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MAX6794TPLD2+T [ROCHESTER]

2-CHANNEL POWER SUPPLY MANAGEMENT CKT, QCC20, 5 X 5 MM, 0.80 MM HEIGHT, LEAD FREE, MO-220WHHC, TQFN-20;
MAX6794TPLD2+T
型号： MAX6794TPLD2+T
厂家： Rochester Electronics    Rochester Electronics
描述：

2-CHANNEL POWER SUPPLY MANAGEMENT CKT, QCC20, 5 X 5 MM, 0.80 MM HEIGHT, LEAD FREE, MO-220WHHC, TQFN-20
文件： 总26页 (文件大小：4212K)
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19-3875; Rev 1; 8/06  
High-Voltage, Micropower, Single/Dual  
Linear Regulators with Supervisory Functions  
General Description  
Features  
♦ Low 68µA Quiescent Current  
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.  
♦ Wide 5V to 72V Supply Voltage Range  
♦ Output Current  
Single Output Up to 300mA  
Dual Outputs Up to 150mA per Output  
♦ Low Dropout Voltage  
420mV (typ) at 100mA (Single)  
840mV (typ) at 100mA (Dual)  
♦ Fixed Output-Voltage Options: 5V, 3.3V, 2.5V,  
1.8V, or Adjustable Output (from 1.8V to 11V)  
♦ ENABLE and HOLD Functionality  
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.  
♦ RESET Output: Open Drain or Push-Pull  
♦ Internally Fixed (35µs, 3.125ms, 12.5ms, 50ms, or  
200ms) or Capacitor-Adjustable Reset Timeout  
Periods  
♦ Internally Fixed or Capacitor-Adjustable  
Watchdog Timeout Periods  
♦ Windowed (Minimum/Maximum) Watchdog Timer  
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.  
Options (MAX6791/MAX6792)  
♦ Watchdog Disable Feature  
♦ Thermal, Short-Circuit, and Output Overvoltage  
Protection  
♦ Fully Specified from -40°C to +125°C  
♦ Small, Thermally Enhanced, 5mm x 5mm TQFN  
Ordering Information  
TEMP  
RANGE  
PIN-  
PACKAGE  
PKG  
CODE  
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).  
PART  
MAX6791TP_D _+  
MAX6792TP_D _+  
MAX6793TP_ D_+  
MAX6794TP_ D_+  
MAX6795TP_ D_+  
MAX6796TP_D _+  
-40°C to +125°C 20 TQFN  
-40°C to +125°C 20 TQFN  
-40°C to +125°C 20 TQFN  
-40°C to +125°C 20 TQFN  
-40°C to +125°C 20 TQFN  
-40°C to +125°C 20 TQFN  
T2055-4  
T2055-4  
T2055-4  
T2055-4  
T2055-4  
T2055-4  
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.  
+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.  
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  
Typical Application Circuit, Pin Configurations, and Selector  
Guide appear at end of data sheet.  
________________________________________________________________ Maxim Integrated Products  
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at  
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.  
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,  
OUT, OUT1, OUT2 Short Circuit  
to GND....................................................................Continuous  
Maximum Current (all pins except IN and OUT_)...............50mA  
GATEP to GND...........................................-0.3V to (IN + 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 (OUT/OUT1 + 0.3V)  
Continuous Power Dissipation (T = +70°C)  
20-Pin TQFN (derate 33.3mW/°C above +70°C) .....2666.7mW  
A
Operating Temperature Range (T )..................-40°C to +125°C  
A
Junction Temperature (T ) .................................................150°C  
J
Storage Temperature Range.............................-65°C to +150°C  
Lead Temperature (soldering, 10s) .................................+300°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  
(V = 14V, C = 1µF, C  
= 10µF, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = T = +25°C.)  
A J A J  
IN  
IN  
OUT  
(Note 1)  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
Supply Voltage Range  
V
5
72  
85  
V
IN  
Regulators on (I  
= 0mA), V = 8V  
68  
LOAD  
IN  
V
= 8V, I  
= 300mA  
IN  
LOAD  
130  
220  
160  
(MAX6795/MAX6796)  
V
= 14V, I = 100mA  
IN  
LOAD  
100  
130  
(MAX6795/MAX6796)  
= 8V, I = I  
LOAD2  
Regulators on,  
OUT/OUT1 =  
OUT2 = 5V  
V
IN  
LOAD1  
= 150mA  
(MAX6791–MAX6794)  
220  
160  
Supply Current  
I
µA  
IN  
V
I
= 14V, I  
=
IN  
LOAD1  
= 50mA  
100  
LOAD2  
(MAX6791–MAX6794)  
Regulators on (I  
Regulators on (I  
= 0mA), V = 42V  
IN  
74  
100  
27  
95  
170  
45  
LOAD  
= 20mA, total)  
LOAD  
OUT1/OUT2/OUT = 5V, V = 42V  
IN  
Shutdown Supply Current  
I
Regulators off, V = 14V  
µA  
SHDN  
IN  
2
_______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
ELECTRICAL CHARACTERISTICS (continued)  
(V = 14V, C = 1µF, C  
= 10µF, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = T = +25°C.)  
