Datasheet MAX8631X, MAX8631Y Datasheet (MAXIM)

EVALUATION KIT

AVAILABLE

General Description

The MAX8631X/Y charge pump drives up to eight white
LEDs with regulated constant current for uniform inten­sity. The main group of LEDs (M1–M4) can be driven
up to 30mA per LED for backlighting. The flash group
of LEDs (F1–F4) is independently controlled and can be
driven up to 100mA per LED (or 400mA total). Two
200mA LDOs are on-board to provide power for cam­era functions. The LDOs’ output voltages are pin-pro­grammable to meet different camera-module
requirements. By utilizing adaptive 1x/1.5x/2x charge­pump modes and very-low-dropout current regulators,
the MAX8631X/Y achieves high efficiency over the full
1-cell lithium-battery voltage range. The 1MHz fixed-fre­quency switching allows for tiny external components,
and the regulation scheme is optimized to ensure low
EMI and low input ripple.

The MAX8631X/Y is available in a 28-pin thin QFN,
4mm x 4mm lead-free package (0.8mm max height).

Applications

Camera Phones and Smartphones

Backlighting and Flash

PDAs, Digital Cameras, and Camcorders

Features

♦ Powers Up to 8 LEDs

Up to 30mA/LED Drive for Backlight

Up to 400mA Total Drive for Flash

♦ Two Internal Low-Noise 200mA LDOs

♦ 94% Max/85% Avg Efficiency (P

LED/PBATT

) over Li+

Battery Discharge

♦ 0.2% Typical LED Current Matching

♦ Adaptive 1x/1.5x/2x Mode Switchover

♦ Single-Wire Serial Pulse Interface for Brightness

Control (32 Steps)

♦ Thermal TADerating Function

♦ Low Input Ripple and EMI

♦ 2.7V to 5.5V Supply Voltage Range

♦ Soft-Start, Overvoltage, and Thermal-Shutdown

Protection

♦ 28-Pin Thin QFN, 4mm x 4mm Package

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with

Two LDOs in 4mm x 4mm Thin QFN

________________________________________________________________

Maxim Integrated Products

1

Ordering Information

19-3688; Rev 3; 6/08

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Pin Configuration appears at end of data sheet.

Typical Operating Circuit

*

EP = Exposed pad.

+

Denotes a lead-free package.

INPUT

2.7V TO 5.5V

10μF

MAIN ON/OFF

AND DIMMING

FLASH ON/OFF

DUAL-LDO ON/OFF

DUAL-LDO

VOLTAGE

SELECTION

C2P C2N

MAX8631X/Y

1μF

OUTPUT

UP TO 480mA

OUT

M1
M2
M3
M4

F1
F2
F3
F4

LDO1
LDO2

REFSETM SETF

0.01μF

10μF

MAIN FLASH

CAMERA
MODULE

1μF1μF

1μF

C1P C1N
PIN

IN

GND

PGND

ENM1

ENM2

ENF

ENLDO

P1

P2

PART TEMP RANGE PIN-PACKAGE

MAX8631XETI+ -40°C to +85°C

MAX8631YETI+ -40°C to +85°C

28 Thin QFN-EP*
4mm x 4mm (T2844-1)

28 Thin QFN-EP*
4mm x 4mm (T2844-1)

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= 3.6V, V

GND

= V

PGND

= 0V, ENM1 = ENM2 = ENF = IN, R

SETM

= R

SETF

= 6.8kΩ, P1 = P2 = unconnected, C

REF

= 0.01µF,

T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

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.

PIN, IN, OUT, REFBP to GND................................-0.3V to +6.0V

SETF, SETM, ENLDO, ENM1, ENM2, ENF,

P1, P2, LDO1, LDO2 to GND....................-0.3V to (V

IN

+ 0.3V)

M1, M2, M3, M4, F1, F2, F3, F4 to GND...-0.3V to (V

OUT

+ 0.3V)

C1N, C2N to GND ......................................... -0.3V to (V

IN

+ 1V)

C1P, C2P

to GND.............. -0.3V to greater of (V

OUT

+ 1V) or (VIN+ 1V)

PGND to GND .......................................................-0.3V to +0.3V

