19-0366; Rev 6; 3/10
3.0V/3.3V Adjustable Microprocessor
Supervisory Circuits
General Description
The MAX793/MAX794/MAX795 microprocessor (µP)
supervisory circuits monitor and control the activities of
+3.0V/+3.3V µPs by providing backup-battery switchover,
among other features such as low-line indication, µP
reset, write protection for CMOS RAM, and a watchdog
(see the
Selector Guide
below). The backup-battery volt-
age can exceed V
CC
, permitting the use of 3.6V lithium
batteries in systems using 3.0V to 3.3V for V
CC
.
The MAX793/MAX795 offer a choice of reset threshold
voltage range (denoted by suffix letter): 3.00V to 3.15V
(T), 2.85V to 3.00V (S), and 2.55V to 2.70V (R). The
MAX794’s reset threshold is set externally with a resistor
divider. The MAX793/MAX794 are available in 16-pin
DIP and narrow SO packages, and the MAX795 comes
in 8-pin DIP and SO packages.
____________________________Features
MAX793/MAX794/MAX795
o
Precision Supply-Voltage Monitor:
Fixed Reset Trip Voltage (MAX793/MAX795)
Adjustable Reset Trip Voltage (MAX794)
o
Guaranteed Reset Assertion to V
CC
= 1V
o
Backup-Battery Power Switching—Battery
Voltage Can Exceed V
CC
o
On-Board Gating of Chip-Enable Signals—7ns
Max Propagation Delay
MAX793/MAX794 Only
o
Battery Freshness Seal
o
Battery OK Output (MAX793)
o
Uncommitted Voltage Monitor for Power-Fail or
Low-Battery Warning
o
Independent Watchdog Timer (1.6s timeout)
o
Manual Reset Input
MAX793/MAX794/MAX795
_____________________Selector Guide
FEATURE
Active-Low Reset
Active-High Reset
Programmable Reset
Threshold
Low-Line Early Warning
Output
Backup-Battery
Switchover
External Switch Driver
Power-Fail Comparator
Battery OK Output
Watchdog Input
Battery Freshness Seal
Manual Reset Input
Chip-Enable Gating
Pin-Package
MAX793
MAX794
MAX795
PART*
MAX793_CPE
MAX793_CSE
Ordering Information
TEMP RANGE
0°C to +70°C
0°C to +70°C
PIN-
PACKAGE
16 Plastic DIP
16 Narrow SO
16-DIP/SO 16-DIP/SO 8-DIP/SO
Ordering Information continued at end of data sheet.
*The
MAX793/MAX795 offer a choice of reset threshold voltage.
Select the letter corresponding to the desired reset threshold
voltage range (T = 3.00V to 3.15V, S = 2.85V to 3.00V, R =
2.55V to 2.70V) and insert it into the blank to complete the part
number. The MAX794’s reset threshold is adjustable.
Devices are available in both leaded and lead-free packaging.
Specify lead free by adding the + symbol at the end of the part
number when ordering.
__________Typical Operating Circuit
3.0V OR 3.3V
0.1µF
PMOS
V
CC
BATT ON OUT
BATT
CE OUT
MAX793
(OPTIONAL)
Si9433DY
SILICONIX
0.1µF
CMOS
RAM
V
CC
CE IN
WDI
LOWLINE
V
CC
ADDRESS
DECODER
A0-A15
I/O
NMI
µP
RESET
________________________Applications
Battery-Powered Computers and Controllers
Embedded Controllers
Intelligent Controllers
Critical µP Power Monitoring
Portable Equipment
3.6V
0.1µF
WDO
+5V SUPPLY
FAILURE
+5V
MR
PFO
PFI
RESET
BATT OK
GND
Pin Configurations appear at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
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.
