Multiple-Output Regulator for

Automotive LCD Displays

A8603

27

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

AB

C

DE

Junction

Temperature

VGH

FAULT

VGL

VCOM

AVDD

Internal

Enable

Target

0 V

Target

0 V

0 V

Target

0 V

- 0 V

30%

90%

Startup

IC Heats Up

Shutdown

IC Cools Down

Hysteresis

TSD

TSD – Hyst

Sequence of events:

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

C: During operation, should the junction temperature rises to TSD threshold (due to high ambient temperature or unexpected heavy load),

the IC turns off all output regulators immediately without following normal shutdown sequence. FAULT is pulled low and fault counter is

incremented by 1.

D: After shutdown is completed, the IC waits for junction temperature to drop to TSD-Hyst (typically 20°C below TSD) before attempting retry.

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

Figure 15: Timing Diagram Showing a Thermal Shutdown and Restart