RT9505 datasheet(8/11 Pages) RICHTEK

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RT9505

DS9505-02 April 2011

www.richtek.com

Application Information

Automatically Power Source Selection

The RT9505 is a battery charger IC which is designed for

Li-ion Battery with 4.2V rated voltage.

ACIN Mode : When the ACIN input voltage is higher than

the UVP voltage level (4.4V), the RT9505 will turn on ACIN

P-MOSFET.

Sleep Mode : The RT9505 will enter Sleep Mode when

ACIN input voltage are removed. This feature provides low

leakage current from the battery during the absence of

input supply.

ACIN Over Voltage Protection

The ACIN input voltage is monitored by an internal OVP

comparator. The comparator has an accurate reference of

2.5V from the band-gap reference. The OVP threshold is

set by the internal resistive. The protection threshold is

set to 6.5V. When the input voltage exceeds the threshold,

the comparator outputs a logic signal to turn off the power

P-MOSFET to prevent the high input voltage from damaging

the electronics in the handheld system. When the input

over oltage condition is removed (ACIN < 6V), the

comparator re-enables the output by running through the

soft-start.

Battery Temperature Monitoring

The RT9505 continuously monitors battery temperature

by measuring the voltage between the TS and GND pins.

The RT9505 has an internal current source to provide the

bias for the most common 10k

Ω negative-temperature

coefficient thermal resistor (NTC) (see Figure 1). The

RT9505 compares the voltage on the TS pin against the

internal VTS_HIGH and VTS_LOW thresholds to determine

if charging is allowed.

When the temperature outside the VTS_HIGH and

VTS_LOW thresholds is detected, the device will

immediately stop the charge. The RT9505 stops charge

and keep monitoring the battery temperature when the

temperature sense input voltage is back to the threshold

between VTS_HIGH and VTS_LOW, the charger will be

resumed. Charge is resumed when the temperature returns

to the normal range. However the user may modify

thresholds by the negative-temperature coefficient thermal

NTC

= I

Turn off when V

2.5V or V

0.5V

≥≤

Figure 1. Temperature Sensing Configuration

0.1uF to 10uF

Battery

Temperature

Sense

ITS

VBATT

NTC

resistor or adding two external resistors. (see Figure 2.)

The capacitor should be placed close to TS(Pin 9) and

connected to the ground plane. The capacitance value

(0.1uF to 10uF) should be selected according to the quality

of PCB layout. It is recommended to use 10uF if the layout

is poor if prevent noise.

Figure 2. Temperature Sensing Circuit

NTC

R(R

+ R

)

= I

+ R

Turn off when V

2.5V or V

0.5V

≥≤

RT2

Battery

Temperature

Sense

ITS

VBATT

NTC

RT1

0.1uF to 10uF

SET

charge_ac

SET

SETA

= K

Fast-Charge Current Setting

The RT9505 offers ISETA pin to determine the ACIN charge

rate from 100mA to 1.2A. The charge current can be

calculated as following equation.

RT9505 Datasheet(PDF) 8 Page - Richtek Technology Corporation

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