Datasheet

Datasheet

8/28

TSZ02201-0F1F0C100300-1-2

© 2013 ROHM Co., Ltd. All rights reserved.

25.Sep.2015 Rev.003

www.rohm.com

TSZ22111 • 15 • 001

BD9420F

Description of pin function



P in 1: REG75

The REG pin is used in the DC/DC converter driver block to output 7.5V power. The maximum operating current is 10mA.

Using the REG pin at a current higher than 10mA can affect the N pin output pulse, causing the IC to malfunction and

leading to heat generation of the IC itself. To avoid this problem, it is recommended to make load setting to the minimum

level.



Pin 2:N

The N pin is used to output power to the external NMOS gate driver for the DC/DC converter in the amplitude range of

approx. 0 to 7.5V. Frequency setting can be made with a resistor connected to the RT pin. For details of frequency

setting, refer to the description of the ＜RT pin＞.



Pin 3: PGND

The PGND pin is a power ground pin for the driver block of the N output pin.



Pin 4: CS

CS pin is current detect for DC/DC current mode inductor current control pin.

Current flowing through the inductor is converted into voltage by the current sensing resistor RCS connected to the CS

pin and this voltage is compared with voltage set with the error amplifier to control the DC/DC output voltage.

The CS pin also incorporates the overcurrent protection (OCP) function. If the CS pin voltage reaches 0.4V (Typ.) or

more, switching operation will be forcedly stopped.



Pin 5: SEL

SEL pin is PWM control select pin. The PWM control mode is switched according to voltages input in the SEL pin. Avoid

using the SEL pin between two states (0.8 to 1.5V).

SEL Voltage

State

SEL= 1.5V~18.0V

PWMA → CH1,CH2 common mode control

PWMB → CH3,CH4 common mode control

PWMC → CH5,CH6 common mode control

SEL= -0.3V～0.8V

PWMA → CH1,CH2,CH3 common mode control

PWMB → no use

PWMC → CH4,CH5,CH6 common mode control



Pin 6: FB

Current mode control DC/DC converter error amplifier output pin. By monitoring voltage of BS（1～6）pin, the highest Vf of

LED column will set 2/3(typ.) of applied VREF voltage to BS pin voltage to control inductor current.

The phase compensation setting has described separately.

In addition, PWM pin will become High Impedance when all PWM signals are in low state, and will maintain FB voltage.



Pin 7: LSP

LED Short detect voltage setting pin. When LSP=OPEN, LSP pin voltage is 0.9V( typ), the BSx pin of LED SHORT

detect voltage is set to 9V.

The 10 times of LSP pin voltage is the BSx pin LED SHORT protection detect voltage.

Please set LSP pin input voltage range from 0.3V～2.5V.



Pin 8: VREF

LED current setting pin.1/3(typ) of applied voltage to VREF pin will be LED current

feedback voltage, 2/3(typ.) of its voltage will be DCDC feedback voltage（the

lowest BSx pin feedback voltage）.

Basically, because high accuracy of resistor divider is inputted to VREF pin

externally, the IC internally will be OPEN（High Impedance）state. Please use

external power to design it. It cannot be used in OPEN state.



Pin 9-14: BS1-BS6

LED DRIVER output pin. Please connect to Base Terminal of external PNP Tr.



Pin 15-20: CL6 – CL1

LED current detect pin. By monitoring voltage of CLx pin to detect LED current.

Please connect resistor to collector pin of external PNP Tr. CLx pin of no use channel set CLx>3.3V.