3.0V/3.3V Adjustable Microprocessor
Supervisory Circuits
MAX793/MAX794/MAX795
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
CC
......................................................................-0.3V to +6.0V
V
BATT
...................................................................-0.3V to +6.0V
All Other Inputs ..................-0.3V to the higher of V
CC
or V
BATT
Continuous Input Current
V
CC
.................................................................................200mA
V
BATT
................................................................................50mA
GND ..................................................................................20mA
Output Current
V
OUT
................................................................................200mA
All Other Outputs ..............................................................20mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) .....727mW
8-Pin SO (derate 5.88mW/°C above +70°C)..................471mW
16-Pin Plastic DIP (derate 10.53mW/°C above +70°C) .842mW
16-Pin Narrow SO (derate 9.52mW/°C above +70°C) ...696mW
Operating Temperature Ranges
MAX793_C_ _/MAX794C_ _/MAX795_C_ _ ......... 0°C to +70°C
MAX793_E_ _/MAX794E_ _/MAX795_E_ _ ........-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°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
(V
CC
= 3.17V to 5.5V for the MAX793T/MAX795T, V
CC
= 3.02V to 5.5V for the MAX793S/MAX795S, V
CC
= 2.72V to 5.5V for the
MAX793R/MAX794/MAX795R, V
BATT
= 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Operating Voltage Range,
V
CC
, V
BATT
(Note 1)
V
CC
Supply Current
(excluding I
OUT
, I
CE OUT
)
V
CC
Supply Current in
Battery-Backup Mode
(excluding I
OUT
)
BATT Supply Current
(excluding I
OUT
) (Note 2)
BATT Leakage Current,
Freshness Seal Enabled
Battery Leakage Current
(Note 3)
OUT Output Voltage in
Normal Mode
OUT Output Voltage in
Battery-Backup Mode
V
OUT
I
OUT
= 75mA
I
OUT
= 30mA (Note 4)
I
OUT
= 250µA (Note 4)
V
BATT
= 2.3V
I
OUT
= 250µA
I
OUT
= 1mA
V
CC
- 0.3
V
CC
- 0.12
V
CC
- 0.001
V
BATT
- 0.1
V
CC
- 0.125
V
CC
- 0.050
V
CC
- 0.5mV
V
BATT
- 0.034
V
BATT
- 0.14
20
2.69
2.55
2.30
2.82
2.68
2.41
65
2.95
2.80
2.52
V
CC
= 0V, V
OUT
= 0V
SYMBOL
MAX79_C
MAX79_E
MAX793/MAX794,
MR = V
CC
MAX795
V
CC
= 2.1V,
V
BATT
= 2.3V
V
CC
< 3.6V
V
CC
< 5.5V
V
CC
< 3.6V
V
CC
< 5.5V
MAX793/MAX794
MAX795
CONDITIONS
MIN
1.0
1.1
46
62
35
49
32
24
TYP
MAX
5.5
5.5
60
80
50
70
45
µA
35
1
1
0.5
µA
µA
µA
µA
µA
UNITS
V
I
SUPPLY
I
SUPPLY
V
V
OUT
V
CC
-
V
BATT
V
mV
V
SW
> V
CC
> 1.75V (Note 5)
MAX793T/MAX795T
MAX793S/MAX795S
V
BATT
> V
CC
(Note 6)
MAX793R/MAX795R/
MAX794
This value is identical to the reset threshold,
V
CC
rising for V
BATT
> V
RST
V
BATT
< V
RST
Battery Switch Threshold
(V
CC
falling)
V
SW
V
Battery Switch Threshold
(V
CC
rising) (Note 7)
V
CC
-
V
BATT
25
65
mV
2
_______________________________________________________________________________________
3.0V/3.3V Adjustable Microprocessor
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 3.17V to 5.5V for the MAX793T/MAX795T, V
CC
= 3.02V to 5.5V for the MAX793S/MAX795S, V
CC
= 2.72V to 5.5V for the
MAX793R/MAX794/MAX795R, V
BATT
= 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SYMBOL
V
CC
falling
Reset Threshold (Note 8)
V
RST
V
CC
rising
RESET IN Threshold
(MAX794 only)
RESET IN Leakage Current
(MAX794 only)
Reset Timeout Period
