RT5002 datasheet(26/40 Pages) RICHTEK

26 / 40 page

RT5002

DS5002-00

November 2011

www.richtek.com

CH7 WLED Current Dimming Control

If CH7 is in synchronous step-up mode or current source

mode, the WLED current is set by an external resistor.

Regardless of the mode, dimming is always controlled

by the I

2C interface.

The WLED current can be set by the following equations :

ILED (mA) = [250mV / R (W)] x EN7_DIM7 [4:0] / 31

where R is the current sense resistor from FB7 to GND

and EN7_DIM7 [4:0] / 31 ratio refers to the I

2C control

connects to the node SYS in order to prevent abnormal

CH7 start-up.

VDDM Bootstrap

To support bootstrap function, the RT5002 includes a

power selection circuit which selects between SYS and

PVD1 to create the internal node voltage VDDI and VDDM.

VDDM is the power of the RT5002 PMU control circuits

which must be connected to an external decoupling

capacitor by way of the VDDM pin. VDDI is the power

input of the RTC LDO. The output PVD1 of CH1 can

bootstrap VDDM and VDDI. The RT5002 includes UVLO

circuits to monitor VDDM and SYS voltage status.

RTC LDO

The RT5002 provides a 3.3V output LDO for real-time clock.

The LDO features low quiescent current (3

µA) and high

output voltage accuracy. This LDO is always on, even when

the system is shut down. For better stability, it is

recommended to connect a 0.1

µF capacitor to the

RTCPWR pin. The RTC LDO includes pass transistor body

diode control to avoid the RTCPWR node from back-

charging into the input node VDDI.

Power On/Off Sequence for CH1 to CH4

EN1234 will turn on/off CH1 to CH4 in preset sequence.

CH1 to CH4 Power on Sequence is :

When EN1234 goes high, CH1 will turn on first. 3.5ms

after CH1 is turned on, CH3 will turn on. 3.5ms after CH3

is turned on, CH4 will turn on. 3.5ms after CH4 is turned

on, CH2 will turn on.

CH1 to CH4 Power off Sequence is :

When EN1234 goes low, CH2 will turn off first and internally

discharge output. When FB2 < 0.1V, CH4 will turn off and

also internally discharge output via the LX4 pin. When

FB4 < 0.1V, CH3 will turn off and internally discharge output

via the LX3 pin. Likewise, when FB3 < 0.1V, CH1 will turn

off and discharge output. After FB1 < 0.1V, CH1 to 4

shutdown sequence will be completed.

Charger Unit

The RT5002 includes a Li-ion battery charger with

Automatic Power Path Management. The charger is

designed to operate in below modes :

Pre-Charge Mode

When the output voltage is lower than 2.8V, the charging

current will be reduced to a fast-charge current ratio set

by RISETA to protect the battery life-time.

Fast-charge Mode

When the output voltage is higher than 3V, the charging

current will be equal to the fast-charge current set by

RISETA.

Constant Voltage Mode

When the output voltage is near 4.2V and the charging

current falls below the termination current, after a deglitch

time check of 25ms, the charger will become disabled.

Re-charge Mode

When the chip is in charge termination mode, the charging

current gradually goes down to zero. However, once the

voltage of the battery drops to below 4.1V, there will be a

deglitch time of 100ms and then the charging current will

resume again.

RT5002 Datasheet(PDF) 26 Page - Richtek Technology Corporation

RT5002 Datasheet(HTML) 26 Page - Richtek Technology Corporation

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