OUT, LDO1, LDO2 Short-Circuit to GND ...................Continuous

Continuous Power Dissipation (T

A

= +70°C)
28-Pin Thin QFN 4mm X 4mm

(derate 20.8mW/°C above +70°C).............................1666mW

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

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

Storage Temperature Range .............................-65°C to +150°C

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

IN Operating Voltage 2.7 5.5 V

Undervoltage-Lockout Threshold VIN rising or falling 2.25 2.45 2.60 V

Undervoltage-Lockout Hysteresis 130 mV

Supply Current

Shutdown Supply Current ENM1 = ENM2 = ENF = ENLDO = GND

EN_ High Voltage VIN = 2.7V to 5.5V 1.4 V

EN_ Low Voltage V

EN_ Input Current V

ENM_ or ENF Low Shutdown
Delay t

SHDN

ENM_ or ENF t

ENM_ or ENF t

Initial ENM_ or ENF t

P1, P2 Shutdown Input Current 1µA

P1, P2 Input Impedance 150 kΩ

Thermal-Shutdown Threshold Temperature rising +160 °C

Thermal-Shutdown Hysteresis 20 °C

CHARGE PUMP

Overvoltage-Protection Threshold V

Soft-Start Time 2ms

PARAMETER CONDITIONS MIN TYP MAX UNITS

LO

HI

1MHz switching, no load, 1.5x or 2x mode 4.0 5.5

1x mode 10% setting, ENF = GND, V

= I

I

LDO1

ENM1 = ENM2 = ENF = GND, V
I

LDO1

See Figure 2 2.5 ms

See Figure 2 0.5 250.0 µs

See Figure 2 0.5 µs

HI

Only required for first ENM_ or ENF pulse, see Figure 2 200 µs

LDO2

= I

LDO2

= 2.7V to 5.5V 0.4 V

IN

= 0V or 5.5V

EN_

rising 5 V

OUT

= 0A

= 0A

ENLDO

= VIN,

ENLDO

= VIN,

TA = +25°C 0.01 5

T

= +85°C 0.1

A

TA = +25°C 0.01 1

= +85°C 0.1

T

A

0.4

110 µA

mA

µA

µA

MAX8631X/Y

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 3.6V, V

GND

= V

PGND

= 0V, ENM1 = ENM2 = ENF = IN, R

SETM

= R

SETF

= 6.8kΩ, P1 = P2 = unconnected, C

REF

= 0.01µF,

T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

1x/1.5x/2x White LED Charge Pump with Two

LDOs in 4mm x 4mm Thin QFN

_______________________________________________________________________________________ 3

1x to 1.5x or 1.5x to 2x Mode
Transition Threshold

Input Voltage-Mode Transition
Hysteresis

Charge-Pump Maximum OUT
Current

Charge-Pump Short-Circuit
Current

Switching Frequency 1 MHz

OUT Pulldown Resistance in
Shutdown

LED DRIVER

SET_ Bias Voltage TA = +25°C 0.6 V

SET_ Leakage in Shutdown ENM_ = ENF = GND

SET_ Current Range 10 145 µA

SETM-to-Main LED Current Ratio

/I

(I

M_

SETM

SETF-to-Flash LED Current Ratio

F_/ISETF

)

(I

M_, F_ Current Accuracy

Maximum Main LED Sink Current R

Maximum Flash LED Sink Current R

Current-Derating-Function Start
Temperature

Current-Derating-Function Slope TA = +40°C to +85°C -1.7 %/°C

Dropout Voltage (Note 2) 40 90 mV

1.5x and 2x Regulation Voltage 150 mV

M_, F_ Leakage in Shutdown ENM_ = ENF = GND

LDO_

Output Voltage Accuracy

Output Current Range 0 200 mA

Current Limit V

Soft-Start Current Limit 160 mA

PARAMETER CONDITIONS MIN TYP MAX UNITS

)

V

≥ 3.15V, V

IN

1x mode, (VIN - V

1.5x mode, (1.5VIN - V

2x mode, (2V

V

< 1.25V 500 mA

OUT

ENM_ = ENF = GND 5 kΩ

100% setting, M1–M4 230 A/A

100% setting, F1–F4 690 A/A

TA = +25°C -1.25 +1.25

T

= -40°C to current derating start temperature -4 +4

A

SETM

= 4.12kΩ, IF1 + IF2 + IF3 + I

SETF

I

= 150mA, relative to V

LDO_

LDO_

OUT

IN

= 4.6kΩ, for each M_ 30 mA

= 0V 280 475 750 mA

= 3.9V 580 mA

) / I

OUT

OUT

) / I

OUT

OUT

- V

) / I

OUT

OUT

TA = +25°C 0.01 1

T

A

F4

TA = +25°C 0.01 1

= +85°C 0.1

T

A

OUT(NOM)

90 100 110 mV

150 mV

0.3 1.0

1.1 4.0Open-Loop OUT Resistance

1.5 4.14

= +85°C 0.1

400 mA

+40 °C

(Note 3) -1.7 0 +1.7 %

Ω

µA

%

µA

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with
Two LDOs in 4mm x 4mm Thin QFN

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 3.6V, V

GND

= V

PGND

= 0V, ENM1 = ENM2 = ENF = IN, R

SETM

= R

SETF

= 6.8kΩ, P1 = P2 = unconnected, C

REF

= 0.01µF,

T

A

= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

Note 1: All devices are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed by

design.

Note 2: LED dropout voltage is defined as the M_ or F_ to GND voltage at which current into M_ or F_ drops 10% from the value at

M_ or F_ = 0.2V.

