BU9794KV Datasheet, PDF (7/23 Pages) Rohm – For 200 Segment type LCD LCD Segment Driver

● Cautions in Power ON/OFF (BU9794KV)
○ Power supply sequence
Please keep Power ON/OFF sequence as below waveform.
VLCD
VDD
FigBU9794KV-5 Power supply sequence
○ Caution in P.O.R circuit use
This device has “P.O.R” (Power-On Reset) circuit and Software Reset function.
Please keep the following recommended Power-On conditions in order to power up properly.
Please set power up conditions to meet the recommended tR, tF, tOFF, and Vbot spec
below in order to ensure P.O.R operation
VDD
tF
tOFF
tR
Vbot
Recommendation condition of tR, tF, tOFF, Vbot (Ta=25℃)
tR
tF
tOFF
Vbot
Less than 5ms Less than 5ms More than Less than 0.3V
20ms
Fig. BU9794KV-6 Power ON/OFF waveform
If it is difficult to meet above conditions, execute the following sequence after Power-On.
But it is not able to accept Command input in Power off status, it has to take care that
software reset is not perfectly alternative method of POR function.
(1) CSB “L” “H”
VDD
CSB
Fig. BU9794KV-7 CSB timing
(2) CSB “L” , execute Software Reset command.
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