BU97981KV-E2 Datasheet, PDF (38/50 Pages) Rohm – Multi-function LCD Segment Drivers

BU97981xxx Series MAX 196 segments (SEG49xCOM4)
Datasheet
Attention About Input Port Pull Down
Satisfy the following sequence if input terminals are pulled down by external resisters (In case MPU output Hi-Z).
CSB
Date transaction period with MPU
Input "L"
period
Input"Hi-Z"
period
SD
SCL
Figure 30. Recommended Sequence When Input Ports are Pulled Down
BU97981KV / BU9798MUV /BU97981GU 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 7, Figure 8;
I/O Equivalent Circuit)
A higher resistor than approximate 10Kωcauses 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 a MPU set SD and SCL lines to LOW before it releases the lines.
The LOW period preceding MPU‟s bus release shall be at least 50ns as same as a minimum CLK width ( tSLW ).
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10.Apr.2015 Rev.006