Rainbow Electronics MAX17127 User Manual
19-5164; Rev 0; 3/10
EVALUATION KIT
AVAILABLE
Six-String WLED Driver with Integrated
General Description
The MAX17127 is a high-efficiency driver for white lightemitting diodes (LEDs). It is designed for large liquidcrystal displays (LCDs) that employ an array of LEDs as
the light source. An internal switch current-mode step-up
converter drives the LED array, which can be configured
for up to six strings in parallel and 13 LEDs per string.
Each string is terminated with ballast that achieves Q2%
current-regulation accuracy, ensuring even LED brightness. The MAX17127 has a wide input voltage range
from 5V to 26V, and provides adjustable 10mA to 30mA
full-scale LED current.
The MAX17127 can implement brightness control through
the PWM signal input, and LED current is directly controlled by the external dimming signal’s frequency and
duty cycle.
The MAX17127 has multiple features to protect the controller from fault conditions. Once an open/short string is
detected, the fault string is disabled while other strings
can still operate normally. The controller features cycleby-cycle current limit to provide constant operation and
soft-start capability. If the MAX17127 is in current-limit
condition, the step-up converter is latched off after an
internal timer expires. A thermal-shutdown circuit provides another level of protection. When thermal shutdown happens, the MAX17127 is latched off.
The MAX17127’s step-up controller features an internal 0.12I (typ), 48V (max) power MOSFET with local
current-sense amplifier for accurate cycle-by-cycle current limit. This architecture greatly simplifies the external
circuitry and saves PCB space. Low-feedback voltage at each LED string helps reduce power loss and
improve efficiency. The MAX17127 features resistoradjustable switching frequency from 250kHz to 1MHz,
which enables a wide variety of applications that can
trade off component size for operating frequency.
The MAX17127 is available in a thermally enhanced,
lead-free, 20-pin, 4mm x 4mm thin QFN package.
Step-Up Converter
MAX17127
Features
S 5V to 26V Input Supply Voltage
S Up to Six Parallel Strings Multiple Series-
Connected LEDs
S 250kHz to 1MHz Adjustable Switching Frequency
S 0.12I Internal HV Power MOSFET (48V max)
S Low String Feedback Voltage: 480mV at 20mA
LED Current
S Full-Scale LED Current Adjustable from 10mA to
30mA
S Q2% Current-Regulation Accuracy Between
Strings
S 400ns Minimum String On-Time
S 100Hz to 25kHz PWM Input Range
S Open and Short LED Protection
S Output Overvoltage Protection
S Thermal Shutdown
S Small 20-Pin, 4mm x 4mm Thin QFN Package
Ordering Information
PART TEMP RANGE PIN-PACKAGE
MAX17127ETP+ -40°C to +85°C 20 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Applications
Notebook, Subnotebook, and Tablet Computer
Displays
Automotive Systems
Handy Terminals
Simplified Operating Circuit appears 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.
Six-String WLED Driver with Integrated
Step-Up Converter
ABSOLUTE MAXIMUM RATINGS
VIN to AGND ........................................................-0.3V to +30V
FB_, SW to PGND .................................................-0.3V to +52V
PGND to AGND ....................................................-0.3V to +0.3V
V
, PWM, EN, FPO, I.C. to AGND .....................-0.3V to +6V
DDIO
COMP, ISET, R_FPWM, OVP, FSLCT
to AGND ................................................-0.3V to V
SW Switch Maximum Continuous RMS Current ...................1.6A
Continuous Power Dissipation (TA = +70NC)
TQFN (derate 16.9mW/NC above +70NC) ..................1349mW
MAX17127
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.
