VOUT
0.90 x
VOUT
V
OUT to Reset Delay VOUT1/VOUT falling 35 µs
D0 35 µs
D1 2.187 3.125 4.063
D2 8.75 12.5 16.25
D3 35 50 65
Reset Timeout Period
(CSRT = OUT/OUT1) tRP VOUT1/VOUT rising
D4 140 200 260
ms
CSRT Ramp Current 800 1000 1250 nA
CSRT Ramp Threshold 1.185 1.218 1.255 V
WATCHDOG INPUT
CSWT = OUT/OUT1 (fixed) 280.0 400.0 520.0
Normal Watchdog Timeout
Period tWD2 CSWT = 1500pF (adjustable) 170 236.2 290 ms
CSWT = OUT/OUT1 (fixed) 37.5 50.0 62.5
Fast Watchdog Timeout Period
SET Ratio = 8 tWD1 CSWT = 1500pF (adjustable) 21.95 29.52 36.90 ms
CSWT = OUT/OUT1 (fixed) 18.75 25.0 31.25
Fast Watchdog Timeout Period
SET Ratio = 16 tWD1 CSWT = 1500pF (adjustable) 10.80 14.76 18.45 ms
CSWT = OUT/OUT1 (fixed) 4.68 6.25 7.81
Fast Watchdog Timeout Period
SET Ratio = 64 tWD1 CSWT = 1500pF (adjustable) 2.52 3.69 4.62 ms
Fast Watchdog Minimum Period tWD0 2000 ns
CSWT Ramp Current Adjustable timeout 800 1000 1250 nA
CSWT Ramp Threshold Adjustable timeout 1.185 1.218 1.255 V
Undercurrent Threshold for
Watchdog Enable 7.0 10 13.8 mA
Undercurrent Threshold for
Watchdog Disable 3 5 7 mA
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
6 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 14V, CIN = 1µF, COUT = 10µF, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= TJ= +25°C.)
(Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LOGIC INPUT (WDS0, WDS1, WD-DIS, WDI)
Input-Voltage Low VIL 0.4 V
Input-Voltage High VIH 1.4 V
Input Current Inputs connected to OUT/OUT1 or GND -100 +100 nA
POWER-FAIL COMPARATOR
PFI Threshold VPFI 1.199 1.231 1.263 V
PFI Hysteresis 0.5 %
PFI Input Current VPFI = 14V -100 +100 nA
PFI to PFO Delay (VPFI + 50mV) to (VPFI - 50mV) 35 µs
LOGIC OUTPUT (RESET,PFO)
ISINK = 50µA (output asserted) 0.3
Output-Voltage Low (Open Drain
or Push-Pull) VOL ISINK = 3.2mA (output asserted) 0.4 V
VOUT 1.0V, ISOURCE = 10µA (output not
asserted)
0.8 x
VOUT
VOUT 1.5V, ISOURCE = 100µA (output not
asserted)
0.8 x
VOUT
Output-Voltage High (Push-Pull) VOH
VOUT 2.2V, ISOURCE = 500µA (output not
asserted)
0.8 x
VOUT
V
Open-Drain Leakage V
RESET = V
PFO = 12V (output not asserted) 100 nA
Note 1: All devices are 100% production tested at TJ= +25°C and +125°C. Limits at -40°C are guaranteed by design.
Note 2: Dropout voltage is defined as (VIN - VOUT) when VOUT is 98% of VOUT for VIN = 8V.
Note 3: Dropout voltage is defined as (VIN - VOUT) when VOUT is 98% of VOUT for VIN = 6V.
Note 4: Operation beyond the absolute maximum power dissipation is not guaranteed and may damage the part.
Note 5: Test at VIN = 8V (L/M), VIN = 6V (T/S), VIN = 5V (Z/Y/W/V).
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
_______________________________________________________________________________________
7
40
50
45
60
55
65
70
75
80
5354515 25 55 65 75
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6791-96 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
MAX6791
NO LOAD
50
60
80
70
90
100
110
120
-40 -10 5 20 35-25 50 65 80 11095 125
SUPPLY CURRENT vs. TEMPERATURE
MAX6791 toc02
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
ILOAD = 100mA
ILOAD = 50mA
ILOAD = 1mA
ILOAD = 0A
MAX6791
10
20
15
30
25
35
40
5354515 25 55 65 75
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6791-96toc03
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
MAX6793/MAX6794
20
25
35
30
40
-40 -10 5 20 35-25 50 65 80 11095 125
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX6791toc04
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (µA)
MAX6795
VIN = 14V
0.980
0.990
1.010
1.000
1.020
-40 -10 5 20 35-25 50 65 80 11095 125
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAX6791toc05
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
MAX6796
0
400
1200
800
1600
200
1000
600
1400
-40 -10 5 20 35-25 50 65 80 11095 125
DROPOUT VOLTAGE
vs. TEMPERATURE
MAX6791toc06
TEMPERATURE (°C)
DROPOUT VOLTAGE (mV)
MAX6792
VOUT = 5V
ILOAD = 100mA
ILOAD = 150mA
ILOAD = 10mA
0
600
1600
1200
2000
200
800
400
1400
1000
1800
-40 -10 5 20 35-25 50 65 80 11095 125
DROPOUT VOLTAGE
vs. TEMPERATURE
MAX6791toc07
TEMPERATURE (°C)
DROPOUT VOLTAGE (mV)
MAX6796
ILOAD = 10mA
ILOAD = 150mA
ILOAD = 100mA
ILOAD = 300mA
4.980
4.983
4.981
4.987
4.985
4.989
4.982
4.986
4.984
4.988
4.990
5354515 25 55 65 75
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX6791-96toc08
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
MAX6795
PRESET VOLTAGE,
NO LOAD
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX6791-96 toc09
LOAD CURRENT (mA)
VOUT (V)
25020050 100 150
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
2.0
0300
MAX6796
VIN = 14V
VOUT = 5V
VOUT = 3.3V
SET EXTERNALLY
Typical Operating Characteristics
(VIN = VEN = 14V, CIN = 0.1µF, COUT = 10µF, TJ= TA= +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VIN = VEN = 14V, CIN = 0.1µF, COUT = 10µF, TJ= TA= +25°C, unless otherwise noted.)
