Rainbow Electronics MAX17061 User Manual

General Description

The MAX17061 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 controller drives the LED array, which can be configured for up to eight strings in parallel and 10 LEDs per string. Each string is terminated with ballast that achieves ±1.5% current-regulation accuracy between strings, ensuring even LED brightness. The MAX17061 has a wide inputvoltage range from 4.5V to 26V, and provides a fixed 25mA or adjustable 15mA to 30mA full-scale LED current.

The MAX17061 internally generates a DPWM signal for accurate WLED dimming control. The DPWM frequency is resistor programmable, while DPWM duty cycle is controlled directly from an external PWM signal or through a control word through the MAX17061’s SMBus™ interface. This DPWM control provides a dimming range with 8-bit resolution and supports Intel display-power-saving technology (DPST) to maximize battery life.

The MAX17061 has multiple features to protect the controller from fault conditions. Separate feedback loops limit the output voltage under any circumstance, ensuring safe operation. Once an open string is detected, the string is disabled while other strings operate normally. The MAX17061 also features short LED detection. The shorted strings are also disabled after a 2ms fault blanking interval. The controller features cycle-bycycle current limit to provide stable operation and softstart capability. If the MAX17061 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.

The MAX17061’s step-up controller features an internal 150mΩ (typ), 45V (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 625mV (typ) at 25mA LED current helps reduce power loss and improve efficiency. The MAX17061 features selectable switching frequency (500kHz, 750kHz, or 1MHz), which enables a wide variety of applications that can trade off component size for operating frequency.

The MAX17061 is available in a thermally enhanced 28-pin, 4mm x 4mm Thin QFN package.

Applications

Features

o Accurate Dimming Control Using SMBus, PWM

Interface

o Dimming Range with 8-Bit Resolution o Adjustable DPWM Frequency with 1.5% Accuracy o Up to Eight Parallel Strings Multiple Series-

Connected LEDs

o ±1.5% Current Regulation Accuracy Between

Strings

o Low String Feedback Voltage: 625mV at 25mA

LED Current

o Full-Scale LED Current Adjustable from 15mA to

30mA, or Preset 25mA

o Open and Short LED Protections o Output Overvoltage Protection o 0.15Ω Internal HV Power MOSFET (45V max) o Wide Input-Voltage Range from 4.5V to 26V o 500kHz/750kHz/1MHz Selectable Switching

Frequency

o Small 28-Pin, 4mm x 4mm, Thin QFN package

MAX17061

8-String White LED Driver with

SMBus for LCD Panel Applications

________________________________________________________________

Maxim Integrated Products

1

Simplified Operating Circuit

Ordering Information

19-3211; Rev 0; 1/08

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.

+

Denotes a lead-free package.

PART

PIN-PACKAGE

MAX17061ETI+

28 Thin QFN (4mm x 4mm)

Pin Configuration appears at end of data sheet.

SMBus is a trademark of Intel Corp.

Notebook, Subnotebook,

and Tablet Computer Displays

Automotive Systems

Handy Terminals

TEMP RANGE

-40oC to +85oC

L1

LX1, 2

PGND1, 2

D1

R1

OV

R2

FB1 FB2 FB3 FB4 FB5 FB6

FB7

FB8

V

IN

V

DD

V

CC

ISET

CCV

MAX17061

PWMIPWM PWMO

GND

OSCN.C.

SCLCLK

SDADATA

FSET

EP

V

OUT

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND,

T

A

= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°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.

IN to GND ..............................................................-0.3V to +28V

FB_, LX_ to GND ....................................................-0.3V to +45V

PGND_ to GND......................................................-0.3V to +0.3V

V

CC

, VDD, PWMI, SDA, SCL to GND........................-0.3V to +6V

ISET, CCV, PWMO, FSET, OSC,

OV to GND................................................-0.3V to V

CC

+ 0.3V

Continuous Power Dissipation (T

A

= +70°C)

28-Pin Thin QFN (derate 16.9mW/°C above +70°C)...1667mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-60°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

MAX17061

8-String White LED Driver with SMBus for LCD Panel Applications

2 _______________________________________________________________________________________

IN Input Voltage Range

IN Quiescent Current

IN Quiescent Current MAX17061 is disabled, V

VCC Output Voltage

VCC Current Limit V

VCC UVLO Threshold Rising edge, typical hysteresis = 85mV 4.00 4.25 4.45 V

BOOST CONVERTER

LX On-Resistance 20mA from LX_ to PGND 0.15 0.3 Ω LX Leakage Current 45V on LX_ 1 µA