DDIO
+ 0.3V
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1. VIN = 12V, C
TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Voltage Range 5 26 V
VIN Quiescent Current
V
Output Voltage
DDIO
V
Current Limit V
DDIO
V
UVLO Threshold Rising edge, typical hysteresis = 250mV 3.90 4.00 4.10 V
DDIO
VIN UVLO Threshold
BOOST CONVERTER
SW On-Resistance 20mA from SW to PGND 0.12 0.25
SW Leakage Current 40V on SW, TA = +25NC 1 FA
Operating Frequency
R
Maximum Duty Cycle At f
Minimum On-Time (Note 1) 50 80 ns
SW Current Limit Duty cycle = 75% 3.12 3.9 4.7 A
CONTROL INPUT
PWM, EN Logic-Input
High Level
PWM, EN Logic-Input Low
Level
EN Pulldown Resistor 120 200 280 kI
Range Operating range 90 500 kI
FSLCT
MAX17127 is enabled, V
MAX17127 is disabled, EN = AGND 5 10 FA
MAX17127 is enabled, V
5.4V < V
MAX17127 is enabled, VEN = 3.3V, VIN = 5V, I
dropout condition
MAX17127 is disabled, EN = AGND, 0A < I
DDIO
Falling edge 4.3 4.5 4.7
Rising edge 4.55 4.75 4.95
R
FSLCT
R
FSLCT
= 0.51nF, C
COMP
< 26V, 0A < I
IN
is forced to 4.2V 25 45 70 mA
= 100kI 0.95 1.0 1.05
= 400kI 0.225 0.25 0.275
= 1MHz 91 95 %
SW
= 4.7µF, R
COUT
= 3.3V, VIN = 26V 2.7 3.2 mA
EN
= 3.3V,
EN
< 10mA
VDDIO
Operating Temperature Range .......................... -40NC to +85NC
Junction Temperature .....................................................+150NC
Storage Temperature Range ............................ -60NC to +150NC
ESD
HBM ...................................................................................2kV
MM ...................................................................................200V
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
COMP
VDDIO
= 82.5kΩ, R
= 10mA,
VDDIO
< 50FA 3.1 3.7 4.1 V
= 180kΩ, R
ISET
= 100kΩ, L = 10µH,
FSLCT
4.85 5 5.15
4.6 4.75
2.1 V
0.8 V
V
V
I
MHz
2 ______________________________________________________________________________________
Six-String WLED Driver with Integrated
Step-Up Converter
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1. VIN = 12V, C
TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
FPO OUTPUT
FPO Off-Leakage Current Fault inactive, TA = +25NC 100 nA
FPO On Output-Voltage
Low
INPUT LEAKAGE
PWM Leakage Current TA = +25NC, V
OVP Leakage Current TA = +25NC, V
LED CURRENT
Full-Scale FB_ Output
Current
R
Range
ISET
Current Regulation
Between Strings
Minimum FB_ Regulation
Voltage
FB_ On-Resistance V
FB_ Bias Current V
FB_ Minimum On-Time 400 580 700 ns
FAULT PROTECTION
OVP Threshold Voltage Rising edge, typical hysteresis = 90mV 1.23 1.25 1.27 V
FB_ Overvoltage
Threshold
FB_ Enable Threshold
Voltage
FB_ Open Threshold
Voltage
FB_ Check LED Source
Current
FB_ Check LED Time 0.7 1.0 1.3 ms
Thermal-Shutdown
Threshold
Overcurrent Fault Timer Latch-off timer 128 Fs
PWM CONTROL
PWM Input On-Time 400 ns
PWM Input Frequency
Range
I
SINK
R
ISET
R
ISET
R
ISET
V
ISET
Operating range 100 400
Accuracy = 3% 120 360
10mA < I
I
FB_
FB_
I
FB_
FB_
FB_
(Note 1) +150 NC
= 0.51nF, C
COMP
= 1mA, fault active 0.4 V
= 0V, V
PWM
= 0V, V
OVP
= 120kI 29.1 30 30.9
= 180kI 19.6 20 20.4
= 360kI 9.7 10 10.3