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
8 _______________________________________________________________________________________
0.98
1.01
1.03
0.99
1.02
1.00
-40 -10 5 20 35-25 50 65 80 11095 125
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX6791toc10
TEMPERATURE (°C)
NORMALIZED RESET TIMEOUT PERIOD
MAX6796
-40
-80
10 100 1k 100k
PSRR vs. FREQUENCY
-75
-65
-55
-70
-60
-50
-45
MAX6791toc11
FREQUENCY (Hz)
PSRR (dB)
10k
VIN = 6V
VOUT = 1.8V
ILOAD = 10mA
0.980
0.995
1.020
0.985
1.000
0.990
1.010
1.005
1.015
-40 -10 5 20 35-25 50 65 80 11095 125
NORMALIZED WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
MAX6791toc12
TEMPERATURE (°C)
NORMALIZED WATCHDOG TIMEOUT PERIOD
MAX6796
0.995
0.998
1.001
0.996
0.999
0.997
1.000
-40 -10 5 20 35-25 50 65 80 11095 125
NORMALIZED PFI THRESHOLD
vs. TEMPERATURE
MAX6791toc13
TEMPERATURE (°C)
NORMALIZED PFI THRESHOLD
MAX6796
0
1.5
0.5
3.5
2.5
4.5
1.0
3.0
2.0
4.0
5.0
0682 4 10 12 14
RESET OUTPUT
vs. SOURCE CURRENT
MAX6791-96toc14
SOURCE CURRENT (mA)
RESET OUTPUT (V)
MAX6796
RESET OUTPUT VOLTAGE
vs. SINK CURRENT
MAX6791-96toc15
SINK CURRENT (mA)
RESET OUTPUT VOLTAGE (V)
986 72 3 4 51
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
010
MAX6796
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
_______________________________________________________________________________________
9
Typical Operating Characteristics (continued)
(VIN = VEN = 14V, CIN = 0.1µF, COUT = 10µF, TJ= TA= +25°C, unless otherwise noted.)
10,000
1000
100
10
1
0.1
0.0001 0.01 0.10.001 1
RESET TIMEOUT PERIOD
vs. CCSRT
MAX6791-96toc16
CCSRT (µF)
RESET TIMEOUT PERIOD (ms)
WATCHDOG TIMEOUT PERIOD
vs. CCSWT
MAX6791-96toc17
CCSWT (µF)
WATCHDOG TIMEOUT PERIOD
0.010.001
10
100
1000
10,000
100,000
1
0.0001 0.1
LOAD-TRANSIENT RESPONSE
MAX6791-96toc18
OUT1
IOUT1
100mA/div
1mA
1V/div
400µs/div
MAX6796
COUT = 10µF
VOUT = 5V
VIN = 14V
VOUT AC-
COUPLED
LOAD-TRANSIENT RESPONSE
MAX6791-96toc19
IOUT
OUT
100mA/div
1mA
500mV/div
400µs/div
OUT AC-
COUPLED
MAX6796
VIN = 14V
VOUT = 5V
LINE-TRANSIENT RESPONSE
MAX6791-96toc20
VIN
OUT
10V/div
(AC-COUPLED)
20mV/div
1ms/div
OUT AC-
COUPLED
MAX6796
ILOAD = 10mA
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
10 ______________________________________________________________________________________
Pin Description
Typical Operating Characteristics (continued)
(VIN = VEN = 14V, CIN = 0.1µF, COUT = 10µF, TJ= TA= +25°C, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE
MAX6791-96toc21
OUT1
AC-COUPLED
IOUT1
100mA/div
1mA
500mV/div
1ms/div
MAX6792
VOUT1 = 5V
COUT = 10µF
LOAD-TRANSIENT RESPONSE
MAX6791-96toc22
IOUT1
OUT1
AC-COUPLED
100mA/div
20mA
500mV/div
1ms/div
MAX6792
VOUT1 = 5V
COUT = 10µF
PIN
MAX6791/
MAX6792
MAX6793/
MAX6794
MAX6795/
MAX6796
NAME FUNCTION
1, 2 1, 2 — OUT1
Regulator 1 Output. Fixed (+1.8V, +2.5V, +3.3V, or +5V) or adjustable (+1.8V
to +11V). VOUT1 = 150mA (max). Connect a 10µF (min) capacitor from OUT1
to GND.
