Multiple-Output Regulator for

Automotive LCD Displays

A8603

26

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

AB

C

DE

FAULT

VGH

VGL

VCOM

AVDD

Internal

Enable

Target

0 V

Target

0 V

0 V

Target

0 V

0 V

30%

80%

Startup

Normal

Operation

Shutdown

Cool Down Timer (10-200 ms)

t_RESTART

Sequence of events:

B: Startup is completed successfully when the last regulator (VCOM in this case) has reached 90% target voltage.

C: VCOM output voltage drops to below 80% target due to an output short or unexpected heavy load. The A8603 detects an Output_UVP fault

and shuts down VCOM immediately. All other regulators are then shut down in normal sequence.

D: When the last regulator (VGH in this case) has finished shutdown, the A8603 waits for a cooldown period (programmable between 10 and

200 ms).

E: Retry startup as long as the maximum number or retries (programmable between 0 and 15) is not exceeded.

Figure 14: Timing Diagram where VCOM Suffered an Output Undervoltage Fault during Normal Operation