Rev. B 12/07/10

2

LNK574

www.powerint.com

Figure 2

Functional Block Diagram.

Figure 3.

Pin Configuration.

Pin Functional Description

DRAIN (D) Pin:

The power MOSFET drain connection provides internal

operating current for both startup and steady-state operation.

BYPASS/MULTI-FUNCTIONAL PROGRAMMABLE (BP/M) Pin:

An external bypass capacitor for the internally generated 5.85 V

supply is connected to this pin. The value of capacitor

establishes the power down period. The minimum value of

capacitor is 0.1

mF. An overvoltage protection disables the

switching if the current into the pin exceeds 6.5 mA (I

FEEDBACK (FB) Pin:

During normal operation, switching of the power MOSFET is

controlled by this pin. MOSFET switching is disabled when a

voltage greater than an internal V

to the FEEDBACK pin.

The V

load to 1.37 V at no-load in CV mode, and 1.70 V to 0.9 V in CC

mode. Below 0.9 V the part enters auto-restart operation.

SOURCE (S) Pin:

This pin is the power MOSFET source connection. It is also the

ground reference for the BYPASS and FEEDBACK pins.

PI-5507-060210

D Package (SO-8C)

BP/M

FB

D

1

2

4

8

7

6

5

S

S

S

S

PI-5509-111810

CLOCK

OSCILLATOR

5.85 V

4.85 V

6.5 V

3 V

PU

OVERVOLTAGE

PROTECTION

RESET

0.9 V

FAULT

SOURCE

(S)

S

R

Q

ADJ

AUTO-RESTART

COUNTER

RESET

JITTER

BYPASS/

MULTI FUNCTION

(BP/M)

+

-

VI

LIMIT

LEADING

EDGE

BLANKING

+

-

DRAIN

(D)

BYPASS PIN

UNDERVOLTAGE

CURRENT LIMIT

FEEDBACK

(FB)

OPEN LOOP

PULL UP

Q

+

REGULATOR

5.85 V

GENERATOR

FEEDBACK REF

1.70 V - 1.37 V

CC CUT BACK

1.70 V - 0.9 V

POWER

DOWN

COUNTER

EVENT

COUNTER

SYSTEM

POWER

DOWN/

RESTART

PU

CYCLES