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L4989

WATCHDOG

WEn

VOLTAGE REGULATOR

The voltage regulator uses a p-channel MOS transistor as a regulating element. With this structure a very

low dropout voltage at current up to 150mA is obtained. The output voltage is regulated up to transient

input supply voltage of 40V. No functional interruption due to over-voltage pulses is generated.

The voltage Regulator is always active and not depending on the state of WEn input pin.

A short circuit protection to GND is provided.

Figure 1. Behavior of output current versus regulated voltage Vo

Pin

Symbol

Parameter

Test condition

min

typ

max

Unit

Wi

Vih

Input high voltage

Vs=13.5V

3.5

V

Wi

Vil

Input low voltage

Vs=13.5V

1.5

V

Wi

Vih

Input hysteresis

Vs=13.5V

500

mV

Wi

Rwi

Pull down resistor

Vs=13.5V

30

100

250

k

Ω

Vcw

Vwhth

Low threshold

Vs=13.5V

10%

13%

16%

Vcw

Vwlth

High threshold

Vs=13.5V

44%

47%

50%

Vcw

Icwc

Charge current

Vs=13.5V, Vcw=0.1V

5

10

20

µA

Vcw

Icwd

Discharge current

Vs=13.5V, Vcw=2.5V

1.25

2.5

5

µA

Vcw

Twop

Watchdog period

Vs=13.5V, Ctw=47nF

20

40

80

ms

Res

twol

Watchdog output low time

Vs=13.5V, Ctw=47nF

4

8

16

ms

Pin

Symbol

Parameter

Test condition

min

typ

max

Unit

WEn

WEn input low voltage

1

V

WEn

WEn input high voltage

3

V

WEn

WEn input hysteresis

600

920

1300

mV

WEn

Pull down current

Vs=13.5V

1

2.5

5

µA

Vo

Vo_ref

Iout

Ishort Ilim

Vo

Vo_ref

Iout

Ishort Ilim