IN  
IN  
OUT  
A
J
A
J
(Note 1)  
PARAMETER  
SYMBOL  
CONDITIONS  
= 1mA  
LOAD1  
MIN  
TYP  
MAX  
UNITS  
L/M, I  
L/M, I  
= I  
4.858  
4.974  
5.090  
LOAD  
= 150mA (MAX6791–MAX6794),  
LOAD  
4.811  
4.945  
5.078  
V
= 8V  
IN  
L/M, I  
= 300mA (MAX6795/MAX6796),  
LOAD  
4.850  
3.206  
3.175  
5
5.150  
3.360  
3.351  
V
= 8V  
IN  
T/S, I  
= I  
= 1mA  
3.282  
3.263  
LOAD  
LOAD1  
T/S, I  
= 150mA (MAX6791–MAX6794),  
LOAD  
V
= 6V  
IN  
T/S, I  
= 300mA (MAX6795/MAX6796),  
LOAD  
3.201  
2.429  
2.405  
3.3  
3.399  
2.546  
2.539  
V
= 6V  
IN  
V
/
OUT  
Output Voltage  
V
V
OUT1  
Z/Y, I  
Z/Y, I  
= I  
= 1mA  
2.487  
2.472  
LOAD  
LOAD1  
= 150mA (MAX6791–MAX6794),  
LOAD  
V
= 5.5V  
IN  
Z/Y, I  
= 300mA (MAX6795/MAX6796),  
LOAD  
2.425  
1.748  
1.731  
2.5  
2.575  
1.832  
1.828  
V
= 5.5V  
IN  
W/V, I  
= I  
= 1mA  
1.791  
1.780  
LOAD  
LOAD1  
W/V, I  
= 150mA (MAX6791–MAX6794),  
LOAD  
V
= 5V  
IN  
W/V, I  
= 300mA (MAX6795/MAX6796),  
LOAD  
1.746  
1.8  
1.854  
V
= 5V  
IN  
I
I
I
= 1mA  
4.858  
4.811  
4.974  
4.945  
5.090  
5.079  
Output Voltage  
(MAX6791–MAX6794)  
LOAD2  
V
V
OUT2  
= 150mA  
= I = 1mA, OUT/OUT1 = 5V  
LOAD2  
SET/SET1 Threshold Voltage  
Adjustable Output Voltage  
V
1.207 1.2315 1.256  
V
V
SET  
LOAD  
LOAD1  
V
1.8  
11.0  
OUT  
SET/SET1 rising  
SET/SET1 falling  
124  
62  
Dual-Mode™ SET Threshold  
SET/SET1 Input Current  
mV  
nA  
SET/SET1 = 1V, V = 11V  
-100  
+100  
130  
IN  
L/M, I  
L/M, I  
= 20mA (Note 2)  
84  
LOAD  
(MAX6795/  
MAX6796)  
1200  
= 300mA (Note 2)  
= 300mA (Note 3)  
= 150mA (Note 2)  
= 10mA (Note 2)  
= 150mA (Note 3)  
1800  
2400  
1800  
130  
LOAD  
LOAD  
T/S, I  
1700  
1000  
84  
Dropout Voltage  
∆V  
mV  
mA  
DO  
L/M, I  
L/M, I  
LOAD  
LOAD  
LOAD  
(MAX6791–  
MAX6794)  
T/S, I  
1700  
2400  
MAX6795/MAX6796, inferred from dropout test  
MAX6791–MAX6794, inferred from dropout test  
300  
150  
Guaranteed Output Current  
(Note 4)  
Dual Mode is a trademark of Maxim Integrated Products, Inc.  
_______________________________________________________________________________________  
3
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
ELECTRICAL CHARACTERISTICS (continued)  
(V = 14V, C = 1µF, C  
= 10µF, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = T = +25°C.)  
IN  
IN  
OUT  
A
J
A
J
(Note 1)  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
MAX6795/MAX6796, output shorted,  
400  
480  
V
= 6V  
IN  
Short-Circuit Output Current Limit  
(Note 4)  
mA  
MAX6791–MAX6794, output shorted,  
= 6V  
200  
240  
V
IN  
Thermal-Shutdown Temperature  
Thermal-Shutdown Hysteresis  
+165  
20  
°C  
°C  
8V ≤ V ≤ 72V, I  
= 1mA  
1
1
IN  
LOAD  
% of  
Line Regulation  
V
8V ≤ V ≤ 72V, I  
= 10mA  
OUT  
IN  
LOAD  
I
= 1mA to 300mA  
OUT  
2
(MAX6795/MAX6796)  
Load Regulation (Note 5)  
Power-Supply Rejection Ratio  
Startup Response Time  
%
I
= 1mA to 150mA  
OUT  
1.5  
(MAX6791–MAX6794)  
PSRR  
I
I
= 10mA, f = 100Hz, V = 500mV  
P-P  
69  
dB  
µs  
LOAD  
IN  
= 300mA, V  
= 5V,  
LOAD  
OUT  
180  
OUT = 90% of its nominal value  
t
START  
I
= 150mA, V = 5V,  
LOAD  
OUT  
360  
OUT1/OUT2 = 90% of its nominal value  
Output Overvoltage Protection  
Threshold  
1.05 x  
1.1 x  
V
OUT  
OV  
I
= 1mA from OUT/OUT1/OUT2  
V
TH  
SINK  
V
OUT  
Output Overvoltage Protection  
Sink Current  
V
= V  
(nominal) x 1.15  
5
10  
mA  
OUT  
OUT  
IN to GATEP Clamp Voltage  
IN to GATEP Drive Voltage  
I
I
= -100µA, V = 20V  
13.8  
8
16.3  
10  
18.8  
12  
V
V
GATEP  
GATEP  
IN  
= 0, V = 20V  
IN  
ENABLE/ENABLE1/ENABLE2/  
HOLD Input-Voltage Low  
V
0.4  
V
V
IL  
ENABLE/ENABLE1/ENABLE2/  
HOLD Input-Voltage High  
V
1.4  
IH  
ENABLE/ENABLE1/ENABLE2  
Input Pulldown Current  
Enable is internally pulled down to GND  
0.5  
2
µA  
µA  
HOLD Input Pullup Current  
HOLD is internally pulled to OUT/OUT1  
4
_______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
ELECTRICAL CHARACTERISTICS (continued)  
(V = 14V, C = 1µF, C  
= 10µF, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = T = +25°C.)  
