RT9515 查看數據表（PDF） - Richtek Technology

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RT9515

Linear Single Cell Li-Ion Battery Charger IC

Richtek Technology 

RT9515

The parameter K = 300 ; VISETA = 2.5V. RSET is the resistor

connected between the ISETA and GND.

1200

1000

800

600

400

200

0

0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5

RSSEETTA(k(Ωk))

Figure 3. Charge Current Setting

Pre- Charge Current Setting

During a charge cycle if the battery voltage is below the

VPRECH threshold, the RT9515 applies a pre-charge mode

to the battery. This feature revives deeply discharged cells

and protects battery life. The RT9515 internally determines

the pre-charge rate as 10% of the fast-charge current.

Battery Voltage Regulation

The RT9515 monitors the battery voltage through the BATT

pin. Once the battery voltage level closes to the VREG

threshold, the RT9515 voltage enters constant phase and

the charging current begins to taper down. When battery

voltage is over the VREG threshold, the RT9515 will stop

charge and keep to monitor the battery voltage. However,

when the battery voltage decreases 100mV below the

VREG, it will be recharged to keep the battery voltage.

Charge Status Outputs

The open-drain CHG_S and PGOOD outputs indicate

various charger operations as shown in the following table.

These status pins can be used to drive LEDs or

communicate to the host processor. Note that ON

indicates the open-drain transistor is turned on and LED

is bright.

Charge State

ACIN

Ch arge

Charge done

CHG_S

ON

OFF

PGOOD

ON

ON

Temperature Regulation and Thermal Protection

In order to maximize the charge rate, the RT9515 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), the

RT9515 throttles back on the charge current in order to

maintain a junction temperature around the thermal

regulation threshold (125°C). The RT9515 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 damaging.

Selecting the Input and Output Capacitors

In most applications, the most important is the high-

frequency decoupling capacitor on the input of the RT9515.

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 10uF

ceramic capacitor to the input. The RT9515 requires a

small output capacitor for loop stability. A 1uF ceramic

capacitor placed between the BATT pin and GND is typically

sufficient.

Thermal Considerations

For continuous operation, do not exceed absolute

maximum operation junction temperature. The maximum

power dissipation depends on the thermal resistance of

IC package, PCB layout, the rate of surroundings airflow

and temperature difference between junction to ambient.

The maximum power dissipation can be calculated by

following formula :

PD(MAX) = ( TJ(MAX) - TA ) / θJA

Where TJ(MAX) is the maximum operation junction

temperature 125°C, TA is the ambient temperature and the

θJA is the junction to ambient thermal resistance.

DS9515-01 April 2011

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