19-5241; Rev 0; 4/10
TION KIT
EVALUA BLE
IL
AVA A
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
The MAX17117 includes a high-performance step-up
regulator, a 350mA low-dropout (LDO) linear regulator,
a high-speed operational amplifier, and a high-voltage
level-shifting scan driver with gate-shading control. The
device is optimized for thin-film transistor (TFT) liquidcrystal display (LCD) applications.
The step-up DC-DC converter provides the regulated
supply voltage for panel source-driver ICs. The high
1.2MHz switching frequency allows the use of ultra-small
inductors and ceramic capacitors. The current-mode
control architecture provides a fast-transient response to
pulsed loads typical of source driver loads. The step-up
regulator features an adjustable soft-start and an adjustable cycle-by-cycle current limit.
S High-Performance Operational Amplifier
200mA Output Short-Circuit Current
40V/µs Slew Rate
16MHz, -3dB Bandwidth
Low-Dropout Linear Regulator
High-Accuracy Output Voltage (1.0%)
S High-Voltage Drivers with Scan Logic
+35V to -15V Outputs
40V Maximum Voltage Swing
Gate-Shading Control
S Thermal-Overload Protection
S 32-Pin, 5mm x 5mm, Thin QFN Package
Simplified Operating Circuit
The high-current operational amplifier is designed to
drive the LCD backplane (VCOM). The amplifier features
high output current (Q200mA typ), fast slew rate (40V/Fs
typ), wide bandwidth (16MHz typ), and rail-to-rail inputs
and outputs.
The MAX17117 is available in a 32-pin, 5mm x 5mm, thin
QFN package with a maximum thickness of 0.8mm for
thin LCD panels.
MAX17117ETJ+
TEMP RANGE
PIN-PACKAGE
-40NC to +85NC
32 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
VGHON
VIN
VMAIN
LX
PGND
FB
COMP
LDOADJ
SS
AGND
(EP)
LINEAR
REGULATOR
LDOO
VLOGIC
DTS
MAX17117
GATESHADING
TIMING
CONTROL
OPAS
OUT
OP
TO VCOM
BACKPLANE
POS
VGHON
GHON
ST
STH
CK1
CKH1
CK3
CKH3
CKH5
CK5
S1
SYSTEM
S3
S5
SCAN DRIVER AND
GATE-SHADING
CONTROL LOGIC
Applications
Notebook Computer Displays
Features
RO
CK2
CKH2
CK4
CKH4
PANEL
CKH6
CK6
S 2.3V to 5.5V IN Supply-Voltage Range
S 1.2MHz Current-Mode Step-Up Regulator
Fast-Transient Response
High-Accuracy Reference (1%)
Integrated 16V, 2A, 200mI MOSFET
High Efficiency (> 85%)
Adjustable Cycle-by-Cycle Current Limit
SETUP
CONTROLLER
ENA
Ordering Information
PART
VVGL
IN
The low-voltage LDO linear regulator has an integrated
0.8I pass element and can provide at least 350mA. The
output voltage is accurate within Q1%.
The high-voltage, level-shifting scan driver with gateshading control is designed to drive the TFT panel gate
drivers. Its seven outputs swing 40V (maximum) between
+35V (maximum) and -15V (minimum) and can swiftly
drive capacitive loads.
MAX17117
General Description
S2
S4
S6
RE
VGLC
VVGL
VGL
________________________________________________________________ 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.
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
ABSOLUTE MAXIMUM RATINGS
IN, ENA, FB, COMP, SS, DTS, LDOADJ, ST,
CK1–CK6, LDOO to AGND................................-0.3V to +7.5V
PGND to AGND.....................................................-0.3V to +0.3V
LX, OPAS to PGND................................................-0.3V to +18V
GHON to PGND.....................................................-0.3V to +45V
VGL to PGND........................................................ -20V to +0.3V
GHON to VGL..................................................................... +45V
STH, CKH1–CKH6, VGLC, RO,
RE to VGL..........................................-0.3V to (VGHON + 0.3V)
OUT, POS to PGND...............................-0.3V to (VOPAS + 0.3V)
GHON and VGL RMS Current Rating...................................0.8A
VGLC, STH, and CKH1–CKH6 RMS Current Rating............0.8A
LX, PGND RMS Current Rating.............................................1.6A
Continuous Power Dissipation (TA = +70NC)
32-Pin TQFN (derate 24.9mW/NC above +70NC)........1990mW
Operating Temperature Range........................... -40NC to +85NC
Junction Temperature......................................................+150NC
Storage Temperature Range............................. -65NC to +160NC
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.
ELECTRICAL CHARACTERISTICS
(VIN = +3V, Circuit of Figure 1, VOPAS = +8.5V, VGHON = +24V, VVGL = -6.2V, VST = VCK_ = 0V, TA = 0NC to +85NC, unless otherwise
noted. Typical values are at TA = +25NC.)
