LSP5502

2A Synchronous Step Down DC/DC Converter

3/11

Rev. 1.7

www.liteon-semi.com

M1

0.12Ω

M2

0.12Ω

Supply Current in Shutdown

VEN = 0

0.3

3.0

µA

IC Supply Current in Operation

VEN = 3V, VFB = 1.0V

1.4

1.5

mA

Input UVLO Threshold Rising

UVLO

VEN Rising

3.80

4.05

4.40

V

Input UVLO Threshold Hysteresis

210

mV

Soft-start Current

VSS = 0V

6

µA

Soft-start Period

CSS = 0.1µF

15

mS

Thermal Shutdown Temperature

Hysteresis = 10°C

160

°C

FUNCTIONAL BLOCK DIAGRAM

6

7

8

5

2

1

3

4

INTERNAL

REGULATORS

FB

SS

COMP

EN

7V

Zener

1.1V

0.3V

0.925V

2.5V

1.5V

OVP

SHUTDOWN

COMPARATOR

ERROR

AMPLIFIER

LOCKOUT

COMPARATOR

EN OK

6uA

OSCILLATOR

150/400KHz

RAMP

CLK

1.2V

OVP

IN<4.10V

IN

CURRENT

COMPARATOR

CURRENT

SENSE

AMPLIFIER

5V

IN

BS

SW

GND

S Q

R Q

FUNCTIONAL DESCRIPTION

The LSP5502 is a synchronous rectified, cur-rent-mode, step-down regulator. It regulates in-put voltages from 4.5V

to 23V down to an out-put voltage as low as 0.925V, and supplies up to 2A of load current.

The LSP5502 uses current-mode control to regulate the output voltage. The output voltage is measured at FB

through a resistive voltage divider and amplified through the internal trans-conductance error amplifier. The voltage

at the COMP pin is compared to the switch current

measured internally to control the output voltage.

The converter uses internal N-Channel MOSFET switches to step-down the input voltage to the regulated output

voltage. Since the high side MOSFET requires a gate voltage greater than the input voltage, a boost capacitor

connected between SW and BS is needed to drive the high side gate. The boost capacitor is charged from the

internal 5V rail when SW is low.

When the LSP5502 FB pin exceeds 20% of the nominal regulation voltage of 0.925V, the over volt-age comparator

is tripped and the COMP pin and the SS pin are discharged to GND, forcing the high-side switch off.

Free Datasheet http://www.nDatasheet.com