MAX6791–MAX6796 High-Voltage, Micropower, Single/Dual Linear Regulators with Supervisory Functions General Description

MAX6791–MAX6796 High-Voltage, Micropower, Single/Dual Linear Regulators with Supervisory Functions General Description
19-3875; Rev 2; 10/11
KIT
ATION
EVALU
E
L
B
A
AVAIL
High-Voltage, Micropower, Single/Dual
Linear Regulators with Supervisory Functions
The MAX6791–MAX6796 ultra-low-quiescent-current,
single-/dual-output linear regulators are ideal for automotive applications. The devices offer a wide 5V to 72V
operating input range, allowing them to withstand automotive load-dump conditions while consuming only
68µA. The MAX6791–MAX6794 are dual-output regulators 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 period adjustable with an external capacitor. The
MAX6791/MAX6792 feature a windowed watchdog
timeout period with selectable window ratio. The watchdog 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 requiring 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, thermally 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
o Low 68µA Quiescent Current
o Wide 5V to 72V Supply Voltage Range
o Output Current
Single Output Up to 300mA
Dual Outputs Up to 150mA per Output
o Low Dropout Voltage
420mV (typ) at 100mA (Single)
840mV (typ) at 100mA (Dual)
o Fixed Output-Voltage Options: 5V, 3.3V, 2.5V,
1.8V, or Adjustable Output (from 1.8V to 11V)
o ENABLE and HOLD Functionality
o RESET Output: Open Drain or Push-Pull
o Internally Fixed (35µs, 3.125ms, 12.5ms, 50ms, or
200ms) or Capacitor-Adjustable Reset Timeout
Periods
o Internally Fixed or Capacitor-Adjustable
Watchdog Timeout Periods
o Windowed (Minimum/Maximum) Watchdog Timer
Options (MAX6791/MAX6792)
o Watchdog Disable Feature
o Thermal, Short-Circuit, and Output Overvoltage
Protection
o Fully Specified from -40°C to +125°C
o Small, Thermally Enhanced, 5mm x 5mm TQFN
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6791TP_D _+
-40°C to +125°C
20 TQFN-EP*
MAX6792TP_D _+
-40°C to +125°C
20 TQFN-EP*
MAX6793TP_ D_+
-40°C to +125°C
20 TQFN-EP*
MAX6794TP_ D_+
-40°C to +125°C
20 TQFN-EP*
MAX6795TP_ D_+
-40°C to +125°C
20 TQFN-EP*
MAX6795TP_D _/V+
-40°C to +125°C
20 TQFN-EP*
MAX6795TPSD2/V+
-40°C to +125°C
20 TQFN-EP*
MAX6796TP_D _+
-40°C to +125°C
20 TQFN-EP*
+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.
Typical Application Circuit, Pin Configurations, and Selector
Guide appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX6791–MAX6796
General Description
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
ABSOLUTE MAXIMUM RATINGS
(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
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.