Note 3: (Greater of 2.7V or (V

LDO_

+ 0.5V)) ≤ VIN≤ 5.5V.

Note 4: LDO dropout voltage is defined as V

IN

- V

OUT

when V

OUT

is 100mV below the value of V

OUT

measured when VIN=

V

OUT(NOM)

+ 1V. Since the minimum input voltage is 2.7V, this specification is only meaningful when V

OUT(NOM)

> 2.5V.

Typical Operating Characteristics

(VIN= V

EN_

= 3.6V, circuit of Figure 1, TA= +25°C, unless otherwise noted.)

EFFICIENCY vs. Li+ BATTERY

VOLTAGE DRIVING FOUR MAIN LEDs

MAX8631X toc01

Li+ BATTERY VOLTAGE (V)

EFFICIENCY P

LED

/P

BATT

(%)

3.93.63.33.0

50

60

70

80

90

100

40

2.7 4.2

15mA/LED

4.5mA/LED

1.5mA/LED

EFFICIENCY vs. Li+ BATTERY

VOLTAGE DRIVING FLASH LED MODULE

MAX8631 toc02

Li+ BATTERY VOLTAGE (V)

EFFICIENCY P

LED

/P

BATT

(%)

3.93.63.33.0

50

60

70

80

90

100

40

2.7 4.2

80mA TOTAL

160mA TOTAL

400mA TOTAL

BATTERY CURRENT vs. SUPPLY VOLTAGE

DRIVING FOUR MAIN LEDs

MAX8631X toc03

SUPPLY VOLTAGE (V)

BATTERY CURRENT (mA)

3.93.63.33.0

20

40

60

80

100

120

0

2.7 4.2

I

LED

= 15mA

I

LED

= 4.5mA

I

LED

= 1.5mA

V

IN

FALLING

V

IN

RISING

Soft-Start Done Time 100 µs

Dropout Voltage I

Load Regulation VIN = 3.7V, 100µA < I

Power-Supply Rejection

/ΔV

ΔV

OUT

Output Noise Voltage (RMS) 10Hz to 100kHz, C

PARAMETER CONDITIONS MIN TYP MAX UNITS

= 200mA (Note 4) 120 320 mV

LDO_

< 200mA 1.3 %

LDO_

IN

10Hz to 10kHz, C

LDO_

LDO_

= 1µF, I

= 1µF, I

= 10µA -60 dB

LDO_

= 10mA 40 µV

LDO_

RMS

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with

Two LDOs in 4mm x 4mm Thin QFN

_______________________________________________________________________________________

5

Typical Operating Characteristics (continued)

(VIN= V

EN_

= 3.6V, circuit of Figure 1, TA= +25°C, unless otherwise noted.)

BATTERY CURRENT vs. SUPPLY

VOLTAGE DRIVING FLASH

900

800

700

I

= 400mA

FLASH

600

500

I

= 160mA

FLASH

400

300

BATTERY CURRENT (mA)

200

100

0

2.7 4.2

I

FLASH

SUPPLY VOLTAGE (V)

INPUT RIPPLE VOLTAGE vs. SUPPLY

VOLTAGE WITH FLASH AND MAIN LEDs

10

FOUR MAIN LEDs AT 15mA EACH

9

I

8

)

7

RMS

6

5

4

3

INPUT RIPPLE (mV

2

1

0

2.7 5.5

= 10mA

FLASH

I

FLASH

SUPPLY VOLTAGE (V)

= 80mA

= 40mA

I

FLASH

3.93.63.33.0

= 100mA

5.14.73.1 3.5 3.9 4.3

INPUT RIPPLE VOLTAGE vs. SUPPLY

VOLTAGE WITH FOUR MAIN LEDs

1.2

I

= 15mA

1.0

)

RMS

0.8

0.6

0.4

INPUT RIPPLE (mV

0.2

0

2.7 5.5

LED

I

= 4.5mA

LED

I

= 1.5mA

LED

SUPPLY VOLTAGE (V)

LED CURRENT MATCHING vs. SUPPLY

VOLTAGE WITH FOUR FLASH LEDs

102.0

101.5

101.0

100.5

100.0

99.5

99.0

FLASH LED CURRENT (mA)

98.5

98.0

2.7 5.5
SUPPLY VOLTAGE (V)

160

150

MAX8631X toc04

140

130

120

110

100

GROUND PIN SUPPLY CURRENT (μA)

90

80

16.0

15.8

15.6

MAX8631X toc07

15.4

15.2

15.0

14.8

14.6

MAIN LED CURRENT (mA)

14.4

14.2

14.0

LDO GROUND PIN SUPPLY

CURRENT vs. SUPPLY VOLTAGE

V

= V

= 0V, V

ENM

ENF

NO LOAD, BOTH LDOs

2.7 5.5
SUPPLY VOLTAGE (V)