IN  
IN  
OUT  
A
J
A
J
(Note 1)  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
RESET OUTPUT  
L
4.500  
4.250  
2.970  
2.805  
2.250  
2.125  
1.620  
1.530  
4.625  
4.375  
3.053  
2.888  
2.313  
2.188  
1.665  
1.575  
4.750  
4.500  
3.135  
2.970  
2.375  
2.250  
1.710  
1.620  
M
T
S
Z
Y
W
V
Reset Threshold (Preset Output  
Voltage)  
SET/SET1 = GND  
V
0.90 x 0.925 x 0.95 x  
L/T/Z/W  
M/S/Y/V  
V
V
V
OUT  
OUT  
OUT  
Reset Threshold (Adjustable  
Output Voltage)  
V
0.85 x 0.875 x 0.90 x  
V
V
V
OUT  
OUT  
OUT  
OUT to Reset Delay  
V
/V  
falling  
rising  
35  
µs  
µs  
OUT1 OUT  
D0  
D1  
D2  
D3  
D4  
35  
2.187  
8.75  
35  
3.125  
12.5  
50  
4.063  
16.25  
65  
Reset Timeout Period  
(CSRT = OUT/OUT1)  
t
RP  
V
/V  
OUT1 OUT  
ms  
140  
200  
260  
CSRT Ramp Current  
CSRT Ramp Threshold  
WATCHDOG INPUT  
800  
1000  
1.218  
1250  
1.255  
nA  
V
1.185  
CSWT = OUT/OUT1 (fixed)  
CSWT = 1500pF (adjustable)  
CSWT = OUT/OUT1 (fixed)  
CSWT = 1500pF (adjustable)  
CSWT = OUT/OUT1 (fixed)  
CSWT = 1500pF (adjustable)  
CSWT = OUT/OUT1 (fixed)  
CSWT = 1500pF (adjustable)  
280.0  
170  
400.0  
236.2  
50.0  
520.0  
290  
Normal Watchdog Timeout Period  
t
t
t
ms  
ms  
ms  
ms  
WD2  
WD1  
WD1  
37.5  
62.5  
Fast Watchdog Timeout Period  
SET Ratio = 8  
21.95  
18.75  
10.80  
4.68  
29.52  
25.0  
36.90  
31.25  
18.45  
7.81  
Fast Watchdog Timeout Period  
SET Ratio = 16  
14.76  
6.25  
Fast Watchdog Timeout Period  
SET Ratio = 64  
t
t
WD1  
WD0  
2.52  
3.69  
4.62  
Fast Watchdog Minimum Period  
CSWT Ramp Current  
2000  
800  
ns  
nA  
V
Adjustable timeout  
Adjustable timeout  
1000  
1250  
CSWT Ramp Threshold  
1.185  
1.218  
1.255  
Undercurrent Threshold for  
Watchdog Enable  
7.0  
3
10  
5
13.8  
7
mA  
mA  
Undercurrent Threshold for  
Watchdog Disable  
_______________________________________________________________________________________  
5
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
ELECTRICAL CHARACTERISTICS (continued)  
(V = 14V, C = 1µF, C  
= 10µF, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = T = +25°C.)  
IN  
IN  
OUT  
A
J
A
J
(Note 1)  
PARAMETER  
SYMBOL  
CONDITIONS  
MIN  
TYP  
MAX  
UNITS  
LOGIC INPUT (WDS0, WDS1, WD-DIS, WDI)  
Input-Voltage Low  
Input-Voltage High  
Input Current  
V
0.4  
V
V
IL  
V
1.4  
IH  
Inputs connected to OUT/OUT1 or GND  
-100  
+100  
1.263  
+100  
nA  
POWER-FAIL COMPARATOR  
PFI Threshold  
V
1.199  
-100  
1.231  
0.5  
V
PFI  
PFI Hysteresis  
%
PFI Input Current  
V
= 14V  
nA  
µs  
PFI  
PFI to PFO Delay  
(V + 50mV) to (V - 50mV)  
35  
PFI  
PFI  
LOGIC OUTPUT (RESET, PFO)  
I
I
= 50µA (output asserted)  
= 3.2mA (output asserted)  
0.3  
0.4  
SINK  
Output-Voltage Low (Open Drain  
or Push-Pull)  
V
V
OL  
SINK  
V
≥ 1.0V, I  
= 10µA (output not  
= 100µA (output not  
= 500µA (output not  
0.8 x  
V
OUT  
OUT  
SOURCE  
SOURCE  
SOURCE  
asserted)  
V
≥ 1.5V, I  
0.8 x  
V
OUT  
OUT  
Output-Voltage High (Push-Pull)  
Open-Drain Leakage  
V
V
OH  
asserted)  
V
≥ 2.2V, I  
0.8 x  
OUT  
asserted)  
V
OUT  
V
= V  
RE  SET  
= 12V (output not asserted)  
PFO  
100  
nA  
Note 1: All devices are 100% production tested at T = +25°C and +125°C. Limits at -40°C are guaranteed by design.  