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)
PARAMETER
Supply Voltage Range
SYMBOL
CONDITIONS
VIN
I IN
2
I SHDN
MAX
UNITS
72
V
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
VIN = 14V, ILOAD1 =
ILOAD2 = 50mA
(MAX6791–MAX6794)
100
160
Regulators on (ILOAD = 0mA), VIN = 42V
74
95
100
170
27
45
Regulators on,
VOUT/OUT1 =
VOUT2 = 5V
Regulators on (ILOAD = 20mA, total)
OUT1/OUT2/OUT = 5V, VIN = 42V
Shutdown Supply Current
TYP
5
Regulators on (ILOAD = 0mA), VIN = 8V
Supply Current
MIN
Regulators off, VIN = 14V
_______________________________________________________________________________________
µA
µA
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
(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
VOUT/
VOUT1
Output Voltage
Output Voltage
(MAX6791–MAX6794)
VOUT2
SET/SET1 Threshold Voltage
VSET
Adjustable Output Voltage
VOUT
Dual-Mode™ SET Threshold
SET/SET1 Input Current
VDO
Dropout Voltage
CONDITIONS
MIN
TYP
MAX
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
W/V, ILOAD = 300mA (MAX6795/MAX6796),
VIN = 5V
1.746
1.8
1.854
ILOAD2 = 1mA
4.858
4.974
5.090
ILOAD2 = 150mA
4.811
4.945
5.079
ILOAD = ILOAD1 = 1mA, VOUT/OUT1 = 5V
1.207
1.2315
1.256
V
11.0
V
1.8
SET/SET1 rising
124
SET/SET1 falling
62
SET/SET1 = 1V, VIN = 11V
L/M, ILOAD = 20mA (Note 2)
(MAX6795/
L/M, ILOAD = 300mA (Note 2)
MAX6796)
T/S, ILOAD = 300mA (Note 3)
(MAX6791–
MAX6794)
-100
1700
2400
1800
L/M, ILOAD = 10mA (Note 2)
84
130
1700
2400
300
MAX6791–MAX6794, inferred from dropout test
150
nA
130
1000
MAX6795/MAX6796, inferred from dropout test
V
1800
L/M, ILOAD = 150mA (Note 2)
T/S, ILOAD = 150mA (Note 3)
Guaranteed Output Current
(Note 4)
V
mV
+100
84
1200
UNITS
mV
mA
Dual Mode is a trademark of Maxim Integrated Products, Inc.
_______________________________________________________________________________________
3
MAX6791–MAX6796
ELECTRICAL CHARACTERISTICS (continued)
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
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
Short-Circuit Output Current Limit
(Note 4)
CONDITIONS
MIN
TYP
MAX6795/MAX6796, output shorted,
VIN = 6V
400
480
MAX6791–MAX6794, output shorted,
VIN = 6V
200
240
+165
Thermal-Shutdown Hysteresis
Load Regulation (Note 5)
Startup Response Time
Output Overvoltage Protection
Threshold
°C
20
Line Regulation
PSRR
t START
OVTH
Output Overvoltage Protection
Sink Current
IN to GATEP Clamp Voltage
1
8V VIN 72V, ILOAD = 10mA
1
I OUT = 1mA to 300mA
(MAX6795/MAX6796)
2
I OUT = 1mA to 150mA
(MAX6791–MAX6794)
1.5
ENABLE/ENABLE1/ENABLE2/
HOLD Input-Voltage Low
VIL
ENABLE/ENABLE1/ENABLE2/
HOLD Input-Voltage High
VIH
% of
VOUT
%
ILOAD = 10mA, f = 100Hz, VIN = 500mV P-P
69
ILOAD = 300mA, VOUT = 5V,
VOUT = 90% of its nominal value
180
ILOAD = 150mA, VOUT = 5V,
VOUT1/OUT2 = 90% of its nominal value
360
dB
µs
1.05 x
VOUT
I SINK = 1mA from OUT/OUT1/OUT2
I GATEP = -100µA, VIN = 20V
I GATEP = 0A, VIN = 20V
IN to GATEP Drive Voltage
°C
8V VIN 72V, ILOAD = 1mA
VOUT = V OUT (nominal) x 1.15
