INTRODUCTION:

FEATURES:

The LR8421 devices provide a power supply

solution for products powered by either a one-cell

Li-Ion or Li-polymer, or a two to three-cell alkaline,

NiCd or NiMH battery. The converter generates a

stable output voltage that is adjusted by an

external resistor divider. It provides high efficient

power conversion and is capable of delivering

output currents up to 2.1A at 5V at a supply

voltage down to 3V.

The implemented boost converter is based on a

fixed

switching

frequency

(500kHz

typical),

current-mode controller using a synchronous

rectifier to obtain maximum efficiency. Boost

switch and rectifier switch are connected internally

to provide the lowest leakage inductance and best

EMI behavior possible. The current-mode control

scheme provides fast transient response and

good output voltage accuracy. At light load, the

converter will automatically enter into Pulse

Frequency Modulation (PFM) operation to reduce

the dominant switching losses. During PFM

operation, the IC consumes very low quiescent

current and maintains high efficiency over a wide

load current range.

The converter can be disabled to minimize battery

drain. During shutdown, the load is completely

disconnected from the battery.

The device allows use of small inductors and

output capacitors for USB devices.

from 3.3V Input

Low Device Quiescent Current: 70 A (Max)

from 3.3V Input

500kHz PWM Switching Frequency

Synchronous and Embedded Power

MOSFETs; No Schottky Diode Required

at 5.0V output: 35/42mohm

Input Voltage Range: 1.8V to 5.25V

Adjustable Output Voltage Range:

from 2.5V to 5.5V

Pulse Frequency Modulation Operation for

Improved Efficiency at Low Output Power

Current Mode Operation with Internal

Compensation for Excellent Line and Load

Transient Response

Logic Controlled Shutdown(<1 A)

Load Disconnect During Shutdown

Automatic output discharge at shutdown:

No output discharge function

Internal Soft-Start to Limit Inrush Current

Over Current Protection

Input Under Voltage Lockout

Output Over Voltage Protection

Over-Temperature Protection

Available in thermally enhanced 8-pin SOP

Package

APPLICATIONS

All Single Cell Li or Dual Cell Battery

Operated Products as Tablet PC, Smartbook

and Other Portable Equipment

Products including portable HDMI and USB-OTG

USB Hosts Without Native 5V Supplies

USB Charging Port (5V)

Power Bank, Battery Backup Units

Wireless Peripherals

Portable Audio Players

Personal Medical Devices

Industrial Metering Equipments

DC/DC Micro Modules

5A, 500KHz Synchronous Boost Converter

with Output Disconnect

LESHAN RADIO COMPANY, LTD.

Ver0.1

1/7

LR8421 Series