LOWLINE-to-Reset
Threshold, (V
LOWLINE
-
V
RST
), V
CC
Falling
Low-Line Comparator
Hysteresis
LOWLINE
Threshold,
V
CC
Rising
t
RP
V
LR
V
CC
< 3.6V
MAX793
MAX794
MAX793
MAX794
MAX793T/MAX795T
V
LL
MAX793S/MAX795S
MAX793R/MAX795R
MAX794
PFI Input Threshold
PFI Input Current
PFI Hysteresis, PFI Rising
BATT OK Threshold
(MAX793)
INPUT AND OUTPUT LEVELS
RESET Output-Voltage High
BATT OK, BATT ON,
WDO,
LOWLINE
Output-Voltage
High
PFO
Output-Voltage High
BATT ON Output-
Voltage High
RESET Output Leakage
Current (Note 9)
PFO
Output Short to GND
Current
PFO, RESET,
RESET,
WDO,
LOWLINE
Output-Voltage
Low
V
OH
V
OH
V
OH
V
OH
I
LEAK
I
SC
I
SOURCE
= 300µA, V
CC
= V
RST
min
I
SOURCE
= 300µA, V
CC
= V
RST
max
I
SOURCE
= 65µA, V
CC
= V
RST
max
I
SOURCE
= 100µA, V
CC
= 2.3V, V
BATT
= 3V
V
CC
= V
RST
max
V
CC
= 3.3V, V
PFO
= 0V
I
SINK
= 1.2mA;
RESET, LOWLINE
tested
with V
CC
= V
RST
min; RESET, BATTOK,
WDO
tested with V
CC
= V
RST
max
0.8V
CC
0.8V
CC
0.8V
CC
0.8V
BATT
-1
180
-1
500
0.86V
CC
0.86V
CC
V
V
V
V
µA
µA
V
BOK
2.00
V
TH
V
PFI
falling
V
PFI
rising
1.212
1.212
-25
1.240
1.250
2
10
2.25
V
CC
falling
V
CC
rising
CONDITIONS
MAX793T/MAX795T
MAX793S/MAX795S
MAX793R/MAX795R
MAX793T/MAX795T
MAX793S/MAX795S
MAX793R/MAX795R
V
RST IN
MIN
3.00
2.85
2.55
3.00
2.85
2.55
1.212
1.212
-25
140
30
5
TYP
3.075
2.925
2.625
3.085
2.935
2.635
1.240
1.250
2
200
45
15
10
10
3.23
3.08
2.78
1.317
1.262
1.287
25
20
2.50
V
nA
mV
V
V
MAX
3.15
3.00
2.70
3.17
3.02
2.72
1.262
1.282
25
280
60
25
mV
mV
V
nA
ms
mV
V
UNITS
MAX793/MAX794/MAX795
V
OL
0.08
0.2V
CC
V
_______________________________________________________________________________________
3
3.0V/3.3V Adjustable Microprocessor
Supervisory Circuits
MAX793/MAX794/MAX795
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 3.17V to 5.5V for the MAX793T/MAX795T, V
CC
= 3.02V to 5.5V for the MAX793S/MAX795S, V
CC
= 2.72V to 5.5V for the
MAX793R/MAX794/MAX795R, V
BATT
= 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
RESET Output-Voltage Low
BATT ON Output-
Voltage Low
All Inputs Including
PFO
(Note 10)
MANUAL RESET INPUT
MR
Pulse Width
MR-to-Reset
Delay
MR
Pullup Current
CHIP-ENABLE GATING
CE
IN Leakage Current
CE
IN-to-CE OUT
Resistance
CE
IN-to-CE OUT
Propagation Delay
V
OH
CE
OUT Drive from
CE
IN
V
OL
Reset to
CE
OUT High Delay
CE
OUT Output-Voltage
High (reset active)
WDI Input Current
Watchdog Timeout Period
WDI Pulse Width
t
WD
V
OH
I
OH
= 500µA, V
CC
< 2.3V
0.8V
BATT
I
LEAK
Disable mode
Enable mode, V
CC
= V
RST
max
V
CC
= V
RST
max, Figure 9
V
CC
= V
RST
max, I
OUT
= -1mA,
V
CE
IN
= V
CC
V
CC
= V
RST
max, I
OUT
= 1.6mA,
V
CE
IN
= 0V
10
0.8V
CC
V
0.2V
CC
µs
V
±10
46
2
7
nA
Ω
ns
t
MR
t
MD
MAX793/MAX794 only
MAX793/MAX794 only
MAX793/MAX794 only,
MR
= 0V
25
100
75
70
250
250
ns
ns
µA
SYMBOL
V
OL
V
OL
V
IH
V
IL
CONDITIONS
MAX79_C, V
BATT
= V
CC
= 1.0V, I
SINK
= 40µA
MAX79_E, V
BATT
= V
CC
= 1.2V, I
SINK
= 200µA
I
SINK
= 3.2mA, V
CC
= V
RST
max
V
RST
max < V
CC
< 5.5V
MIN
TYP
0.13
0.17
MAX
0.3
0.3
0.2V
CC
0.7V
CC
0.3V
CC
UNITS
V
V
V
WATCHDOG (MAX793/MAX794 only)
0V < V
CC
< 5.5V
-1
1.00
100
0.01
1.60
1
2.25
µA
s
ns
Note 1:
V
CC
supply current, logic-input leakage, watchdog functionality (MAX793/MAX794),
MR
functionality (MAX793/MAX794),
PFI functionality (MAX793/MAX794), and state of
RESET
and RESET (MAX793/MAX794) tested at V
BATT
= 3.6V and V
CC
=
5.5V. The state of RESET is tested at V
CC
= V
CC
min.
