AP2007

Synchronous PWM with VFC Controller

(Preliminary)

Anachip Corp

www.anachip.com.tw

Rev. 1.0 Apr 1, 2005

6/7

Function Description (Continued)

Hiccup Mode

During power up, the SS/ SHDN pin is internally

SS/ SHDN pin is released and begins to source

10uA of current to the external soft-start capacitor.

As the soft-start voltage rises, the inverting input of

the error comparator is clamped to this voltage.

When the error signal reaches the level of the

internal 0.8V reference, the output voltage is to have

reached its programmed voltage. If an over-current

condition has not occurred the soft-start voltage will

continue to rise and level off at about 2.5V.

An over-current condition occurs when the high-side

drive is turned on, but the PHASE node does not

reach the voltage level set at the OCSET pin. Once

an over-current occurs, the high-side drive is turned

off and the low-side drive turns on and the

SS/ SHDN pin begins to sink 2uA. The soft-start

voltage will begin to decrease as the 2uA of current

discharge the external capacitor. When the soft-start

voltage reaches 0.2V, the SS/ SHDN pin will begin to

source 10uA and begin to charge the external

capacitor causing the soft-start voltage to rise again.

If the over-current condition is no longer present,

normal operation will continue. If the over-current

condition is still present, the SS/ SHDN pin will again

begin to sink 2uA. This cycle will continue indefinitely

until the over-current condition is removed.

In order to prevent substrate glitching, a small-signal

diode should be placed in close proximity to the chip

with cathode connected to PHASE and anode

connected to GND.

Marking Information

(Top View)

SOP-8L

AP2007

YY WW X

Logo

Part No.

ID code: internal

Year: "01" =2001

"02" =2002

Xth week: 01~52