= VIN

ENLDO

150mA, BOTH LDOs

5.14.73.9 4.33.53.1

LED CURRENT MATCHING vs. SUPPLY

VOLTAGE WITH FOUR MAIN LEDs

2.7 5.5

SUPPLY VOLTAGE (V)

5.14.73.9 4.33.53.1

MAX8631X toc05

MAX8631X toc08

MAX8631X toc06

5.14.74.33.93.53.1

MAX8631X toc09

5.14.74.33.93.53.1

LED CURRENT vs. AMBIENT

TEMPERATURE WITH FOUR MAIN LEDs

70

60

50

40

30

20

TOTAL LED CURRENT (mA)

10

0

-40 85
AMBIENT TEMPERATURE (°C)

LED CURRENT vs. AMBIENT
TEMPERATURE WITH FLASH

450

400

MAX8631X toc10

350

300

250

200

150

TOTAL LED CURRENT (mA)

100

50

0

603510-15

-40 85
AMBIENT TEMPERATURE (°C)

603510-15

MAX8631X toc11

MAIN LED CURRENT (mA)

INDIVIDUAL MAIN LED CURRENT

vs. R

100

10

1

R

SETM

SETM

10

(kΩ)

MAX8631X toc12

1001

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VIN= V

EN_

= 3.6V, Circuit of Figure 1, TA= +25°C, unless otherwise noted.)

INDIVIDUAL FLASH LED CURRENT

1000

100

10

FLASH LED CURRENT (mA)

1

1 100

OPERATING WAVEFORMS (1.5x MODE)

V

OUT

V

IN

I

IN

vs. R

SETF

10

R

(kΩ)

SETF

4 MAIN LEDS AT 20mA EACH

MAX8631X toc15

MAX8631X toc13

50mV/div
AC-COUPLED

20mV/div
AC-COUPLED

2mA/div
AC-COUPLED

OPERATING WAVEFORMS (1x MODE)

V

OUT

V

IN

I

IN

4 MAIN LEDS AT 20mA EACH

400ns/div

OPERATING WAVEFORMS (2x MODE)

V

OUT

V

IN

4 MAIN LEDS AT 20mA EACH,

FLASH AT 400mA TOTAL

I

IN

MAX8631X toc14

MAX8631X toc16

50mV/div
AC-COUPLED

20mV/div
AC-COUPLED

2mA/div
AC-COUPLED

50mV/div
AC-COUPLED

20mV/div
AC-COUPLED

2mA/div
AC-COUPLED

400ns/div

STARTUP AND SHUTDOWN

FLASH LED RESPONSE

4 MAIN LEDS AT 20mA EACH,

400mA TOTAL FLASH

1ms/div

MAX8631X toc18

V

ENM_

I

OUT

V

OUT

400ns/div

STARTUP AND SHUTDOWN

MAIN LED RESPONSE

4 MAIN LEDS AT 20mA EACH

1ms/div

MAX8631X toc17

5V/div
0V

100mA/div

0A

5V/div
0V

V

ENF

I

IN

I

OUT

V

OUT

5V/div
0V

500mA/div

0A

500mA/div

0A

5V/div
0V

MAX8631X/Y

SINGLE-WIRE DIMMING RESPONSE

MAX8631X toc19

5V/div
0V

500mA/div

2V/div

0A

0V

V

ENM1,

V

ENM2

I

OUT

V

OUT

10ms/div

LOAD-TRANSIENT RESPONSE

NEAR DROPOUT

MAX8631X toc23

50mV/div
AC-COUPLED

100mA

1mA

V

LDO_

I

LDO_

10μs/div

VIN - V

OUT

= 77mV, V

LDO_

= 2.6V

1x/1.5x/2x White LED Charge Pump with Two

LDOs in 4mm x 4mm Thin QFN

_______________________________________________________________________________________

7

Typical Operating Characteristics (continued)

(VIN= V

EN_

= 3.6V, circuit of Figure 1, TA= +25°C, unless otherwise noted.)

LDO OUTPUT VOLTAGE

ACCURACY vs. OUTPUT CURRENT

1.0

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

OUTPUT VOLTAGE ACCURACY (%)

-0.8

-1.0
0 200

OUTPUT CURRENT (mA)

15010050

XMAX8631X toc21

LDO DROPOUT VOLTAGE

vs. OUTPUT CURRENT

140

120

100

80

60

40

DROPOUT VOTLAGE (mV)

20

0

0 200

OUTPUT CURRENT (mA)

LOAD-TRANSIENT RESPONSE

V

= 2.6V

LDO_

V

LDO_

I

LDO_

10μs/div

15010050

MAX8631X toc22

MAX8631X toc20

50mV/div
AC-COUPLED

100mA

1mA

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN

8 _______________________________________________________________________________________