J
Note 2: Dropout voltage is defined as (V - V  
) when V  
) when V  
is 98% of V  
is 98% of V  
for V = 8V.  
for V = 6V.  
IN  
IN  
OUT  
OUT  
OUT  
OUT  
OUT  
OUT  
IN  
Note 3: Dropout voltage is defined as (V - V  
IN  
Note 4: Operation beyond the absolute maximum power dissipation is not guaranteed and may damage the part.  
Note 5: Test at V = 8V (L/M), V = 6V (T/S), V = 5V (Z/Y/W/V).  
IN  
IN  
IN  
6
_______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Typical Operating Characteristics  
(V = V = 14V, C = 0.1µF, C  
= 10µF, T = T = +25°C, unless otherwise noted.)  
J A  
IN  
EN  
IN  
OUT  
SUPPLY CURRENT  
vs. SUPPLY VOLTAGE  
SHUTDOWN SUPPLY CURRENT  
vs. SUPPLY VOLTAGE  
SUPPLY CURRENT vs. TEMPERATURE  
80  
75  
70  
65  
60  
55  
50  
45  
40  
120  
40  
35  
30  
25  
20  
15  
10  
MAX6793/MAX6794  
110  
100  
I
= 100mA  
LOAD  
I
= 50mA  
= 0  
LOAD  
MAX6791  
NO LOAD  
90  
80  
70  
60  
50  
I
= 1mA  
LOAD  
I
LOAD  
MAX6791  
-40 -25 -10  
5
15  
25  
35  
45  
55  
65  
75  
5
20 35 50 65 80 95 110 125  
5
15  
25  
35  
45  
55  
65  
75  
SUPPLY VOLTAGE (V)  
TEMPERATURE (°C)  
SUPPLY VOLTAGE (V)  
SHUTDOWN SUPPLY CURRENT  
vs. TEMPERATURE  
NORMALIZED RESET THRESHOLD  
vs. TEMPERATURE  
DROPOUT VOLTAGE  
vs. TEMPERATURE  
40  
35  
30  
25  
20  
1.020  
1.010  
1.000  
0.990  
0.980  
1600  
1400  
1200  
1000  
800  
600  
400  
200  
0
MAX6792  
MAX6795  
= 14V  
MAX6796  
I
= 150mA  
V
= 5V  
LOAD  
OUT  
V
IN  
I
= 100mA  
LOAD  
I
= 10mA  
LOAD  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
-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  
OUTPUT VOLTAGE vs. LOAD CURRENT  
6.0  
5.5  
5.0  
4.5  
4.0  
3.5  
3.0  
2.5  
2.0  
2000  
1800  
1600  
1400  
1200  
1000  
800  
4.990  
4.989  
4.988  
4.987  
4.986  
4.985  
4.984  
4.983  
4.982  
4.981  
4.980  
MAX6796  
MAX6795  
PRESET VOLTAGE,  
NO LOAD  
MAX6796  
V
= 14V  
IN  
I
= 300mA  
LOAD  
V
= 5V  
OUT  
I
= 150mA  
= 10mA  
LOAD  
V
= 3.3V  
OUT  
I
= 100mA  
LOAD  
600  
400  
200  
I
LOAD  
SET EXTERNALLY  
200 250 300  
LOAD CURRENT (mA)  
0
0
50  
100  
150  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
5
15  
25  
35  
45  
55  
65  
75  
TEMPERATURE (°C)  
INPUT VOLTAGE (V)  
_______________________________________________________________________________________  
7
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Typical Operating Characteristics (continued)  
(V = V = 14V, C = 0.1µF, C  
= 10µF, T = T = +25°C, unless otherwise noted.)  
J A  
IN  
EN  
IN  
OUT  
NORMALIZED RESET TIMEOUT PERIOD  
vs. TEMPERATURE  
PSRR vs. FREQUENCY  
1.03  
1.02  
1.01  
1.00  
0.99  
0.98  
-40  
-45  
-50  
-55  
-60  
-65  
-70  
-75  
-80  
V
V
= 6V  
IN  
MAX6796  
= 1.8V  
OUT  
I
= 10mA  
LOAD  
-40 -25 -10  
5
20 35 50 65 80 95 110 125  
TEMPERATURE (°C)  
10  
100  
1k  
10k  
100k  
FREQUENCY (Hz)  
NORMALIZED PFI THRESHOLD  
vs. TEMPERATURE  
NORMALIZED WATCHDOG TIMEOUT PERIOD  
vs. TEMPERATURE  
1.001  
1.000  
0.999  
0.998  
0.997  
0.996  
0.995  
1.020  
MAX6796  
MAX6796  
1.015  
1.010  
1.005  
1.000  
0.995  
0.990  
0.985  
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  
1.0  
0.9  
0.8  
0.7  
0.6  
0.5  
0.4  
0.3  
0.2  
0.1  
0
5.0  
4.5  
4.0  
3.5  
3.0  
2.5  
2.0  
1.5  
1.0  
0.5  
0
MAX6796  
MAX6796  
0
2
4
6
8
10  
12  
14  
0
1
2
3
4
5
6
7
8
9
10  
SOURCE CURRENT (mA)  
SINK CURRENT (mA)  
8
_______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Typical Operating Characteristics (continued)  
(V = V = 14V, C = 0.1µF, C  
= 10µF, T = T = +25°C, unless otherwise noted.)  