3 3 — SET1
Feedback Input for Setting the OUT1 Voltage. Connect SET1 to GND to select
the preset output voltage. Connect to an external resistive divider for
adjustable output operation.
4 4 4 PFO
Active-Low, Open-Drain, Power-Fail Comparator Output. PFO asserts low
when PFI is below the internal 1.231V threshold. PFO deasserts when PFI is
above the internal 1.231V threshold.
5 5 5 CSWT
Watchdog Timeout Period Adjust Input. Connect CSWT to OUT1/OUT for the
internally fixed watchdog timeout period. For adjustable watchdog timeout
period, connect a capacitor from CSWT to GND. See the Selecting Watchdog
Timeout Period section for more details.
6 6 6 CSRT
Reset Timeout Period Adjust Input. Connect CSRT to OUT1/OUT for the
internally fixed timeout period. For adjustable timeout, connect a capacitor
from CSRT to GND. See the Reset Output section for more details.
7 7 7 GND Ground
8 8 8 RESET
Active-Low Reset Output. RESET remains low while OUT1/OUT is below the
reset threshold. RESET remains low for the duration of the reset timeout
period after the reset conditions end. RESET is available in push-pull and
open-drain options.
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
______________________________________________________________________________________ 11
Pin Description (continued)
PIN
MAX6791/
MAX6792
MAX6793/
MAX6794
MAX6795/
MAX6796
NAME FUNCTION
9 — — WDS1
10 — — WDS0
Min/Max Watchdog Logic-Select Input. WDS0 and WDS1 select the watchdog
window ratio or disable the watchdog timer. Drive WDS0 and WDS1 high or
low to select the desired ratio, see Table 4.
11 11 11 WDI
Watchdog Input.
MAX6793–MAX6796: A falling or rising transition must occur on WDI within the
selected watchdog timeout period or a reset pulse occurs. The watchdog timer
clears when a transition occurs on WDI or whenever RESET is asserted.
MAX6791/MAX6792: WDI falling and rising transitions within periods shorter
than tWD1 or longer than tWD2 force RESET to assert low for the reset timeout
period. The watchdog timer begins to count after RESET is deasserted. The
watchdog timer clears when a valid transition occurs on WDI or whenever
RESET is asserted. Connect WDS0 high and WDS1 low to disable the watchdog
timer function. See the Watchdog Timer section.
12 12 12 HOLD
Active-Low Regulator Hold Input. When HOLD is forced low, OUT1/OUT
remains ON even if ENABLE1/ENABLE is pulled low. To shut down the
output of the regulator (OUT/OUT1), release HOLD after ENABLE1/ENABLE is
pulled low. Connect HOLD to OUT1/OUT or leave unconnected if unused.
HOLD is internally connected to OUT/OUT1 through a 2µA current source.
13, 14 13, 14 — OUT2 Regulator 2 Output. OUT2 is a fixed +5V output. Connect a 10µF (min)
capacitor from OUT2 to GND.
15 15 — ENABLE2
Active-High Enable Input 2. Drive ENABLE2 high to turn on OUT2. ENABLE2
is internally connected to ground through a 0.5µA current sink.
16 16 16 PFI
Adjustable Power-Fail Comparator Input. Connect PFI to a resistive-divider to
set the desired PFI threshold. The PFI input is referenced to an accurate
1.231V threshold.
17, 18 17, 18 17, 18 IN Regulator Inputs. Bypass IN with a 1µF capacitor to GND.
19 19 19 GATEP
pFET Gate Drive. Connect GATEP to the gate of a p-channel MOSFET to
provide low drop reverse-battery voltage protection.
20 20 — ENABLE1
Active-High Enable Input 1. Drive ENABLE1 high to turn on OUT1. ENABLE1
is internally connected to ground through a 0.5µA current sink.
— 9 9 WD-DIS
Watchdog Disable Input. Drive WD-DIS low to disable the watchdog timer.
Drive WD-DIS high or connect to OUT/OUT1 to enable the watchdog timer.
The watchdog timer clears when reset asserts.
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
12 ______________________________________________________________________________________
Detailed Description
The MAX6791–MAX6796 ultra-low-quiescent-current,
single-/dual-output, high-input-voltage linear regulators
operate from 5V to 72V. The MAX6791–MAX6794 fea-
ture dual regulators that deliver up to 150mA of load
current per output. One output is available with preset
output-voltage options (+1.8V, +2.5V, +3.3V, and
+5.0V) and can be adjusted to any voltage between
+1.8V to +11V using an external resistive-divider at
SET1. The other output provides a fixed 5V output volt-
age. The MAX6795/MAX6796 feature a single regulator
that delivers up to 300mA of current with preset output-
voltage options (+1.8V, +2.5V, +3.3V, and +5.0V) or
can be adjusted to any voltage between +1.8V to +11V.