Figure 1. Functional Diagram and Application Circuit

INPUT

2.7V TO 5.5V

10μF

C1

PIN
IN

GND

PGND

REFBP

C8

0.01μF

ENM1

ENM2

ENF

ENLDO

P1

P2

IN

CONTROL AND

REFERENCE

FLASH CONTROL

MAIN CONTROL

C3

1μF

C1P

C1N C2P C2N

1x/1.5x/2x REGULATING

CHARGE PUMP

ERROR

AMP 1

0.15V

0.6V

C4

1μF

OUT

LDO1

LDO2

M1

M2

M3

M4

C7
1μF

OUTPUT
UP TO 480mA

C5
10μF

D1

D2

D3

D4

C6
1μF

LOW-

DROPOUT

LINEAR

REGULATORS

OVD

1.25V

SELMIN

+

–

+

–

+

–

+

–

R

SETM

6.81kΩ

R

SETF

4.12kΩ

SETM

SETF

ERROR

AMP 2

IN

ERROR

AMP 3

+

–

GND

+

–

GND

+

–

+

–

MAX8631X
MAX8631Y

F1

D5

F2

D6

F3

D7

F4

D8

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two

LDOs in 4mm x 4mm Thin QFN

_______________________________________________________________________________________ 9

Pin Description

PIN NAME FUNCTION

1 PIN

2IN

3 GND

4 LDO1

5 LDO2

6 REFBP Reference Filter. Bypass REFBP with a 0.01µF ceramic capacitor to GND.

7 SETF

8 SETM

9–12 F4–F1

Supply Voltage Input. Bypass to PGND with a 10µF ceramic capacitor. The input voltage range is

2.7V to 5.5V. PIN is high impedance during shutdown.

Chip Supply Voltage Input. Bypass to GND with a 10µF ceramic capacitor as close to the IC as
possible. The input voltage range is 2.7V to 5.5V. IN is high impedance during shutdown.

Ground. Connect GND to system ground and the input bypass capacitor as close to the IC as
possible.

LDO1 Output. Bypass with a 1µF ceramic capacitor to GND. LDO1 is pulled to ground through an
internal 400kΩ during shutdown.

LDO2 Output. Bypass with a 1µF ceramic capacitor to GND. LDO2 is pulled to ground through an
internal 400kΩ during shutdown.

Bias Current Set Input for F1–F4. The current flowing out of SETF sets the maximum (100%) bias
current into each LED. V
GND to set the flash current. R

Bi as C ur r ent S et Inp ut for M 1–M 4. The cur r ent fl ow i ng out of S E TM sets the m axi m um ( 100%) b i as
cur r ent i nto each LE D . V
to set the m ai n LE D cur r ent. R

400m A C om b i ned C ur r ent Fl ash LE D C athod e C onnecti on and C har g e- P um p Feed b ack. C ur r ent fl ow i ng
i nto F_ i s b ased on I
i np ut for ces OU T to op er ate at ap p r oxi m atel y 5V . C onnect F_ to OU T i f thi s LE D i s not p op ul ated .

S E T F

is internally biased to 0.6V. Connect a resistor (R

SETF

S E T M

. The char g e p um p r eg ul ates the l ow est F_ vol tag e to 0.15V . Gr ound i ng any F_

= 414 / I

SETF

i s i nter nal l y b i ased to 0.6V . C onnect a r esi stor ( R

= 138 / I

S E T M

LED(MAX)

L E D ( M AX )

. SETF is high impedance during shutdown.

. S E TM i s hi g h i m p ed ance d ur i ng shutd ow n.

) from SETF to

SETF

) fr om S E TM to GN D

S E T M

13–16 M4–M1

17 P2

18 ENLDO

19 ENM2

20 ENM1

21 ENF

22 C1N

30mA M ai n LE D Cathod e Connecti on and C har g e- P ump Feed b ack. C ur rent fl owi ng i nto M _ i s based on the
E N _ confi g ur ation and I
any M _ for ces OU T to oper ate at ap pr oxim atel y 5V . Connect M_ to OU T i f thi s LE D i s not p op ul ated .

Default Output-Voltage Select Input. P1 and P2 set the LDO1 and LDO2 voltages to one of nine
combinations (Table 2). P2 is high impedance in an off condition and shortly after an on condition.

LDO Output Enable. Drive to a logic-level high to turn on both LDOs. Drive to a logic-level low to turn
off both LDOs.

Enable and Dimming Control for M1–M4. Drive both ENM1 and ENM2 to a logic-level high to turn on
the main LEDs. Drive both ENM1 and ENM2 to a logic-level low to turn off the main LEDs. The
dimming technique is discussed in the Applications Information section.

Enable and Dimming Control for M1–M4. Drive both ENM1 and ENM2 to a logic-level high to turn on
the main LEDs. Drive both ENM1 and ENM2 to a logic-level low to turn off the main LEDs. The
dimming technique is discussed in the Applications Information section.

Enable and Dimming Control for F1–F4. Drive ENF to a logic-level high to turn on the flash LEDs.
Drive ENF to a logic-level low to turn off the flash LEDs. The dimming technique is discussed in the
Applications Information section.

