BU9794AKV Datasheet, PDF (18/26 Pages) Rohm – Standard LCD Segment Driver

BU9794AKV MAX 200 Segments (SEG50×COM4)
●Cautions on Power ON/OFF
○Power supply sequence
Please keep Power ON/OFF sequence as below waveform.
To prevent incorrect display, malfunction and abnormal current,
VDD must be turned on before VLCD In power up sequence.
VDD must be turned off after VLCD In power down sequence.
Please satisfies VLCD≥VDD, t1>0ns, t2>0ns
t1
t2
VLCD
VDD
10%
VDD min
10%
VDD min
Figure 20. Power supply sequence
○Caution on 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
tR
tOFF
Vbot
Recommended condition of tR, tF, tOFF, Vbot (Ta=25℃)
tR
tF
tOFF
Vbot
Less than
5ms
Less than
5ms
More than
20ms
Less than
0.3V
Figure 21. Power ON/OFF waveform
If it is difficult to meet above conditions, execute the following sequence after Power-On.
Command input is not accepted during power off. It has to take care that software reset is not perfect substitute to POR
function.
(1) CSB “L”→ “H”
VDD
CSB
Figure 22. CSB timing
(2) CSB→ “L”, execute SWRST command.
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TSZ02201-0A0A2D300010-1-2
10.Apr.2015 Rev.004