點晶科技股份有限公司

SILICON TOUCH TECHNOLOGY INC.

Voltage Detecting IC

-5 -

Version

：A.017

PS121

Note1: Once AC power is turned on, Vpgi will be pulled high before +5V input. At this time,

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

×

=

×

=

×

=

−

−

μ

μ

7

.

8

85

.

1

sec,

)

(

216

.

0

d

ON

d

thcd

d

d

ON

d

C

I

V

C

T

pF

C

T

Note2: Diode D1 is connected to Vpgi to control the PG delay time when AC is off. The AC

off delay time can be controlled as follows,

1

1

2

)

85

.

1

(

2

1

85

.

1

)

(

2

1

R

V

C

R

V

V

V

C

I

V

C

I

I

V

C

T

Cd

d

thcd

Cd

thcd

d

OFF

d

thcd

d

d

thcd

d

OFF

d

+

×

×

=

+

×

×

=

×

=

−

×

−

−

≒

Among

OFF

d

equation, the

)

(

2

1

thcd

Cd

V

V

+

×

is discharged average current.

has to be higher than 2V at normal operation.

Note4: In PCB layout condition, when the input-pin(VDD) smaller than detecting threshold

ground-pin(VSS) must connect to the most clean ground of the power supply

system to avoid noise appear.

Note5: Suggested using RC filter circuit (Rx and Cx) to decrease ripples.