FUNCTIONAL DEVICE OPERATION
LOGIC COMMANDS AND REGISTERS
Here is how the SSTIME bits interacts with the SSSETx
register bits:
Percentage Change
0.00% (Default)
+2.50%
MSB
0
LSB
0
1. SSTIME is set by a value read through the SS pin.
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
2. SSTIME is copied into the bits SSSET5, SSSET6,
SSSET7, and SSSET8.
0
1
+5.00%
0
0
3. The soft start time of REG2, REG3, and REG4 are only
affected by the value of SSTIME bits.
+7.50%
0
1
4. The soft start time of REG5, REG6, REG7, and REG8
are affected by the value of bits SSSET5, SSSET6,
SSSET7, and SSSET8 respectively.
+10.00%
+12.50%
+15.00%
+17.50%
-20.00%
0
0
0
1
34704 assigns 2 bits to store the value programmed by the
SS pin. Bits SSTIME[1:0] can only be read by the user.
0
0
0
1
1
0
Soft Start
0.5ms
2ms
MSB
LSB
0
-17.50%
1
1
0
0
1
1
-15.00%
1
0
1
-12.50%
1
1
8ms
0
-10.00%
1
0
32ms
1
-7.50%
1
1
34704 assigns 2 bits for REG5 through REG8 to program
the soft start times for these regulators (SSSETx[1:0]) where
x corresponds to each regulator from REG5 through REG8.
-5.00%
1
0
-2.50%
1
1
On/Off Control for each group of regulators as defined
previously and for the whole IC
Soft Start
0.5ms
2ms
MSB
LSB
0
0
0
1
1
34704 assigns 1 bit per group to turn each group on/off
(ONOFFA, C, D, or E bits). Please note that GrpB does not
have a dedicated enable register which is enabled by default.
1
8ms
0
32ms
1
GrpA, C, D, or E ONOFF
OFF (Default)
ON
bit
0
REG8 Regulation Mode
The 34704 assigns 1 bit to indicate REG8’s regulation
mode (REG8MODE). The processor assigns this bit to either
regulation mode before enabling the REG8 output.
1
Also, 34704 assigns 1 bit (ALLOFF) for disabling the whole
IC through the I2C. (ALLOFF bit)
REG8 Regulation
Current (Default)
Voltage
bit
0
ALL OFF
False (Default)
True
bit
0
1
1
When REG8 is current regulated, LED backlight current
can be reduced from the maximum in 16 steps through
the I2C interface
Soft Start Time
There are two set of bits for setting the soft start value for
all of the regulators except REG1. The SSTIME[1:0] bits
reads the soft start value set by the SS pin and is used to
initially set the soft start value for all of the regulators except
REG1. Then, the SSSET bits for REG5 through REG8 can be
used to change the soft start value for these regulators from
the value set by the SSTIME.
The maximum LED current can be set using the external
resistor at the bottom of the LED string, then through I2C
programming, this current value can be reduced in 16 steps.
34704 assigns 4 bits for this function (ILED[3:0])
The ILED setting is not a guaranteed characteristic from
IMAX* (1/16) to IMAX* (9/16), due to an error amp common
mode limitation.
34704
Analog Integrated Circuit Device Data
Freescale Semiconductor
33
FREESCALE [ Freescale ]
