RT8208A/B

3

DS8208A/B-04 May 2011

www.richtek.com

Function Block Diagram

QTRIG

1-SHOT

+

-

+

-

GM

SQ

Latch

SQ

Latch

+

-

OV

+

-

UV

+

-

SS Timer

Thermal

Shutdown

Diode

Emulation

DRV

DRV

On-time

Compute

1-SHOT

CS

FB

VOUT

VDD

UGATE

PHASE

VDDP

PGOOD

GND

LGATE

TON

BOOT

TRIG

EN

R

Q

S

SS

(internal)

Control

Logic

G0 G1

D0

D1

R

R

G0, G1

Counter

Blanking Signal

EN

-

+

GM

+

-

10µA

Pin No.

Pin Name

Pin Function

7

G0

Control Input Pin for the D0 MOSFET. A logic high for RT8208A and low for

RT8208B turn on the D0 MOSFET on, pulling D0 to the ground.

8

LGATE

Low side N-MOSFET gate driver output for PWM. This pin swings between GND

and VDDP.

9

VDDP

VDDP is the gate driver supply for external MOSFETs. Bypass to GND with a 1

μF

ceramic capacitor.

10

CS

Over Current Trip Point Set Input. Connect a resistor from this pin to signal ground

to set threshold for both over current and negative over current limit.

11

PHASE

The UGATE High Side Gate Driver Return. Also serves as anode of over current

comparator.

12

UGATE

High side N-MOSFET floating gate driver output for the PWM converter. This pin

swings between PHASE and BOOT.

13

BOOT

Boost Capacitor Connection for PWM Converter. Connect to an external ceramic

capacitor to PHASE.

14

G1

Control Input Pin for the D1 MOSFET. A logic high for RT8208A and low for

RT8208B turn on the D1 MOSFET on, pulling D1 to the ground.

15

EN/DEM

Enable/Diode Emulation Mode Control Input. Connect to VDD for diode–emulation

mode, connect to GND for shutdown and floating the pin for CCM mode.

16

TON

On Time/Frequency Adjustment Pin. Connect to PHASE through a resistor. TON is

an input for the PWM controller.

17 (Exposed pad) GND

The exposed pad must be soldered to a large PCB and connected to GND for

maximum power dissipation.