MAX8738EUA Maxim Integrated Products, MAX8738EUA Datasheet - Page 8

• Manufacturer Part Number: MAX8738EUA
• Description: LCD Drivers
• Manufacturer: Maxim Integrated Products

Specifications of MAX8738EUA

• Maximum Clock Frequency: 100 KHz
• Operating Supply Voltage: 4.5 V to 20 V
• Maximum Power Dissipation: 362 mW
• Maximum Operating Temperature: + 85 C
• Package / Case: uMAX-8
• Maximum Supply Current: 60 uA
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX8738 is a solid-state alternative to mechanical
potentiometers used for adjusting the LCD backplane
voltage (VCOM) in TFT LCD displays. The MAX8738
attaches to an external resistive voltage-divider and
sinks a programmable current (I
VCOM level (Figure 2). An internal 7-bit DAC controls
the sink current and allows the user to increase or
decrease the VCOM level (Figure 3). The DAC is ratio-
metric relative to V
ating conditions. The user can store the DAC setting in
an internal EEPROM. On power-up, the EEPROM pre-
sets the DAC to the last stored setting. The 2-wire I
interface between the LCD panel and the programming
circuit adjusts the DAC and programs the EEPROM.
The resistive voltage-divider and the AVDD supply set
the maximum value of VCOM. The MAX8738 sinks cur-
rent from the voltage-divider to reduce the VCOM level.
The external resistor R
rent and the minimum value of VCOM.
The MAX8738 has an internal linear regulator that gen-
erates a 3.6V V
age. The V
and should not be used for external loads. AVDD
accepts voltages from 4.5V to 20V. Bypass AVDD and
V
Calibrator with I
Figure 3. Simplified Functional Diagram
8
DD
EEPROM-Programmable TFT VCOM
_______________________________________________________________________________________
to GND with a 0.1µF capacitor each.
BUS
I
DD
2
C
VGON
voltage supplies power to the MAX8738
DD
+3.3V
AVDD
voltage from the AVDD supply volt-
Detailed Description
SDA
SCL
SET
HV
and is monotonic over all oper-
sets the full-scale sink cur-
INTERFACE
CONTROL
V
DD
I
2
C
OUT
Supply Voltages
REGULATOR
7
LINEAR
), which sets the
7
AVDD and V
2
C Interface
DAC
EEPROM
BLOCK
19R
R
DD
2
C
The HV input provides the high voltage required to pro-
gram the EEPROM. The HV pin is typically connected to
the TFT LCD positive gate driver supply (VGON) supply.
VGON should be between 16.1V and 28V. EEPROM
programming is disabled when HV is below 15.6V (typ).
Bypass HV to GND with a 0.1µF capacitor.
The EEPROM programming block is turned off when
the MAX8738 first powers up, and also immediately
after the EEPROM is programmed. When the EEPROM
programming block is off, the HV supply current is less
than 1µA.
After the MAX8738 receives any command that
changes the DAC value, the EEPROM programming
block is enabled, and the HV supply current increases
to 15µA (typ). During the programming of the EEPROM,
the HV supply current may draw up to 60µA (max).
The external resistive voltage-divider sets the maximum
value of the VCOM adjustment range. R
full-scale sink current, I
mum value of the VCOM adjustment range. Large R
values increase resolution but decrease the VCOM
adjustment range. Calculate R1, R2, and R
the following procedure:
MAX8738
AVDD
GND
OUT
SET
Setting the VCOM Adjustment
AVDD
R1
R2
R
OUT
SET
, which determines the mini-
Range (R
SET
VCOM
SET
sets the
using
SET
HV
SET
)