J A  
IN  
EN  
IN  
OUT  
RESET TIMEOUT PERIOD  
WATCHDOG TIMEOUT PERIOD  
vs. C  
vs. C  
CSRT  
CSWT  
100,000  
10,000  
1000  
100  
10,000  
1000  
100  
10  
10  
1
1
0.1  
0.0001  
0.001  
0.01  
0.1  
0.0001  
0.001  
0.01  
0.1  
1
C
(µF)  
C
CSRT  
(µF)  
CSWT  
LOAD-TRANSIENT RESPONSE  
LOAD-TRANSIENT RESPONSE  
MAX6791-96toc18  
MAX6796  
MAX6796  
C
= 10µF  
OUT  
V
V
= 14V  
IN  
I
V
= 5V  
OUT1  
OUT  
= 5V  
OUT  
I
OUT  
V
= 14V  
IN  
100mA/div  
100mA/div  
1mA  
1mA  
OUT1  
1V/div  
500mV/div  
OUT  
V
AC-  
OUT  
OUT AC-  
COUPLED  
COUPLED  
400µs/div  
400µs/div  
LINE-TRANSIENT RESPONSE  
MAX6791-96toc20  
MAX6796  
= 10mA  
I
LOAD  
10V/div  
(AC-COUPLED)  
V
IN  
OUT  
20mV/div  
OUT AC-  
COUPLED  
1ms/div  
_______________________________________________________________________________________  
9
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Typical Operating Characteristics (continued)  
(V = V = 14V, C = 0.1µF, C  
= 10µF, T = T = +25°C, unless otherwise noted.)  
IN  
EN  
IN  
OUT  
J
A
LOAD-TRANSIENT RESPONSE  
LOAD-TRANSIENT RESPONSE  
MAX6791-96toc21  
MAX6791-96toc22  
100mA/div  
1mA  
100mA/div  
20mA  
I
OUT1  
I
OUT1  
OUT1  
AC-COUPLED  
OUT1  
AC-COUPLED  
500mV/div  
500mV/div  
MAX6792  
OUT1 = 5V  
MAX6792  
OUT1 = 5V  
C
= 10µF  
OUT  
C
= 10µF  
OUT  
1ms/div  
1ms/div  
Pin Description  
PIN  
NAME  
OUT1  
SET1  
FUNCTION  
MAX6791/ MAX6793/ MAX6795/  
MAX6792 MAX6794 MAX6796  
Regulator 1 Output. Fixed (+1.8V, +2.5V, +3.3V, or +5V) or adjustable (+1.8V to  
+11V). OUT1 = 150mA (max). Connect a 10µF (min) capacitor from OUT1 to GND.  
1, 2  
1, 2  
—
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.  
3
3
—
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.  
4
5
4
5
4
5
PFO  
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.  
CSWT  
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.  
6
7
8
6
7
8
6
7
8
CSRT  
GND  
Ground  
Active-Low Reset Output. RES ET remains low while OUT1/OUT is below the reset  
threshold. RES ET remains low for the duration of the reset timeout period after the  
reset conditions end. RES ET is available in push-pull and open-drain options.  
RESET  
10 ______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Pin Description (continued)  
PIN  
NAME  
FUNCTION  
MAX6791/ MAX6793/ MAX6795/  
MAX6792 MAX6794 MAX6796  
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  
WDS0  
10  
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  
11  
11  
11  
WDI  
than t  
or longer than t  
force RESET to assert low for the reset timeout  
WD1  
WD2  
period. The watchdog timer begins to count after RESET is deasserted. The  
watchdog timer clears when a valid transition occurs on WDI or whenever RES ET  
is asserted. Connect WDS0 high and WDS1 low to disable the watchdog timer  
function. See the Watchdog Timer section.  
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.  
12  
12  
12  
HOLD  
Regulator 2 Output. OUT2 is a fixed +5V output. Connect a 10µF (min)  
capacitor from OUT2 to GND.  
13, 14  
15  
13, 14  
15  
—
—
OUT2  
Active-High Enable Input 2. Drive ENABLE2 high to turn on OUT2. ENABLE2 is  
internally connected to ground through a 0.5µA current sink.  
ENABLE2  
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.  
16  
16  
16  
PFI  
17, 18  
19  
17, 18  
19  
17, 18  
19  
IN  
Regulator Inputs. Bypass IN with a 1µF capacitor to GND.  
pFET Gate Drive. Connect GATEP to the gate of a p-channel MOSFET to  
provide low drop reverse-battery voltage protection.  
GATEP  
Active-High Enable Input 1. Drive ENABLE1 high to turn on OUT1. ENABLE1 is  
internally connected to ground through a 0.5µA current sink.  
20  
—
20  
9
—
9
ENABLE1  
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.  
______________________________________________________________________________________ 11  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Pin Description (continued)  
PIN  
NAME  
FUNCTION  
MAX6791/ MAX6793/ MAX6795/  
MAX6792 MAX6794 MAX6796  
10, 13, 14,  
—
—
10  
—
N.C.  
OUT  
Not Internally Connected  
15  
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.  
1, 2  
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.  