Transfer Capacitor 1 Negative Connection. Connect a 1µF ceramic capacitor between C1P and C1N.
C1N is internally shorted to IN during shutdown.

. The char ge p um p reg ulates the l owest M _ inp ut voltag e to 0.15V . Gr ound i ng

S E TM

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN

10 ______________________________________________________________________________________

Detailed Description

The MAX8631X/Y charge pump drives up to 4 white
LEDs in the main display for backlighting and up to 4
white LEDs for flash, all with regulated constant current
for uniform intensity. By utilizing adaptive 1x/1.5x/2x
charge-pump modes and very-low-dropout current reg­ulators, it achieves high efficiency over the 1-cell lithi­um-battery input voltage range. 1MHz fixed-frequency
switching allows for tiny external components and low
input ripple. Two on-board 200mA programmable-out­put-voltage LDOs are provided to meet camera-module
requirements.

1x to 1.5x Switchover

When VINis higher than V

OUT

, the MAX8631X/Y oper-

ates in 1x mode and V

OUT

is pulled up to VIN. The
internal current regulators regulate the LED current. As
V

IN

drops, VM_(or VF_) eventually falls below the
switchover threshold of 100mV and the MAX8631X/Y
starts switching in 1.5x mode. When the input voltage
rises above V

OUT

by approximately 50mV, the

MAX8631X/Y switches back to 1x mode.

1.5x to 2x Switchover

When VINis less than V

OUT

but greater than two-thirds

V

OUT

, the MAX8631X/Y operates in 1.5x mode. The
internal current regulators regulate the LED current. As
VINdrops, VM_(or VF_) eventually falls below the
switchover threshold of 100mV, and the MAX8631X/Y
starts switching in 2x mode. When the input voltage
rises above two-thirds V

OUT

by approximately 50mV,

the MAX8631X/Y switches back to 1.5x mode.

Soft-Start

The MAX8631X/Y includes soft-start circuitry to limit
inrush current at turn-on. Once the input voltage is
applied, the output capacitor is charged directly from
the input with a ramped current source (with no charge­pump action) until the output voltage approaches the
input voltage. Once the output capacitor is charged,
the charge pump determines if 1x, 1.5x, or 2x mode is
required. In the case of 1x mode, the soft-start is termi­nated and normal operation begins. In the case of 1.5x
or 2x mode, soft-start operates until the lowest voltage
of M1–M4 and F1–F4 reaches regulation. If the output is
shorted to ground or is pulled to less than 1.25V, the
output current is limited by soft-start.

True Shutdown™ Mode

When ENM1, ENM2, and ENF are simultaneously held
low for 2.5ms or longer, the MAX8631X/Y is shut down
and put in a low-current shutdown mode, and the input
is isolated from the output. OUT is internally pulled to
GND with 5kΩ during shutdown.

Thermal Derating

The MAX8631X/Y limits the maximum LED current
depending on the die temperature. The maximum LED
current is set by the R

SETM

and R

SETF

resistors. Once
the temperature reaches +43°C, the LED current
decreases by 1.7%/°C. Due to the package’s exposed
paddle, the die temperature is always very close to the
PC board temperature.

The temperature derating function allows the LED cur­rent to be safely set higher at normal operating temper­atures, thereby allowing either a brighter display or
fewer LEDs to be used for normal display brightness.

Pin Description (continued)

True Shutdown is a trademark of Maxim Integrated Products, Inc.

PIN NAME FUNCTION

23 C1P

24 PGND Power Ground. Connect PGND to system ground. PGND is used for charge-pump switching currents.

25 OUT

26 C2P

27 C2N

28 P1

— EP Exposed Paddle. Connect to GND and PGND.

Transfer Capacitor 1 Positive Connection. Connect a 1µF ceramic capacitor between C1P to C1N.
During shutdown, if OUT > IN, C1P is shorted to OUT. If OUT < IN, C1P is shorted to IN.

Charge-Pump Output. Bypass OUT to GND with a 10µF ceramic capacitor. Connect to the anodes of
all the LEDs. OUT is internally pulled to ground through a 5kΩ resistor during

Transfer Capacitor 2 Positive Connection. Connect a 1µF ceramic capacitor between C2P to C2N.
During shutdown, if OUT > IN, C2P is shorted to OUT. If OUT < IN, C2P is shorted to IN.

Transfer Capacitor 2 Negative Connection. Connect a 1µF ceramic capacitor between C2P and C2N.
C2N is internally shorted to IN during shutdown.

Default Output-Voltage Select Input. P1 and P2 set the LDO1 and LDO2 voltages to one of nine
combinations (Table 2). P1 is high impedance in an off condition and shortly after an on condition.

shutdown.

