ISL97635 datasheet(21/28 Pages) RENESAS

21 / 28 page

ISL97635

FN6434 Rev.3.00

Page 21 of 28

Sep 26, 2017

• When an SMBus mode is selected, Register 0x00 reflects the

last value written to it. But, when any non-SMBus mode is

selected, Register 0x00 reflects the current brightness value

based on the current mode of operation, with the exception of

SMBus mode with DPST, where PWM_MD = 0 and

PWM_SEL = 0.

• 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 that the BL is

commanded on and then 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.

• The default value for Register 0x02 is 0x00.

Identification Register (0x03)

The ID register contains 3-bit fields to denote the LED driver (always

set to 1), manufacturer and the silicon revision of the controller IC.

The bit field widths allow up to 16 vendors with up to 8 silicon

revisions each. In order to keep the number of silicon revisions low,

the revision field will not be updated unless the part will make it out

to the user’s factory. Thus, if during the engineering development

process, 3 silicon spins were needed, the next available revision ID

would be used for all 3 spins until that same ID made it to the

factory. Except Bit 7, which has to be 1, all of the bits in this register

are read-only.

• Vendor ID 9 represents Intersil Corporation.

• The default value for Register 0x03 is 0xC8.

The initial value of REV shall be 0. Subsequent values of REV will

increment by 1.

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