SM8133B Datasheet, PDF (11/20 Pages) Nippon Precision Circuits Inc – White LED Driver IC

SM8133B
FUNCTIONAL DESCRIPTION
Serial Interface
The SM8133B uses a 3-wire serial interface to control each setting. Input data on SDA is input MSB first in an
8 clock pulse cycle structure, with the first 4 cycles of data setting the mode and the next 4 the corresponding
mode data. Data bits on SDA are read as received data on the rising edges of the SCK clock after EN goes
HIGH. Only the leading 8 bits on SDA are read after EN goes HIGH and all subsequent input data bits are
ignored, but the received data is reflected in SM8133B operation with timing almost simultaneous with the EN
falling edge. Conversely, if less than 8 bits are input on SDA, the data is ignored to prevent incorrect operation.
All registers are write-only, and their status cannot be read. After power is applied, an internal power-ON reset
circuit initializes all registers to logic level LOW in standby mode. However, the possibility exists that there
may be insufficient reset time, depending on the VIN input voltage rise time and fall time, so reset mode (0H or
EH) should be expressly invoked after power is applied. There is no restriction in the input sequence when set-
ting parameters. However, since the parameters are set in the same order as the data input sequence and the
time taken from LED ON/OFF data input to LED dimming data input can exceed the soft start time, it is highly
advisable to enter the LED dimming data first. The charge pump circuit, that supplies the LED drive voltage,
starts whenever any parameter in address 5H (LED ON register) is set to 1, with the LED drive voltage output
on VOUT. Conversely, when all parameters in address 5H are set to 0, all other parameter data settings input
after reset are retained in standby mode. The serial interface pins EN, SDA, CSK, and RESETB are CMOS
inputs, thus the input voltage on VIN must be a logic-level voltage and should not be left open circuit (floating).
Control Data
Mode selection data
Setting data
M1
M2
M3
M4
D1
D2
D3
D4
MSB
Data 1
Data 2
Data 3
Data 4
Data 5
Data 6
LSB
EN
SCK
SDA
M1
M2
M3
M4
D1
D2
D3
D4
I Mode selection
Mode data
Mode
M1-M2-M3-M4
Mode data
Mode
M1-M2-M3-M4
0H
Reset
L-L-L-L
5H
LED ON
L-H-L-H
Control data input sequence
1H
Grouping
L-L-L-H
6H
System settings
L-H-H-L
2H
A group dimming
L-L-H-L
EH
Reset
H-H-H-L
3H
B group dimming
L-L-H-H
FH
Serial input test
H-H-H-H
4H
DIN7 dimming
L-H-L-L
Other
NPC test
−
NIPPON PRECISION CIRCUITS INC.—11