NCV8508D2T50R4G(2009) 查看數據表（PDF） - ON Semiconductor

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NCV8508D2T50R4G
(Rev.:2009)

5.0 V, 250 mA LDO with Watchdog and RESET

ON Semiconductor 

NCV8508

DETAILED OPERATING DESCRIPTION

The NCV8508 is a precision micropower voltage

regulator with very low quiescent current (100 mA typical at

250 mA load). A typical dropout voltage is 450 mV at

150 mA. Microprocessor control logic includes Watchdog,

Wakeup and RESET. This unique combination of extremely

low quiescent current and full microprocessor control

makes the NCV8508 ideal for use in battery operated,

microprocessor controlled equipment in addition to being a

good fit in the automotive environment.

The NCV8508 Wakeup function brings the

microprocessor out of Sleep mode. The microprocessor in

turn signals its Wakeup status back to the NCV8508 by

issuing a Watchdog signal.

The Watchdog logic function monitors an input signal

(WDI) from the microprocessor. The NCV8508 responds to

the falling edge of the Watchdog signal which it expects at

least once during each Wakeup period. When the correct

Watchdog signal is received, a falling edge is issued on the

Wakeup signal line.

RESET is independent of VIN and operates correctly to an

output voltage as low as 1.0 V. A signal is issued in any of

three situations. During power up, the RESET is held low

until the output voltage is in regulation. During operation, if

the output voltage shifts below the regulation limits, the

RESET toggles low and remains low until proper output

voltage regulation is restored. Finally, a RESET signal is

issued if the regulator does not receive a Watchdog signal

within the Wakeup period.

The RESET pulse width, Wakeup signal frequency, and

Wakeup delay time are all set by one external resistor,

RDelay.

The Delay pin is a buffered bandgap voltage (1.25 V). It

can be used as a reference for an external tracking regulator

as shown in Figure 16.

The regulator is protected against short circuit and thermal

runaway conditions. The device runs through 45 volt

transients, making it suitable for use in automotive

environments.

MRA4004T3

VBAT

VIN

0.1 mF

NCV8508

Delay

GND

VIN

1.0 mF

VOUT

200 mA

12 k

CS8182 Adj

VREF/ENABLE

60 k

0.1 mF

GND

3.9 k

5V

10 mF

Figure 16. Application Circuit

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