All devices include an integrated µP reset circuit with a
fixed/adjustable reset and watchdog timeout period.
The MAX6791–MAX6796 monitor OUT/OUT1 and
assert a reset output when the output falls below the
reset threshold.
Regulators
The single and dual regulators accept an input voltage
from 5V to 72V. The MAX6791–MAX6796 offer fixed
preset output voltages of +1.8V, +2.5V, +3.3V, and
+5V, or an adjustable output voltage of +1.8V to +11V,
selected using an external resistive-divider network
connected between OUT1/OUT, SET1/SET, and GND
(see Figure 1). In addition to an adjustable output, the
MAX6791–MAX6794 feature a fixed 5V output voltage.
Reset Output
The reset output is typically connected to the reset
input of a µP. A µP’s reset input starts or restarts the µP
in a known state. The MAX6791–MAX6796 supervisory
circuits provide the reset logic output to prevent code-
execution errors during power-up, power-down, and
brownout conditions (see the
Typical Application
Circuit
). RESET changes from high to low whenever the
monitored output voltage drops below the reset thresh-
old voltage or the watchdog timeout expires. Once the
monitored voltage exceeds its respective reset thresh-
old voltage, RESET remains low for the reset timeout
period, then goes high.
Pin Description (continued)
PIN
MAX6791/
MAX6792
MAX6793/
MAX6794
MAX6795/
MAX6796
NAME FUNCTION
— 10
10, 13, 14,
15 N.C. Not Internally Connected
— — 1, 2 OUT
Regulator Output. Fixed +5V, +3.3V, +2.5V, +1.8V, or adjustable output
(+1.8V to +11V). Connect a 10µF (min) capacitor from OUT to GND.
— — 3 SET
Feedback Input for Setting the OUT Voltage. Connect SET to GND to select
the preset output voltage. Connect to an external resistive-divider for
adjustable output operation.
— — 20 ENABLE
Active-High Enable Input. Drive ENABLE high to turn on the regulator.
ENABLE is internally connected to ground through a 0.5µA current sink.
— — — EP
Exposed Pad. EP is internally connected to GND. Connect EP to the ground
plane to provide a low thermal-resistance path from the IC junction to the PC
board. Do not use as the electrical connection to GND.
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
______________________________________________________________________________________ 13
Functional Diagrams
MAX6791/MAX6792
THERMAL
PROTECTION
CONTROL
LOGIC
1.23V
124mV
OUT2
OUT1
SET1
RESET
CSRT
WDI
CSWT
WDS0
WDS1
PFO
GND PFI
1.138V
OR
1.076V
OVERCURRENT
PROTECTION
RESET
TIMEOUT
RESET
ENABLE2
IN
GATEP
ENABLE1
HOLD
WATCHDOG
TIMEOUT
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
14 ______________________________________________________________________________________
Functional Diagrams (continued)
MAX6793/MAX6794
THERMAL
PROTECTION
CONTROL
LOGIC
1.23V
124mV
OUT2
OUT1
SET1
RESET
CSRT
WDI
CSWT
WD-DIS
PFO
GND PFI
1.138V
OR
1.076V
OVERCURRENT
PROTECTION
RESET
TIMEOUT
RESET
ENABLE2
IN
GATEP
ENABLE1
HOLD
WATCHDOG
TIMEOUT
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
______________________________________________________________________________________ 15
Functional Diagrams (continued)
MAX6795/MAX6796
THERMAL
PROTECTION
CONTROL
LOGIC
1.23V
124mV
OUT
SET
RESET
CSRT
WDI
CSWT
WD-DIS
PFO
GND PFI
1.138V
OR
1.076V
OVERCURRENT
PROTECTION
RESET
TIMEOUT
RESET
IN
GATEP
ENABLE
HOLD
WATCHDOG
TIMEOUT
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
16 ______________________________________________________________________________________
Watchdog Timer
The MAX6791–MAX6796 include a watchdog timer
that asserts RESET if the watchdog input (WDI) does
not toggle high to low or low to high within the watch-
dog timeout period tWD (280ms min or externally
adjustable). RESET remains low for the fixed or user-
adjustable reset timeout period, tRP. If the watchdog is
not updated for lengthy periods of time, the reset out-
put appears as a pulse train, asserted for tRP,
deasserted for tWD, until WDI is toggled again. Once
RESET asserts, it stays low for the entire reset timeout
period ignoring any WDI transitions that may occur. To
prevent the watchdog from asserting RESET, toggle
WDI with a valid rising or falling edge before tWD from
the last edge. The watchdog counter clears when WDI
toggles prior to tWD from the last edge or when RESET
asserts. The watchdog resumes counting after RESET
deasserts.