PARAMETER
CONDITIONS
MAX
UNITS
5.5
V
2.00
2.20
V
VFB = 1.3V, LX not switching
1.0
2.5
VFB = 1.2V, LX switching
2.5
5
IN Standby Current
VENA = VVGL = 0V, VIN = 5.5V, VGHON = 4V
0.7
2
mA
GHON Standby Current
VENA = VVGL = 0V, VIN = 5.5V, VGHON = 4V
100
200
FA
OPAS Standby Current
VENA = VVGL = 0V, VIN = 5.5V, VGHON = 4V
20
50
FA
Thermal Shutdown
Temperature rising
145
OPAS rising
16.5
17
18
V
1000
1200
1400
kHz
91
94
97
%
V
IN Input Voltage Range
IN Undervoltage-Lockout
Threshold
IN Quiescent Current
MIN
TYP
2.3
VIN rising, typical hysteresis = 150mV
1.80
170
mA
NC
STEP-UP REGULATOR
Output Voltage Range
OPAS Overvoltage Threshold
VIN
Operating Frequency
Oscillator Maximum Duty Cycle
15
FB Regulation Voltage
No load
1.227
1.240
1.252
FB Fault-Trip Level
Falling edge
1.05
1.10
1.15
Fault-Trigger Delay
FB Load Regulation
160
V
V
ms
0 < ILOAD < full load
-0.2
FB Line Regulation
VIN = 2.5V to 5.5V, TA = +25NC
0.1
0.25
%/V
FB Input-Bias Current
VFB = 1.24V, TA = +25NC
65
200
nA
FB Transconductance
DICOMP = Q2.5FA, FB = COMP
75
160
280
FS
2
2.4
A
LX On-Resistance
RENA = 10kW, duty cycle = 60%
ILX = 1A
1.6
200
500
mI
LX Input-Bias Current
VLX = 13.5V, TA = +25NC
LX Current Limit
Current-Sense Transresistance
Soft-Start Pullup Current
%
10
20
FA
0.10
0.20
0.30
V/A
2
4
6
FA
2 _______________________________________________________________________________________
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
(VIN = +3V, Circuit of Figure 1, VOPAS = +8.5V, VGHON = +24V, VVGL = -6.2V, VST = VCK_ = 0V, TA = 0NC to +85NC, unless otherwise
noted. Typical values are at TA = +25NC.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
15
V
0.8
1.2
mA
VCOM BUFFER
OPAS Voltage Range
5
OPAS Supply Current
VPOS = VOPAS/2, no load
OUT Voltage Swing High
IOUT = 5mA
OUT Voltage Swing Low
IOUT = 5mA
VOPAS
- 100
VOPAS
- 50
Sourcing, short to VOPAS/2 - 1V
100
200
Sinking, short to VOPAS/2 + 1V
100
200
POS Input-Bias Current
VPOS = VOPAS/2, TA = +25NC
-50
POS Input-Offset Voltage
VOUT = VOPAS/2
-15
OUT Short-Circuit Current
50
Gain-Bandwidth Product
-3dB Bandwidth
RLOAD = 10kI, CLOAD = 10pF
Slew Rate
5V pulse applied to POS, OUT measured from 10% to
90%
10
mV
100
mV
mA
+50
+15
nA
mV
8
MHz
16
MHz
40
V/Fs
HIGH-VOLTAGE SCAN DRIVER
GHON Voltage Range
12
35
V
VGL Voltage Range
-15
-3
V
40
V
550
FA
GHON-to-VGL Voltage Range
VGHON - VVGL
GHON Supply Current
CK1 through CK6 and ST low
VGL Supply Current
CK1 through CK6 and ST low
Output Impedance Low
STH, CKH_, VGLC, IOUT = -20mA
80
I
Output Impedance High
STH, CKH_, VGLC, IOUT = +20mA
80
I
CKH1, CKH3, CKH5, IRE = 10mA
100
CKH2, CKH4, CKH6, IRO = 10mA
100
Gate-Shading Switch Resistance
RO, RE Resistance Range
Propagation Delay from ST
Rising Edge to STH Rising Edge
350
-500
-300
FA
100
I
I
CLOAD = 100pF, RLOAD = 0I
100
200
ns
Propagation Delay from ST
CLOAD = 100pF, RLOAD = 0I
Falling Edge to STH Falling Edge
100
200
ns
Propagation Delay from CK_
Rising Edge to CKH_ Rising
Edge
CLOAD = 100pF, RLOAD = 0I
100
200
ns
Propagation Delay from CK_
Falling Edge to CKH_ Falling
Edge
CLOAD = 100pF, RLOAD = 0I
100
200
ns
STH, VGLC, CKH_ Rise Time
CLOAD = 5nF, RLOAD = 0I; VGHON = 30V,
VVGL = -10V; measured from 10% to 90%
0.5
1
Fs
STH, VGLC, CKH_ Fall Time
CLOAD = 5nF, RLOAD = 0I; VGHON = 30V,
VVGL = -10V; measured from 10% to 90%
0.5
1
Fs
100
kHz
STH, CKH_ Operating Frequency
CLOAD = 5nF, RLOAD = 0I
Range
_______________________________________________________________________________________ 3
MAX17117
ELECTRICAL CHARACTERISTICS (continued)
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +3V, Circuit of Figure 1, VOPAS = +8.5V, VGHON = +24V, VVGL = -6.2V, VST = VCK_ = 0V, TA = 0NC to +85NC, unless otherwise
noted. Typical values are at TA = +25NC.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
100
150
mV
10
15
µA
10
50
I
1.240
1.265
V
100
150
mV
GATE-SHADING TIMING CONTROL
Gate-Shading Detection
Threshold
DTS falling
Gate-Shading Detection Current
VDTS = 0.5V
DTS Switch Resistance
VDTS = 1.3V, IDTS = 1mA
5
DTS Rising Edge Threshold
1.215
DTS Falling Edge Threshold
LDO
LDOO Output Voltage Range
VIN
V
Dropout Voltage
VIN = 3.3V, VLDOADJ = 1.1V, ILDOO = 350mA
1.8
300
500
mV
LDOO Line Regulation
VIN = 2.8V to 5.5V, VLDOO = 2.5V, ILDOO = 100mA
0.1
0.3
%/V
LDOO Load Regulation
VLDOO = 2.5V, ILDOO = 1mA to 300mA
LDOO Current Limit
VLDOADJ = 1.0V
LDOADJ Feedback Voltage
LDOADJ Input-Bias Current
0.2
0.5
%/V
0.4
0.62
0.8
A
1.227
1.240
1.252
V
100
200
nA
VLDOADJ = 1.3V, TA = +25NC
DIGITAL INPUTS
ST, CK_ Input High Level
1.8V < VLDOO < 5.5V
ST, CK_ Input Low Level
1.8V < VLDOO < 5.5V
ENA Input Logic-High Level
1.8V < VLDOO < 3.0V
VLDOO > 3.0V
ENA Input Logic-Low Level
0.7 x
VLDOO
V
0.3 x
VLDOO
0.7 x
VLDOO
V
2.1
V
0.3 x
VLDOO
1.8V < VLDOO < 3.0V
VLDOO > 3.0V
ENA Resistor Range
V
0
V
0.8
V
200
kI
ELECTRICAL CHARACTERISTICS
(VIN = +3V, Circuit of Figure 1, VOPAS = +8.5V, VGHON = +24V, VVGL = -6.2V, VST = VCK_ = 0V, TA = -40NC to +85NC, unless otherwise noted.)
