19-0793; Rev 4; 6/11
KIT
ATION
EVALU
BLE
AVAILA
TFT-LCD DC-DC Converter with
Operational Amplifiers
General Description
Features
o
2.5V to 5.5V Input Supply Range
o
1.2MHz Current-Mode Step-Up Regulator
Fast Transient Response to Pulsed Load
High-Accuracy Output Voltage (1%)
Built-In 20V, 3A, 0.16Ω n-Channel MOSFET
High Efficiency (85%)
o
Linear-Regulator Controllers for V
GON
and V
GOFF
o
High-Performance Operational Amplifiers
±130mA Output Short-Circuit Current
45V/µs Slew Rate
20MHz, -3dB Bandwidth
Rail-to-Rail Inputs/Outputs
o
Logic-Controlled, High-Voltage Switch with
Adjustable Delay
o
Timer-Delay Fault Latch for All Regulator Outputs
o
Thermal-Overload Protection
o
0.6mA Quiescent Current
MAX8795A
The MAX8795A includes a high-performance step-up
regulator, two linear-regulator controllers, and five high-
current operational amplifiers for active-matrix, thin-film
transistor (TFT), liquid-crystal displays (LCDs). Also
included is a logic-controlled, high-voltage switch with
adjustable delay.
The step-up DC-DC converter provides the regulated
supply voltage for the panel source driver ICs. The con-
verter is a high-frequency (1.2MHz) current-mode regu-
lator with an integrated 20V n-channel MOSFET that
allows the use of ultra-small inductors and ceramic
capacitors. It provides fast transient response to pulsed
loads while achieving efficiencies over 85%.
The gate-on and gate-off linear-regulator controllers
provide regulated TFT gate-on and gate-off supplies
using external charge pumps attached to the switching
node. The MAX8795A includes five high-performance
operational amplifiers. These amplifiers are designed to
drive the LCD backplane (VCOM) and/or the gamma-
correction divider string. The device features high out-
put current (±130mA), fast slew rate (45V/µs), wide
bandwidth (20MHz), and rail-to-rail inputs and outputs.
The MAX8795A is available in a lead-free, 32-pin, thin
QFN package with a maximum thickness of 0.8mm for
ultra-thin LCD panels, as well as in a 32-pin LQFP
package with 0.8mm pin pitch.
Minimal Operating Circuit
V
CN
V
CP
V
IN
LX
IN
STEP-UP
CONTROLLER
PGND
AGND
FB
V
MAIN
Applications
Notebook Computer Displays
LCD Monitor Panels
Automotive Displays
COMP
V
CP
MAX8795A
DRVP
GATE-ON
CONTROLLER
FBP
V
GON
SRC
DEL
COM
SWITCH
CONTROL
CTL
V
CN
DRN
Ordering Information
PART
MAX8795AETJ+
MAX8795AGCJ+
MAX8795AGTJ+
MAX8795AGTJ/V+
TEMP RANGE
-40°C to +85°C
-40°C to +105°C
-40°C to +105°C
-40°C to +105°C
PIN-PACKAGE
32 Thin QFN
32 LQFP
32 TQFN
32 TQFN
DRVN
GATE-OFF
CONTROLLER
V
GOFF
SUP
NEG1
FBN
OUT1
OP1
REF
NEG4
POS1
NEG2
REF
+Denotes
a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive-qualified part.
OUT2
OP2
OP4
OUT4
POS2
POS4
NEG5
OUT3
OP3
OP5
OUT5
POS3
EP
BGND
POS5
Pin Configurations appear at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
TFT-LCD DC-DC Converter with
Operational Amplifiers
MAX8795A
ABSOLUTE MAXIMUM RATINGS
IN, CTL to AGND ...................................................-0.3V to +7.5V
COMP, FB, FBP, FBN, DEL, REF to AGND ....-0.3V to (V
IN
+ 0.3V)
PGND, BGND to AGND ......................................................±0.3V
LX to PGND ............................................................-0.3V to +20V
SUP to AGND .........................................................-0.3V to +20V
DRVP to AGND.......................................................-0.3V to +36V
POS_, NEG_, OUT_ to AGND ...................-0.3V to (V
SUP
+ 0.3V)
DRVN to AGND ...................................(V
IN
- 30V) to (V
IN
+ 0.3V)
SRC to AGND .........................................................-0.3V to +40V
COM, DRN to AGND ................................-0.3V to (V
SRC
+ 0.3V)
DRN to COM............................................................-30V to +30V
POS_ to NEG_ RMS Current ...................................5mA (Note 1)
Note 1:
See Figure 2 for the op amp clamp structure.
