Rev. D 11/15

2

LNK574/576

www.power.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

SD).

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

FB reference voltage is applied to the

FEEDBACK pin.

The V

FB reference voltage is internally adjusted from 1.70 V at full

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-5509-032714

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

DCMAX

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

160 or 416

fOSC

CYCLES