PARAMETER
CONDITIONS
IN Input Voltage Range
IN Undervoltage-Lockout
Threshold
IN Quiescent Current
VIN rising, typical hysteresis = 150mV
MIN
MAX
UNITS
2.3
TYP
5.5
V
1.80
2.20
V
VFB = 1.3V, LX not switching
2.5
mA
VFB = 1.2V, LX switching
5
IN Standby Current
VENA = VVGL = 0V, VIN = 5.5V, VGHON = 4V
2
mA
GHON Standby Current
VENA = VVGL = 0V, VIN = 5.5V, VGHON = 4V
160
FA
OPAS Standby Current
VENA = VVGL = 0V, VIN = 5.5V, VGHON = 4V
50
FA
Thermal Shutdown
Temperature rising
145
4 _______________________________________________________________________________________
NC
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
(VIN = +3V, Circuit of Figure 1, VOPAS = +8.5V, VGHON = +24V, VVGL = -6.2V, VST = VCK_ = 0V, TA = -40NC to +85NC, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
STEP-UP REGULATOR
Output Voltage Range
OPAS Overvoltage Threshold
OPAS rising
Operating Frequency
Oscillator Maximum Duty Cycle
VIN
15
V
16.5
18
V
1000
1400
kHz
91
97
%
V
FB Regulation Voltage
No load
1.227
1.252
FB Fault-Trip Level
Falling edge
1.05
1.15
V
FB Line Regulation
VIN = 2.5V to 5.5V, TA = +25NC
0.3
%/V
FB Input-Bias Current
VFB = 1.3V, TA = +25NC
200
nA
FB Transconductance
DICOMP = Q2.5FA, FB = COMP
75
280
FS
LX Current Limit
VFB = 1.2V, duty cycle = 60%
1.6
2.4
A
LX On-Resistance
ILX = 1A
500
mI
LX Input-Bias Current
VLX = 13.5V, TA = +25NC
Current-Sense Transresistance
Soft-Start Pullup Current
20
FA
0.10
0.30
V/A
2
6
FA
VCOM BUFFER
OPAS Voltage Range
5
OPAS Supply Current
VPOS = VOPAS/2, no load
OUT Voltage Swing High
IOUT = 5mA
OUT Voltage Swing Low
IOUT = 5mA
15
V
1.2
mA
VOPAS
- 100
mV
100
mV
Sourcing, short to VOPAS/2 - 1V
100
Sinking, short to VOPAS/2 + 1V
100
POS Input-Bias Current
VPOS = VOPAS/2, TA = +25NC
-50
+50
nA
POS Input-Offset Voltage
VOUT = VOPAS/2
-15
+15
mV
Slew Rate
5V pulse applied to POS, OUT measured from 10% to
90%
10
OUT Short-Circuit Current
mA
V/Fs
HIGH-VOLTAGE SCAN DRIVER
GHON Voltage Range
12
VGL Voltage Range
-15
35
V
-3
V
GHON-to-VGL Voltage Range
VGHON - VVGL
40
V
GHON Supply Current
CK1 through CK6 and ST low
550
FA
VGL Supply Current
CK1 through CK6 and ST low
Output Impedance Low
STH, CKH_, VGLC, IOUT = -20mA
80
I
Output Impedance High
STH, CKH_, VGLC, IOUT = +20mA
80
I
CKH1, CKH3, CKH5, IRE = 10mA
100
CKH2, CKH4, CKH6, IRO = 10mA
100
Gate-Shading Switch Resistance
RO, RE Resistance Range
Propagation Delay from ST
Rising Edge to STH Rising Edge
-500
FA
100
CLOAD = 100pF, RLOAD = 0I
I
I
200
ns
_______________________________________________________________________________________ 5
MAX17117
ELECTRICAL CHARACTERISTICS (continued)
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +3V, Circuit of Figure 1, VOPAS = +8.5V, VGHON = +24V, VVGL = -6.2V, VST = VCK_ = 0V, TA = -40NC to +85NC, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Propagation Delay from ST
CLOAD = 100pF, RLOAD = 0I
Falling Edge to STH Falling Edge
200
ns
Propagation Delay from CK_
Rising Edge to CKH_ Rising Edge
CLOAD = 100pF, RLOAD = 0I
200
ns
Propagation Delay from CK_
Falling Edge to CKH_ Falling
Edge
CLOAD = 100pF, RLOAD = 0I
200
ns
STH, VGLC, CKH_ Rise Time
CLOAD = 5nF, RLOAD = 0I; VGHON = 30V,
VVGL = -10V; measured from 10% to 90%
1
Fs
STH, VGLC, CKH_ Fall Time
CLOAD = 5nF, RLOAD = 0I; VGHON = 30V,
VVGL = -10V; measured from 10% to 90%
1
Fs
100
kHz
100
150
mV
10
15
µA
50
I
STH, CKH_ Operating Frequency
CLOAD = 5nF, RLOAD = 0I
Range
GATE-SHADING TIMING CONTROL
Gate-Shutdown Detection
Threshold
DTS falling
Gate-Shutdown Detection Current VDTS = 0.5V
DTS Switch Resistance
VDTS = 1.3V, IDTS = 1mA
DTS Rising Edge Threshold
5
1.210
DTS Falling Edge Threshold
1.265
V
150
mV
LDO
LDOO Output Voltage Range
VIN
V
Dropout Voltage
VIN = 3.3V, VLDOADJ = 1.1V, ILDOO = 350mA
1.8
500
mV
LDOO Line Regulation
VIN = 2.8V to 5.5V, VLDOO = 2.5V, ILDOO = 100mA
0.3
%/V
LDOO Load Regulation
VLDOO = 2.5V, ILDOO = 1mA to 300mA
0.5
LDOO Current Limit
VLDOADJ = 1.0V
%/V
A
LDOADJ Feedback Voltage
LDOADJ Input-Bias Current
0.4
0.8
1.227
1.252
V
200
nA
VLDOADJ = 1.3V, TA = +25NC
DIGITAL INPUTS
ST, CK_ Input High Level
1.8V < VLDOO < 5.5V
ST, CK_ Input Low Level
1.8V < VLDOO < 5.5V
ENA Input Logic-High Level
1.8V < VLDOO < 3.0V
VLDOO > 3.0V
ENA Input Logic-Low Level
0.7 x
VLDOO
0.3 x
VLDOO
0.7 x
VLDOO
V
V
2.1
0.3 x
VLDOO
1.8V < VLDOO < 3.0V
VLDOO > 3.0V
ENA Resistor Range
V
V
0.8
0
6 _______________________________________________________________________________________
200
kI
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
STEP-UP REGULATOR LINE REGULATION
vs. INPUT VOLTAGE
VIN = 2.3V
VIN = 3.0V
60
0.10
IMAIN = 0mA
0.10
VIN = 5.0V
0
MAX17117 toc03
MAX17117 toc02
IMAIN = 200mA
0.15
0.05
50
-0.10
VIN = 2.3V
-0.20
-0.30
VIN = 3.0V
-0.40
VMAIN = 8.5V
0
40
10
1
100
-0.50
2.7
2.3
1000
3.1
LOAD CURRENT (mA)
3.5
3.9
4.3
4.7
5.1
5.5
1
10
IN VOLTAGE (V)
2.5
1000
STEP-UP REGULATOR LOAD-TRANSIENT
