MAX6316 Maxim, MAX6316 Datasheet - Page 10

• Manufacturer Part Number: MAX6316
• Description: 5-Pin P Supervisory Circuits with Watchdog and Manual Reset
• Manufacturer: Maxim

The WDI input is internally driven through a buffer and
series resistor from the watchdog counter. For minimum
watchdog input current (minimum overall power con-
sumption), leave WDI low for the majority of the watch-
dog timeout period. When high, WDI can draw as much
as 160µA. Pulsing WDI high at a low duty cycle will
reduce the effect of the large input current. When WDI
is left unconnected, the watchdog timer is serviced
within the watchdog timeout period by a low-high-low
pulse from the counter chain.
These supervisors are immune to short-duration, nega-
tive-going V
not require the entire system to shut down. Typically,
200ns large-amplitude pulses (from ground to V
the supply will not cause a reset. Lower amplitude puls-
es result in greater immunity. Typically, a V
that goes 100mV under the reset threshold and lasts
less than 4µs will not trigger a reset. An optional 0.1µF
bypass capacitor mounted close to V
tional transient immunity.
The MAX6316_/MAX6317H/MAX6318_H/MAX6319_H/
MAX6321HP/MAX6322HP are guaranteed to operate
properly down to V
valid reset levels down to V
to active-low outputs (push/pull and bidirectional only,
Figure 8) and a pull-up resistor to active-high outputs
(push/pull only, Figure 9) will ensure that the reset line
is valid while the reset output can no longer sink or
5-Pin µP Supervisory Circuits with
Watchdog and Manual Reset
Figure 7. Watchdog Timing Relationship
10
RESET
V
WDI
CC
______________________________________________________________________________________
CC
t
RST
t
RP
Negative-Going V
Applications Information
transients (glitches), which usually do
Ensuring Valid Reset Outputs
CC
= 1V. In applications that require
Watchdog Input Current
CC
= 0, a pull-down resistor
Down to V
MAX6316/MAX6317
MAX6318/MAX6320
t
WD
CC
CC
MAX6321
provides addi-
Transients
CC
transient
t
RP
CC
CC
) on
= 0
source current. This scheme does not work with the
open-drain outputs of the MAX6320/MAX6321/MAX6322.
The resistor value used is not critical, but it must be
large enough not to load the reset output when V
above the reset threshold. For most applications,
100k is adequate.
One way to help the watchdog timer monitor software
execution more closely is to set and reset 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 inside the
loop, keeping the watchdog from timing out.
Figure 8. Ensuring RESET Valid to V
Push/Pull and Bidirectional Outputs
Figure 9. Ensuring RESET Valid to V
Push/Pull Outputs
*THIS SCHEMATIC DOES NOT WORK ON THE OPEN-DRAIN
OUTPUTS OF THE MAX6321/MAX6322.
Watchdog Software Considerations
GND
GND
(MAX6316/MAX6317/MAX6318/
MAX6316
MAX6318
MAX6319
MAX6321*
MAX6322*
MAX6317
MAX6318
MAX6319
RESET
RESET
V
V
CC
CC
MAX6320/MAX6321)
CC
CC
V
V
CC
CC
= 0 on Active-Low
= 0 on Active-High
100k
100k
CC
is