ISL97635A datasheet(21/29 Pages) RENESAS

21 / 29 page

ISL97635A

FN6564 Rev.3.00

Page 21 of 29

Sep 26, 2017

• When SMBus mode with DPST is selected, register 0x00

reflects the last value written to it from SMBus.

• When a write to register 0x01 (Device Control Register) causes

the backlight controller to transition to an SMBus mode, the

brightness of the BL does not change. On the other hand, when

a write to register 0x01causes the backlight controller to

transition to a non-SMBus mode, the brightness of the BL

changes as appropriate for the new mode.

• The default value for register 0x01 is 0x00.

Fault/Status Register (0x02)

This register has six status bits that allow monitoring of the

backlight controller’s operating state. Bit 0 is a logical “OR” of all

fault codes to simplify error detection. Not all of the bits in this

remaining bits are reserved and return a “0” when read and ignore

the bit value when written. All of the bits in this register are

read only, with the exception of Bit 0, which can be cleared by

writing to it.

• A Read Byte cycle to register 0x02 indicates the current BL

on/off status in BL_STAT (1 if the BL is on, 0 if the BL is off).

• A Read Byte cycles to register 0x2 also returns FAULT as the

logical OR of THRM_SHDN, OV_CURR, 2_CH_SD, and 1_CH_SD

should these events occur.

• 1_CH_SD returns a 1 if one or more channels have faulted out.

• 2_CH_SD returns a 1 if two or more channels have faulted out.

• A fault will not be reported in the event the BL is commanded

on and immediately off by the system.

• When FAULT is set to 1, it will remain at 1 even if the signal

which sets it goes away. FAULT will be cleared when the

BL_CTL bit of the Device Control Register is toggled or when

written low. At that time, if the fault condition is still present or

reoccurs, FAULT will be set to 1 again. BL_STAT will not cause

FAULT to be set

• The controller will not indicate a fault if the VBL+ goes away,

whether or not the LEDs were on at the time of the power loss.

This can occur if there is some hang condition that causes the

user to force the system off by holding the power button down

for 4s.

Default value for register 0x02 is 0x00.

FAULT/STATUS REGISTER

RESERVED

2_CH_SD

1_CH_SD

BL_STAT

OV_CURR

THRM_SHDN

FAULT

Bit 7 (R)

Bit 6 (R)

Bit 5 (R)

Bit 4 (R)

Bit 3 (R)

Bit 2 (R)

Bit 1 (R)

Bit 0 (R)

BIT

BIT ASSIGNMENT

BIT FIELD DEFINITIONS

Bit 5

2_CH_SD

= Two LED output channels are shutdown (1 = shutdown, 0 = OK)

Bit 4

1_CH_SD

= One LED output channel is shutdown (1 = shutdown, 0 = OK)

Bit 3

BL_STAT

= BL Status (1 = BL On, 0 = BL Off)

Bit 2

OV_CURR

= Input Overcurrent (1 = Overcurrent condition, 0 = Current OK)

Bit 1

THRM_SHDN

= Thermal Shutdown (1 = Thermal Fault, 0 = Thermal OK)

Bit 0

FAULT

= Fault occurred (Logic “OR” of all of the fault conditions)

FIGURE 26. DESCRIPTIONS OF FAULT/STATUS REGISTER

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