RESPONSE (20mA TO 300mA)
MAX17117 toc05
MAX17117 toc04
3.0
100
LOAD CURRENT (mA)
STEP-UP CONVERTER PEAK INDUCTOR
CURRENT LIMIT vs. RENA
VLX
10V/div
0V
INDUCTOR
CURRENT
2.0
1A/div
0A
1.5
VMAIN
0V
VIN = 3.3V
VMAIN = 8.5V
VLDO = 2.5V
L1 = 10µH
1.0
200mA/div
50
L1 = 10µH
RCOMP = 56.2kI
CCOMP = 1000pF
20mA
0.5
0
(AC-COUPLED)
200mV/div
IMAIN
100
150
200
250
100µs/div
RENA (kI)
STEP-UP REGULATOR PULSED
LOAD-TRANSIENT RESPONSE (20mA TO 1A)
MAX17117 toc06
0.10
0V
VLX
10V/div
0A
INDUCTOR
CURRENT
500mA/div
0V
VMAIN
(AC-COUPLED)
100mV/div
IMAIN
1A/div
20mA
10µs/div
L1 = 10µH
RCOMP = 56.2kI
CCOMP = 1000pF
VIN = 5.0V
0
MAX17117 toc07
LDO OUTPUT LOAD REGULATION
vs. LOAD CURRENT
LOAD-REGULATION ERROR (%)
PEAK INDUCTOR CURRENT LIMIT (A)
EFFICIENCY (%)
80
70
0.20
LINE REGULATION (%)
VIN = 5.0V
90
0.25
MAX17117 toc01
100
STEP-UP REGULATOR OUTPUT LOAD
REGULATION vs. LOAD CURRENT
LOAD-REGULATION ERROR (%)
STEP-UP REGULATOR EFFICIENCY
vs. LOAD CURRENT
-0.10
VIN = 3.0V
-0.20
-0.30
-0.40
-0.50
1
10
100
1000
LOAD CURRENT (mA)
_______________________________________________________________________________________ 7
MAX17117
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
POWER-UP SEQUENCE
(CK1 AND ST CONNECTED TO VLDO)
LDO LINE REGULATION
vs. INPUT VOLTAGE
MAX17117 toc09
MAX17117 toc08
0.15
0.12
LINE REGULATION (%)
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
0V
0V
0V
0.09
ILDO = 250mA
0V
0V
0.06
VIN
5V/div
VLDO
5V/div
VMAIN
10V/div
VGHON
20V/div
VVGL
10V/div
VSTH
0V
0.03
ILDO = 100mA
50V/div
VCKH1
0V
0V
0
2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4
50V/div
VVGLC
20V/div
40ms/div
IN VOLTAGE (V)
OPERATIONAL AMPLIFIER
LOAD-TRANSIENT RESPONSE
OPERATIONAL AMPLIFIER
LARGE-SIGNAL STEP RESPONSE
MAX17117 toc10
MAX17117 toc11
VVCOM
(AC-COUPLED)
1V/div
VPOS
2V/div
0V
0mV
VVCOM
2V/div
IVCOM
100mA/div
0mA
0V
2µs/div
200ns/div
OPERATIONAL AMPLIFIER
SMALL-SIGNAL STEP RESPONSE
CKH_ OUTPUT WAVEFORMS WITH LOGIC
INPUT AND GATE-SHADING CONTROL
MAX17117 toc12
MAX17117 toc13
VPOS
(AC-COUPLED)
100mV/div
0mV
VCK1
5V/div
VCK2
5V/div
VDTS
2V/div
0V
0V
0V
VVCOM
(AC-COUPLED)
100mV/div
0mV
VCKH1
20V/div
0V
VCKH2
20V/div
0V
200ns/div
4µs/div
8 _______________________________________________________________________________________
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
FB
COMP
OPAS
POS
OUT
RO
GHON
VGL
24
23
22
21
20
19
18
17
TOP VIEW
16
PGND 25
STH
LX 26
15
CKH1
ENA 27
14
CKH2
13
CKH3
12
CKH4
11
CKH5
10
CKH6
9
VGLC
IN 28
MAX17117
LDOO 29
LDOADJ 30
DTS 31
EP
+
1
2
3
4
5
6
7
8
CK5
CK4
CK3
CK2
CK1
ST
CK6
RE
SS 32
THIN QFN
Pin Description
PIN
NAME
1–5, 7
CK5–CK1,
CK6
FUNCTION
6
ST
Start-Pulse, Level-Shifter Logic-Level Input
8
RE
Gate-Shading Discharge for CKH2, CKH4, and CKH6
9
VGLC
VGL Voltage Output
10–15
CKH6–CKH1
Level-Shifter Outputs
16
STH
Start-Pulse Level-Shifter Output
17
VGL
Gate-Off Supply. VGL is the negative supply voltage for the STH, CKH1–CKH6, and VGLC high-voltage driver outputs. Bypass to PGND with a minimum of 0.1FF ceramic capacitor.
18
GHON
19
RO
20
OUT
Operational Amplifier Output
21
POS
Operational Amplifier Noninverting Input
22
OPAS
Operational Amplifier Supply Input. Connect to VMAIN (Figure 1) and bypass to AGND with a 0.1FF or
greater ceramic capacitor.
23
COMP
Compensation for Error Amplifier. Connect a series RC from this pin to AGND. Typical values are
56kI and 1000pF.
24
FB
Level-Shifter Logic-Level Inputs
Gate-On Supply. GHON is the positive supply voltage for the STH, CKH1–CKH6, and VGLC highvoltage scan-driver outputs. Bypass to PGND with a minimum of 0.1FF ceramic capacitor.
Gate-Shading Discharge for CKH1, CKH3, and CKH5
Step-Up Regulator Feedback. Reference voltage is 1.24V nominal. Connect the midpoint of an external resistor-divider to FB and minimize trace area. Set VMAIN according to VMAIN = 1.24V (1 + R1/R2).
_______________________________________________________________________________________ 9
MAX17117
Pin Configuration
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
Pin Description (continued)
PIN
NAME
FUNCTION
25
PGND
26
LX
27
ENA
Chip-Enable Control and OCP Set Input. When ENA = low, the step-up converter and op amp are
disabled, the LDO remains active, and the level-shifter outputs are high impedance.
28
IN
Step-Up Regulator and Low-Dropout Regulator Supply. Bypass IN to AGND with a 1FF or greater
ceramic capacitor.
Power Ground. Source connection of the internal step-up regulator power switch.
Switching Node. Connect inductor/catch diode here and minimize trace area for lowest EMI.
29
LDOO
30
LDOADJ
31
DTS
Gate-Shading Discharge Time Adjust
32
SS
Step-Up Regulator Soft-Start Control
—
EP
Exposed Backside Pad. Connect to the analog ground plane for proper electrical and thermal
performance.
Internal Linear Regulator Output. Bypass LDOO to AGND with a 1FF capacitor.
Linear Regulator Feedback Input. Reference voltage is 1.24V nominal.
