MAX795SCSA+ Maxim Integrated Products, MAX795SCSA+ Datasheet - Page 18
![IC SUPERVISOR MPU 8-SOIC](/photos/1/39/13902/8-soic_21-0042b_sml.jpg)
MAX795SCSA+
Manufacturer Part Number
MAX795SCSA+
Description
IC SUPERVISOR MPU 8-SOIC
Manufacturer
Maxim Integrated Products
Type
Battery Backup Circuitr
Datasheet
1.MAX795TCSA.pdf
(20 pages)
Specifications of MAX795SCSA+
Number Of Voltages Monitored
1
Output
Open Drain or Open Collector
Reset
Active Low
Reset Timeout
140 ms Minimum
Voltage - Threshold
2.925V
Operating Temperature
0°C ~ 70°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (3.9mm Width)
Monitored Voltage
3 V or 3.3 V
Undervoltage Threshold
Adj V
Overvoltage Threshold
Adj V
Manual Reset
No
Watchdog
No
Battery Backup Switching
Yes
Power-up Reset Delay (typ)
280 ms
Supply Voltage (max)
5.5 V
Supply Voltage (min)
1 V
Supply Current (typ)
49 uA (Typ)
Maximum Power Dissipation
471 mW
Mounting Style
SMD/SMT
Maximum Operating Temperature
+ 70 C
Chip Enable Signals
No
Minimum Operating Temperature
0 C
Output Type
Active Low or Open Drain
Power Fail Detection
No
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Figure 18 shows maximum transient duration vs. reset-
comparator overdrive, for which reset pulses are not
generated. The graph was produced using negative-
going V
the reset threshold by the magnitude indicated (reset
comparator overdrive). The graph shows the maximum
pulse width a negative-going V
have without causing a reset pulse to be issued. As
the amplitude of the transient increases (i.e., goes far-
ther below the reset threshold), the maximum allowable
pulse width decreases. Typically, a V
goes 40mV below the reset threshold and lasts for 10µs
or less does not cause a reset pulse to be issued.
A 0.1µF bypass capacitor mounted close to the V
pin provides additional transient immunity.
3.0V/3.3V Adjustable Microprocessor
Supervisory Circuits
Figure 18. Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
18
______________________________________________________________________________________
CC
100
pulses, starting at 3.3V and ending below
90
80
70
50
30
20
10
60
40
0
10 20
RESET COMPARATOR OVERDRIVE, V
30
40
50
CC
60 70
transient can typically
RST
CC
80
- V
CC
transient that
90
(mV)
100
CC
There is a way to help the watchdog timer monitor soft-
ware execution more closely, which involves setting
and resetting the watchdog input at different points in
the program rather than pulsing the watchdog input
high-low-high or low-high-low. This technique avoids a
stuck loop, in which the watchdog timer would continue
to be reset within the loop, keeping the watchdog from
timing out. Figure 19 shows an example of a flow dia-
gram where the I/O driving the watchdog input is set
high at the beginning of the program, set low at the
beginning of every subroutine or loop, then set high
again when the program returns to the beginning. If the
program should hang in any subroutine, the problem
would quickly be corrected, since the I/O is continually
set low and the watchdog timer is allowed to time out,
causing a reset or interrupt to be issued.
Figure 19. Watchdog Flow Diagram
Watchdog Software Considerations
Program Loop
SET WDI LOW
Subroutine or
PROGRAM
SET WDI
RETURN
START
CODE
HIGH