RT5002 datasheet(24/40 Pages) RICHTEK

24 / 40 page

RT5002

DS5002-00

November 2011

www.richtek.com

Application Information

Power Converter Unit

The RT5002 is an integrated power system for digital still

cameras and other small handheld devices. It includes

six DC/DC converters as well as one WLED driver, one

RTC LDO, and a fully integrated single-cell Li-ion battery

charger ideal for portable applications.

CH1 : Step-up synchronous current mode DC/DC converter

with internal power MOSFETs and compensation network.

The P-MOSFET body can be controlled to disconnect the

load. It is suitable for providing power to the motor.

CH2 to CH4 : Step-down synchronous current mode DC/

DC converter with internal power MOSFETs and

compensation network. These channels supply the power

for I/O, DRAM, and core. They can be operated at 100%

maximum duty cycle to extend battery operating voltage

range. When the input voltage is close to the output

voltage, the converter enters low dropout mode with low

output ripple.

CH5 : High voltage step-up synchronous current mode

DC/DC converter with internal power MOSFET and

compensation network. The P-MOSFET body can be

controlled to disconnect the load. This channel supplies

the CCD+ bias.

CH6 : Asynchronous inverting current mode DC/DC

converter with internal power MOSFET and compensation

network. An external Schottky diode is required. This

channel supplies the CCD

− bias.

CH7 : WLED driver operating in either current source mode

or synchronous step-up mode with internal power

MOSFET and compensation network. The operation mode

is determined via the I2C interface. The P-MOSFET body

in step-up mode can be controlled to disconnect the load.

CH1 to CH4 operate in PWM mode with 2MHz, while

CH5 to CH7 operate in PWM mode with 1MHz switching

frequency.

RTC_LDO : 3.3V output LDO with low quiescent current

and reverse leakage prevention from output node.

Output Voltage Design Equation of CH1 to CH4 :

The output voltage can be set by the following equation :

VOUT = (1 + RH / RL) x VFB

where VFB is 0.8V typically, RH is R1, R3, R5, and R7

respectively for CH1 to 4, and RL is R2, R4, R6, and R8

respectively for CH1 to 4.

Output Voltage Design Equation of CH5 :

The output voltage can be set by the following equation :

VOUT_CH5 = (1 + R9 / R10) x VFB5

where VFB5 is 1.25V typically.

Output Voltage Design Equation of CH6 :

The output voltage can be set by the following equation :

VOUT_CH6 =

−(R11 / R12) x (1.2V) + 0.6V

where R11 and R12 are the feedback resistors connected

to FB6, 1.2V equals to (VREF

− VFB6), and 0.6V is the

typical value of VFB6.

Reference Voltage

The RT5002 provides a precise 1.8V reference voltage,

VREF, with sourcing capability of 100

μA. Connect a 0.1μF

ceramic capacitor from the VREF pin to GND. Reference

voltage is enabled by I2C register bit EN56 = 1.

Furthermore, this reference voltage is internally pulled to

GND at shutdown.

CH5 and CH6 Power Sequence :

CH5 and CH6 are enabled together via I2C interface and

their power on sequence can be chosen via I2C register

setting.

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