10
�������������������������������������������������������������������������������������
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
0.22µF
D2
86.6I
VVGL
-6.0V, 10mA
0.1µF
2.2µF
D5
6.2V,
200mW
L1
10µH
D1
8.5V, 200mA
IN
ENA
C5
10µF
C4
10µF
LX
R1
102kI
FB
LDOADJ
COMP
RCOMP
56.2kI
CCOMP
1000pF
SS
LDOO
VLOGIC
DTS
MAX17117
R2
17.4kI
CSS
0.33µF
AGND
(EP)
C1
1µF
CSET
100pF
C6
10µF
PGND
R6
49.9kI
RSET
29.4kI
VMAIN
C3
10µF
C2
1µF
R5
51.1kI
D4
0.1µF
0.22µF
VIN
RENA
62kI
OPAS
0.1µF
OUT
TO VCOM
BACKPLANE
R3
56.2kI
GHON
VGHON
VGHON
23V, 25mA
POS
0.1µF
R4
56.2kI
STH
ST
CKH1
CK1
CKH3
CK3
CKH5
CK5
RO
SYSTEM
R0
1kI
PANEL
CK2
CKH2
CK4
CKH4
CK6
CKH6
RE
RE
1kI
VGL
VVGL
0.1µF
VGLC
Figure 1. Typical Application Circuit
______________________________________________________________________________________ 11
MAX17117
D3
0.1µF
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
Table 1. Component List
DESIGNATION
DESCRIPTION
C1, C2
1FF ±10%, 16V X5R ceramic capacitors
(0603)
Murata GRM188R61C105K
TDK C1608X5R1C105K
C3
10FF Q10%, 10V X5R ceramic capacitor
(0805)
TDK C2012X5R1A106K
Murata GRM21BR61A106K
C4, C5, C6
D1
D2, D3, D4
10FF Q10%, 16V X5R ceramic capacitors (1206)
Murata GRM31CR61C106K
TDK C3216X5R1C106K
1A, 30V Schottky diode (S-Flat)
Central CMMSH1-40 LEAD FREE
Nihon EP10QY03
Toshiba CRS02 (TE85L, Q, M)
200mA, 100V dual diodes (SOT23)
Fairchild MMBD4148SE (Top Mark: D4)
Central CMPD7000+ (Top Mark: C5C)
D5
6.2V, 200mW zener diode (SOD-323)
ROHM UDZSTE-176.2B
Fairchild MM3Z6V2B
L1
10FH, 1.85A, 74.4mI inductor (6mm x
6mm x 3mm)
Sumida CDRH5D28RHPNP-100M
Typical Application Circuit
The MAX17117 typical application circuit (Figure 1) generates a +8.5V source-driver supply and approximately
+23V and -6V gate-driver supplies for TFT displays. The
input voltage range for the IC is from +2.3V to +5.5V,
but the circuit in Figure 1 is designed to run from 2.5V to
3.6V. Table 1 lists the recommended components and
Table 2 lists the component suppliers.
Detailed Description
The MAX17117 includes a high-performance step-up
regulator, a 350mA low-dropout (LDO) linear regulator,
a high-speed operational amplifier, and a high-voltage,
level-shifting scan driver with gate-shading control.
Figure 2 shows the functional diagram.
Step-Up Regulator
The step-up regulator employs a peak current-mode
control architecture with a fixed 1.2MHz switching frequency that maximizes loop bandwidth and provides
a fast-transient response to pulsed loads found in
source drivers of TFT LCD panels. The high switching
frequency allows the use of low-profile inductors and
ceramic capacitors to minimize the thickness of LCD
panel designs. The integrated high-efficiency MOSFET
reduces the number of external components required.
The output voltage can be set from VIN to 15V with an
external resistive voltage-divider.
Table 2. Component Suppliers
SUPPLIER
WEBSITE
Central Semiconductor Corp.
www.centralsemi.com
Fairchild Semiconductor
www.fairchildsemi.com
Murata Electronics North America, Inc.
www.murata-northamerica.com
Nihon Inter Electronics Corp.
www.niec.co.jp
ROHM Co., Ltd.
www.rohm.com
Sumida Corp.
www.sumida.com
TDK Corp.
www.component.tdk.com
Toshiba America Electronic Components, Inc.
www.toshiba.com/taec
12
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Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
VVGL
VMAIN
VIN
IN
LX
PGND
ENA
FB
SET-UP
CONTROLLER
LDOADJ
COMP
SS
AGND
(EP)
LINEAR
REGULATOR
LDOO
VLOGIC
MAX17117
GATESHADING
TIMING
CONTROL
DTS
OPAS
OUT
OP
SDTS
VGHON
TO VCOM
BACKPLANE
POS
GHON
ST
STH
CK1
CKH1
CK3
CKH3
CK5
CKH5
S1
SYSTEM
S3
S5
CK2
SCAN DRIVER
AND GATESHADING
CONTROL LOGIC
RO
PANEL
CKH2
CKH4
CK4
CKH6
CK6
S2
S4
S6
RE
VGLC
VVGL
VGL
Figure 2. Functional Diagram
______________________________________________________________________________________ 13
MAX17117
VGHON
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
The regulator controls the output voltage and the power
delivered to the output by modulating the duty cycle (D)
of the internal power MOSFET in each switching cycle.
The duty cycle of the MOSFET is approximated by:
V
− VIN
D ≈ MAIN
VMAIN
Figure 3 shows the step-up regulator block diagram.
An error amplifier compares the signal at FB to 1.24V
and changes the COMP output. The voltage at COMP
determines the current trip point each time the internal
MOSFET turns on. As the load varies, the error amplifier
sources or sinks current to the COMP output accordingly to produce the inductor peak current necessary to
service the load. To maintain stability at high duty cycles,
a slope compensation signal is summed with the currentsense signal.
On the rising edge of the internal clock, the controller sets
a flip-flop, turning on the n-channel MOSFET and applying the input voltage across the inductor. The current
through the inductor ramps up linearly, storing energy in
its magnetic field. Once the sum of the current-feedback
signal and the slope compensation exceed the COMP
voltage, the controller resets the flip-flop and turns off
the MOSFET. Since the inductor current is continuous,
a transverse potential develops across the inductor that
turns on the diode (D1). The voltage across the inductor
then becomes the difference between the output voltage
and the input voltage. This discharge condition forces
the current through the inductor to ramp back down,
transferring the energy stored in the magnetic field to the
output capacitor and the load. The MOSFET remains off
for the rest of the clock cycle.
Undervoltage Lockout (UVLO)
The UVLO circuit compares the input voltage at IN with
the UVLO threshold (2.0V typ) to ensure that the input
voltage is high enough for reliable operation. The 150mV
(typ) hysteresis prevents supply transients from causing a restart. Once the input voltage exceeds the UVLO
rising threshold, startup begins. When the input voltage
falls below the UVLO falling threshold, the controller
turns off the main step-up regulator.
LX
CLOCK
LOGIC AND
DRIVER
PGND
ILIM
COMPARATOR
ILIMIT
SLOPE COMP
1.2MHz
OSCILLATOR
TO FAULT LOGIC
PWM
COMPARATOR
CURRENT
SENSE
FB
1.10V
FAULT
COMPARATOR
ERROR AMP
1.24V
COMP
Figure 3. Step-Up Regulator Block Diagram
14
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Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
Overcurrent Protection
The step-up regulator features an adjustable cycleby-cycle current limit. The inductor current is sensed
through the LX switch during the LX switch on-time. If
the peak inductor current rises above the current-limit
threshold set by RENA, the LX switch immediately turns
off until the next switching cycle, effectively limiting the
peak-inductor current each cycle.
Soft-Start
The soft-start feature effectively limits the inrush current
at startup by slowly raising the regulation voltage of the
step-up converter’s feedback pin (VFB) at a rate determined by the selection of the soft-start capacitor (CSS).
