RT9501APF datasheet(7/9 Pages) RICHTEK

7 / 9 page

RT9501A/B

Preliminary

DS9501A/B-07 March 2007

www.richtek.com

Constant Voltage Regulation and Charge

Termination Mode

When the battery voltage reaches the regulation voltage

VO(REG), the constant voltage feedback control starts, and

then the charge current begins to decrease as the typical

charge profile shown. As the charge current decreases

to lower than charge terminated current threshold, the

RT9501 will terminate the charge cycle.

Recharge Mode

After the charge termination mode, if the battery voltage

falls to lower than the recharge threshold voltage VO(RCH),

the RT9501 will begin a new charge cycle according to

the battery voltage.

Battery Temperature Detection

The RT9501 continuously detects the battery temperature

by measuring the TS pin voltage. A NTC or PTC

thermistor can parallel with RT2 to deviate the TS pin

voltage. (As shown in Figure 5) The TS pin voltage must

be within normal temperature voltage range that is shown

in Figure 6 and electrical characteristics, and then RT9501

can start working normally.

The RT1 and RT2 can be derived from following equations.

For NTC Thermistors:

For PTC Thermistors:

Where RTL is the resistance value in lowest desired

operation temperature and RTH is the resistance value in

highest desired operation temperature. The resistances

of thermistors are specified by the thermistor

manufacturer. If the temperature monitoring function is

not desired, there's an easy method to set RT1 and RT2 at

the same value and disconnect the thermistor to disable

this function.

××

3(R

- R )

[(2 R )-(7 R )]

FB/CE Pin Functions

This pin has two functions, one is to enable/disable the

charge function, and the other is to finely adjust battery

regulation voltage. Connect this pin to VDD to enable

RT9501, and connect to ground to disable it (Figure 7). If

this pin is connected to a voltage divider as shown in

Figure 8, it can be a 2.1V reference voltage to adjust the

output regulation voltage as desired.

VDD

GND

TS1

TS2

Temperature Fault Range

Normal Temperature Range

Temperature Fault Range

Figure 6

××

3(R - R )

××

[(2 R )-(7 R )]

Figure 5

FB/CE

BATT

STAT

VDD

GND

Thermistor

Battery

Pack

Figure 7. For CE pin Function

BATT

STAT

VDD

GND

Battery

GPIO

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