BUF08630_14 Datasheet, PDF (9/35 Pages) Texas Instruments – Programmable Gamma-Voltage Generator and High Slew Rate VCOM

BUF08630
www.ti.com
SBOS515A – OCTOBER 2010 – REVISED AUGUST 2012
APPLICATION INFORMATION
GENERAL DESCRIPTION
The BUF08630 programmable voltage reference
allows fast and easy adjustment of eight
programmable gamma reference outputs and a V_COM
output, each with 10-bit resolution. The BUF08630 is
programmed through a high-speed, two-wire
interface. The final gamma and V_COM values can be
stored in the onboard, nonvolatile memory. To allow
for programming errors or liquid crystal display (LCD)
panel rework, the BUF08630 supports up to 16 write
operations to the onboard memory. The BUF08630
has two separate memory banks, allowing
simultaneous storage of two different gamma curves
to facilitate dynamic switching between gamma
curves.
The BUF08630 can be powered using an analog
supply voltage from 9 V to 20 V, and a digital supply
from 2 V to 5.5 V. The digital supply must be applied
before the analog supply to avoid excessive current
and power consumption, or possibly even damage to
the device if left connected only to the analog supply
for extended periods of time. In addtion, analog
supply voltage V_S should be turned on before V_SH.
Power-Up Sequence
When applying power to the BUF08630, the digital
supply must be powered up first. The analog supply
for the V_COM amplifier (V_COM-VS), and the analog
supply (V_S) should be brought up at least 1.2 ms later
so that the programmed values in the nonvolatile
memory can be written to the DAC registers. The
analog supply voltage (V_COM-VS) must always preceed
V_S, or the two supply pins should be tied together so
that they turn on and off simultaneously. The supply
voltage V_SH must always follow V_S.
It is recommended that the TPS65168 be used
together with the BUF08630 for best performance, as
shown in Figure 24. Note that the TPS65168 provides
the power sequence previously described and
required by the BUF08630.
Figure 20 shows the proper power-up sequence
when two supplies are used (that is, V_S and V_COM-VS
are connected together).Figure 21 shows the proper
power-up sequence when three supplies are used
(that is, V_SH, V_S, and V_COM-VS are separate supplies).
16
14
12
10
8
6
4
2
0
0
Digital Supply
V_S
V_SH
V_S and V_COM−VS May
Come Up Together
2
4
6
8
Time (ms)
Figure 20. Startup Requirement with Two
Supplies
16
Digital Supply
14
V_COM−VS
V_S
12
V_SH
10
CAUTION
If V_COM-VS is brought up
after V_S, damage will occur
to the analog switches for
V_COM.
8
6
4
2
V_S and V_COM−VS May
Come Up Together
0
0
2
4
6
8
Time (ms)
Figure 21. Startup Requirement with Three
Supplies
Copyright © 2010–2012, Texas Instruments Incorporated
Product Folder Links: BUF08630
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