RT9526AGE datasheet(8/10 Pages) RICHTEK

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RT9526A

DS9526A-01 April 2011

www.richtek.com

c. Battery Voltage Regulation (CV Mode)

The battery voltage regulation feedback is through the

BATT pin. The RT9526A monitors the battery voltage

between the BATT and GND pins. When battery voltage is

close to battery regulation voltage threshold, the voltage

regulation phase begins and the charging current begins

to taper down. When battery voltage is over battery

regulation voltage threshold and charge mode stops, the

RT9526A still monitors the battery voltage. Charge current

is resumed when the battery voltage falls under battery

regulation voltage threshold.

Sleep Mode

The RT9526A enters sleep mode if both AC and USB are

removed from the input. This feature prevents draining the

battery during the absence of input supply.

Power Good

This open-drain output pin is used to indicate the input

voltage status. The PGB output asserts low when

1. VIN > VPOR

2. VIN

−−−−− VBATT > VOS

3. VIN < VOVP

It can be used to drive an LED or communicate to the

host processor. Note that ON indicates the open-drain

transistor is turned on and LED is bright.

CHG_SB Indication

The CHG_SB pin is an open-drain output capable to at

least 10mA current when the charger starts to charge and

turns off when the EOC current is reached. The CHG_SB

signal is interfaced either with a micro processor GPIO or

an LED for indication.

End-Of-Charge Current (EOC)

Connect a resistor between the IMIN pin and GND to set

the EOC current. The EOC current level, IIMIN, is

programmable via the external resistor, RIMIN (k

Ω), as

shown in the following equation :

IMIN

10935

(mA)

Upon reaching the End-Of-Charge (EOC) current, the

charger indicates charge completion via the CHG_SB pin,

but the charger continues to output 4.2V voltage. Figure

1 shows the typical charge profile and the EOC/reset

event. The CHG_SB signal asserts low when the trickle

charge starts and changes to high at EOC. After EOC is

reached, the charge current has to rise above 75% of

ICHG_FAST before the CHG_SB signal is allowed to turn on

again. A current surge after EOC may occur due to a load

connected to the battery.

Temperature Regulation and Thermal Protection

In order to maximize charge rate, the RT9526A features a

junction temperature regulation loop. If the power

dissipation of the IC results in junction temperature greater

than the thermal regulation threshold (115

°C), the RT9526A

will cut back on the charge current and disconnect the

battery in order to maintain thermal regulation at around

115

°C. This operation continues until the junction

temperature falls below thermal regulation threshold

(115

°C) by the hysteresis level. This feature prevents the

maximum power dissipation from exceeding typical design

conditions.

Selecting the Input and Output Capacitors

In most applications, a 1

μF high frequency decoupling

capacitor placed in close proximity to the input is sufficient.

However, depending on the power supply characteristics

and cable length, it may be necessary to add an additional

μF ceramic capacitor to the input. For the RT9526A, a

small output capacitor is required for loop stability. A 1

μF

ceramic capacitor placed between the BATT pin and GND

is typically sufficient.

Thermal Considerations

For recommended operating condition specifications of

the RT9526A, the maximum junction temperature is 125

°C

and TA is the ambient temperature. The junction to ambient

thermal resistance,

θJA, is layout dependent. For WDFN-

8L 2x3 packages, the thermal resistance,

θJA, is 120°C/

W on a standard JEDEC 51-3 single-layer thermal test

board. The maximum power dissipation at TA = 25

°C can

be calculated by the following formula :

RT9526AGE Datasheet(PDF) 8 Page - Richtek Technology Corporation

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