+5 V, Lo w -P o w e r µP S u p e rvis o ry Circ u it s
w it h Ad ju s t a b le Re s e t /Wa t c h d o g
1–MAX6304
______________________________________________________________P in De s c rip t io n
PIN
NAME
RESET IN
GND
FUNCTION
Reset Input. High-impedance input to the reset comparator. Connect this pin to the center point of an
external resistor voltage-divider network to set the reset threshold voltage. The reset threshold voltage
1
is calculated as follows: V
= 1.22 x (R1 + R2) / R2 (see Typical Operating Circuit).
RST
2
Ground
Set Reset-Timeout Input. Connect a capacitor between this input and ground to select the reset timeout
3
SRT
period (t ). Determine the period as follows: t = 2.67 x C
, with C
SRT
in pF and t in µs (see
SRT RP
RS
RP
Typical Operating Circuit).
Set Watchdog-Timeout Input. Connect a capacitor between this input and ground to select the basic
watchdog timeout period (t ). Determine the period as follows: t = 2.67 x C , with C in pF
4
5
SWT
WDS
WD
WD
SWT
SWT
and t
in µs. The watchdog function can be disabled by connecting this pin to ground.
WD
Watchdog-Select Input. This input selects the watchdog mode. Connect to ground to select normal mode
and the basic watchdog timeout period. Connect to V to select extended mode, multiplying the basic
CC
timeout period by a factor of 500. A change in the state of this pin resets the watchdog timer to zero.
Watchdog Input. A rising or falling transition must occur on this input within the selected watchdog
timeout period, or a reset pulse will occur. The capacitor value selected for SWT and the state of WDS
determine the watchdog timeout period. The watchdog timer clears and restarts when a transition
occurs on WDI or WDS. The watchdog timer is cleared when reset is asserted and restarted after reset
6
WDI
deasserts. In the extended watchdog mode (WDS = V ), the watchdog function can be disabled by
CC
driving WDI with a three-stated driver or by leaving WDI unconnected.
RESET changes from high to low whenever the monitored voltage
Open-Drain, Active-Low Reset
Output (MAX6301)
(V ) drops below the selected reset threshold (V ). RESET
IN
RST
RESET
remains low as long as V is below V . Once V exceeds V
,
IN
RST
IN
RST
(MAX6301/3)
RESET remains low for the reset timeout period and then goes high.
The watchdog timer triggers a reset pulse (t ) whenever the watch-
dog timeout period (t ) is exceeded.
WD
Push/Pull, Active-Low Reset
Output (MAX6303)
RP
7
8
RESET changes from low to high whenever the monitored voltage
Open-Drain, Active-High Reset
Output (MAX6302)
(V ) drops below the selected reset threshold (V ). RESET
IN
RST
RESET
(MAX6302/4)
remains high as long as V is below V . Once V exceeds V
,
IN
RST
IN
RST
RESET remains high for the reset timeout period and then goes low.
The watchdog timer triggers a reset pulse (t ) whenever the watch-
Push/Pull, Active-High Reset
Output (MAX6304)
RP
dog timeout period (t ) is exceeded.
WD
V
CC
Supply Voltage
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5
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