UNITS
mA
Thermal-Shutdown Temperature
Power-Supply Rejection Ratio
MAX
1.1 x
VOUT
V
5
10
13.8
16.3
18.8
V
8
10
12
V
0.4
V
1.4
mA
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
4
_______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
(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
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
UNITS
RESET OUTPUT
Reset Threshold (Preset Output
Voltage)
SET/SET1 = GND
W
1.620
1.665
1.710
V
1.530
1.575
1.620
L/T/Z/W
0.90 x
VOUT
0.925 x
VOUT
0.95 x
VOUT
M/S/Y/V
0.85 x
VOUT
0.875 x
VOUT
0.90 x
VOUT
Reset Threshold (Adjustable
Output Voltage)
OUT to Reset Delay
VOUT1/VOUT falling
D0
Reset Timeout Period
(CSRT = OUT/OUT1)
tRP
VOUT1/VOUT rising
CSRT Ramp Current
CSRT Ramp Threshold
V
V
35
µs
35
µs
D1
2.187
3.125
4.063
D2
8.75
12.5
16.25
D3
35
50
65
D4
140
200
260
800
1000
1250
nA
1.185
1.218
1.255
V
280.0
400.0
520.0
170
236.2
290
ms
WATCHDOG INPUT
Normal Watchdog Timeout
Period
tWD2
Fast Watchdog Timeout Period
SET Ratio = 8
tWD1
Fast Watchdog Timeout Period
SET Ratio = 16
tWD1
Fast Watchdog Timeout Period
SET Ratio = 64
tWD1
Fast Watchdog Minimum Period
tWD0
CSWT = OUT/OUT1 (fixed)
CSWT = 1500pF (adjustable)
CSWT = OUT/OUT1 (fixed)
37.5
50.0
62.5
CSWT = 1500pF (adjustable)
21.95
29.52
36.90
CSWT = OUT/OUT1 (fixed)
18.75
25.0
31.25
CSWT = 1500pF (adjustable)
10.80
14.76
18.45
CSWT = OUT/OUT1 (fixed)
4.68
6.25
7.81
CSWT = 1500pF (adjustable)
2.52
3.69
4.62
2000
ms
ms
ms
ms
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
_______________________________________________________________________________________
5
MAX6791–MAX6796
ELECTRICAL CHARACTERISTICS (continued)
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
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
Input-Voltage High
VIH
Input Current
0.4
1.4
Inputs connected to OUT/OUT1 or GND
V
V
-100
+100
nA
POWER-FAIL COMPARATOR
PFI Threshold
VPFI
1.199
PFI Hysteresis
1.231
1.263
0.5
PFI Input Current
VPFI = 14V
PFI to PFO Delay
(VPFI + 50mV) to (VPFI - 50mV)
-100
V
%
+100
35
nA
µs
LOGIC OUTPUT (RESET, PFO)
Output-Voltage Low (Open Drain
or Push-Pull)
Output-Voltage High (Push-Pull)
Open-Drain Leakage
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
6
VOL
VOH
I SINK = 50µA (output asserted)
0.3
I SINK = 3.2mA (output asserted)
0.4
VOUT 1.0V, I SOURCE = 10µA (output not
asserted)
0.8 x
VOUT
VOUT 1.5V, I SOURCE = 100µA (output not
asserted)
0.8 x
VOUT
VOUT 2.2V, I SOURCE = 500µA (output not
asserted)
0.8 x
VOUT
V RESET = V PFO = 12V (output not asserted)
V
100
All devices are 100% production tested at TJ = +25°C and +125°C. Limits at -40°C are guaranteed by design.
Dropout voltage is defined as (VIN - VOUT) when VOUT is 98% of VOUT for VIN = 8V.
Dropout voltage is defined as (VIN - VOUT) when VOUT is 98% of VOUT for VIN = 6V.
Operation beyond the absolute maximum power dissipation is not guaranteed and may damage the part.
Test at VIN = 8V (L/M), VIN = 6V (T/S), VIN = 5V (Z/Y/W/V).