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two

LDOs in 4mm x 4mm Thin QFN

______________________________________________________________________________________ 11

Thermal Shutdown

The MAX8631X/Y includes a thermal-limit circuit that
shuts down the IC at approximately +160°C. Turn-on
occurs after the IC cools by approximately 20°C.

Applications Information

Setting the Main Output Current

SETM controls M1–M4 regulation current. Current flow­ing into M1, M2, M3, and M4 is a multiple of the current
flowing out of SETM:

IM1= IM2= IM3= IM4= K x (0.6V / R

SETM

)

where K = 230, and R

SETM

is the resistor connected

between SETM and GND (see the

Typical Operating

Circuit

).

Setting the Flash Output Current

SETF controls the F1–F4 regulation current. Current
flowing into F1, F2, F3, and F4 is a multiple of the cur­rent flowing out of SETF.

IF1= IF2= IF3= IF4= N x (0.6V / R

SETF

)

where N = 690.

Single-Wire Pulse Dimming

For more dimming flexibility or to reduce the number of
control traces, the MAX8631X/Y supports serial pulse
dimming. Connect ENM1 and ENM2 together to enable
single-wire pulse dimming of the main LEDs (or ENF
only for single-wire pulse dimming of the flash LEDs).
See Figure 3. When ENM1 and ENM2 (or ENF) go high
simultaneously, the main (or flash) LEDs are enabled at
full brightness. Each subsequent low-going pulse

(500ns to 250µs pulse width) reduces the LED current
by 3.125% (1/32), so after one pulse the LED current is

96.9% (or 31/32) x I

LED

. The 31st pulse reduces the

current to 0.03125 x I

LED

. The 32nd pulse sets the LED

current back to I

LED

. Figure 2 shows a timing diagram
for single-wire pulse dimming. Because soft-start is
longer than the initial tHI, apply dimming pulses quickly
upon startup (after initial tHI) to avoid LED current tran­sitioning through full brightness.

Simple On/Off Control

If dimming control is not required, connect ENM1 to
ENM2 for simple on/off control. Drive both ENM1 and
ENM2 to a logic-level high to turn on the main LEDs.
Drive both ENM1 and ENM2 to a logic-level low to turn
off the main LEDs. ENF is the simple on/off control for
the flash LEDs. Drive ENF to a logic-level high to turn
on the flash LEDs. Drive ENF to a logic-level low to turn
off the flash LEDs. In this case, LED current is set by
the values of R

SETM

and R

SETF

.

Driving Fewer than 8 LEDs

When driving fewer than 8 LEDs, two different connec­tion schemes can be used. The first scheme is shown
in Figure 4 where LED drivers are connected together.
This method allows increased current through the LED
and effectively allows total LED current to be I

LED

multi­plied by the number of connected drivers. The second
method of connection is shown in Figure 5 where stan­dard white LEDs are used and fewer than 8 are con­nected. This scheme does not alter current through
each LED but ensures that the unused LED driver is
properly disabled.

Input Ripple

For LED drivers, input ripple is more important than out­put ripple. Input ripple is highly dependent on the
source supply’s impedance. Adding a lowpass filter to
the input further reduces input ripple. Alternately,
increasing CINto 22µF cuts input ripple in half with only
a small increase in footprint. The 1x mode always has
very low input ripple.

Figure 2. ENM_ and ENF Timing Diagram

Table 1. ENM1/ENM2 States

INITIAL t

HI

≥ 200μs

ENM1 AND ENM2

OR

ENF

I

OR I

M_

F_

SHUTDOWN

t

SOFT-START

32/32

10243 5 27 28 29 30 31 32

31/32

t

30/32

500ns TO 250μs

29/32

28/32

27/32

t

LO

t

HI

≥500ns

5/32

4/32

3/32

2/32

32/32

1/32

31/32

SHDN

(2.5ms)

SHUTDOWN

ENM1/ENM2 STATES BRIGHTNESS

ENM1 = low, ENM2 = low Shutdown 0

ENM1 = high, ENM2 = high Full brightness 230 x I

M1–M4

CURRENT

SETM

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN

12 ______________________________________________________________________________________

Figure 4. Providing Increased LED Current per LED

Figure 3. Dimming Using Single-Wire, Serial-Pulse Interface

INPUT

2.7V TO 5.5V

10μF

MAIN ON/OFF

AND DIMMING

FLASH ON/OFF

AND DIMMING

ON/OFF

VOLTAGE

SELECTION

C1P C1N

PIN

IN

GND

ENM2

ENM1

ENF

ENLDO

P1

P2

6.81kΩ

1μF

4.12kΩ

1μF

C2P C2N

MAX8631X
MAX8631Y

REFBPSETM SETF PGND

0.01μF

1μF

1μF

LDO1

LDO2

OUT

1μF

1μF

OUTPUT

UP TO 480mA

10μF

M1
M2
M3
M4

F1
F2
F3
F4

MAIN FLASH

INPUT

2.7V TO 5.5V

10μF

ON/OFF AND

VOLTAGE

SELECTION

6.81kΩ

C1P C1N

PIN

IN

GND

ENM2

ENM1

ENF

ENLDO

P1

P2

4.12kΩ

C2P C2N

MAX8631X
MAX8631Y

REFBPSETM SETF PGND

0.01μF

LDO1

LDO2

OUT

1μF

1μF

OUTPUT

UP TO 480mA

MAIN FLASH

10μF

M1
M2
M3
M4

F1
F2
F3
F4

Typical operating waveforms shown in the

Typical

Operating Characteristics

show input ripple current in

1x, 1.5x, and 2x mode.

