ADM8693ANZ データシートの表示（PDF） - Analog Devices

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ADM8693ANZ

Microprocessor Supervisory Circuits

Analog Devices 

ADM8690/ADM8691/ADM8692/ADM8693/ADM8695

POWER-FAIL WARNING COMPARATOR

An additional comparator is provided for early warning of

failure in the microprocessor power supply. The power-fail

input (PFI) is compared to an internal 1.3 V reference. The

power-fail output (PFO) goes low when the voltage at PFI is less

than 1.3 V. Typically, PFI is driven by an external voltage divider

that senses either the unregulated dc input to the system 5 V

regulator or the regulated 5 V output. The voltage divider ratio

can be chosen such that the voltage at PFI falls below 1.3 V

several milliseconds before the 5 V power supply falls below the

reset threshold. PFO is normally used to interrupt the

microprocessor so that data can be stored in RAM and the shut-

down procedure executed before power is lost.

INPUT

POWER

ADM869x

R1

POWER

R2

FAIL

INPUT

1.3V

PFO

POWER

FAIL

OUTPUT

Figure 23. Power-Fail Comparator

Table 6. Input and Output Status in Battery Backup Mode

Signal Status

VOUT

VOUT is connected to VBATT via an internal PMOS

switch.

RESET

Logic low.

RESET

Logic high. The open-circuit output voltage is equal

to VOUT.

LOW LINE Logic low.

BATT ON

WDI

Logic high. The open-circuit voltage is equal to VOUT.

WDI is ignored. It is internally disconnected from the

internal pull-up resistor and does not source or sink

current as long as its input voltage is between GND

and VOUT. The input voltage does not affect supply

current.

WDO

PFI

Logic high. The open circuit voltage is equal to VOUT.

The power-fail comparator is turned off and has no

effect on the power-fail output.

PFO

Logic low.

CEIN

CEIN is ignored. It is internally disconnected from its

internal pull-up and does not source or sink current

as long as its input voltage is between GND and

VOUT. The input voltage does not affect supply

current.

CEOUT

OSC IN

Logic high. The open circuit voltage is equal to VOUT.

OSC IN is ignored.

OSC SEL OSC SEL is ignored.

Rev. B | Page 13 of 20

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