ST7558
Set VOP value:
The operation voltage VLCD can be set by software.
V0=( a + VOP×b )
(1)
The parameters are explained in table 4.The maximum voltage that can be generated is depending on the VDD voltage
and the display load current. Two overlapping VLCD ranges are selectable via the command “Booster control”. For the
LOW (PS=0) range a=a1 and for the HIGH (PRS=1) range a=a2 with steps equal to “b” in both ranges. Note that the
charge pump is turned off if VOP [6;0] and the bit PRS are all set to zero.
Table 4 Typical values for parameter for the HV-Generator programming
SYMBOL
VALUE
2.94(PRS=0)
6.75(PRS=1)
0.03
UNIT
a1
a2
b
V
V
V
V
L2
b
a2
a1+b
00 01 02 03 04 05 06 ..... 7D 7E 7F 00 01 02 03 04 05 06 ..... 7D 7E 7F
LOW (PRS=0)
HIGH(PRS=1)
VOP [6:0](programmed) {00 hex… 7F hex}
Fig.19 VOP programming of ST7558
Caution
As the programming range for the internally generated VLCDIN allows values above the max allowed VLCDIN, the
customer has to ensure while setting the VOP register that under all condition and including all tolerances the
VLCD limit of max. 13V will never be exceeded. As VLCDIN increases with lower temperatures, care must be taken
not to set a Vop generating a VLCDIN voltage that will exceed the maximum of 10.6V when operating at – 40 ℃.
Ver 2.3
32/56
2005/10/05
SITRONIX [ SITRONIX TECHNOLOGY CO., LTD. ]