_______________________________________________________________________________________
V
nA
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
70
MAX6791
NO LOAD
60
55
MAX6791 toc02
110
ILOAD = 100mA
100
ILOAD = 50mA
90
ILOAD = 1mA
80
ILOAD = 0A
70
50
40
MAX6793/MAX6794
35
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
75
120
SUPPLY CURRENT (µA)
MAX6791-96 toc01
80
65
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT vs. TEMPERATURE
30
25
20
15
60
45
MAX6791-96toc03
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6791
50
15
25
35
45
55
65
75
5
15
25
35
45
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
DROPOUT VOLTAGE
vs. TEMPERATURE
30
25
MAX6796
1.010
1.000
0.990
MAX6792
VOUT = 5V
1400
ILOAD = 150mA
ILOAD = 100mA
1000
800
600
400
ILOAD = 10mA
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
DROPOUT VOLTAGE
vs. TEMPERATURE
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
1200
1000
ILOAD = 150mA
800
ILOAD = 100mA
ILOAD = 10mA
4.986
4.985
4.984
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
VOUT = 5V
5.0
4.5
4.0
VOUT = 3.3V
3.5
4.983
3.0
2.5
4.981
4.980
0
MAX6796
VIN = 14V
5.5
4.987
4.982
400
MAX6791-96 toc09
MAX6791-96toc08
4.988
6.0
VOUT (V)
DROPOUT VOLTAGE (mV)
1400
MAX6795
PRESET VOLTAGE,
NO LOAD
4.989
OUTPUT VOLTAGE (V)
ILOAD = 300mA
OUTPUT VOLTAGE vs. LOAD CURRENT
4.990
MAX6791toc07
MAX6796
1600
200
0
0.980
-40 -25 -10 5 20 35 50 65 80 95 110 125
2000
600
75
1200
200
20
65
1600
DROPOUT VOLTAGE (mV)
35
1.020
MAX6791toc05
MAX6791toc04
MAX6795
VIN = 14V
1800
55
SUPPLY VOLTAGE (V)
40
SHUTDOWN SUPPLY CURRENT (µA)
10
-40 -25 -10 5 20 35 50 65 80 95 110 125
NORMALIZED RESET THRESHOLD
5
MAX6791toc06
40
SET EXTERNALLY
2.0
5
15
25
35
45
55
INPUT VOLTAGE (V)
65
75
0
50
100
150
200
250
300
LOAD CURRENT (mA)
_______________________________________________________________________________________
7
MAX6791–MAX6796
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.)
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
1.02
PSRR (dB)
1.00
-55
-60
-65
-70
0.99
-75
-80
0.98
10
-40 -25 -10 5 20 35 50 65 80 95 110 125
10k
1k
FREQUENCY (Hz)
NORMALIZED WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED PFI THRESHOLD
vs. TEMPERATURE
1.015
1.010
1.005
1.000
0.995
0.990
100k
1.001
MAX6791toc13
MAX6796
MAX6796
NORMALIZED PFI THRESHOLD
MAX6791toc12
1.000
0.999
0.998
0.997
0.996
0.985
0.995
0.980
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET OUTPUT
vs. SOURCE CURRENT
RESET OUTPUT VOLTAGE
vs. SINK CURRENT
MAX6796
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.8
0.7
0.6
0.5
0.4
0.3
1.0
0.2
0.5
0.1
0
MAX6796
0.9
RESET OUTPUT VOLTAGE (V)
4.5
MAX6791-96toc14
5.0
MAX6791-96toc15
NORMALIZED WATCHDOG TIMEOUT PERIOD
100
TEMPERATURE (°C)
1.020
0
0
2
4
6
8
10
SOURCE CURRENT (mA)
8
VIN = 6V
VOUT = 1.8V
ILOAD = 10mA
-45
-50
1.01
MAX6791toc11
MAX6796
NORMALIZED RESET TIMEOUT PERIOD
PSRR vs. FREQUENCY
-40
MAX6791toc10
1.03
RESET OUTPUT (V)
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
12
14
0
1
2
3
4
5
6
7
8
SINK CURRENT (mA)
_______________________________________________________________________________________
9
10
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
RESET TIMEOUT PERIOD
vs. CCSRT
WATCHDOG TIMEOUT PERIOD
vs. CCSWT
WATCHDOG TIMEOUT PERIOD
1000
10,000
100
10
1
1000
0.001
0.01
0.1
100
10
1
0.0001
0.1
0.0001
MAX6791-96toc17
100,000
MAX6791-96toc16
1
0.001
0.01
0.1
CCSWT (µF)
CCSRT (µF)
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
MAX6791-96toc18
MAX6796
COUT = 10µF
VOUT = 5V
VIN = 14V
IOUT1
MAX6796
VIN = 14V
VOUT = 5V
IOUT
100mA/div
100mA/div
1mA
OUT1
MAX6791-96toc19
RESET TIMEOUT PERIOD (ms)
10,000
1mA
1V/div
500mV/div
OUT
VOUT ACCOUPLED
OUT ACCOUPLED
400µs/div
400µs/div
LINE-TRANSIENT RESPONSE
MAX6791-96toc20
MAX6796
ILOAD = 10mA
10V/div
(AC-COUPLED)
VIN
OUT
20mV/div
OUT ACCOUPLED
1ms/div
_______________________________________________________________________________________
9
MAX6791–MAX6796
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
Typical Operating Characteristics (continued)
(VIN = VEN = 14V, CIN = 0.1µF, COUT = 10µF, TJ = TA = +25°C, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
MAX6791-96toc21
MAX6791-96toc22
100mA/div
IOUT1
100mA/div
IOUT1
20mA
1mA
OUT1
AC-COUPLED
500mV/div
OUT1
AC-COUPLED
500mV/div
MAX6792
VOUT1 = 5V
COUT = 10µF
MAX6792
VOUT1 = 5V
COUT = 10µF
1ms/div
1ms/div
Pin Description
PIN
MAX6791/ MAX6793/ MAX6795/
MAX6792 MAX6794 MAX6796
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
10
NAME
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.
