STM802DS6F datasheet(6/37 Pages) STMICROELECTRONICS

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STM690A/692A/703/704/802/805/817/818/819

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Pin Descriptions

MR. A logic low on /MR asserts the reset output.

Reset remains asserted as long as MR is low and

for trec after MR returns high. This active-low input

has an internal pull-up. It can be driven from a TTL

or CMOS logic line, or shorted to ground with a

switch. Leave open if unused.

WDI. If WDI remains high or low for 1.6sec, the in-

ternal watchdog timer runs out and reset is trig-

gered. The internal watchdog timer clears while

reset is asserted or when WDI sees a rising or fall-

ing edge.

The watchdog function can be disabled by allow-

ing the WDI pin to float.

RST. Pulses low for trec when triggered, and stays

low whenever VCC is below the reset threshold or

when MR is a logic low. It remains low for trec after

either VCC rises above the reset threshold, the

watchdog triggers a reset, or MR goes from low to

high.

RST. Pulses high for trec when triggered, and

stays high whenever VCC is above the reset

threshold or when MR is a logic high. It remains

high for trec after either VCC falls below the reset

threshold, the watchdog triggers a reset, or MR

goes from high to low.

VOUT. When VCC is above the switchover voltage

(VSO), VOUT is connected to VCC through a P-

channel MOSFET switch. When VCC falls below

VSO, VBAT connects to VOUT. Connect to VCC if no

battery is used.

VBAT. When VCC falls below VSO, VOUT switches

from VCC to VBAT. When VCC rises above VSO +

hysteresis, VOUT reconnects to VCC. VBAT may ex-

ceed VCC. Connect to VCC if no battery is used.

E. The input to the chip-enable gating circuit. Con-

nect to ground if unused.

ECON. ECON goes low only when E is low and re-

set is not asserted. If ECON is low when reset is as-

serted, ECON will remain low for 15µs or until E

goes high, whichever occurs first. In the disabled

mode, ECON is pulled up to VOUT.

PFI. When PFI is less than VPFI or when VCC falls

below 2.4V (or VSO), PFO goes low; otherwise,

PFO remains high. Connect to ground if unused.

PFO. When PFI is less than VPFI, or VCC falls be-

low 2.4V (or VSO), PFO goes low; otherwise, PFO

remains high. Leave open if unused.

Table 3. Pin Description

Name

Function

STM818

STM690A

STM692A

STM802

STM817

STM703

STM704

STM819

STM805

––6–

Push-button Reset Input

66–6

WDI

Watchdog Input

777–

RST

Active-Low Reset Output

–––7

RST

Active-High Reset Output

1111

VOUT

Supply Output for External LPSRAM

2222

VCC

Supply Voltage

8888

VBAT

Backup-Battery Input

4–––

Chip Enable Input

5–––

ECON

Conditioned Chip Enable Output

–444

PFI

PFI Power-fail Input

–555

PFO

PFO Power-fail Output

3333

VSS

Ground

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