RT5021 datasheet(33/67 Pages) RICHTEK

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RT5021

DS5021-01 April 2013

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

CH5 : Step-Down Synchronous DC/ DC Converter

The step-down synchronous DC/ DC converter includes internal power MOSFETs and compensation network. 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. The output voltage can be selected as

the following list or set by external feedback network.

CH5 regulation voltage can be selected by I

2C interface. The default voltage is 1.8V.

Code

Voltage

Code

Voltage

Code

Voltage

Code

Voltage

0000

REF

0001

1.1V

0010

1.2V

0011

1.3V

0100

1.4V

0101

1.5V

0110

1.6V

0111

1.7V

1000

1.8V

1001

1010

2.2V

1011

2.3V

1100

2.5V

1101

2.6V

1110

2.7V

1111

2.8V

VOUT5 [3:0]

Note : VOUT5 [3:0] = 0000 (REF) means using external feedback network and FB5

regulation target is 0.8V

± 1.5%

CH6 : Low Voltage LDO

CH6 is a low voltage LDO and its output voltage is controlled by I

2C interface. This supplies the multiple purpose power.

The output voltage of CH6 can be adjusted by the I

2C interface in the range of 1.1V to 3.3V.

CH6 regulation voltage can be selected by I

2C interface. The default voltage is 1.3V.

Code

Voltage

Code

Voltage

Code

Voltage

Code

Voltage

0000

Switch

0001

1.1V

0010

1.2V

0011

1.3V

0100

1.4V

0101

1.5V

0110

1.6V

0111

1.7V

1000

1.8V

1001

1010

2.2V

1011

2.5V

VOUT6 [3:0]

1100

2.8V

1101

3.1V

1110

3.2V

1111

3.3V

CH7 : Current Source/Step-Up WLED Driver

The WLED drivers operating in either current source mode or synchronous step-up mode include internal power MOSFET

and compensation network. The operation mode is determined by setting I2C. The P-MOSFET in step-up mode can be

controlled to disconnect the output loading.

When CH7 works in current source mode, it likes a LDO and regulates the current by FB7 voltage. The LED current is

defined by the FB7 voltage as well as the external resistor between FB7 and GND. The FB7 regulation voltage can be set

in 31 steps from 8mV to 250mV. If CH7 works in synchronous step-up mode, it can support an output voltage up to 15V

or 21V controlled by I2C interface. The LED current is also set via an external resistor and FB7 regulation voltage.

The WLED current can be set by the following equation :

ILED (mA) = [250mV / R (

Ω)] 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 I2C control register

file.

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