______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
PIN
MAX6791/ MAX6793/ MAX6795/
MAX6792 MAX6794 MAX6796
NAME
FUNCTION
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.
9
—
—
WDS1
10
—
—
WDS0
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
20
20
—
ENABLE1
—
9
9
WD-DIS
pFET Gate Drive. Connect GATEP to the gate of a p-channel MOSFET to
provide low drop reverse-battery voltage protection.
Active-High Enable Input 1. Drive ENABLE1 high to turn on OUT1. ENABLE1
is internally connected to ground through a 0.5µA current sink.
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.
______________________________________________________________________________________
11
MAX6791–MAX6796
Pin Description (continued)
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
Pin Description (continued)
PIN
MAX6791/ MAX6793/ MAX6795/
MAX6792 MAX6794 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
—
—
—
EP
Active-High Enable Input. Drive ENABLE high to turn on the regulator.
ENABLE is internally connected to ground through a 0.5µA current sink.
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.
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 feature 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 voltage. The MAX6795/MAX6796 feature a single regulator
that delivers up to 300mA of current with preset outputvoltage 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.
12
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 codeexecution 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 threshold voltage or the watchdog timeout expires. Once the
monitored voltage exceeds its respective reset threshold voltage, RESET remains low for the reset timeout
period, then goes high.
______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
ENABLE2
MAX6791/MAX6792
OUT2
THERMAL
PROTECTION
OUT1
IN
GATEP
ENABLE1
HOLD
OVERCURRENT
PROTECTION
CONTROL
LOGIC
1.23V
SET1
124mV
1.138V
OR
1.076V
RESET
TIMEOUT
RESET
CSRT
WATCHDOG
TIMEOUT
WDI
CSWT
RESET
WDS0
WDS1
PFO
GND
PFI
______________________________________________________________________________________
13
MAX6791–MAX6796
Functional Diagrams
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
MAX6791–MAX6796
Functional Diagrams (continued)
ENABLE2
MAX6793/MAX6794
OUT2
THERMAL
PROTECTION
OUT1
IN
GATEP
ENABLE1
HOLD
OVERCURRENT
PROTECTION
CONTROL
LOGIC
1.23V
SET1
124mV
1.138V
OR
1.076V
RESET
TIMEOUT
RESET
CSRT
WATCHDOG
TIMEOUT
WDI
CSWT
RESET
WD-DIS
PFO
GND
14
PFI
______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
THERMAL
PROTECTION
MAX6795/MAX6796
OUT
IN
GATEP
ENABLE
HOLD
OVERCURRENT
PROTECTION
CONTROL
LOGIC
1.23V
SET
124mV
1.138V
OR
1.076V
RESET
TIMEOUT
RESET
CSRT
WATCHDOG
TIMEOUT
WDI
CSWT
RESET
WD-DIS
PFO
GND
PFI
______________________________________________________________________________________
15
MAX6791–MAX6796
Functional Diagrams (continued)
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
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 watchdog timeout period t WD (280ms min or externally
adjustable). RESET remains low for the fixed or useradjustable reset timeout period, tRP. If the watchdog is
not updated for lengthy periods of time, the reset output appears as a pulse train, asserted for t RP ,
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 independently 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 implement a self-holding circuit without external components.