OSC High-Level Threshold

OSC Midlevel Threshold 1.5

OSC Low-Level Threshold 0.4 V

Minimum Duty Cycle

Maximum Duty Cycle 94.0 95.5 97.0 % LX Current Limit Duty cycle = 75% (Note 1) 1.6 A

CONTROL INPUT

SDA, SCL Logic Input-High Level 2.1 V SDA, SCL Logic Input-Low Level 0.8 V PWMI Logic Input-High Level 2.1 V PWMI Logic Input-Low Level 0.8 V

PARAMETER CONDITIONS MIN TYP MAX UNITS

V

= V

IN

CC

V

= open 5.5 26.0

CC

MAX17061 is enabled at minimum brightness, no load

M AX 17061 i s enab l ed , 6V < V

MAX17061 is disabled, V

is forced to 4.5V 15 40 70 mA

C C

V

= V

V V

OSC

CC

= open 675 750 825Operating Frequency = GND 450 500 550

4.5 5.5

VIN = 26V

V

= VCC = 5V

IN

= 12V 10 µA

I N

< 26V , 0 < I

I N

12V 3.90 4.35 4.80

I N =

< 10m A 4.7 5.0 5.3

V C C

1.24 2 mA

0.9 1.0 1.1 MHz

V

-

CC

0.4

V

PWM mode (Note 1) 10 Pulse skipping, no load (Note 1) 0

V

CC

2.0

-

V

kHz

V

%

MAX17061

8-String White LED Driver with

SMBus for LCD Panel Applications

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND,

T

A

= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

INPUT LEAKAGE

PWMI Leakage Current -0.3 +0.3 µA ISET, FSET Leakage Current ISET , FSET to V OV Leakage Current -0.1 +0.1 µA SDA, SCL Input Bias Current -1 +1 µA SDA Output Low-Sink Current V OSC Leakage Current -3 +3 µA

LED CURRENT

Full-Scale FB_ Output Current

ISET High-Level Threshold

ISET Output Voltage 1.166 1.236 1.306 V C ur r ent Reg ul ati on Betw een S tr i ng s Full brightness -1.5 +1.5 %

Minimum FB_ Regulation Voltage

Maximum FB_ Ripple I FB_ On-Resistance V

FB_ Leakage Current

FAULT PROTECTION

OV Threshold Voltage Rising edge, typical hysteresis = 60mV 1.166 1.236 1.306 V FB_ Overvoltage Threshold VIN > 5.5V 5.2 5.6 6.0 V FB_ Undervoltage Threshold 130 175 220 mV

OV Undervoltage Threshold (Boost Global Fail)

Thermal-Shutdown Threshold (Note 1) 160 °C Over cur r ent FAU LT S hutd ow n Ti m er I FB_ Overvoltage Fault Timer Full brightness 1.7 2 2.3 ms

PARAMETER CONDITIONS MIN TYP MAX UNITS

= 0.4V 4 mA

SDA

ISET = V R R R

I I I I

V V

CC

133kΩ 28.8 30.0 31.2

ISET =

= 200kΩ 19.3 20.0 20.7

ISET

266kΩ 14.4 15.0 15.6

ISET =

= 25mA 475 625 910

FB_

= 30mA 575 750 1100

FB_

= 20mA 380 500 740

FB_

= 15mA 285 375 560

FB_

= 20mA (C

FB_

= 50mV (includes 10Ω sense resistor) 17.5 28.4 Ω

FB_

= 26V, TA = +25°C 1

FB_

= 45V, TA = +25°C 2.5 4

FB_

CC

OUT

= 1µF, V

+1 µA

24.5 25.0 25.5

V

-

CC

0.4

= VCC) (Note1) 120 200 mV

OSC

V

48 84 120 mV

> 3.3A at duty = 0% 88 128 168 µs

PEAK

mA

mV

P/P

µA

MAX17061

8-String White LED Driver with SMBus for LCD Panel Applications

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND,

T

A

= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND,

T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 2)

PARAMETER CONDITIONS MIN TYP MAX UNITS

PWM FILTER

PWM Output Impedance 20 40 60 kΩ

DPWM Oscillator Frequency

PWMI Input-Frequency Range 5 10 100 kHz PWMI Full-Range Accuracy 5 LSB

PWMI Brightness Setting

SMBus TIMING SPECIFICATION

SMBus Frequency FSMB 10 100 kHz Bus Free Time TBUF 4.7 µs

START Condition Hold Time from SCL

START Condition Setup Time from SCL

STOP Condition Setup Time from SCL

SDA Hold Time from SCL THD:DAT 300 ns SDA Setup Time from SCL TSU:DAT 250 ns

SCL Low Period T

SCL High Period T

R

FSET

R

FSET

R

FSET

R

FSET

= 464kΩ 197 200 203 = 113kΩ 750 785 820 = 65kΩ 1.270 1.335 1.400 = 42kΩ 2

PWMI duty cycle = 100% 98 100 PWMI duty cycle = 50% 48 50 52 PWMI duty cycle = 0% 2.6 2.7 2.8