< 0.7V 0.2 0.3 0.4
< 30mA -2.0 +2.0 %
FB_
= 30mA 400 555 770
= 20mA 460 670
= 10mA 350 630
= 50mV (includes 10I sense resistor) 17.5 28.4
= 40V, TA = +25NC 0.1 1 FA
= 4.7µF, R
COUT
= 5V -1 +1 FA
PWM
= 5V -0.1 +0.1 FA
OVP
COMP
= 82.5kΩ, R
= 180kΩ, R
ISET
= 100kΩ, L = 10µH,
FSLCT
7 8 9 V
1.2 V
130 280 mV
0.4 1.3 mA
0.1 25 kHz
MAX17127
mA
kI
mVI
I
_______________________________________________________________________________________ 3
Six-String WLED Driver with Integrated
Step-Up Converter
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1. VIN = 12V, C
TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Voltage Range 5 26 V
VIN Quiescent Current
MAX17127
V
Output Voltage
DDIO
V
Current Limit V
DDIO
V
UVLO Threshold Rising edge, typical hysteresis = 250mV 3.90 4.10 V
DDIO
VIN UVLO Threshold
BOOST CONVERTER
SW On-Resistance 20mA from SW to PGND 0.25 ω
SW Leakage Current 40V on SW, TA = +25NC 1 µA
Operating Frequency
R
Maximum Duty Cycle At fSW = 1MHz 92 %
Boost Output Voltage With suitable OVP network 45 V
Minimum On-Time (Note 1) 80 ns
CONTROL INPUT
PWM, EN Logic-Input High Level 2.1 V
PWM, EN Logic-Input Low Level 0.8 V
EN Pulldown Resistor 110 290 kω
FPO OUTPUT
FPO On Output-Voltage Low I
LED CURRENT
Full-Scale FB_ Output Current
R
Current Regulation Between
Strings
Minimum FB_ Regulation Voltage
FB_ On-Resistance V
FB_ Bias Current V
Operative Range 90 500 kω
FSLCT
Range
ISET
= 0.51nF, C
COMP
MAX17127 is enabled, V
MAX17127 is disabled, EN = AGND 15 µA
MAX17127 is enabled, VEN = 3.3V,
5.4V < V
MAX17127 is enabled , VEN = 3.3V, VIN = 5V,
I
VDDIO
EN = AGND, 0A < I
DDIO
Falling edge 4.3 4.7
Rising edge 4.55 4.95
R
FSLCT
R
FSLCT
SINK
R
ISET
R
ISET
R
ISET
V
ISET
Operating range 100 400
Accuracy = 3% 120 360
10mA < I
I
FB_
FB_
I
FB_
FB_
FB_
< 26V, 0A < I
IN
= 10mA, dropout condition
is forced to 4.2V 25 70 mA
= 100kI 0.95 1.05
= 400kI 0.225 0.28
= 1mA, fault active 0.4 V
= 120kI 29.1 30.9
= 180kI 19.4 20.6
= 360kI 9.7 10.3
< 0.7V 0.2 0.4
< 30mA -2.0 +2.0 %
FB_
= 30mA 400 770
= 20mA 670
= 10mA 630
= 50mV (includes 10I sense resistor) 28.4 ω
= 40V, TA = +25NC 1 µA
COUT
VDDIO
= 4.7µF, R
= 3.3V, V
EN
< 10mA
VDDIO
< 50FA 3.1 4.1
= 82.5kΩ, R
COMP
= 26V 3.2 mA
IN
= 180kΩ, R
ISET
FSLCT
4.85 5.15
4.6
= 100kΩ, L = 10µH,
V
V
MHz
mA
kω
mVI
4 ______________________________________________________________________________________
Six-String WLED Driver with Integrated
Step-Up Converter
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1. VIN = 12V, C
TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
FB_ Minimum On-Time 400 700 ns
FAULT PROTECTION
OVP Threshold Voltage Rising edge, typical hysteresis = 90mV 1.23 1.27 V
FB_ Overvoltage Threshold 7 9 V
FB_ Open Threshold Voltage 130 280 mV
FB_ Check LED Source Current 0.4 1.3 mA
FB_ Check LED Time 0.7 1.3 ms
Overcurrent Fault Timer Latch-off timer 88 168 µs
PWM CONTROL
PWM Input On-Time 400 ns
PWM Input Frequency Range 0.1 25 kHz
Note 1: Specifications are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1. VIN = 12V, TA = +25NC, unless otherwise noted.)
