BU97941FV_15 Datasheet, PDF (19/27 Pages) Rohm – Multifunction LCD Segment Driver

BU97941FV MAX 104 segments (SEG26×COM4)
●Attention about using LEDCTL(85h) command
Please input CSB="H" after LEDCTL command is issued. To avoid noise and reset interface.
LEDCTL (85h)
CSB
Parameter
2nd Command
SCL
SD
1 0 0 0 0 1 0 1 _{0 0} 0 0 P3 P2 P1 P0
D/C ^{D6 D5 D4 D3 D2 D1 D0 D/C} _D6
Figure 18. Recommended sequence when using LEDCTL (85h) command
●Attention about input port pull down
Satisfy the following sequence if input terminals are pulled down by external resistors (In case MPU output Hi-Z).
CSB
Date transaction period with MPU
Input "L"
period
Input"Hi-Z"
period
SD
SCL
Figure 19. Recommended sequence when input ports are pulled down
BU97941FV adopts a 5V tolerant I/O for the digital input. This circuit includes a bus-hold function to keep the level of HIGH.
A pull down resistor of below 10KΩshall be connected to the input terminals to transit from HIGH to LOW because the
bus-hold transistor turns on during the input‟s HIGH level. (Refer to the Figure 5. I/O Equivalent Circuit)
A higher resistor than 10KΩ (approximate) causes input terminals being steady by intermediate potential between HIGH and
LOW level so unexpected current is consumed by the system.
The potential depends on the pull down resistance and bus-hold transistor‟s resistance.
As the bus-hold transistor turns off upon the input level cleared to LOW a higher resistor can be used as a pull down resistor
if an MPU sets SD and SCL lines to LOW before it releases the lines.
The LOW period preceding the MPU‟s bus release shall be at least 50ns as same as a minimum CLK width ( tSLW ).
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