The MAX6791/MAX6792 have a windowed watchdog
timer that asserts RESET for the adjusted reset timeout
period when the watchdog recognizes a fast watchdog
fault (tWDI < tWD1), or a slow watchdog fault (tWDI >
tWD2). The reset timeout period is adjusted indepen-
dently of the watchdog timeout period.
Enable and Hold Inputs
The MAX6791–MAX6796 support two logic inputs,
ENABLE1/ENABLE and HOLD, making these devices
suitable for automotive applications. For example, when
the ignition key signal drives ENABLE1/ENABLE high,
the regulator turns on and remains on even if
ENABLE1/ENABLE goes low, as long as HOLD is forced
low and stays low after initial regulator power-up. In this
state, releasing HOLD turns the regulator output
(OUT/OUT1) off. This feature makes it possible to imple-
ment a self-holding circuit without external components.
Forcing ENABLE1/ENABLE low and HOLD high or
unconnected places the MAX6791–MAX6796 into shut-
down mode in which the MAX6791–MAX6796 draw less
than 27µA of supply current.
Table 3 shows the state of the regulator output with
respect to the voltage level at ENABLE1/ENABLE and
HOLD. Connect HOLD to OUT1/OUT or leave it uncon-
nected to allow the ENABLE1/ENABLE input to act as a
standard ON/OFF switch for the regulator output
(OUT/OUT1).
Power-Fail Comparator
PFI is the noninverting input to a comparator. If PFI is
less than VPFI (1.231V), PFO goes low. Common uses
for the power-fail comparator include monitoring the
preregulated input of the power supply (such as a bat-
tery) or providing an early power-fail warning so soft-
ware can conduct an orderly system shutdown. Set the
power-fail threshold with a resistive-divider, as shown in
Figure 5. The typical comparator delay is 35µs from PFI
to PFO. Connect PFI to GND or IN if unused.
Reverse-Battery Protection Circuitry
The MAX6791–MAX6796 include an overvoltage pro-
tection circuit that is capable of driving a p-channel
MOSFET to protect against reverse-battery conditions.
This MOSFET eliminates the need for external diodes,
thus minimizing the input voltage drop. See the
Typical
Application Circuit
. The low p-channel MOSFET on-
resistance of 30mΩor less yields a forward-voltage
drop of only a few millivolts versus hundreds of milli-
volts for a diode, thus improving efficiency in battery-
operated devices. Connecting a positive battery
voltage to the drain of Q1 (see the
Typical Application
Circuit
) forward biases its body diode. When the source
voltage exceeds Q1’s threshold voltage, Q1 turns on.
Once the FET is on, the battery is fully connected to the
system and can deliver power to the device and the
load. An incorrectly inserted battery reverse-biases the
FET’s body diode. The gate remains at the ground
potential. The FET remains off and disconnects the
reversed battery from the system. The internal zener
diode and resistor combination at GATEP prevent dam-
age to the p-channel MOSFET during an overvoltage
condition. See the
Functional Diagrams
.
Thermal Protection
When the junction temperature exceeds TJ= +165°C,
the internal protection circuit turns off the internal pass
transistor and allows the IC to cool. The thermal sensor
turns the pass transistor on again after the junction tem-
perature drops to +145°C, resulting in a cycled output
during continuous thermal-overload conditions.
Thermal protection protects the MAX6791–MAX6796 in
the event of fault conditions. For continuous operation,
do not exceed the absolute maximum junction temper-
ature rating of +150°C.
Proper Soldering of Package Heatsink
The MAX6791–MAX6796 package features an exposed
thermal pad on its underside that should be used as a
heatsink. This pad lowers the package’s thermal resis-
tance by providing a direct heat-conduction path from
the die to the PC board. Connect the exposed pad and
GND to the system ground using a large pad or ground
plane, or multiple vias to the ground plane layer.
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
______________________________________________________________________________________ 17
Applications Information
Output Voltage Selection
The MAX6791–MAX6796 feature dual-mode operation:
these devices operate in either a preset voltage mode
or an adjustable mode. In preset voltage mode, internal
trimmed feedback resistors set the internal linear regula-
tor to +1.8V, +2.5V, +3.3V, or +5V (see the
Selector
Guide
). Select preset voltage mode by connecting SET1
(MAX6791–MAX6794)/SET(MAX6795/MAX6796) to
GND. In adjustable mode, select an output voltage
between +1.8V and +11V using two external resistors
connected as a voltage-divider to SET1/SET (see Figure
1). Set the output voltage using the following equation:
where VSET = 1.2315V and R1, R2 ≤200kΩ.
Available Output-Current Calculation
The MAX6791–MAX6794 provide up to 150mA per out-
put, and the MAX6795/MAX6796 provide up to 300mA
of load current. Since the input voltage can be as high
as +72V, package power dissipation limits the amount
of output current available for a given input/output volt-
age and ambient temperature. Figure 2 shows the max-
imum power-dissipation curve for the MAX6791–
MAX6796. The graph assumes that the exposed metal
pad of the device package is soldered to a solid 1in2
section of PC board copper. Use Figure 2 to determine
the allowable package dissipation for a given ambient
temperature. Alternately, use the following formula to
calculate the allowable package dissipation:
PDMAX = Maximum Power Dissipation
PDMAX = 2.666W, for TA≤+70°C
PDMAX = [2.666W - 0.0333W x (TA- 70°C)], for +70°C
< TA≤+125°C
where 0.0333W is the MAX6791–MAX6796 package
thermal derating in W/°C and TAis the ambient temper-
ature in °C.