—
—
—
—
—
—
3
SET  
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.  
20  
—
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.  
+5V, or an adjustable output voltage of +1.8V to +11V,  
Detailed Description  
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.  
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.  
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.  
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  
12 ______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Functional Diagrams  
ENABLE2  
MAX6791/MAX6792  
OUT2  
THERMAL  
PROTECTION  
OUT1  
IN  
GATEP  
OVERCURRENT  
PROTECTION  
ENABLE1  
HOLD  
CONTROL  
LOGIC  
1.23V  
SET1  
124mV  
RESET  
CSRT  
RESET  
TIMEOUT  
1.138V  
OR  
1.076V  
RESET  
WDI  
CSWT  
WATCHDOG  
TIMEOUT  
WDS0  
WDS1  
PFO  
GND PFI  
______________________________________________________________________________________ 13  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Functional Diagrams (continued)  
ENABLE2  
MAX6793/MAX6794  
OUT2  
THERMAL  
PROTECTION  
OUT1  
IN  
GATEP  
OVERCURRENT  
PROTECTION  
ENABLE1  
HOLD  
CONTROL  
LOGIC  
1.23V  
SET1  
124mV  
RESET  
CSRT  
RESET  
TIMEOUT  
1.138V  
OR  
1.076V  
RESET  
WDI  
CSWT  
WATCHDOG  
TIMEOUT  
WD-DIS  
PFO  
GND PFI  
14 ______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Functional Diagrams (continued)  
THERMAL  
PROTECTION  
MAX6795/MAX6796  
OUT  
IN  
GATEP  
OVERCURRENT  
PROTECTION  
ENABLE  
HOLD  
CONTROL  
LOGIC  
1.23V  
SET  
124mV  
RESET  
CSRT  
RESET  
TIMEOUT  
1.138V  
OR  
1.076V  
RESET  
WDI  
CSWT  
WATCHDOG  
TIMEOUT  
WD-DIS  
PFO  
GND PFI  
______________________________________________________________________________________ 15  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
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.  
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 t  
(280ms min or externally  
WD  
adjustable). RESET remains low for the fixed or user-  
adjustable reset timeout period, t . If the watchdog is  
RP  
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 30mΩ or 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.  
not updated for lengthy periods of time, the reset out-  
put appears as a pulse train, asserted for t  
,
RP  
deasserted for t , until WDI is toggled again. Once  
WD  
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 t  
from  
WD  
the last edge. The watchdog counter clears when WDI  
toggles prior to t  
from the last edge or when RESET  
WD  
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 (t  
WD2  
< t  
), or a slow watchdog fault (t  
>
WDI  
WDI  
WD1  
t
). 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.  
Thermal Protection  
When the junction temperature exceeds T = +165°C,  
J
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.  
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).  
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.  
Power-Fail Comparator  
PFI is the noninverting input to a comparator. If PFI is  
less than V  
(1.231V), PFO goes low. Common uses  
PFI  
for the power-fail comparator include monitoring the  
16 ______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Selecting Reset Timeout Period  
The reset timeout period is adjustable to accommodate  
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:  
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
A
6
t
= C  
1.218 × 10  
RP  
CSRT  
where t is in seconds and C  
is in Farads.  
RP  
CSRT  
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  
R1  
R2  
V
= V  
1 +  
low. C  
must be a low-leakage (< 10nA) type  
OUT  
SET  
CSRT  
capacitor. Ceramic capacitors are recommended; do  
not use capacitors lower than 100pF to avoid the influ-  
ence of parasitic capacitances.  
where V  
= 1.2315V and R1, R2 ≤ 200kΩ.  
SET  
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  
V
IN  
IN  
OUT1/OUT  
R1  
2
MAX6791–MAX6796  
pad of the device package is soldered to a solid 1in  
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:  
SET1/SET  
R2  
GND  
PD  
= Maximum Power Dissipation  
MAX  
PD  
= 2.666W, for T ≤ +70°C  
A
MAX  
Figure 1. Setting the Output Voltage Using a Resistive-Divider  
PD  
= [2.666W - 0.0333W x (T - 70°C)], for +70°C  
A
MAX  
< T ≤ +125°C  
A
I
vs. (V - V  
)
OUT  
IN  
OUT  
where 0.0333W is the MAX6791–MAX6796 package  
350  
300  
250  
200  
150  
100  
50  
V
= 1.8V  
OUT  
thermal derating in W/°C and T is the ambient temper-  
A
+70°C  
ature in °C.  
SAFE OPERATION REGION FOR  
EACH TEMPERATURE POINT IS  
UNDER THE CURVE  
After determining the allowable package dissipation,  
calculate the maximum output current using the follow-  
ing formula:  
+85°C  
+125°C  
PD = Power Dissipation  
PD < PD  
where PD = [(IN - OUT1) x I  
] + [(IN -  
OUT1  
MAX  
OUT2) x I  
], for MAX6791–MAX6794.  
OUT2  
Also, I  
should be ≤ 150mA and I  
should be  
OUT2  
OUT1  
≤ 150mA in any case.  
0
0
10 20  
30 40  
50  
60 70 75  
PD < PD where PD = [(IN - OUT) x I  
], for  
OUT  
MAX  
(V - V ) (V)  
IN  
OUT  
MAX6795/MAX6796.  
Figure 2. Maximum Power Dissipation for MAX6791–MAX6796  
Also, I should be ≤ 300mA in any case.  
