MAX1512 Datasheet, PDF (10/12 Pages) Maxim Integrated Products – EEPROM-Programmable TFT VCOM Calibrator

EEPROM-Programmable TFT VCOM Calibrator
To avoid unintentional VCOM adjustment, the MAX1512
is guaranteed to reject CTL pulses shorter than 20µs. In
addition, to avoid the possibility of a single false pulse
caused by power-up sequencing between V_DD and
CTL, the very first pulse is ignored.
CTL VOLTAGE
V_PP
V_DD / 2
0
T1
T2
T3
T4
TIME
Figure 7. EEPROM Programming
EEPROM Programming (CTL)
To program the EEPROM, apply the EEPROM program-
ming waveform through the CTL interface (Figure 7).
The control interface delivers programming power and
DAC adjustment commands on the same wire. This
1-wire approach minimizes the number of connections
from the programming circuit to the LCD panel.
To apply the EEPROM programming waveform, carefully
ramp CTL from midscale (V_DD / 2) to the programming
voltage, V_PP, in 7.5ms as shown in Figure 7. If the ramp
is generated digitally, use at least 45 steps to achieve
the required 320mV ramp resolution. During the ramp
time, VCOM adjustment is disabled and the EEPROM
cells are biased in preparation for programming. After
reaching V_PP, hold CTL at V_PP for 1ms. During the
EFPROM program time, the EEPROM stores the DAC
setting. Next, drive CTL to ground in less than 1ms and
hold for at least 200µs. Finally, drive CTL to V_DD / 2 to
complete the write cycle. The EEPROM is factory set to
half scale. Follow the EEPROM Programming Spec-
ifications in Table 1 to guarantee reliable EEPROM pro-
gramming. Violating the specifications can damage the
EEPROM or affect data retention.
A complete evaluation kit is available to simplify evalua-
tion and production development.
Table 1. EEPROM Programming Specifications
PARAMETER
SYMBOL
MIN
TYP
CTL Programming Voltage
V_PP
15.25
15.5
CTL Programming Ramp
T1
7.0
7.5
EEPROM Program Time
T2
0.9
1.0
V_PP Fall Time
Done Hold Time
T3
10
T4
200
MAX
15.75
8.0
1.1
1000
UNITS
V
ms
ms
µs
µs
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