MAX1512 Datasheet, PDF (6/12 Pages) Maxim Integrated Products – EEPROM-Programmable TFT VCOM Calibrator

EEPROM-Programmable TFT VCOM Calibrator
Pin Description
PIN
NAME
FUNCTION
Adjustable Sink-Current Output. OUT connects to the resistive voltage-divider between AVDD and GND that
1
OUT sets the VCOM voltage. I_OUT lowers the divider voltage by an adjustable amount. See the SET pin
description.
2
AVDD High-Voltage Analog Supply. Connects to the panel source-driver supply rail.
3
N.C. No Connect. Not internally connected.
4
GND Ground
5
V_DD Supply Input. +2.6V to +3.6V input range.
VCOM Adjustment and EEPROM Programming Control. CTL sets the internal DAC code and programs the
EEPROM. A pulse-control method is used to adjust the VCOM level. See the VCOM Adjustment (CTL)
6
CTL section. To program the DAC setting into the EEPROM as the power-on default, drive CTL to the EEPROM
programming voltage using the correct timing and voltage ramp rates. See the EEPROM Programming
(CTL) section.
7
CE
Control Interface Enable. Connect CE to V_DD to enable the CTL input. Connect CE to GND to disable the
CTL input and reduce the supply current.
Full-Scale Sink-Current Adjustment Input. Connect a resistor, R_SET, from SET to GND to set the full-scale
8
SET ^{adjustable sink current. The full-scale adjustable sink current is equal to:}
 V_AVDD  _{IOUT is equal to the current through RSET.}
 20 × R_SET 
Detailed Description
The MAX1512 is a solid-state alternative to mechanical
V_DD
potentiometers used for adjusting the LCD backplane
3V
voltage (VCOM) in TFT LCD displays. The MAX1512
attaches to an external resistive voltage-divider and
AVDD
10V
sinks a programmable current (I_OUT), which sets the
V_DD
VCOM level (Figure 1). An internal 7-bit DAC controls
CE
AVDD
the sink current and allows the user to increase or
decrease the VCOM level (Figure 2). The DAC is ratio-
metric relative to AVDD and is monotonic over all oper-
MAX1512
R1
200kΩ
ating conditions. The user can store the DAC setting in
OUT
VCOM
an internal EEPROM. On power-up, the EEPROM pre-
R2
5V
sets the DAC to the last stored setting. The single-wire
interface between the LCD panel and the programming
245kΩ
CTL
SET
circuit adjusts the DAC, programs the EEPROM, and
GND
provides programming power.
R_SET
The resistive voltage-divider and the AVDD supply set
25kΩ
the maximum value of VCOM. The MAX1512 sinks cur-
rent from the voltage-divider to reduce the VCOM level.
The external resistor R_SET sets the full-scale sink cur-
rent and the minimum value of VCOM.
Figure 1. Standard Application Circuit
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