After determining the allowable package dissipation,
calculate the maximum output current using the follow-
ing formula:
PD = Power Dissipation
PD < PDMAX where PD = [(IN - OUT1) x IOUT1] + [(IN -
OUT2) x IOUT2], for MAX6791–MAX6794.
Also, IOUT1 should be ≤150mA and IOUT2 should be
≤150mA in any case.
PD < PDMAX where PD = [(IN - OUT) x IOUT], for
MAX6795/MAX6796.
Also, IOUT should be ≤300mA in any case.
Selecting Reset Timeout Period
The reset timeout period is adjustable to accommodate
a variety of µP applications. Adjust the reset timeout
period by connecting a capacitor between CSRT and
GND. Use the following formula to set the reset timeout
period:
where tRP is in seconds and CCSRT is in Farads.
Connect CSRT to OUT1 (MAX6791–MAX6794) or to
OUT (MAX6795/MAX6796) to select an internally fixed
timeout period. Connect CSRT to GND to force RESET
low. CCSRT must be a low-leakage (< 10nA) type
capacitor. Ceramic capacitors are recommended; do
not use capacitors lower than 100pF to avoid the influ-
ence of parasitic capacitances.
tC V
A
RP CSRT
. =×
⎛
⎝
⎜⎞
⎠
⎟
1 218 106
VV R
R
OUT SET
=+
⎛
⎝
⎜⎞
⎠
⎟
11
2
MAX6791–MAX6796
VIN
R1
R2
OUT1/OUT
SET1/SET
IN
GND
Figure 1. Setting the Output Voltage Using a Resistive-Divider
IOUT vs. (VIN - VOUT)
(VIN - VOUT) (V)
IOUT (mA)
70 75605040302010
50
100
150
200
250
300
350
0
0
+70°C
+85°C
+125°C
VOUT = 1.8V
SAFE OPERATION REGION FOR
EACH TEMPERATURE POINT IS
UNDER THE CURVE
Figure 2. Maximum Power Dissipation for MAX6791–MAX6796
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
18 ______________________________________________________________________________________
Selecting Watchdog Timeout Period
The watchdog timeout period is adjustable to accommo-
date a variety of µP applications. With this feature, the
watchdog timeout can be optimized for software execu-
tion. The programmer can determine how often the
watchdog timer should be serviced. Adjust the watch-
dog timeout period (tWD) by connecting a capacitor
between CSWT and GND. For normal-mode operation,
calculate the watchdog timeout capacitor as follows:
where tWD is in seconds and CCSWT is in Farads.
To select the internally fixed watchdog timeout period
for the MAX6791–MAX6794, connect CSWT to OUT1.
To select the internally fixed watchdog timeout period
for the MAX6795/MAX6796, connect CSWT to OUT.
CCSWT must be a low-leakage (< 10nA) type capacitor.
Ceramic capacitors are recommended; do not use
capacitors lower than 100pF to avoid the influence of
parasitic capacitances.
The MAX6791/MAX6792 have a windowed watchdog
timer that asserts RESET for tRP when the watchdog
recognizes a fast watchdog fault (time between transi-
tions < tWD1), or a slow watchdog fault (time between
transitions > tWD2). The reset timeout period is adjust-
ed independently of the watchdog timeout period. The
slow watchdog period, tWD2, is calculated as follows:
where tWD2 is in seconds and CCSWT is in Farads.
The fast watchdog period, tWD1, is selectable as a ratio
from the slow watchdog fault period (tWD2). Select the
fast watchdog period by connecting WDS0 and WDS1 to
OUT/OUT1 or GND according to Table 4, which illus-
trates the settings for the 8, 16, and 64 window ratios
(tWD2/tWD1). For example, if CCSWT is 2000pF, and
WDS0 and WDS1 are low, then tWD2 is 318ms (typ) and
tWD1 is 40ms (typ). RESET asserts if the watchdog input
has two edges too close to each other (faster than tWD1);
or has edges that are too far apart (slower than tWD2).
All WDI inputs are ignored while RESET is asserted. The
watchdog timer begins to count after RESET is
deasserted. If the time difference between two transi-
tions on WDI is shorter than tWD1 or longer than tWD2,
RESET is forced to assert low for the reset timeout peri-
od. If the time difference between two transitions on WDI
is between tWD1 (min) and tWD1 (max) or tWD2 (min)
and tWD2 (max), RESET is not guaranteed to assert or
deassert; see Figure 3. To guarantee that the window
watchdog does not assert RESET, strobe WDI between
tWD1 (max) and tWD2 (min). The watchdog timer is
cleared when RESET is asserted. Disable the watchdog
timer by connecting WDS0 high and WDS1 low.