At startup, once ENA is pulled high through RENA, an
internal 4FA (typ) current source begins to charge the
soft-start capacitor (CSS), slowly bringing up the voltage at the soft-start pin (VSS). VFB follows VSS for VSS <
1.24V. Once VSS exceeds 1.24V, VFB remains at 1.24V,
allowing VMAIN to reach its full regulation voltage.
Fault Protection
During steady-state operation, the MAX17117 monitors
the FB voltage. If the FB voltage falls below 1.1V (typ),
the MAX17117 activates an internal fault timer. If there is
a continuous fault more than 160ms (typ), the MAX17117
sets the fault latch, turning off all outputs except LDOO.
Once the fault condition is removed, cycle the input voltage to clear the fault latch and reactivate the device. The
fault-detection circuit is disabled during the soft-start time.
Operational Amplifier
The MAX17117 has an operational amplifier that is
typically used to drive the LCD backplane (VCOM) or
the gamma-correction-divider string. The operational
amplifier features Q200mA (typ) output short-circuit current, 40V/Fs (typ) slew rate, and 16MHz (typ) bandwidth.
While the op amp is a rail-to-rail input and output design,
its accuracy is significantly degraded for input voltages
within 1V of its supply rails (OPAS and AGND).
Short-Circuit Current Limit
The operational amplifier limits short-circuit current to
approximately Q200mA (typ) if the output is directly
shorted to OPAS or to AGND. If the short-circuit condition persists, the junction temperature of the IC rises until
it reaches the thermal-shutdown threshold (+170NC typ).
Once the junction temperature reaches the thermal-shutdown threshold, an internal thermal sensor immediately
shuts down all outputs until the input voltage is cycled
off, then on again.
Driving Pure Capacitive Loads
The operational amplifier is typically used to drive the
LCD backplane (VOUT) or the gamma-correction-divider
string. The LCD backplane consists of a distributed
series capacitance and resistance, a load that can be
easily driven by the operational amplifier. However, if the
operational amplifier is used in an application with a pure
capacitive load, steps must be taken to ensure stable
operation. As the operational amplifier’s capacitive load
increases, the amplifier’s bandwidth decreases and gain
peaking increases. A 5I to 50I small resistor placed
between VOUT and the capacitive load reduces peaking, but also reduces the gain. An alternative method
of reducing peaking is to place a series RC network
(snubber) in parallel with the capacitive load. The RC
network does not continuously load the output or reduce
the gain. Typical values of the resistor are between 100I
and 200I and the typical value of the capacitor is 10pF.
High-Voltage Scan Driver
The high-voltage, level-shifting scan driver with gateshading control is designed to drive the TFT panel
gate drivers. Its seven outputs swing 40V (maximum)
between +35V (maximum) and -15V (minimum) and can
swiftly drive capacitive loads. The driver outputs (STH,
CKH_) swing between their power-supply rails (GHON
and VGL), according to the input logic levels on their
corresponding inputs (ST, CK_) except during a gateshading period. During a gate-shading period, a CKH_
output driver becomes high impedance and an internal
switch connected between the CKH_ output’s capacitive load and either RO or RE closes (S1–S6) whenever
the state of its corresponding CK_ input is logic-low.
This allows part of an output’s GHON-to-VGL transition
to be completed by partially discharging its capacitive
load through an external resistor attached to either RO
or RE for a duration set by the gate-shading period. See
Figure 4.
______________________________________________________________________________________ 15
MAX17117
Overvoltage Protection
The MAX17117 monitors OPAS for an overvoltage condition. If the OPAS voltage is above 17V (typ), the
MAX17117 disables the gate driver of the step-up regulator and prevents the internal MOSFET from switching. The
OPAS overvoltage condition does not set the fault latch.
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
If the gate-shading control is enabled, a gate-shading
period is initiated by a falling edge of a CK_ input whenever VDTS is less than 100mV. Once the gate-shading
period is initiated, a switch across CSET (SDTS) opens,
allowing CSET to be charged through RSET. Once VDTS
reaches 1.24V, SDTS closes to discharge CSET, the
gate-shading period is terminated, and the CKH_ output
states are directly determined by their corresponding
CK_ input logic states again. Once a gate-shading
period is initiated, VDTS must charge to 1.24V and subsequently discharge back below 100mV, before the next
CK_ falling can activate a new gate-shading period.
By configuring RSET and CSET as shown in Figure 1, the
gate-shading period time duration is determined by RSET
and CSET and VLDOO (see the Setting the Gate-Shading
Period Time Duration section). The gate-shading control
can be disabled by removing RSET. If RSET is removed,
the states of the CKH_ outputs are always determined by
their corresponding CK_ input logic states. See Figure 5.
Low-Dropout Linear Regulator (LDO)
The MAX17117 has an integrated 0.8I pass element
and can provide at least 350mA. The output voltage is
accurate within Q1%.
Thermal-Overload Protection
When the junction temperature exceeds TJ = +170NC
(typ), a thermal sensor activates a fault-protection latch,
which shuts down all outputs, allowing the IC to cool
down. All outputs remain off until the IC cools and the
input voltage is cycled below, then back above the IN
UVLO threshold.
The thermal-overload protection protects the IC in the
event of fault conditions. For continuous operation, do
not exceed the absolute maximum junction temperature
rating of TJ = +150NC.
CKH1
CK1
CKH3
CK2
CKH5
CK3
CK4
S1
S3
CK5
S5
CK6
LDOO
LEVEL SHIFTER
AND
GATE-SHADING
LOGIC
RO
MAX17117
RO
CKH2
LDO
CKH4
RSET
CKH6
DTS
CSET
SDTS
S2
S4
S6
RE
RE
Figure 4. Scan-Driver Block Diagram
16
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Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
0
CK2
0
CK3
0
CK4
0
CK5
0
CK6
0
1.24V
DTS
0
CKH1
0
CKH2
0
CKH3
0
CKH4
0
CKH5
0
CKH6
0
Figure 5. Scan-Driver Operation with Gate-Shading Control Enabled
______________________________________________________________________________________ 17
MAX17117
CK1
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
Design Procedure
Main Step-Up Regulator
Inductor Selection
The minimum inductance value, peak current rating, and
series resistance are factors to consider when selecting the inductor. These factors influence the converter’s
efficiency, maximum output-load capability, transientresponse time, and output-voltage ripple. Physical size
and cost are also important factors to be considered.
The maximum output current, input voltage, output voltage, and switching frequency determine the inductor
value. Very high-inductance values minimize the current
ripple and therefore reduce the peak current, which
decreases core losses in the inductor and I2R losses in
the entire power path. However, large inductor values
also require more energy storage and more turns of wire,
which increase physical size and can increase I2R losses in the inductor. Low-inductance values decrease the
physical size but increase the current ripple and peak
current. Finding the best inductor involves choosing the
best compromise among circuit efficiency, inductor size,
and cost.