OUT_ Maximum Continuous Output Current....................±75mA
LX Switch Maximum Continuous RMS Current .....................1.6A
Continuous Power Dissipation (T
A
= +70°C)
32-Pin Thin QFN (derate 34.5mW/°C above +70°C) 2758mW
32-Pin LQFP (derate 48.4mW/°C above +70°C)....1652.9mW
Operating Temperature Range, E Grade ............-40°C to +85°C
Operating Temperature Range, G Grade .........-40°C to +105°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
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.
ELECTRICAL CHARACTERISTICS
(V
IN
= 3V, V
MAIN
= V
SUP
= 14V, V
PGND
= V
AGND
= V
BGND
= 0V, I
REF
= 25µA,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
IN Supply Range
IN Undervoltage-Lockout
Threshold
SYMBOL
V
IN
V
UVLO
(Note 2)
V
IN
rising, typical hysteresis = 50mV
V
FB
= V
FBP
= 1.3V, V
FBN
= 0V,
LX not switching
IN Quiescent Current
I
IN
V
FB
= 1.2V, V
FBP
= 1.4V, V
FBN
= 0V,
LX switching
FB or FBP below threshold or FBN above
threshold
No external load
0 < I
LOAD
< 50µA
In regulation
Rising edge; typical hysteresis = 160mV
Temperature rising
Hysteresis
V
MAIN
f
OSC
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
V
IN
1000
86
V
FB
No load
V
FB
falling
0 < I
MAIN
< full load, transient only
V
IN
= 2.5V to 6V
V
FB
= 1.233V
1.221
1.212
1.10
1200
90
1.233
1.233
1.14
-1
0.1
+100
±0.4
+200
+160
15
18
1400
93
1.245
1.248
1.17
10
1.15
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
1.238
1.232
CONDITIONS
MIN
2.5
2.05
2.25
0.6
2
200
1.250
1.250
1.262
1.266
10
TYP
MAX
6.0
2.45
1.0
mA
3
ms
V
mV
µA
V
°C
UNITS
V
V
Duration-to-Trigger Fault
Condition
REF Output Voltage
REF Load Regulation
REF Sink Current
REF Undervoltage Lockout
Threshold
Thermal Shutdown
MAIN STEP-UP REGULATOR
Output Voltage Range
Operating Frequency
Oscillator Maximum Duty Cycle
FB Regulation Voltage
FB Fault Trip Level
FB Load Regulation
FB Line Regulation
FB Input Bias Current
V
kHz
%
V
V
%
%/ V
nA
2
_______________________________________________________________________________________
TFT-LCD DC-DC Converter with
Operational Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3V, V
MAIN
= V
SUP
= 14V, V
PGND
= V
AGND
= V
BGND
= 0V, I
REF
= 25µA,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
FB Transconductance
FB Voltage Gain
LX On-Resistance
LX Leakage Current
LX Current Limit
Current-Sense Transresistance
Soft-Start Period
Soft-Start Step Size
OPERATIONAL AMPLIFIERS
SUP Supply Range
SUP Overvoltage Fault Threshold
SUP Supply Current
Input Offset Voltage
Input Bias Current
Input Common-Mode Voltage
Range
Common-Mode Rejection Ratio
Open-Loop Gain
