RT9526 datasheet(9/14 Pages) RICHTEK

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RT9526

DS9526-01 April 2011

www.richtek.com

KSET = 3640; VSET = 1.21 (typ.)

c. Battery Voltage Regulation (CV Mode)

The battery voltage regulation feedback is through the

BATT pin. The RT9526 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

RT9526 still monitors the battery voltage. Charge current

is resumed when the battery voltage falls under battery

regulation voltage threshold.

Sleep Mode

The RT9526 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.

Application Information

The RT9526 is a fully integrated low cost single cell Li-ion

battery charger operable in Constant Current (CC) mode

or Constant Voltage (CV) mode. The CC mode current is

set with the external resistor, RISET, and the CV mode

voltage is fixed at 4.2V. If the battery voltage is below a

typical 2.8V pre-charge threshold, the RT9526 charges

the battery with a trickle current until the battery voltage

rises above the pre-charge threshold. The RT9526 is

capable of being powered up from AC adapter and USB

(Universal Serial Bus) port inputs.

VIN Over Voltage Protection

The input voltage is monitored by the internal comparator.

The OVP threshold is set at 11V (typ.). When the input

voltage exceeds the threshold, the controller outputs a

logic signal to turn off the power P-MOSFET to prevent

high input voltage from damaging the electronics in the

handheld system. Nevertheless, an AC input voltage over

28V will still damage the RT9526. When the input over

voltage condition is removed, the controller will enable

the output again by running through soft-start.

Charger Enable Input

ENB is an active-low logic input to enable the charger.

Drive the ENB pin low or leave it floating to enable the

charger. This pin has a 200k

Ω internal pull down resistor.

So when left floating, the input is equivalent to logic-low.

Drive this pin high to disable the charger.

Battery Charge Profile

The RT9526 charges a Li-ion battery under Constant

Current (CC) mode or Constant Voltage (CV) mode. The

constant current of ISET is set via the external resistor,

RISET, and the constant voltage is fixed at 4.2V. If the battery

voltage is below a typical 2.8V pre-charge threshold, the

RT9526 charges the battery with a trickle current until

the battery voltage rises above the pre-charge threshold.

When the battery voltage reaches 4.2V, the charger enters

CV mode and regulates the battery voltage at 4.2V to

fully charge the battery without the risk of over charge.

Trickle

4.2V

ICHG_FAST

2.8V

16.7 %

ICHG_FAST

CHG_SB

CHG

Indication

IIMIN

Charge

Current

75 %

ICHG_FAST

Time

Charge

Voltage

Figure 1. Typical Charge Profile

a. Battery Pre-Charge Current

During a charge cycle, if the battery voltage is below the

pre-charge threshold, the RT9526 applies a pre-charge

mode to the battery. This feature revives deeply discharged

cells and protects battery life. The internally determined

pre-charge rate of the RT9526 is 16.7% of the constant

charge current.

b. Battery Fast-Charge Current (CC Mode)

The RT9526 offers ISET pin to determine the fast-charge

current via an external resistor, RISET, connected between

ISET and GND. The fast-charge current can be calculated

by the following equation :

ISET

CHG_FAST

ISET

= K

(mA)

RT9526 Datasheet(PDF) 9 Page - Richtek Technology Corporation

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