RT9516 查看數據表（PDF） - Richtek Technology

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RT9516

Linear Single Cell Li-lon Battery Charger with Single Input Supply for Portable Applications

Richtek Technology 

RT9516

c. Battery Voltage Regulation (CV Mode)

The battery voltage regulation feedback is through the

BATT pin. The RT9516 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

RT9516 still monitors the battery voltage. Charge current

is resumed when the battery voltage under battery

regulation voltage threshold.

Sleep Mode

The RT9516 enters the 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

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

voltage status. The PGOOD output asserts low when

VIN > 4.25V and (VIN − VBATT) > 40mV. These PGOOD pin

can be used to drive LED or communicate to the host

processor. Note that ON indicates the open-drain transistor

is turned on and LED is bright.

Auto-Booting

The RT9516 has an internal “OR” gate that generates an

enable signal for system booting. The battery supplies

power to the “OR” gate, the RT9516 will keep BATT pin

voltage to supply the “OR” gate function when the battery

isn connected at BATT pin. The first input is the AC_PG

and the second input is an external signal (ABI). When

the (VIN − VBATT) > 90mV, the AC_PG signal is high. The

ABI signal is driven by an external system, when external

signal is floating, the ABI has an internal pull low resistor.

AC_PG

VBATT

ABO

200k

ABI

Figure 3

Temperature Regulation and Thermal Protection

In order to maximize charge rate, the RT9516 features a

junction temperature regulation loop. If the power

dissipation of the IC results in a junction temperature that

is greater than the thermal regulation threshold (115°C),

the RT9516 throttles back on the charge current in order

to maintain a junction temperature around the thermal

regulation threshold (115°C). The RT9516 monitors the

junction temperature, TJ, of the die and disconnects the

battery from the input if TJ exceeds 115°C. This operation

continues until 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 high-frequency decoupling capacitor

on the input.(1μF ceramic capacitor), placed in close

proximity to the input works well. In some applications

depending on the power supply characteristics and cable

length, it may be necessary to add an additional 10μF

ceramic capacitor to the input. The RT9516 requires a

small output capacitor for loop stability. A 1μF ceramic

capacitor placed between the BATT pin and GND is typically

sufficient.

Thermal Conderations

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, TA is the ambient temperature and the θJA is

the junction to ambient thermal resistance.

For recommended operating conditions specification of

RT9516, where TJ(MAX) is 125° C and TA is the operated

ambient temperature. The junction to ambient thermal

resistance θJA for WDFN-8L 2x2 package is 165°C/W on

the standard JEDEC 51-3 single-layer thermal test board.

DS9516-01 April 2011

www.richtek.com

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