Output Voltage Swing, High
Output Voltage Swing, Low
Short-Circuit Current
Power-Supply Rejection Ratio
Slew Rate
-3dB Bandwidth
FBP Regulation Voltage
FBP Fault Trip Level
FBP Input Bias Current
FBP Effective Load-Regulation
Error (Transconductance)
FBP Line (IN) Regulation Error
DRVP Sink Current
DRVP Off-Leakage Current
Soft-Start Period
Soft-Start Step Size
t
SS
I
DRVP
I
FBP
V
FBP
R
L
= 10kΩ, C
L
= 10pF, buffer configuration
I
DRVN
= 100µA
V
FBP
falling
V
FBP
= 1.25V
V
DRVP
= 10V, I
DRVP
= 50µA to 1mA
I
DRVP
= 100µA, 2.5V < V
IN
< 6V
V
FBP
= 1.1V, V
DRVP
= 10V
V
FBP
= 1.4V, V
DRVP
= 34V
1
1.231
0.96
-50
-0.7
±1
5
0.01
14
V
REF
/
128
10
GATE-ON LINEAR-REGULATOR CONTROLLER
1.250
1.00
1.269
1.04
+50
-1.5
±10
V
V
nA
%
mV
mA
µA
ms
V
PSRR
V
OH
V
OL
I
OUT
_ = 5mA
I
OUT
_ = -5mA
To V
SUP
/ 2, source or sink
DC, 6V
≤
V
SUP
≤
18V,
(V
NEG
_, V
POS
_)
≅
V
SUP
/ 2
75
60
45
20
V
SUP
-
100
I
SUP
V
OS
I
BIAS
V
CM
CMRR
0
≤
(V
NEG
_, V
POS
_)
≤
V
SUP
Buffer configuration, V
POS
_ = V
SUP
/ 2,
no load
(V
NEG
_, V
POS
_, V
OUT
_)
≅
V
SUP
/ 2
(V
NEG
_ , V
POS
_, V
OUT
_)
≅
V
SUP
/ 2
-50
0
45
80
125
V
SUP
-
50
50
130
100
V
SUP
6.0
18.0
19
3.5
0
0
18.0
19.9
5.0
12
+50
V
SUP
V
V
mA
mV
nA
V
dB
dB
mV
mV
mA
dB
V/µs
MHz
t
SS
R
LX(ON)
I
LX
I
LIM
SYMBOL
CONDITIONS
∆I
COMP
=
±2.5µA
From FB to COMP
I
LX
= 200mA
V
LX
= 19V
V
FB
= 1.2V, duty cycle = 75%
2.5
0.1
MIN
75
TYP
160
700
160
10
3.0
0.2
14
V
REF
/
128
260
20
3.5
0.3
MAX
280
UNITS
µS
V/ V
mΩ
µA
A
V/A
ms
V
MAX8795A
_______________________________________________________________________________________
3
TFT-LCD DC-DC Converter with
Operational Amplifiers
MAX8795A
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3V, V
MAIN
= V
SUP
= 14V, V
PGND
= V
AGND
= V
BGND
= 0V, I
REF
= 25µA,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C,
unless otherwise noted.)
PARAMETER
FBN Regulation Voltage
FBN Fault Trip Level
FBN Input Bias Current
FBN Effective Load-Regulation
Error (Transconductance)
FBN Line (IN) Regulation Error
DRVN Source Current
DRVN Off-Leakage Current
Soft-Start Period
Soft-Start Step Size
POSITIVE GATE-DRIVER TIMING AND CONTROL SWITCHES
DEL Capacitor Charge Current
DEL Turn-On Threshold
DEL Discharge Switch
On-Resistance
CTL Input Low Voltage
CTL Input High Voltage
CTL Input Leakage Current
CTL-to-SRC Propagation Delay
SRC Input Voltage Range
SRC Input Current
SRC-to-COM Switch On-Resistance
DRN-to-COM Switch
On-Resistance
I
SRC
R
SRC(ON)
R
DRN(ON)
V
DEL
= 1.5V, CTL = IN
V
DEL
= 1.5V, CTL = AGND
V
DEL
= 1.5V, CTL = IN
V
DEL
= 1.5V, CTL = AGND
200
115
5
30
V
TH(DEL)
During UVLO, V
IN
= 2.0V
V
IN