The equations used here include a constant called LIR,
which is the ratio of the inductor peak-to-peak ripple current to the average DC inductor current at the full-load
current. The best trade-off between inductor size and
circuit efficiency for step-up regulators generally has an
LIR between 0.3 and 0.5. However, depending on the
AC characteristics of the inductor core material and ratio
of inductor resistance to other power-path resistances,
the best LIR can shift up or down. If the inductor resistance is relatively high, more ripple can be accepted to
reduce the number of turns required and increase the
wire diameter. If the inductor resistance is relatively low,
increasing inductance to lower the peak current can
decrease losses throughout the power path. If extremely
thin high-resistance inductors are used, as is common
for LCD panel applications, the best LIR can increase to
between 0.5 and 1.0.
Once a physical inductor is chosen, higher and lower
values of the inductor should be evaluated for efficiency
improvements in typical operating regions.
In Figure 1, the LCD’s gate-on and gate-off supply
voltages are generated from two unregulated charge
pumps driven by the step-up regulator’s LX node. The
additional load on LX must therefore be considered in
the inductance and current calculations. The effective
maximum output current, IMAIN(EFF), becomes the sum
of the maximum load current of the step-up regulator’s
output plus the contributions from the positive and negative charge pumps:
IMAIN(EFF) = IMAIN(MAX) + n VN × I VN + (n VP + 1) × I VP
where IMAIN(MAX) is the maximum step-up output current, nVN is the number of negative charge-pump stages, nVP is the number of positive charge-pump stages,
IVN is the negative charge-pump output current, and IVP
is the positive charge-pump output current, assuming
the initial pump source for IVP is VMAIN.
Calculate the approximate inductor value using the
typical input voltage (VIN), the maximum output current (IMAIN(EFF)), the expected efficiency (ETYP) taken
from an appropriate curve in the Typical Operating
Characteristics, the desired switching frequency (fOSC),
and an estimate of LIR based on the above discussion:
V
L = IN
V
MAIN
2
VMAIN − VIN η TYP
IMAIN(EFF) × fOSC LIR
Choose an available inductor value from an appropriate
inductor family. Calculate the maximum DC input current
at the minimum input voltage VIN(MIN) using conservation of energy and the expected efficiency at that operating point (EMIN) taken from an appropriate curve in the
Typical Operating Characteristics:
IIN(DC,MAX) =
IMAIN(EFF) × VMAIN
VIN(MIN) × ηMIN
Calculate the ripple current at that operating point and
the peak current required for the inductor:
IRIPPLE =
(
VIN(MIN) × VMAIN − VIN(MIN)
)
L × VMAIN × fOSC
I
IPEAK = IIN(DC,MAX) + RIPPLE
2
The inductor’s saturation current rating and the
MAX17117 LX current limit should exceed IPEAK and the
inductor’s DC current rating should exceed IIN(DC,MAX).
For good efficiency, choose an inductor with less than
0.1I series resistance.
Considering the typical application circuit, the maximum
load current (IMAIN(MAX)) is 200mA, with an 8.5V output
and a typical input voltage of 3.3V. The effective full-load
step-up current is:
IMAIN(EFF) = 200mA + 1× 10mA + (2 + 1) × 25mA = 285mA
18
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Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
2
3.3V 8.5V − 3.3V 0.85
L=
≈ 9.7µH
8.5V 0.285A × 1.2MHz 0.2
A 10FH inductor is chosen. Then, using the circuit’s
minimum input voltage (3.0V) and estimating efficiency
of 83% at that operating point:
IIN(DC,MAX) =
0.285A × 8.5V
≈ 0.973A
3V × 0.83
The ripple current and the peak current at that input voltage are:
IRIPPLE =
3V × (8.5V − 3V)
10µH × 8.5V × 1.2MHz
IPEAK = 0.973A +
≈ 0.162A
0.162A
= 1.05A
2
Peak Inductor Current-Limit Setting
Connecting RENA between the ENA pin and the LDOO
output, as shown in Figure 1, allows the inductor peak
current limit to be adjusted up to 2A max by choosing the
appropriate RENA resistor with the following equation:
RENA ≈
(VLDOO − 1.25V)(80000)
I OCP
The above threshold set by RENA varies depending on
the step-up converter’s input voltage, output voltage,
and duty cycle. Place RENA close to the IC such that the
connection between RENA and the ENA pin is as short
as possible.
Output Capacitor Selection
The total output-voltage ripple has two components: the
capacitive ripple caused by the charging and discharging of the output capacitance, and the ohmic ripple due
to the capacitor’s equivalent series resistance (ESR):
VRIPPLE = VRIPPLE(C) + VRIPPLE(ESR)
V
I
− VIN
VRIPPLE(C) ≈ MAIN MAIN
C OUT VMAINfOSC
and:
VRIPPLE(ESR) ≈ IPEAKR ESR(COUT)
where IPEAK is the peak inductor current (see the
Inductor Selection section). For ceramic capacitors,
the output-voltage ripple is typically dominated by
VRIPPLE(C). The voltage rating and temperature characteristics of the output capacitor must also be considered.
Input-Capacitor Selection
The input capacitor (C3) reduces the current peaks
drawn from the input supply and reduces noise injection into the IC. A 10FF ceramic capacitor is used in the
typical application circuit (Figure 1) because of the high
source impedance seen in typical lab setups. Actual
applications usually have much lower source impedance
since the step-up regulator often runs directly from the
output of another regulated supply.
Rectifier Diode
The MAX17117 high switching frequency demands a
high-speed rectifier. Schottky diodes are recommended
for most applications because of their fast recovery time
and low forward voltage. In general, a 1A Schottky diode
complements the internal MOSFET well.
Output-Voltage Selection
The output voltage of the main step-up regulator is
adjusted by connecting a resistive voltage-divider from
the output (VMAIN) to AGND with the center tap connected to FB (see Figure 1). Select R2 in the 10kI to
50kI range. Calculate R1 with the following equation:
V
R1 = R2 × MAIN − 1
VREF
Place R1 and R2 close to the IC such that the connections between these components and the FB pin are kept
as short as possible.
Loop Compensation
Choose RCOMP to set the high-frequency integrator gain
for fast-transient response. Choose CCOMP to set the
integrator zero to maintain loop stability.
For low-ESR output capacitors, use the following equations to obtain stable performance and good transient
response:
1.45k × VIN × VMAIN × C OUT
R COMP ≈
L × IMAIN(MAX)
C COMP ≈
40 × VMAIN× L × IMAIN(MAX)
(VIN ) 2 × R COMP
To further optimize transient response, vary RCOMP in
20% steps and CCOMP in 50% steps while observing
transient-response waveforms.