Forcing ENABLE1/ENABLE low and HOLD high or
unconnected places the MAX6791–MAX6796 into shutdown 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 unconnected 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
16
preregulated input of the power supply (such as a battery) or providing an early power-fail warning so software 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 protection 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 onresistance of 30mΩ or less yields a forward-voltage
drop of only a few millivolts versus hundreds of millivolts for a diode, thus improving efficiency in batteryoperated 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 damage 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 temperature 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 temperature 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 resistance 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.
______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
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 regulator 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:
R1 ⎞
⎛
VOUT = VSET ⎜1 +
⎟
⎝
R2 ⎠
where VSET = 1.2315V and R1, R2 ≤ 200kΩ.
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:
V⎞
⎛
tRP = CCSRT ⎜1.218 × 106 ⎟
⎝
A⎠
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. C CSRT 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.
Available Output-Current Calculation
The MAX6791–MAX6794 provide up to 150mA per output, 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 voltage and ambient temperature. Figure 2 shows the maximum 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:
VIN
IN
OUT1/OUT
R1
MAX6791–MAX6796
SET1/SET
R2
GND
PDMAX = Maximum Power Dissipation
After determining the allowable package dissipation,
calculate the maximum output current using the following 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 < PD MAX where PD = [(IN - OUT) x I OUT ], for
MAX6795/MAX6796.
Also, IOUT should be ≤ 300mA in any case.
Figure 1. Setting the Output Voltage Using a Resistive-Divider
IOUT vs. (VIN - VOUT)
350
VOUT = 1.8V
300
+70°C SAFE OPERATION REGION FOR
EACH TEMPERATURE POINT IS
UNDER THE CURVE
+85°C
250
IOUT (mA)
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 TA is the ambient temperature in °C.
200
150
+125°C
100
50
0
0
10
20
30
40
50
60
70 75
(VIN - VOUT) (V)
Figure 2. Maximum Power Dissipation for MAX6791–MAX6796
______________________________________________________________________________________
17
MAX6791–MAX6796
Applications Information
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
Selecting Watchdog Timeout Period
The watchdog timeout period is adjustable to accommodate a variety of µP applications. With this feature, the
watchdog timeout can be optimized for software execution. The programmer can determine how often the
watchdog timer should be serviced. Adjust the watchdog timeout period (tWD) by connecting a capacitor
between CSWT and GND. For normal-mode operation,
calculate the watchdog timeout capacitor as follows:
V⎞
⎛
t WD2 = CCSWT ⎜155 × 106
⎟
⎝
A⎠
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 transitions < tWD1), or a slow watchdog fault (time between
transitions > tWD2). The reset timeout period is adjusted independently of the watchdog timeout period. The
slow watchdog period, tWD2, is calculated as follows:
V⎞
⎛
t WD2 = CCSWT ⎜155 × 106
⎟
⎝
A⎠
where tWD2 is in seconds and CCSWT is in Farads.
tWD0
RESET:
MIN
tWD1
MAX
GUARANTEED
TO ASSERT
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 illustrates the settings for the 8, 16, and 64 window ratios
(t WD2/t WD1). 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 transitions on WDI is shorter than tWD1 or longer than tWD2,
RESET is forced to assert low for the reset timeout period. 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
t WD1 (max) and t WD2 (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 purposes 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
MIN
tWD2
MAX
GUARANTEED
TO NOT ASSERT
UNDETERMINED
GUARANTEED
TO ASSERT
UNDETERMINED
WDI INPUT:
FAST
FAULT
NORMAL
OPERATION
SLOW
FAULT
Figure 3. Windowed Watchdog Timing Diagram
18
______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
VIN
IN
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 capacitors (such as Z5U and Y5V), much higher-value capacitors are required to maintain stability over the
temperaure range. With X7R dielectrics, a 10µF capacitor should be sufficient at all operating temperatures.
