Rev. G 08/16

2

TOP221-227

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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 inter-

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

the connection point for the supply bypass and auto-restart/

compensation capacitor.

SOURCE Pin:

YN package – Output MOSFET source connection for high

voltage power return. Primary side circuit

common and reference point.

PN and GN 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

+

-

VILIMIT

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

C

S

S

S (HV RTN)

S (HV RTN)

S (HV RTN)

D

S

P Package (DIP-8)

G Package (SMD-8)

8

5

7

1

4

2

2

6

Figure 3. Pin Configuration.