THD:STA 4

TSU:STA 4.7

TSU:STO 4

LOW

HIGH

4.7 µs 4 µs

µs

Hz

kHz

%

IN Input Voltage Range

IN Quiescent Current

VCC Output Voltage

VCC Current Limit VCC is forced to 4.5V 12 70 mA

VCC UVLO Threshold Rising edge, typical hysteresis = 85mV 4.00 4.45 V

PARAMETER CONDITIONS MIN TYP MAX UNITS

V

= V

IN

CC

4.5 5.5

VCC = open 5.5 26.0

MAX17061 is enabled at minimum brightness, no load

MAX17061 is disabled, V

MAX17061 is enabled, 6V < VIN < 26V, 0 < I

MAX17061 is disabled, V

VIN = 26V 2

V

= VCC = 5V 2

IN

= 12V 10 µA

IN

< 10mA 4.7 5.3

VCC

= 12V 3.9 4.8

IN

V

mA

V

MAX17061

8-String White LED Driver with

SMBus for LCD Panel Applications

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND,

T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 2)

BOOST CONVERTER

LX On-Resistance 20mA from LX_ to PGND 0.3 Ω LX Leakage Current 45V on LX_ 1 µA

OSC High-Level Threshold

OSC Midlevel Threshold 1.5

OSC Low-Level Threshold 0.4 V Maximum Duty Cycle 94 97 % LX Current Limit Duty cycle = 75% 1.6 A

CONTROL INPUT

S D A, S C L Log i c Inp ut- H i g h Level 2.1 V SDA, SCL Logic Input-Low Level 0.8 V PWMI Logic Input-High Level 2.1 V PWMI Logic Input-Low Level 0.8 V

INPUT LEAKAGE

PWMI Leakage Current -0.3 +0.3 µA ISET, FSET Leakage Current ISET , FSET to V OV Leakage Current -0.1 +0.1 µA SDA, SCL Input Bias Current -1 +1 µA SDA Output-Low Sink Current V OSC Leakage Current -3 +3 µA

LED CURRENT

Full-Scale FB_ Output Current

ISET High-Level Threshold

ISET Output Voltage 1.166 1.306 V C ur r ent Reg ul ati on Betw een S tr i ng s Full brightness -1.5 +1.5 %

Minimum FB_ Regulation Voltage

Maximum FB_ Ripple I FB_ On-Resistance V

PARAMETER CONDITIONS MIN TYP MAX UNITS

V

= V

OSC

V

OSC

V

OSC

SDA

ISET = V R

ISET =

R

ISET

R

ISET =

I

FB_

I

FB_

I

FB_

I

FB_

CC

= open 675 825 kHzOperating Frequency = GND 450 560 kHz

= 0.4V 4 mA

CC

133kΩ 28.6 31.4

= 200kΩ 19.0 21.0

266kΩ 14.3 15.7

= 25mA 425 910 = 30mA 575 1100 = 20mA 380 740 = 15mA 285 560

= 20mA (C

= 50mV (includes 10Ω sense resistor) 28.4 Ω

CC

OUT

= 1µF, V

0.89 1.10 MHz

V

-

CC

0.4

V

+1 µA

24.5 25.5

V

-

CC

0.4

= VCC) 200 mV

OSC

V

CC

2.0

-

V

mA

mV

P/P

MAX17061

8-String White LED Driver with SMBus for LCD Panel Applications

6 _______________________________________________________________________________________

Note 1: Specifications are guaranteed by design, not production tested. Note 2: Specifications to -40°C are guaranteed by design, not production tested.

ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND,

T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 2)

FAULT PROTECTION

OV Threshold Voltage Rising edge, typical hysteresis = 60mV 1.166 1.306 V FB_ Overvoltage Threshold 5.2 6.0 V FB_ Undervoltage Threshold 130 220 mV

OV Undervoltage Threshold (Boost Global Fail)

Over cur r ent FAU LT S hutd ow n Ti m er I FB_ Overvoltage Fault Timer 1.6 2.4 ms