COMP
= 0.51nF, C
COUT
= 4.7µF, R
COMP
= 82.5kΩ, R
= 180kΩ, R
ISET
= 100kΩ, L = 10µH,
FSLCT
MAX17127
BOOST CONVERTER EFFICIENCY vs. INPUT VOLTAGE (VS)
= 32V, I
(V
OUT
92
90
88
86
84
EFFICIENCY (%)
82
80
78
5 26
= 120mA, BRIGHTNESS = 100%)
OUT
23201714118
INPUT VOLTAGE (V)
MAX17127 toc01
BOOST CONVERTER EFFICIENCY vs. BRIGHTNESS
= 2V, V
(V
S
90
80
70
EFFICIENCY (%)
60
50
0 100
= 32V, I
OUT
BRIGHTNESS (%)
= 120mA AT 100%)
OUT
80604020
MAX17127 toc02
_______________________________________________________________________________________ 5
Six-String WLED Driver with Integrated
Step-Up Converter
Typical Operating Characteristics (continued)
(Circuit of Figure 1. VIN = 12V, TA = +25NC, unless otherwise noted.)
LED CURRENT vs. BRIGHTNESS SETTING
20
f
= 200Hz
PWM
15
MAX17127
10
LED CURRENT (mA)
5
0
0 100
LED CURRENT (I
2.04
2.02
2.00
LED CURRENT (mA)
1.98
PWM DUTY CYCLE (%)
= 20mA AT 10% BRIGHTNESS)
LED
vs. INPUT VOLTAGE (V
LED CURRENT (I
20.20
MAX17127 toc03
80604020
20.15
20.10
LED CURRENT (mA)
20.05
20.00
5 26
= 20mA AT 100% BRIGHTNESS)
LED
vs. INPUT VOLTAGE (V
INPUT VOLTAGE (V)
)
S
MAX17127 toc04
23201714118
IN QUIESCENT CURRENT
)
S
MAX17127 toc05
6
5
4
3
2
QUIESCENT CURRENT (mA)
1
vs. IN VOLTAGE
MAX17127 toc06
100% BRIGHTNESS
200Hz/1% BRIGHTNESS
1.96
5 26
INPUT VOLTAGE (V)
IN SHUTDOWN CURRENT
vs. IN VOLTAGE
10
EN = LOW
8
6
4
SHUTDOWN CURRENT (µA)
2
0
5 26
IN VOLTAGE (V)
23201714118
MAX17127 toc07
23201714118
0
5 26
IN VOLTAGE (V)
SWITCHING WAVEFORMS
= 5V, BRIGHTNESS = 100%)
(V
S
V
= 32V, I
OUT
= 120mA
1µs/div
OUT
MAX17127 toc08
23201714117
6 ______________________________________________________________________________________
V
LX
20V/div
0V
INDUCTOR
CURRENT
500mA/div
0mA
Six-String WLED Driver with Integrated
Step-Up Converter
Typical Operating Characteristics (continued)
(Circuit of Figure 1. VIN = 12V, TA = +25NC, unless otherwise noted.)
MAX17127
SWITCHING WAVEFORMS
= 26V, BRIGHTNESS = 100%)
(V
S
V
OUT
= 32V, I
OUT
= 120mA
1µs/div
STARTUP WAVEFORMS
(BRIGHTNESS = 20%)
12V
2ms/div
MAX17127 toc09
MAX17127 toc11
V
LX
20V/div
0V
INDUCTOR
CURRENT
200mA/div
0mA
V
EN
5V/div
0V
INDUCTOR
CURRENT
500mA/div
0A
V
LX
20V/div
0V
V
OUT
20V/div
0V
STARTUP WAVEFORMS
(BRIGHTNESS = 100%)
12V
1ms/div
MAX17127 toc10
LED CURRENT WAVEFORMS
(BRIGHTNESS = 50%)
1ms/div
MAX17127 toc12
V
EN
5V/div
0V
INDUCTOR
CURRENT
500mA/div
0A
V
LX
20V/div
0V
V
OUT
20V/div
0V
V
FB1
10V/div
0V
I
LED
20mA/div
0mA
INDUCTOR
CURRENT
500mA/div
0mA
LED CURRENT WAVEFORMS
(BRIGHTNESS = 1%)
1ms/div
MAX17127 toc13
V
FB1
10V/div
0V
I
FB1
20mA/div
0mA
INDUCTOR
CURRENT
500mA/div
0mA
LED-OPEN FAULT PROTECTION
(BRIGHTNESS = 100%, LED OPEN ON FB1)
20mA
200ms/div
0mA
MAX17127 toc14
32V
V
FB1
1V/div
0V
V
FB2
10V/div
0V
V
OUT
10V/div
10V
I
FB2
10mA/div
_______________________________________________________________________________________ 7
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