Note 2:
Tested at V
BATT
= 3.6V, V
CC
= 3.5V and 0V. The battery current rises to 10µA over a narrow transition window around V
CC
= 1.9V.
Note 3:
Leakage current into the battery is tested under the worst-case conditions at V
CC
= 5.5V, V
BATT
= 1.8V and V
CC
= 1.5V,
V
BATT
= 1.0V.
Note 4:
Guaranteed by design.
Note 5:
When V
SW
> V
CC
> V
BATT
, OUT remains connected to V
CC
until V
CC
drops below V
BATT
. The V
CC
-to-V
BATT
comparator
has a small 15mV typical hysteresis to prevent oscillation. For V
CC
< 1.75V (typical), OUT switches to BATT regardless of
V
BATT
.
Note 6:
When V
BATT
> V
CC
> V
SW
, OUT remains connected to V
CC
until V
CC
drops below the battery switch threshold (V
SW
).
Note 7:
OUT switches from BATT to V
CC
when V
CC
rises above the reset threshold, if V
BATT
> V
RST
. In this case, switchover back
to V
CC
occurs at the exact voltage that causes reset to be asserted, however, switchover occurs 200ms prior to reset. If
V
BATT
< V
RST
, OUT switches from BATT to V
CC
when V
CC
exceeds V
BATT
.
Note 8:
The reset threshold tolerance is wider for V
CC
rising than for V
CC
falling to accommodate the 10mV typical hysteresis,
which prevents internal oscillation.
Note 9:
The leakage current into or out of the RESET pin is tested with RESET not asserted (RESET output high impedance).
Note 10:
PFO
is normally an output, but is used as an input when activating the battery freshness seal.
4
_______________________________________________________________________________________
3.0V/3.3V/Adjustable Microprocessor
Supervisory Circuits
__________________________________________Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
MAX793/MAX794/MAX795
V
CC
-TO-OUT ON-RESISTANCE
vs. TEMPERATURE
MAX793 TOC1
BATT-TO-OUT ON-RESISTANCE
vs. TEMPERATURE
MAX793 TOC2
V
CC
SUPPLY CURRENT vs. TEMPERATURE
(NORMAL OPERATING MODE)
MAX793/4, V
CC
= 5V
MAX795, V
CC
= 5V
50
40
30
20
10
V
BATT
= V
CC
= V
OUT
0
100
-40
-20
0
20
40
60
80
100
MAX793/4, V
CC
= 3.3V
MAX795, V
CC
= 3.3V
MAX793 TOC3
3.0
2.8
V
CC
-TO-OUT ON-RESISTANCE (Ω)
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
-40
-20
0
20
40
60
80
V
CC
= 5V
V
CC
= 3.0V
V
CC
= 3.3V
I
OUT
= 30mA
160
BATT-TO-OUT ON-RESISTANCE (Ω)
140
120
100
80
60
V
BATT
= 5V
40
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
I
OUT
= 250µA
V
CC
= 0V
V
BATT
= 3.6V
V
BATT
= 3.0V
70
60
V
CC
SUPPLY CURRENT (µA)
100
TEMPERATURE (°C)
TEMPERATURE (°C)
BATTERY SUPPLY CURRENT vs.
TEMPERATURE (BATTERY-BACKUP MODE)
MAX793 TOC4
RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX793 TOC5
RESET COMPARATOR PROPAGATION DELAY
vs. TEMPERATURE (V
CC
FALLING)
MAX793 TOC6
0.10
V
CC
= 0V
V
BATT
= 3.6V
250
30
25
PROPAGATION DELAY (µs)
20
15
10
5
0
0.06
RESET TIMEOUT PERIOD (ms)
0.08
SUPPLY CURRENT (µA)
200
150
0.04
100
0.02
50
V
CC
RISING FROM
OV TO V
RST
MAX
0
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
0
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
MAX793
LOWLINE-TO-RESET THRESHOLD
vs. TEMPERATURE
MAX793 TOC7
MAX793/MAX794
LOWLINE COMPARATOR PROPAGATION DELAY
vs. TEMPERATURE
40mV OVERDRIVE
PROPAGATION DELAY (µs)
8
V
CC
RISING
PFI THRESHOLD (V)
MAX793 TOC8
MAX793/MAX794
PFI THRESHOLD vs. TEMPERATURE
MAX793 TOC9
100
LOWLINE-TO-RESET THRESHOLD (mV)
90
80
70
60
50
40
30
20
10
0
-40
-20
0
20
40
60
80
V
CC
FALLING
10
1.250
1.245
6
1.240
4
V
CC
FALLING
2
1.235
0
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
1.230
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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