OUT  
______________________________________________________________________________________ 17  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
The fast watchdog period, t  
, is selectable as a ratio  
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-  
WD1  
from the slow watchdog fault period (t  
). Select the  
WD2  
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  
(t  
/t  
). For example, if C  
is 2000pF, and  
WD2 WD1  
WDS0 and WDS1 are low, then t  
CSWT  
is 318ms (typ) and  
dog timeout period (t ) by connecting a capacitor  
WD  
WD2  
t
is 40ms (typ). RESET asserts if the watchdog input  
between CSWT and GND. For normal-mode operation,  
calculate the watchdog timeout capacitor as follows:  
WD1  
has two edges too close to each other (faster than t  
);  
WD1  
or has edges that are too far apart (slower than t  
).  
WD2  
V
A
6
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-  
t
= C  
155 × 10  
WD2  
CSWT  
tions on WDI is shorter than t  
or longer than t  
,
where t  
is in seconds and C  
is in Farads.  
WD1  
WD2  
WD  
CSWT  
RESET is forced to assert low for the reset timeout peri-  
od. If the time difference between two transitions on WDI  
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.  
is between t  
(min) and t  
(max) or t  
(min)  
WD2  
WD1  
WD1  
and t  
(max), RESET is not guaranteed to assert or  
WD2  
deassert; see Figure 3. To guarantee that the window  
C
must be a low-leakage (< 10nA) type capacitor.  
CSWT  
watchdog does not assert RESET, strobe WDI between  
Ceramic capacitors are recommended; do not use  
capacitors lower than 100pF to avoid the influence of  
parasitic capacitances.  
t
(max) and t  
(min). The watchdog timer is  
WD2  
WD1  
cleared when RESET is asserted. Disable the watchdog  
timer by connecting WDS0 high and WDS1 low.  
The MAX6791/MAX6792 have a windowed watchdog  
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  
timer that asserts RESET for t  
when the watchdog  
RP  
recognizes a fast watchdog fault (time between transi-  
tions < t ), or a slow watchdog fault (time between  
WD1  
transitions > t  
ed independently of the watchdog timeout period. The  
slow watchdog period, t  
). The reset timeout period is adjust-  
WD2  
, is calculated as follows:  
WD2  
V
A
6
t
= C  
155 × 10  
WD2  
CSWT  
where t  
is in seconds and C  
is in Farads.  
CSWT  
WD2  
t
t
WD2  
WD1  
t
MIN  
MAX  
MIN  
MAX  
WD0  
GUARANTEED  
TO ASSERT  
GUARANTEED  
TO NOT ASSERT  
GUARANTEED  
TO ASSERT  
RESET:  
UNDETERMINED  
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  
watchdog re-enables immediately when any of these  
conditions are removed (as long as the RESET is not  
V
IN  
asserted). Note that the output current threshold limit  
includes hysteresis so that output current must exceed  
13.8mA (max) to reenable the watchdog timer.  
IN  
Capacitor Selection and Regulator  
Stability  
MAX6792  
MAX6794  
MAX6796  
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.  
RESET  
GND  
Figure 4. Ensuring RESET Valid to V = 0V  
IN  
V
IN  
V
TERM  
Ensuring a Valid RESET Output Down to  
V
= 0  
IN  
IN  
When V falls below 1V, RESET current-sinking capa-  
IN  
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 0,  
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; 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  
R5  
R6  
MAX6791  
PFI  
PFO  
GND  
Figure 5. Setting Power-Fail Comparator to Monitor V  
IN  
requiring valid logic for V down to 0.  
IN  
V
IN  
Adding Hysteresis to PFI  
The power-fail comparator has a typical input hystere-  
sis of 0.5% (of V ). This is sufficient for most applica-  
TH  
R7  
V
TERM  
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  
IN  
R8  
R5  
R6  
when V falls to the desired trip point (V  
). Since  
TRIP  
IN  
MAX6791  
PFI  
PFO  
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.  
GND  
Figure 6. Adding Hysteresis Power-Fail Comparator  
______________________________________________________________________________________ 19  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Use the following formulas to determine the high/low  
Table 1. Preset Output Voltage and Reset  
Threshold  
threshold levels and the hysteresis:  
V
= V  
x (1 + R5 / R6 +R5 / R7)  
L-H  
PFI  
PART  
SUFFIX (_)  
OUTPUT  
VOLTAGE (V)  
RESET THRESHOLD  
(NOMINAL)  
V
= V  
x (1 + R5 / R6 ) + (V  
- V  
) [R5 / (R7 +  
TERM  
H-L  
R8)]  
PFI  
PFI  
L
M
T
5.0  
5.0  
3.3  
3.3  
2.5  
2.5  
1.8  
1.8  
4.625  
4.375  
3.053  
2.888  
2.313  
2.188  
1.665  
1.575  
V
= V  
x (R5 / R7 ) - (V  
- V  
) [R5 / (R7 +  
TERM  
HYS  
R8)]  
PFI  
PFI  
where V  
is the threshold level for the monitored volt-  
L-H  
S
age rising and V  
is the threshold level for the moni-  
H-L  
Z
tored voltage falling.  