______________________________________________________________________________________ 19
MAX17117
Choosing an LIR of 0.2 and estimating efficiency of 85%
at this operating point:
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
Operational Amplifier Output Voltage
Using the buffer configuration as shown in Figure 1, the
output voltage of the operational amplifier is adjusted by
connecting a resistive voltage-divider from the output
(VMAIN) to AGND with the center tap connected to POS
(see Figure 1). Select R3 in the 10kI to 100kI range.
Calculate R4 with the following equation:
V
R3 = R4 × 1 − MAIN
VOUT
Applications Information
Power Dissipation
Place R3 and R4 close to the IC such that the connections between these components and the POS pin are
kept as short as possible.
LDO Output Voltage
The output voltage of the LDO is adjusted by connecting a resistive voltage-divider from the output (VLDOO)
to AGND with the center tap connected to LDOADJ
(see Figure 1). Select R6 in the 10kI to 50kI range.
Calculate R5 with the following equation:
V
R5 = R6 × LDOO − 1
1.24V
Place R5 and R6 close to the IC such that the connections between these components and the LDOADJ pin
are kept as short as possible.
Connect a 1FF low ESR capacitor between LDOO and
AGND to ensure stability and to provide good outputtransient performance.
Scan Driver
Setting the Gate-Shading Period Time Duration
To set the gate-shading period time duration, configure
RSET and CSET as shown in Figure 1. Choose a CSET
value greater than 35pF, then calculate the required
RSET value that gives the desired gate-shading period
time duration with the following equation:
R SET =
Gate-Shading Discharge Resistors
For proper operation, choose RO and RE discharge
resistors that are greater than 100I. Place RO and RE
close to the IC such that the connections between these
components and their respective pins are kept as short
as possible.
−t
1.24V
ln1 −
× C SET
V
LDOO
Increase or decrease CSET as needed and repeat the
above calculation to achieve the desired gate-shading
period time duration, while ensuring CSET remains greater than 35pF and RSET is within the 8kI to 100kI range.
Place RSET and CSET close to the IC such that the connections between these components and the DTS pin
are kept as short as possible.
An IC’s maximum power dissipation depends on the
thermal resistance from the die to the ambient environment and the ambient temperature. The thermal resistance depends on the IC package, PCB copper area,
other thermal mass, and airflow.
The MAX17117, with its exposed backside paddle soldered to 1in2 of PCB copper, can dissipate approximately 1990mW into +70NC still air. More PCB copper, cooler
ambient air, and more airflow increase the possible
dissipation, while less copper or warmer air decreases
the IC’s dissipation capability. The major components of
power dissipation are the power dissipated in the stepup regulator and the power dissipated by the operational
amplifiers.
The MAX17117’s largest on-chip power dissipation
occurs in the step-up switch, the VCOM amplifier, the
CKH_ level shifters, and the LDO.
Step-Up Regulator
The largest portions of the power dissipated by the
step-up regulator are the internal MOSFET, the inductor, and the output diode. If the step-up regulator with
3.3V input and 285mA output has approximately 85%
efficiency, approximately 5% of the power is lost in the
internal MOSFET, approximately 3% in the inductor, and
approximately 5% in the output diode. The remaining
few percent are distributed among the input and output capacitors and the PCB traces. If the input power
is approximately 2.85W, the power lost in the internal
MOSFET is approximately 143mW.
Operational Amplifier
The power dissipated in the operational amplifier
depends on the output current, the output voltage, and
the supply voltage:
PD SOURCE = I VCOM_SOURCE × (VAVDD − VVCOM )
PD SINK = I VCOM_SINK × VVCOM
where IVCOM_SOURCE is the output current sourced by
the operational amplifier, and IVCOM_SINK is the output
current that the operational amplifier sinks. In a typical
20
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Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
LDO
The power dissipated in the LDO depends on the LDO’s
output current, input voltage, and output voltage:
PD LDO = ILDOO × (VIN − VLDOO )
Scan-Driver Outputs
The power dissipated by the six CKH_ scan-driver outputs depends on the scan frequency, the capacitive load
on each output, and the difference between the GHON
and VGL supply voltages:
PD SCAN = 6 × fSCAN × C PANEL × (VGHON − VVGL )
2
If the scan frequency is 50kHz, the load of the six CKH_
outputs is 3.4nF, and the supply voltage difference is
30V, then the power dissipated is 0.92W.
PCB Layout and Grounding
Careful PCB layout is important for proper operation. Use
the following guidelines for good PCB layout:
• M
inimize the area of high-current loops by placing the
inductor, output diode, and output capacitors near the
input capacitors and near LX and PGND. The highcurrent input loop goes from the positive terminal of
the input capacitor to the inductor, to the IC’s LX pin,
out of PGND, and to the input capacitor’s negative terminal. The high-current output loop is from the positive
terminal of the input capacitor to the inductor, to the
output diode (D1), to the positive terminal of the output
capacitors, reconnecting between the output capacitor and input capacitor ground terminals. Connect
these loop components with short, wide connections.
Avoid using vias in the high-current paths. If vias are
unavoidable, use many vias in parallel to reduce resistance and inductance.
• C
reate a power ground island (PGND) consisting of
the input and output capacitor grounds, PGND pin,
and any charge-pump components. Connect all these
together with short, wide traces or a small ground
plane. Maximizing the width of the power ground traces improves efficiency and reduces output-voltage
ripple and noise spikes. Create an analog ground
plane (AGND) consisting of all the feedback-divider
ground connections; the operational-amplifier-divider ground connection; the OPAS bypass capacitor
ground connection; the COMP, SS, and SET capacitor ground connections; and the device’s exposed
backside pad. Connect the AGND and PGND islands
by connecting the PGND pin directly to the exposed
backside pad. Make no other connections between
these separate ground planes.
• P
lace the feedback voltage-divider resistors as close
as possible to their respective feedback pins. The
divider’s center trace should be kept short. Placing
the resistors far away causes the feedback trace to
become an antenna that can pick up switching noise.
Care should be taken to avoid running the feedback
trace near LX or the switching nodes in the charge
pumps.
• P
lace the IN pin bypass capacitor as close as possible to the device. The ground connections of the
IN bypass capacitor should be connected directly to
AGND at the backside pad of the IC.
• M
inimize the length and maximize the width of the
traces between the output capacitors and the load for
best transient responses.
• M
inimize the size of the LX node while keeping it wide
and short. Keep the LX node away from the feedback
node and analog ground. Use DC traces as a shield
if necessary.
Refer to the MAX17117 Evaluation Kit for an example of
proper board layout.
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
32 TQFN-EP
T3255N+1
21-0140
______________________________________________________________________________________ 21
MAX17117
case where the supply voltage is 8.5V and the output
voltage is 4.25V with an output source current of 30mA,
the power dissipated is 128mW.
MAX17117
Internal-Switch Boost Regulator with Integrated
7-Channel Scan Driver, Op Amp, and LDO
Revision History
REVISION
NUMBER
REVISION
DATE
0
4/10
DESCRIPTION
Initial release
PAGES
CHANGED
—
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time.
22
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Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
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