PWM Control 1.2A Step-Down Converter

EC4304B

E-CMOS Corp. (www.ecmos.com.tw)

Page 2 of 11

2011/10/06

PIN DESCRIPTION

SYMBO

L

SOT-23

SOT-89

DESCRIPTION

LX

1

1

Drain of NDMOS switch

GND

2

2

Ground

ADJ

3

3

Multi-function On/Off and brightness control pin:

• Leave floating for normal operation.(VADJ = VREF = 1.25V giving

nominal average output current IOUTnom = 0.1/RS)

• Drive with DC voltage (0V < VADJ < 2.5V) to adjust output current

from 0% to 200% of IOUTnom

• Drive with PWM signal from open-collector or open-drain transistor, to

adjust output current. Adjustment range 0% to 100% of IOUTnom for

f >10kHz and 0% to 100% of IOUTnom for f < 500Hz

ISENS

E

4

4

Connect resistor RS from this pin to VIN to define nominal average output

current IOUTnom = 0.1/RS

VIN

5

5

Input voltage (7V to 30V). Decouple to ground with 10uF or higher

X7R ceramic capacitor close to device

ABSOLUTE MAXIMUM RATINGS

Parameter

Symbol

Value

Unit

Voltage on intput pin relative to GND

VIN

-0.3 to +36

V

ISENSE pin Voltage

-5 to +0.3

V

ADJ and EN pin Voltage

-0.3 to +6

V

Operating Temperature Rang

TA

-40 to +125

C

Maximum Soldering Temperature (at leads, 10 sec)

TLEAD

300

C

Storage Temperature Rang

TS

-65 to +150

C

Power Dissipation, PD @ TA = 25°C

SOT-23

0.35

W

SOT-89

0.5

Package Thermal Resistance, θJA

SOT-23

250

°C/W

SOT-89

200