Y
Chip Information  
W
V
PROCESS: BiCMOS  
Table 2. Preset Timeout Period  
PART  
RESET TIMEOUT PERIOD  
SUFFIX (_)  
(NOMINAL)  
D0  
D1  
D2  
D3  
D4  
35µs  
3.125ms  
12.5ms  
50ms  
200ms  
Table 3. ENABLE/ENABLE1 and HOLD Truth Table/State Table  
OPERATING  
STATE  
ENABLE1/  
ENABLE  
REGULATOR 1  
OUTPUT  
HOLD  
Don’t care  
Don’t care  
Low  
COMMENT  
ENABLE/ENABLE1 is pulled to GND through internal pulldown.  
OUT/OUT1 is disabled.  
Initial state  
Turn-on state  
Hold setup state  
Low  
High  
High  
Off  
On  
On  
ENABLE/ENABLE1 is externally driven high turning OUT/OUT1  
on. HOLD is pulled up to OUT/OUT1.  
HOLD is externally pulled low while ENABLE/ENABLE1  
remains high, and the regulator latches on.  
ENABLE/ENABLE1 is driven low (or allowed to float low by an  
internal pulldown). HOLD remains externally pulled low  
keeping OUT/OUT1 on.  
Hold state  
Off state  
Low  
Low  
Low  
On  
Off  
HOLD is driven high (or allowed to float 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.  
High (floats  
high)  
20 ______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Table 4. MIN/MAX Watchdog Setting  
WDS0  
WDS1  
RATIO  
0
0
1
1
0
1
0
1
8
16  
Watchdog disabled  
64  
Table 5. Standard Version Part Number  
OUTPUT  
VOLTAGE (V)  
RESET TIMEOUT PERIOD (ms)  
RESET THRESHOLD (V)  
(NOMINAL)  
PART NUMBER  
(NOMINAL)  
MAX6791TPLD2+  
MAX6791TPSD2+  
MAX6792TPLD2+  
MAX6792TPSD2+  
MAX6793TPLD2+  
MAX6793TPSD2+  
MAX6794TPLD2+  
MAX6794TPSD2+  
MAX6795TPLD2+  
MAX6795TPSD2+  
5.0  
3.3  
5.0  
3.3  
5.0  
3.3  
5.0  
3.3  
5.0  
3.3  
5.0  
3.3  
12.5  
12.5  
12.5  
12.5  
12.5  
12.5  
12.5  
12.5  
12.5  
12.5  
12.5  
12.5  
4.625  
2.888  
4.625  
2.888  
4.625  
2.888  
4.625  
2.888  
4.625  
2.888  
4.625  
2.888  
MAX6796TPLD2+  
MAX6796TPSD2+  
+Denotes lead-free package.  
Selector Guide  
NUMBER OF  
OUTPUTS  
WINDOWED  
WATCHDOG TIMEOUT  
ENABLE  
INPUTS  
WATCHDOG  
DISABLE INPUT  
PART  
RESET OUTPUT  
MAX6791TP_D_  
MAX6792TP_D_  
MAX6793TP_D_  
MAX6794TP_D_  
MAX6795TP_D_  
MAX6796TP_D_  
Open drain  
Push-pull  
2
2
2
2
1
1
✓
✓
Dual  
Dual  
✓
✓
✓
✓
✓
✓
Open drain  
Push-pull  
—
—
—
—
Dual  
Dual  
Open drain  
Push-pull  
Single  
Single  
______________________________________________________________________________________ 21  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Typical Application Circuit  
12V  
BATT  
TO OTHER CIRCUITRY  
GATEP  
IN  
IN  
ENABLE1  
PFI  
OUT1  
SET1  
ENABLE2  
OUT2  
MAX6791/MAX6792  
CSWT  
PFO  
WDI  
CSRT GND  
RESET HOLD  
WDS1  
WDS0  
V
CC  
INH  
BATT  
RESET I/O  
I/O  
TXD  
RXD  
CANH  
CANL  
V
CC  
µC  
XCVR  
INT  
22 ______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Pin Configurations  
TOP VIEW  
TOP VIEW  
15  
14  
13  
12  
11  
15  
14  
13  
12  
11  
WDS0  
WDS1  
N.C.  
10  
9
PFI 16  
IN 17  
IN 18  
10  
9
PFI 16  
IN 17  
WD-DIS  
8
RESET  
GND  
18  
19  
20  
8
IN  
RESET  
GND  
MAX6791/MAX6792  
MAX6793/MAX6794  
GATEP  
7
19  
20  
GATEP  
7
6
CSRT  
CSRT  
ENABLE1  
6
ENABLE1  
+
+
1
2
3
4
5
1
2
3
4
5
THIN QFN  
5mm x 5mm  
THIN QFN  
5mm x 5mm  
TOP VIEW  
15  
14  
13  
12  
11  
N.C.  
10  
9
PFI 16  
IN 17  
IN 18  
WD-DIS  
8
RESET  
GND  
MAX6795/MAX6796  
GATEP  
7
19  
20  
6
CSRT  
ENABLE  
+
1
2
3
4
5
THIN QFN  
5mm x 5mm  
______________________________________________________________________________________ 23  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Package Information  
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information  
go to www.maxim-ic.com/packages.)  
24 ______________________________________________________________________________________  
High-Voltage, Micropower, Single/Dual Linear  
Regulators with Supervisory Functions  
Package Information (continued)  
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information  
go to www.maxim-ic.com/packages.)  
Revision History  
Pages changed at Rev 1: 1, 10, 11, 18, 19, 24, 25  
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.  
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 25  
© 2006 Maxim Integrated Products  
is a registered trademark of Maxim Integrated Products, Inc.  

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