Multiple-Output Regulator for

Automotive LCD Displays

A8603

15

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

All faults and critical signals are recorded into log registers.

External devices can read these log registers for diagnostic or

maintenance purposes.

The A8603 provides two types of diagnostic status registers:

• Registers 0x14-16 (#20-22 in decimal) store the real-time

status bits for regulator voltage, current, and fault conditions.

• Registers 0x17-1B (#23-27 in decimal) store the ‘latched’

status bits for voltage, current, and fault conditions. In case

of a fault shutdown, the real-time status bits may be cleared,

but the user can read the latched status bits and determine the

cause for the shutdown.

Real-Time Status Registers

Registers 0x14 to 0x16 are read-only (refer to Tables 6 - 8).

Table 6: Register 0x14 – Output Voltage Status During Startup/Shutdown

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

VGH > 90%

VGL > 90%

VCOM > 90%

AVDD > 90%

VGH > 30%

VGL > 30%

VCOM > 10%

AVDD > 10%

Each bit is set to ‘1’ when its corresponding regulator voltage is above threshold. They are only useful during startup and shutdown.

Table 7: Register 0x15 – Output Current Status During Operation

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

-

-

-

-

VGH ILimit

VGL ILimit

VCOM ILimit

AVDD ILimit

Each bit is set to ‘1’ when its corresponding regulator is operating at current limit. Note that those bits are ignored during startup phase (where all regulators must work at cur-

rent limit to charge up output capacitors quickly). During normal operation mode, it is acceptable for any regulator to reach its current limit momentarily. Only if the overcurrent

condition persists for 50 ms, then the FAULT pin is pulled down and a RailFault (Reg0x16 bit2) is recorded.

Table 8: Register 0x16 – Fault Status

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

FAULT

MaxRetry

WatchDog

SW ILimit2

SW OVP

Rail Fault

FSET fault

TSD

Explanation of each bit:

Bit7 = 1 if any Fault has occurred (it is not set in case of a POR or Hard-Reset).

Bit6 = 1 if the number of fault retries has reached MaxRetry limit.

Bit5 = 1 if the startup watchdog timer (Reg0x09) has expired before all output regulators can reach 90% target.

Bit4 = 1 if the boost switch current has exceeded its secondary OCP limit (150% of cycle-by-cycle current limit).

Bit3 = 1 if the boost switch voltage has exceeded its OVP threshold.

Bit2 = 1 if any output regulator reached its OCP limit for 50 ms.

Bit1 = 1 if the FSET pin is either open or shorted to GND.

Bit0 = 1 if a thermal shutdown has occurred.

DIAGNOSTIC REGISTERS