There are several options available to disable the
watchdog timer (for system development or test pur-
poses or when the µP is in a low-power sleep mode).
One way to disable the watchdog timer is to drive
WD-DIS low for the MAX6793–MAX6796 and drive
WDS0 high and WDS1 low for the MAX6791/MAX6792.
This prevents the capacitor from ramping up. Finally,
reducing the OUT/OUT1 regulator current below the
specified regulator current watchdog-disable threshold
(3mA min) also disables the watchdog timer. The
tC V
A
WD CSWT2 6
155 10 =×
⎛
⎝
⎜⎞
⎠
⎟
tC V
A
WD CSWT26
155 10 =×
⎛
⎝
⎜⎞
⎠
⎟
tWD1 tWD2
tWD0 MIN
GUARANTEED
TO ASSERT
UNDETERMINED UNDETERMINED
GUARANTEED
TO NOT ASSERT
GUARANTEED
TO ASSERT
FAST
FAULT
NORMAL
OPERATION
SLOW
FAULT
RESET:
WDI INPUT:
MAX MIN MAX
Figure 3. Windowed Watchdog Timing Diagram
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
______________________________________________________________________________________ 19
watchdog re-enables immediately when any of these
conditions are removed (as long as the RESET is not
asserted). Note that the output current threshold limit
includes hysteresis so that output current must exceed
13.8mA (max) to reenable the watchdog timer.
Capacitor Selection and Regulator
Stability
For stable operation over the full temperature range
and with load currents up to 150mA, use a 10µF (min)
output capacitor with an ESR < 0.5Ω. To reduce noise
and improve load-transient response and power-supply
rejection, use larger output-capacitor values. Some
ceramic dielectrics exhibit large capacitance and ESR
variation with temperature. For these types of capaci-
tors (such as Z5U and Y5V), much higher-value capaci-
tors are required to maintain stability over the
temperaure range. With X7R dielectrics, a 10µF capaci-
tor should be sufficient at all operating temperatures.
To improve power-supply rejection and transient
response, increase the capacitor between IN and GND.
Ensuring a Valid
RESET
Output Down to
VIN = 0V
When VIN falls below 1V, RESET current-sinking capa-
bilities decline drastically. High-impedance CMOS-
logic inputs connected to RESET can drift to
undetermined voltages. This presents no problems in
most applications, since most µPs and other circuitry
do not operate with a supply voltage below 1V. In those
applications where RESET must be valid down to 0V,
adding a pulldown resistor between RESET and GND
sinks any stray leakage currents, holding RESET low
(Figure 4). The value of the pulldown resistor is not criti-
cal; 100kΩis large enough not to load RESET and
small enough to pull RESET to ground. Open-drain
RESET versions are not recommended for applications
requiring valid logic for VIN down to 0V.
Adding Hysteresis to PFI
The power-fail comparator has a typical input hystere-
sis of 0.5% (of VTH). This is sufficient for most applica-
tions where a power-supply line is being monitored
through an external resistive-divider (Figure 5). Figure 6
shows how to add hysteresis to the power-fail com-
parator. Select the ratio of R5 and R6 so PFI sees 1.23V
when VIN falls to the desired trip point (VTRIP). Since
PFO is an open-drain output, resistors R7 and R8 add
hysteresis. R7 typically is an order of magnitude
greater than R5 or R6. The current through R5 and R6
should be at least 10µA to ensure that the 100nA (max)
PFI input current does not shift the trip point. R7 should be
larger than 50kΩto prevent it from loading down the PFO.
MAX6792
MAX6794
MAX6796
VIN
RESET
IN
GND
Figure 4. Ensuring RESET Valid to VIN = 0V
MAX6791
VIN VTERM
R5
R6
PFOPFI
IN
GND
Figure 5. Setting Power-Fail Comparator to Monitor VIN
MAX6791
VIN
VTERM
R5
R7
R8
R6
PFOPFI
IN
GND
Figure 6. Adding Hysteresis Power-Fail Comparator
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
20 ______________________________________________________________________________________
Use the following formulas to determine the high/low
threshold levels and the hysteresis:
VL-H = VPFI x (1 + R5 / R6 +R5 / R7)
VH-L = VPFI x (1 + R5 / R6 ) + (VPFI - VTERM) [R5 / (R7 +
R8)]
VHYS = VPFI x (R5 / R7 ) - (VPFI - VTERM) [R5 / (R7 +
R8)]
where VL-H is the threshold level for the monitored volt-
age rising and VH-L is the threshold level for the moni-
tored voltage falling.
Chip Information
PROCESS: BiCMOS
Table 2. Preset Timeout Period
PART
SUFFIX (_)
RESET TIMEOUT PERIOD
(NOMINAL)
D0 35µs
D1 3.125ms
D2 12.5ms
D3 50ms
D4 200ms
Table 1. Preset Output Voltage and Reset
Threshold
PART
SUFFIX (_)
OUTPUT
VOLTAGE (V)
RESET THRESHOLD
(NOMINAL)
L 5.0 4.625
M 5.0 4.375
T 3.3 3.053
S 3.3 2.888
Z 2.5 2.313
Y 2.5 2.188
W 1.8 1.665
V 1.8 1.575
OPERATING
STATE
ENABLE1/
ENABLE HOLD REGULATOR 1
OUTPUT COMMENT
Initial state Low Don’t care Off ENABLE/ENABLE1 is pulled to GND through internal pulldown.
