MAX690A(1993) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX690A
(Rev.:1993)

Microprocessor Supervisory Circuits

Maxim Integrated 

Microprocessor Supervisory Circuits

______________________________________________________________Pin Description

PIN

MAX690A/MAX692A

MAX802L/MAX802M

MAX805L

NAME

FUNCTION

Supply Output for CMOS RAM. When VCC is above the reset threshold,

1

1

VOUT

VOUT connects to VCC through a P-channel MOSFET switch. When VCC

is below the reset threshold, the higher of VCC or VBATT will be

connected to VOUT.

2

2

VCC

+5V Supply Input

3

3

GND Ground

4

4

PFI

Power-Fail Comparator Input. When PFI is less than 1.25V, PFO goes

low. Connect PFI to GND or VCC when not used.

5

5

Power-Fail Output. When PFI is less than 1.25V, PFO goes low;

PFO otherwise PFO stays high.

Watchdog Input. If WDI remains high or low for 1.6sec, the internal

watchdog timer runs out and reset is triggered. If WDI is left floating or

6

6

WDI connected to a high-impedance three-state buffer, the watchdog

feature is disabled. The internal watchdog timer clears whenever reset

is asserted, WDI is three-stated, or WDI sees a rising or falling edge.

Reset Output. Whenever RESET is triggered, it pulses low for 200ms. It

stays low when VCC is below the reset threshold (4.65V in the

7

RESET MAX690A/MAX802L and 4.4V in the MAX692A/MAX802M) and remains

low for 200ms after VCC rises above the reset threshold. A watchdog

timeout also triggers RESET.

Active-High Reset Output is the inverse of RESET. When RESET is

–

7

RESET asserted, the RESET output voltage = VCC or VBATT, whichever is

higher.

Backup-Battery Input. When VCC falls below the reset threshold, VBATT

8

8

VBATT

will be switched to VOUT if VBATT is 20mV greater than VCC. When VCC

rises to 20mV above VBATT, VOUT will be reconnected to VCC. The 40mV

hysteresis prevents repeated switching if VCC falls slowly.

_______________________________________________________________________________________ 5

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