= 2.5V to 5.5V
V
IN
= 2.5V to 5.5V
CTL = AGND or IN
2
-1
100
36
300
200
10
60
+1
During startup, V
DEL
= 1V
4
1.19
5
1.25
20
0.6
6
1.31
µA
V
Ω
V
V
µA
ns
V
µA
Ω
Ω
t
SS
I
DRVN
I
FBN
SYMBOL
V
FBN
CONDITIONS
I
DRVN
= 100µA, V
REF
- V
FBN
V
FBN
rising
V
FBN
= 0.25V
V
DRVN
= -10V, I
DRVN
= 50µA to 1mA
I
DRVN
= 0.1mA, 2.5V < V
IN
< 6V
V
FBN
= 300mV, V
DRVN
= -10V
V
FBN
= 0V, V
DRVN
= -25V
1
MIN
0.984
370
-50
11
±0.7
5
-0.01
14
(V
REF
-
V
FBN
) /
128
-10
TYP
1
420
MAX
1.015
470
+50
25
±5
UNITS
V
mV
nA
mV
mV
mA
µA
ms
V
GATE-OFF LINEAR-REGULATOR CONTROLLER
4
_______________________________________________________________________________________
TFT-LCD DC-DC Converter with
Operational Amplifiers
ELECTRICAL CHARACTERISTICS
(V
IN
= 3V, V
MAIN
= V
SUP
= 14V, V
PGND
= V
AGND
= V
BGND
= 0V, I
REF
= 25µA,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 3)
PARAMETER
IN Supply Range
IN Undervoltage-Lockout
Threshold
SYMBOL
V
IN
V
UVLO
(Note 2)
V
IN
rising, typical hysteresis = 150mV
V
FB
= V
FBP
= 1.3V, V
FBN
= 0V,
LX not switching
V
FB
= 1.2V, V
FBP
= 1.4V, V
FBN
= 0V,
LX switching
No external load
Rising edge; typical hysteresis = 160mV
1.218
CONDITIONS
MIN
2.5
2.05
MAX
6.0
2.45
1.0
mA
3
1.277
1.15
V
V
UNITS
V
V
MAX8795A
IN Quiescent Current
I
IN
REF Output Voltage
REF Undervoltage-Lockout
Threshold
MAIN STEP-UP REGULATOR
Output Voltage Range
Operating Frequency
FB Regulation Voltage
FB Line Regulation
FB Transconductance
LX On-Resistance
LX Current Limit
OPERATIONAL AMPLIFIERS
SUP Supply Range
SUP Overvoltage Fault Threshold
SUP Supply Current
Input Offset Voltage
Input Common-Mode Voltage
Range
Output Voltage Swing, High
Output Voltage Swing Low
Short-Circuit Current
I
SUP
V
OS
V
CM
V
OH
V
OL
V
SUP
R
LX(ON)
I
LIM
V
MAIN
f
OSC
V
FB
V
IN
900
No load
V
IN
= 2.5V to 6V
∆I
COMP
=
±2.5µA
I
LX
= 200mA
V
FB
= 1.2V, duty cycle = 75%
2.5
6
18.0
Buffer configuration, V
POS
_ = V
SUP
/ 2,
no load
(V
NEG
_, V
POS
_, I
OUT
_) =
≅
V
SUP
/ 2
0
I
OUT
_ = 5mA
I
OUT
_ = -5mA
To V
SUP
/ 2
Source
Sink
75
75
1.210
V
SUP
-
100
75
1.198
18
1400
1.260
±0.4
280
260
3.5
18
19.9
5
12
V
SUP
V
kHz
V
%/ V
µS
mΩ
A
V
V
mA
mV
V
mV
100
mA
GATE-ON LINEAR-REGULATOR CONTROLLER
FBP Regulation Voltage
FBP Effective Load-Regulation
Error (Transconductance)
FBP Line (IN) Regulation Error
DRVP Sink Current
I
DRVP
V
FBP
I
DRVP
= 100µA
V
DRVP
= 10V, I
DRVP
= 50µA to 1mA
I
DRVP
= 100µA, 2.5V < V
IN
< 6V
V
FBP
= 1.1V, V
DRVP
= 10V
1
1.280
-1.5
10
V
%
mV
mA
_______________________________________________________________________________________
5
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