PARAMETER CONDITIONS MIN TYP MAX UNITS

PWM FILTER

PWM Output Impedance 20 60 kΩ

PWMI Input Frequency Range 5 100 kHz PWMI Full-Range Accuracy 5 LSB

PWMI Brightness Setting

SMBus TIMING SPECIFICATION

SMBus Frequency FSMB 10 100 kHz Bus Free Time TBUF 4.7 µs

START Condition Hold Time from SCL

START Condition Setup Time from SCL

STOP Condition Setup Time from SCL

SDA Hold Time from SCL THD:DAT 300 ns SDA Setup Time from SCL TSU:DAT 250 ns

SCL Low Period T

SCL High Period T

48 120 mV

> 3.3A at duty = 0% 88 168 µs

PEAK

R

= 464kΩ 197 203 kHz

FSET

R

= 113kΩ 750 820 HzDPWM Oscillator Frequency

FSET

R

= 65kΩ 1.27 1.40 kHz

FSET

PWMI duty cycle = 100% 98 PWMI duty cycle = 50% 48 52 PWMI duty cycle = 0% 2.6 2.8

THD:STA 4

TSU:STA 4.7

TSU:STO 4

LOW

HIGH

4.7 µs 4 µs

µs

%

MAX17061

8-String White LED Driver with

SMBus for LCD Panel Applications

_______________________________________________________________________________________

7

Typical Operating Characteristics

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND, LEDs =

10 series x 4 parallel strings, T

A

= +25°C, unless otherwise noted.)

BOOST CONVERTER EFFICIENCY

vs. INPUT VOLTAGE (BRIGHTNESS = 100%)

90

89

88

87

86

BOOST CONVERTER EFFICIENCY (%)

85

7

INPUT VOLTAGE (V)

LED CURRENT vs. AMBIENT TEMPERATURE

26.0

25.8

25.6

25.4

25.2

25.0

24.8

LED CURRENT (mA)

24.6

24.4

24.2

24.0

0

vs. SMBus BRIGHTNESS SETTING

30

25

MAX17061 toc01

20

15

LED CURRENT (mA)

10

5

19161310

0

SMBus BRIGHTNESS SETTING

(BRIGHTNESS = 100%)

MAX17061 toc04

60 804020

AMBIENT TEMPERATURE (°C)

LED CURRENT

200 250150100500

30

25

20

15

LED CURRENT (mA)

10

5

0

5

30

25

MAX17061 toc02

20

15

LED CURRENT (mA)

10

5

0

LED CURRENT

vs. INPUT VOLTAGE

SMBus = 0xFF

INPUT VOLTAGE (V)

vs. PWMI DUTY CYCLE

PWMI DUTY CYCLE (%)

SMBus = 0x1F

LED CURRENT

SMBus = 255

MAX17061 toc05

17 2014118

MAX17061 toc03

SMBus = 128

80 100604020

5

4

SMBus = 255

3

2

SUPPLY CURRENT (mA)

1

0

5

SUPPLY CURRENT

vs. INPUT VOLTAGE

SMBus = 0

INPUT VOLTAGE (V)

10

MAX17061 toc06

17 2014118

8

6

4

SHUTDOWN CURRENT (μA)

2

0

SHUTDOWN CURRENT

vs. INPUT VOLTAGE

5

MAX17061 toc07

17 2014118

INPUT VOLTAGE (V)

MAX17061

8-String White LED Driver with SMBus for LCD Panel Applications

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 1, VIN= 12V, C

CCV

= 0.022µF, R

CCV

= 5.1kΩ, V

ISET

= V

OSC

= VDD= VCC, R

FSET

= 464kΩ, V

PWMI

= GND, LEDs =

10 series x 4 parallel strings, T

A

= +25°C, unless otherwise noted.)

SWITCHING WAVEFORMS

(V

IN

= 7V, BRIGHTNESS = 100%)

MAX17061 toc08

1μs/div

V

LX

20V/div

I

L

200mA/div

0V

0mA

SWITCHING WAVEFORMS

(V

IN

= 20V, BRIGHTNESS = 100%)

MAX17061 toc09

1μs/div

V

LX

20V/div

I

L

200mA/div

0V

0mA

STARTUP WAVEFORMS

(BRIGHTNESS = 100%)

MAX17061 toc10

400μs/div

V

LX

20V/div

I

L

1A/div

V

OUT

20V/div

V

CCV

2V/div

0V

0A

STARTUP WAVEFORMS

(SMBus = 0x04)

MAX17061 toc11

400μs/div

V

LX

20V/div

I

L

1A/div

V

OUT

20V/div

V

CCV

2V/div

0V

0A

LED CURRENT WAVEFORMS

(SMBus = 0x80)

MAX17061 toc12

2ms/div

V

FB1

10V/div

I

L

500mA/div

I

LED

20mA/div

V

OUT

20V/div

0V

0mA

0V

LED CURRENT WAVEFORMS

(SMBus = 0x04)

MAX17061 toc13

2ms/div

V

FB1

10V/div

I

L

500mA/div

I

LED

20mA/div

V

OUT

20V/div

0V

0mA

0V