ISL97635_14 Datasheet, PDF (21/28 Pages) Intersil Corporation – SMBus 8-Channel LED Driver

ISL97635
• 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 6 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
register are fault related (Bit 3 is a simple BL status indicator).
The 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.
21
FN6434.2
December 22, 2008