MAX9679
12-Channel, 10-Bit Programmable Gamma
and VCOM Reference Voltages
General Description
The MAX9679 provides multiple programmable
reference voltages for gamma correction in TFT LCDs
and a programmable reference voltage for VCOM
adjustment. All gamma and VCOM reference voltages
have a 10-bit digital-to-analog converter (DAC) and high-
current buffer, which reduces the recovery time of the
output voltages when critical levels and patterns are
displayed. A programmable internal reference sets the
full-scale voltage of the DACs.
Two independent sets of gamma curves and VCOM
codes can be stored in the IC's volatile memory; BKSEL
signal selects between the two sets.
The IC has multiple-time programmable (MTP) memory
to store gamma and VCOM codes on the chip, eliminat-
ing the need for external EEPROM.
Features
S
12 Channels of Programmable Gamma Voltages
with 10-Bit Resolution
S
Programmable VCOM Voltage with 10-Bit
Resolution
S
Programmable Reference for DACs
S
Multiple-Time Programmable Memory to Store
Gamma and VCOM Codes
S
Switching Between Two Gamma Curves and
VCOM Voltages
S
AVDD1, AVDD2, and AVDD_AMP Supplies to
Reduce Heat
S
I
2
C Interface (1MHz Fast-Mode Plus)
Ordering Information
PART
MAX9679ETG+
TEMP RANGE
-40NC to +85NC
PIN-PACKAGE
24 TQFN-EP*
Applications
TFT LCDs
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Simplified Block Diagram
BKSEL
MTP
REG
PROG
REF
I
2
C
REG
PROG
REF
DAC
REG
PROG
REF
PROG
REF
MAX9679
GAMMA
BANK 1
GAMMA
BANK 1
GAMMA
BANK 1
2:1
MUX
12 DACs
12 GAMMA
BUFFERS
12
GAMMA
OUTPUTS
GAMMA
BANK 2
GAMMA
BANK 2
VCOM1
VCOM1
VCOM2
VCOM1
VCOM2
2:1
MUX
DAC
VCOM
AMPLIFIER
VCOM
OUTPUT
I
2
C
CONTROL
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-5756; Rev 2; 5/13
MAX9679
12-Channel, 10-Bit Programmable Gamma
and VCOM Reference Voltages
Functional Diagram
BKSEL
AVDD1
PROG
REF
PROG
REF
PROG
REF
10
PROG
REF
V
PREF
10
10
10
GAMMA
BANK 1
GAMMA
BANK 1
GAMMA
BANK 1
10
10
10
DAC
DAC
DAC
DAC
DAC
DAC
GMA1
GMA2
GMA3
GMA4
GMA5
GMA6
MTP
MEMORY
I
2
C
REG
DAC
REG
2:1
MUX
10
10
10
AGND
AVDD2
GMA7
GMA8
GMA9
GMA10
GMA11
GMA12
DAC
DAC
DAC
DAC
DAC
DAC
GAMMA
BANK 2
GAMMA
BANK 2
10
10
10
AGND
AVDD_AMP
VCOM1
VCOM1
VCOM2
VCOM1
VCOM2
2:1
MUX
10
DAC
VCOM
VCOM_FB
DVDD
SDA
SCL
A0
I
2
C
INTERFACE
AGND
MAX9679
12 GAMMA, 1 VCOM
2
Maxim Integrated
MAX9679
12-Channel, 10-Bit Programmable Gamma
and VCOM Reference Voltages
Typical Application Circuit
12V
PMIC
BKSEL
AVDD1
PROG
REF
PROG
REF
PROG
REF
10
PROG
REF
V
PREF
10
10
10
GAMMA
BANK 1
GAMMA
BANK 1
GAMMA
BANK 1
10
10
10
DAC
DAC
DAC
DAC
DAC
DAC
GMA1
GMA2
GMA3
GMA4
GMA5
GMA6
SOURCE
DRIVER
CHIP
SERVICE
DRIVER
CHIP
TO LCD
PANEL
MTP
MEMORY
I
2
C
REG
I
2
C
REG
2:1
MUX
AGND
AVDD2
HVDD
10
10
10
GAMMA
BANK 2
GAMMA
BANK 2
10
10
10
DAC
DAC
DAC
DAC
DAC
DAC
GMA7
GMA8
GMA9
GMA10
GMA11
GMA12
AGND
AVDD_AMP
HVDD
VCOM1
VCOM1
VCOM2
VCOM1
VCOM2
2:1
MUX
10
DAC
VCOM
TO LCD PANEL
VCOM_FB
DVDD
TCON
SDA
SCL
A0
I
2
C
INTERFACE
AGND
MAX9679
12 GAMMA, 1 VCOM
Maxim Integrated
3
MAX9679
12-Channel, 10-Bit Programmable Gamma
and VCOM Reference Voltages
(All voltages are with respect to AGND.)
Supply Voltages
AVDD1, AVDD2, AVDD_AMP ............................-0.3V to +22V
DVDD ...................................................................-0.3V to +4V
Outputs
GMA1–GMA6...................................-0.3V to (V
AVDD1
+ 0.3V)
GMA7–GMA12.................................-0.3V to (V
AVDD2
+ 0.3V)
VCOM ....................................... -0.3V to (V
AVDD_AMP
+ 0.3V)
Inputs
SDA, SCL, A0, BKSEL .........................................-0.3V to +6V
VCOM_FB ................................. -0.3V to (V
AVDD_AMP
+ 0.3V)
ABSOLUTE MAXIMUM RATINGS
Continuous Current
SDA, SCL.....................................................................
