LP28009 datasheet(11/12 Pages) POWER

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Preliminary Datasheet

LP28009

LP28009 – 02

May.-2013

Email: marketing@lowpowersemi.com

www.lowpowersemi.com

Page 11 of 12

Temperature Regulation and Thermal Protection

In order to maximize the charge rate, the LP28009

features a junction temperature regulation loop. If the

power dissipation of the IC results in a junction

temperature greater than the thermal regulation

threshold (125°C), theLP28009 throttles back on the

charge current in order to maintain a junction

temperature around the thermal regulation threshold

(125°C). The LP28009 monitors the junction

temperature, TJ, of the die and disconnects the battery

from the input if TJ exceeds 125°C. This operation

continues until junction temperature falls below

thermal regulation threshold (125°C) by the hysteresis

level. This feature prevents the chip from damage.

Selecting the Input and Output Capacitors

In most applications, the most important is the

high-frequency decoupling capacitor on the input of

the LP28009.A 1uF ceramic capacitor, placed in close

proximity to input pin and GND pin is recommended. In

some applications depending on the power supply

characteristics and cable length, it may be necessary

to add an additional 10uFceramic capacitor to the

input.

The LP28009 requires a small output capacitor for

loop stability. A 1uF ceramic capacitor placed between

the BATT pin and GND is typically sufficient.

Layout Consideration

The LP28009 is a fully integrated low cost single-cell

Li-Ion battery charger ideal for portable applications.

Careful PCB layout is necessary. For best

performance, place all peripheral components as close

to the IC as possible. A short connection is highly

recommended. The following guide lines should be

strictly followed when designing a PCB layout for the

LP28009.Input capacitor should be placed close to IC

and connected to ground plane.

The trace of input in the PCB should be placed far

away the sensitive devices or shielded by the ground.

The GND should be connected to a strong ground

plane for heat sinking and noise protection. The

connection of RSETA should be isolated from other

noisy traces.

The short wire is recommended to prevent EMI and

noise coupling.

Output capacitor should be placed close to IC and

connected to ground plane to reduce noise coupling.

When PCB has poor layout, the 10uF is recommended

to prevent noise.

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