TOP221-227

D

7/01

2

Figure 2. Functional Block Diagram.

Pin Functional Description

DRAIN Pin:

Output MOSFET drain connection. Provides internal bias

current during start-up operation via an internal switched high-

voltage current source. Internal current sense point.

CONTROL Pin:

Error amplifier and feedback current input pin for duty cycle

control. Internal shunt regulator connection to provide internal

bias current during normal operation. It is also used as the

connection point for the supply bypass and auto-restart/

compensation capacitor.

SOURCE Pin:

Y package – Output MOSFET source connection for high

voltage power return. Primary side circuit

common and reference point.

P and G package – Primary side control circuit common and

reference point.

SOURCE (HV RTN) Pin: (P and G package only)

Output MOSFET source connection for high voltage power return.

PI-1935-091696

SHUTDOWN/

AUTO-RESTART

PWM

COMPARATOR

CLOCK

SAW

OSCILLATOR

CONTROLLED

TURN-ON

GATE

DRIVER

INTERNAL

SUPPLY

5.7 V

4.7 V

SOURCE

S

R

Q

Q

DMAX

-

+

CONTROL

-

+

5.7 V

IFB

RE

ZC

VC

MINIMUM

ON-TIME

DELAY

+

-

VI

LIMIT

LEADING

EDGE

BLANKING

POWER-UP

RESET

S

R

Q

Q

÷ 8

0

1

THERMAL

SHUTDOWN

SHUNT REGULATOR/

ERROR AMPLIFIER

+

-

DRAIN

PI-2084-040401

CONTROL

DRAIN

SOURCE

Y Package (TO-220/3)

Tab Internally

Connected to SOURCE Pin

CONTROL

8

5

7

6

DRAIN

SOURCE (HV RTN)

SOURCE

SOURCE

1

4

2

3

SOURCE (HV RTN)

SOURCE (HV RTN)

SOURCE

P Package (DIP-8)

G Package (SMD-8)

Figure 3. Pin Configuration.