Datasheet

Datasheet

15/36

BD81A24MUV-M/EFV-M

TSZ02201-0T3T0C600070-1-2

© 2016 ROHM Co., Ltd. All rights reserved.

2016.10.19 Rev.003

www.rohm.com

TSZ22111・15・001

Timing Chart (Start up and Protection)

Figure 19. Startup and Protect function timing chart

*1 Vcc, EN, PWM, SYNC are input sequence free.

*3 Above timing chart is the case of pulling up FAIL1 and FAIL2 terminal to VREG.

1.

When VOVP less than 1.0V, regardless of PWM input, the DC/DC switching operation will be active (Pre-Boost function).

And if VOVP reaches 1.0V, the Pre-Boost is finished.

2.

When VLED2 less than 0.3V and VOVP more than 2.0V, LED Open Protect is active and LED2 is turned OFF. Then

FAIL2 becomes Low.

3.

If The condition of VLED3 more than 4.5V passes 100ms (@fosc=300kHz), LED3 is turned OFF. Then FAIL2 becomes

Low.

4.

When VLED4 short to GND, increase the Vout voltage. Then VOVP rises over 2.0V, FAIL1 becomes Low. If OVP occur,

DCDC switching is OFF and decrease Vout voltage, then OVP repeats ON/OFF. And DCDC switching and LED current

of each CH is OFF after approximately 100ms. (In case of fosc=300kHz).

VCC

EN *1

UVLO

SYNC *1

PWM *1

SS

ILED1

ILED2

ILED3

ILED4

VLED1

VLED2

VLED3

VLED4

FAIL1 *3

3.5V

100ms *2

VREG

①

Under 0.3V

Over 4.5V

2.0V

Under 0.3V

100ms *2

OVP

2.0V

④

LED4=GND

③

LED3=SHORT

②

LED2=OPEN

Hi-z

Hi-z

Hi-z

Hi-z

1.0V

FAIL2 *3

SW/OUTL/

OUTH

4.5V

VOUT

VOVP

1.0V

Vf

1.94V

1.94V