OUT/OUT1 is disabled.
Turn-on state High Don’t care On ENABLE/ENABLE1 is externally driven high turning OUT/OUT1
on. HOLD is pulled up to OUT/OUT1.
Hold setup state High Low On HOLD is externally pulled low while ENABLE/ENABLE1 remains
high, and the regulator latches on.
Hold state Low Low On
ENABLE/ENABLE1 is driven low (or allowed to float low by an
internal pulldown). HOLD remains externally pulled low keeping
OUT/OUT1 on.
Off state Low High Off
HOLD is driven high (or pulled high by the internal pullup) while
ENABLE/ENABLE1 is low. OUT/OUT1 is turned off and
ENABLE/ENABLE1 and HOLD logic returns to the initial state.
Table 3. ENABLE/ENABLE1 and HOLD Truth Table/State Table
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
______________________________________________________________________________________ 21
Table 4. MIN/MAX Watchdog Setting
WDS0 WDS1 RATIO
00 8
01 16
1 0 Watchdog disabled
11 64
PART NUMBER OUTPUT
VOLTAGE (V)
RESET TIMEOUT PERIOD (ms)
(NOMINAL)
RESET THRESHOLD (V)
(NOMINAL)
MAX6791TPLD2+ 5.0 12.5 4.625
MAX6791TPSD2+ 3.3 12.5 2.888
MAX6792TPLD2+ 5.0 12.5 4.625
MAX6792TPSD2+ 3.3 12.5 2.888
MAX6793TPLD2+ 5.0 12.5 4.625
MAX6793TPSD2+ 3.3 12.5 2.888
MAX6794TPLD2+ 5.0 12.5 4.625
MAX6794TPSD2+ 3.3 12.5 2.888
MAX6795TPLD2+ 5.0 12.5 4.625
MAX6795TPSD2+ 3.3 12.5 2.888
MAX6796TPLD2+ 5.0 12.5 4.625
MAX6796TPSD2+ 3.3 12.5 2.888
Table 5. Standard Version Part Number
PART RESET OUTPUT NUMBER OF
OUTPUTS
WINDOWED
WATCHDOG TIMEOUT
ENABLE
INPUTS
WATCHDOG
DISABLE INPUT
MAX6791TP_D_ Open drain 2 ✓Dual ✓
MAX6792TP_D_ Push-pull 2 ✓Dual ✓
MAX6793TP_D_ Open drain 2 — Dual ✓
MAX6794TP_D_ Push-pull 2 — Dual ✓
MAX6795TP_D_ Open drain 1 — Single ✓
MAX6796TP_D_ Push-pull 1 — Single ✓
+
Denotes lead-free package.
Selector Guide
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
22 ______________________________________________________________________________________
Typical Application Circuit
MAX6791/MAX6792
IN
I/O
µC
RESET I/O
ENABLE1
12V
BATT
PFI
ENABLE2
TO OTHER CIRCUITRY
OUT2
WDI
OUT1
SET1
INT
VCC
CSWT
PFO
INGATEP
HOLD WDS1 WDS0
XCVR
TXD VCC INH BATT
RXD
CANH
CANL
RESETGNDCSRT
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.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.
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
20 TQFN-EP T2055+4 21-0140 90-0009
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
______________________________________________________________________________________ 23
MAX6791/MAX6792
THIN QFN
5mm x 5mm
TOP VIEW
19
20
18
17
7
6
8
OUT1
PFO
CSWT
9
OUT1
OUT2
HOLD
WDI
ENABLE2
1
+
2
IN
45
15 14 12 11
GATEP
ENABLE1
WDS1
RESET
GND
CSRT
SET1 OUT2
3
13
IN
16 10 WDS0
PFI
TOP VIEW
TOP VIEW
MAX6793/MAX6794
THIN QFN
5mm x 5mm
19
20
18
17
7
6
8
OUT1
PFO
CSWT
9
OUT1
OUT2
HOLD
WDI
ENABLE2
1
+
2
IN
45
15 14 12 11
GATEP
ENABLE1
WD-DIS
RESET
GND
CSRT
SET1 OUT2
3
13
IN
16 10 N.C.
PFI
MAX6795/MAX6796
THIN QFN
5mm x 5mm
19
20
18
17
7
6
8
OUT
PFO
CSWT
9
OUT
N.C.
HOLD
WDI
N.C.
1
+
2
IN
45
15 14 12 11
GATEP
ENABLE
WD-DIS
RESET
GND
CSRT
SET N.C.
3
13
IN
16 10 N.C.
PFI
Pin Configurations
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
24
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 10/05 Initial release —
1 8/06 Correct text in data sheet. 10, 11, 18, 19
2 10/11 Added /V automotive-qualified part to data sheet 1