To improve power-supply rejection and transient
response, increase the capacitor between IN and GND.
MAX6792
MAX6794
MAX6796
RESET
GND
Figure 4. Ensuring RESET Valid to VIN = 0V
VIN
Ensuring a Valid RESET Output Down to
VIN = 0V
When VIN falls below 1V, RESET current-sinking capabilities decline drastically. High-impedance CMOSlogic 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 critical; 100kΩ is 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 hysteresis of 0.5% (of VTH). This is sufficient for most applications 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 comparator. 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 50kΩ to prevent it from loading down the PFO.
MAX6791–MAX6796
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.
VTERM
IN
R5
PFI
MAX6791
PFO
R6
GND
Figure 5. Setting Power-Fail Comparator to Monitor VIN
VIN
R7
VTERM
IN
R8
R5
PFI
MAX6791
PFO
R6
GND
Figure 6. Adding Hysteresis Power-Fail Comparator
______________________________________________________________________________________
19
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
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
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 voltage rising and VH-L is the threshold level for the monitored 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 3. ENABLE/ENABLE1 and HOLD Truth Table/State Table
OPERATING
STATE
ENABLE1/
ENABLE
HOLD
REGULATOR 1
OUTPUT
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.
20
COMMENT
______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
MAX6791–MAX6796
Table 4. MIN/MAX Watchdog Setting
WDS0
WDS1
0
0
RATIO
8
0
1
16
1
0
Watchdog disabled
1
1
64
Table 5. Standard Version Part Number
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
4.625
MAX6793TPLD2+
5.0
12.5
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
+Denotes lead-free package.
Selector Guide
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
✓
______________________________________________________________________________________
21
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
MAX6791–MAX6796
Typical Application Circuit
12V
BATT
TO OTHER CIRCUITRY
GATEP
IN
IN
ENABLE1
PFI
OUT1
ENABLE2
OUT2
SET1
MAX6791/MAX6792
CSWT
PFO
WDI
CSRT GND
RESET HOLD
RESET
VCC
I/O
WDS1
I/O
WDS0
TXD
µC
INT
VCC INH
BATT
CANH
XCVR
RXD
CANL
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.
22
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
LAND PATTERN NO.
20 TQFN-EP
T2055+4
21-0140
90-0009
______________________________________________________________________________________
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
11
WDI
WDI
12
HOLD
HOLD
13
OUT2
OUT2
14
OUT2
OUT2
15
TOP VIEW
ENABLE2
ENABLE2
TOP VIEW
15
14
13
12
11
PFI 16
10
WDS0
PFI 16
10
N.C.
IN 17
9
WDS1
IN 17
9
WD-DIS
8
RESET
IN 18
8
RESET
7
GND
7
GND
6
CSRT
6
CSRT
3
4
5
1
CSWT
OUT1
THIN QFN
5mm x 5mm
2
3
4
5
CSWT
2
PFO
+
SET1
1
ENABLE1 20
OUT1
+
OUT1
N.C.
N.C.
HOLD
WDI
TOP VIEW
N.C.
THIN QFN
5mm x 5mm
15
14
13
12
11
PFI 16
10
N.C.
IN 17
9
WD-DIS
8
RESET
7
GND
6
CSRT
IN 18
MAX6795/MAX6796
GATEP 19
2
3
4
5
PFO
CSWT
1
SET
+
OUT
ENABLE 20
OUT
ENABLE1 20
GATEP 19
PFO
GATEP 19
MAX6793/MAX6794
SET1
MAX6791/MAX6792
OUT1
IN 18
THIN QFN
5mm x 5mm
______________________________________________________________________________________
23
MAX6791–MAX6796
Pin Configurations
MAX6791–MAX6796
High-Voltage, Micropower, Single/Dual Linear
Regulators with Supervisory Functions
Revision History
REVISION
NUMBER
REVISION
DATE
0
10/05
1
8/06
2
10/11
DESCRIPTION
Initial release
PAGES
CHANGED
—
Correct text in data sheet.
10, 11, 18, 19
Added /V automotive-qualified part to data sheet
1
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.
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