RT8294

3

DS8294-02

March 2011

www.richtek.com

Functional Pin Description

Function Block Diagram

Pin No.

SOP-8

SOP-8

(Exposed Pad)

Pin Name

Pin Function

1

1

BOOT

Bootstrap for High Side Gate Driver. Connect a 10nF or greater

ceramic capacitor from BOOT to SW pins.

2

2

VIN

Input Supply Voltage, 4.5V to 23V. Must bypass with a suitably large

ceramic capacitor.

3

3

SW

Phase Node. Connect this pin to external L-C filter.

4

4,

9 (Exposed Pad)

GND

Ground. The exposed pad must be soldered to a large PCB and

connected to GND for maximum power dissipation.

5

5

FB

Feedback Input Pin. This pin is connected to the converter output. It

is used to set the output of the converter to regulate to the desired

value via an internal resistive voltage divider. For an adjustable

output, an external resistive voltage divider is connected to this pin.

6

6

COMP

Compensation Node. COMP is used to compensate the regulation

control loop. Connect a series RC network from COMP to GND. In

some cases, an additional capacitor from COMP to GND is required.

7

7

EN

Enable Input pin. A logic high enables the converter; a logic low

forces the RT8294 into shutdown mode reducing the supply current

to less than 3

µA. Attach this pin to VIN with a 100kΩ pull up resistor

for automatic startup.

8

8

SS

Soft-Start Control Input. SS controls the soft-start period. Connect a

capacitor from SS to GND to set the soft-start period. A 0.1

µF

capacitor sets the soft-start period to 15.5ms .

VA

+

-

+

-

+

-

UV

Comparator

Oscillator

Foldback

Control

0.5V

Internal

Regulator

+

-

2.7V

Shutdown

Comparator

Current Sense

Amplifier

BOOT

VIN

GND

SW

FB

EN

COMP

3V

5k

6

µA

Slope Comp

Current

Comparator

+

-

0.923V

S

R

Q

Q

SS

+

-

1.2V

Lockout

Comparator

+

Error Amp

Ω

130m

Ω

130m