Q20mA
GMA1–GMA8.............................................................
Q200mA
VCOM ........................................................................
Q600mA
Continuous Power Dissipation (T
A
= +70NC)
TQFN Multilayer Board
(derate 25.6mW/NC above +70NC) .........................2051.3mW
Junction Temperature .....................................................+125NC
Operating Temperature Range .......................... -40NC to +85NC
Storage Temperature Range............................ -65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
TQFN
Junction-to-Ambient Thermal Resistance (q
JA
) ..........39°C/W
Junction-to-Case Thermal Resistance (q
JC
) .................6°C/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to
www.maximintegrated.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(V
AVDD1
= 18V, V
AVDD2
= V
AVDD_AMP
= 9V, V
DVDD
= 3.3V, V
AGND
= 0V, VCOM = VCOM_FB, programmable reference code = 905,
no load, T
A
= -40NC to +85NC, unless otherwise noted. Typical values are at T
A
= +25NC.) (Note 2)
PARAMETER
SUPPLIES
AVDD1 Analog Supply Voltage
Range
AVDD2 Analog Supply Voltage
Range
AVDD_AMP Analog Supply
Voltage Range
Digital Supply Voltage
Slowest DVDD Ramp-Up Time
AVDD1 Analog Quiescent
Current
AVDD2 Quiescent Current
AVDD_AMP Quiescent Current
Digital Quiescent Current
Thermal Shutdown
Thermal-Shutdown Hysteresis
Undervoltage-Lockout Threshold
Analog Supply Voltage Range
for Programming MTP
4
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
AVDD1
V
AVDD2
Guaranteed by PSRR
Guaranteed by PSRR
9
6
9
2.7
20
20
20
3.6
25
7
6
5
11
9
8
3
V
V
V
V
ms
mA
mA
mA
mA
NC
NC
V
AVDD_AMP
Guaranteed by PSRR
V
DVDD
DVDD ramp-up time from 1.5V to 2.3V to
ensure correct MTP loading
I
AVDD1
I
AVDD2
I
AVDD_AMP
I
DVDD
No SCL or SDA transitions
20
1.5
+160
15
UVLO
DVDD undervoltage-lockout threshold
2.1
15
2.3
2.6
20
V
V
Maxim Integrated
MAX9679
12-Channel, 10-Bit Programmable Gamma
and VCOM Reference Voltages
ELECTRICAL CHARACTERISTICS (continued)
(V
AVDD1
= 18V, V
AVDD2
= V
AVDD_AMP
= 9V, V
DVDD
= 3.3V, V
AGND
= 0V, VCOM = VCOM_FB, programmable reference code = 905,
no load, T
A
= -40NC to +85NC, unless otherwise noted. Typical values are at T
A
= +25NC.) (Note 2)
PARAMETER
Full-Scale Voltage
Resolution
Integral Nonlinearity Error
Differential Nonlinearity Error
DAC
Resolution
Integral Nonlinearity Error
Differential Nonlinearity Error
GAMMA
Short-Circuit Current
Total Output Error
Output connected to either supply rail
T
A
= +25NC, code = 768 for
GMA1–GMA6 and code = 256 for GMA7–
GMA12
-5mA
P
I
LOAD
P
+5mA, code = 768 for
GMA1–GMA6 and code = 256 for
GMA7–GMA12
Sinking 4mA, referred to lower supply rail
Sourcing 4mA, referred to upper supply rail
GMA1–GMA6, code = 768, V
AVDD1
= 9V
to 20V; GMA7–GMA12, code = 256,
V
AVDD2
= 5V to 20V
GMA1–GMA6, code = 768,
frequency = 120kHz; GMA7–GMA12,
code = 256, frequency = 120kHz
Buffer is disabled
Placed directly at output
RMS noise (10MHz bandwidth)
Output connected to either VCOM
amplifier supplies
T
A
= +25NC, code = 256,
V
AVDD_AMP
= 9V and 20V
-80mA
P
I
LOAD
P
+80mA, code = 256
Sinking 10mA, referred to lower
supply rail
Sourcing 10mA, referred to upper
supply rail
-0.2
-0.2
60
200
40
mA
mV
T
A
= +25NC, 16
P
code
P
1008 for gamma,
256
P
code
P
1008 for VCOM
T
A
= +25NC, 16
P
code
P
1008 for gamma,
256
P
code
P
1008 for VCOM
10
0.5
0.5
1
1
Bits
LSB
LSB
T
A
= +25NC, 336
P
reference code
P
1007
T
A
= +25NC, 336
P
reference code
P
1007
SYMBOL
CONDITIONS
Referred to output, T
A
= +25NC
MIN
19.96
10
0.5
0.5
1
1
TYP
19.98
MAX
20.00
UNITS
V
Bits
LSB
LSB
PROGRAMMABLE REFERENCE (V
PREF
)
Load Regulation
Low Output Voltage
High Output Voltage
0.5
0.15
-0.15
90
0.2
mV/mA
V
V
Power-Supply Rejection Ratio
dB
40
78
150
375
kI
pF
FV
Output Resistance
Maximum Capacitive Load
Noise
VCOM OUTPUT (VCOM)
Short-Circuit Current
Total Output Error
Load Regulation
Low Output Voltage
High Output Voltage
600
40
0.5
0.15
-0.15
0.2
mA
mV
mV/mA
V
V
Maxim Integrated
5
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