STM6821 STMicroelectronics, STM6821 Datasheet - Page 7

• Manufacturer Part Number: STM6821
• Description: Reset + Watchdog
• Manufacturer: STMicroelectronics

STM6321/6322STM6821/6822/6823/6824/6825
1.1
1.1.1
1.1.2
1.1.3
1.1.4
1.1.5
Pin descriptions
Pulses low when triggered, and stays low whenever V
when MR is a logic low. It remains low for t
threshold, the watchdog triggers a reset, or MR goes from low to high.
Pulses low when triggered, and stays low whenever V
when MR is a logic low. It remains low for t
threshold, the watchdog triggers a reset, or MR goes from low to high. Connect a pull-up
resistor to supply voltage.
A logic low on MR asserts the reset output. Reset remains asserted as long as MR is low
and for t
be driven from a TTL or CMOS logic line, or shorted to ground with a switch. Leave open if
unused.
If WDI remains high or low for at least 1.6s, the internal watchdog timer expires and reset is
asserted. The internal watchdog timer clears while reset is asserted or when WDI sees
a rising or falling edge. The watchdog function CAN be disabled if WDI is left unconnected
or is connected to a tri-state buffer output.
Active-high, push-pull reset output; inverse of RST.
Table 3.
Active-low, push-pull reset output (RST) - 6823/6824/6825
Active-low, open drain reset output (RST) - STM6321/6322/6822
Push-button reset input (MR)
Watchdog input (WDI)
Active-high reset output (RST)
STM6822
STM6823
—
1
3
4
5
2
rec
after MR returns high. This active-low input has an internal 52 kΩ pull-up. It can
Pin functions
STM6821
—
3
4
1
5
2
Pin
STM6321
STM6824
—
1
4
3
5
2
Doc ID 11110 Rev 11
STM6322
STM6825
—
1
4
3
5
2
rec
rec
after either V
after either V
Name
RST
RST
WDI
V
V
MR
CC
SS
CC
CC
is below the reset threshold or
is below the reset threshold or
CC
CC
Active-low reset output
Push-button reset input
Watchdog Input
Active-high reset output
Supply voltage
Ground
rises above the reset
rises above the reset
Function
Description
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