LDO Output Voltage Selection (P1 and P2)

As shown in Table 2, the LDO output voltages, LDO1
and LDO2 are pin-programmable by the logic states of
P1 and P2. P1 and P2 are tri-level inputs: IN, open, and
GND. The input voltage, VIN, must be greater than the
selected LDO1 and LDO2 voltages. The logic states of
P1 and P2 can be programmed only during ENLDO
low. Once the LDO_ voltages are programmed, their
values do not change by changing P1 or P2 during
ENLDO high.

Component Selection

Use only ceramic capacitors with an X5R, X7R, or better
dielectric. See Table 3 for a list of recommended parts.

Connect a 1µF ceramic capacitor between LDO1 and
GND, and a second 1µF ceramic capacitor between
LDO2 and GND for 200mA applications. The LDO out­put capacitor’s (C

LDO

) equivalent series resistance
(ESR) affects stability and output noise. Use output
capacitors with an ESR of 0.1Ω or less to ensure stability
and optimum transient response. Connect C

LDO_

as
close to the MAX8631X/Y as possible to minimize the
impact of PC board trace inductance.

PC Board Layout and Routing

The MAX8631X/Y is a high-frequency switched-capaci­tor voltage regulator. For best circuit performance, use
a solid ground plane and place CIN, C

OUT

, C3, and C4
as close to the MAX8631X/Y as possible. There should
be no vias on CIN. Connect GND and PGND to the
exposed paddle directly under the IC. Refer to the
MAX8631X/Y evaluation kit for an example.

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with Two

LDOs in 4mm x 4mm Thin QFN

______________________________________________________________________________________ 13

Figure 5. Schematic for When Fewer than 8 LEDs Is Acceptable

Table 2. P1 and P2, LDO Output Voltage
Selection

1μF

INPUT

2.7V TO 5.5V

10μF

ON/OFF AND

VOLTAGE

SELECTION

6.81kΩ

C1P C1N

PIN

IN

GND

ENM2

ENM1

ENF

ENLDO

P1

P2

4.12kΩ

MAX8631X
MAX8631Y

REFBPSETM SETF PGND

1μF

C2P C2N

0.01μF

LDO1

LDO2

OUT

1μF

1μF

OUTPUT

UP TO 240mA

MAIN FLASH

10μF

M1
M2
M3
M4

F1
F2
F3
F4

P1 P2

IN IN 3.3 1.8 2.8 2.6

IN OPEN 3.0 1.5 2.8 2.8

IN GND 2.8 1.5 2.9 1.5

OPEN IN 3.3 1.5 2.6 1.9

OPEN OPEN 2.6 1.8 2.6 2.6

OPEN GND 2.6 1.5 2.8 1.9

GND IN 3.0 1.8 2.9 1.8

GND OPEN 2.8 1.8 2.9 1.9

GND GND 2.5 1.8 2.9 2.9

MAX8631X MAX8631Y

LDO1 (V) LDO2 (V) LDO1 (V) LDO2 (V)

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with
Two LDOs in 4mm x 4mm Thin QFN

14 ______________________________________________________________________________________

Table 3. Recommended Components for Figure 1

Chip Information

PROCESS: BiCMOS

Pin Configuration

Package Information

For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages

.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

28 TQFN-EP T2844-1

21-0139

DESIGNATION VALUE MANUFACTURER PART NUMBER DESCRIPTION

C1, C5 10µF TDK C2012X5R0J106M 10µF ±20%, 6.3V X5R ceramic capacitors (0805)

C3, C4, C6, C7 1µF TDK C1005X5R0J105M 1µF ±20%, 6.3V X5R ceramic capacitors (0402)

C8 0.01µF TDK C1005X7R1E103K 0.01µF ±10%, 25V X7R ceramic capacitor (0402)

D1–D4 — Nichia NSCW215T White LEDs

D5 (D5–D8) — Nichia NBCW011T White LEDs, 4 LEDs in one package

R

SETM

, R

SETF

As

Required

Panasonic

Vishay

— 1% resistor

TOP VIEW

PGND

ENM2

ENF

ENM1

21 20 19 18 17 16 15

C1N

22

C1P

23

24

25

OUT

C2P

26

27

C2N

28

P1

+

1234567

IN

PIN

4mm x 4mm, 0.4mm LEAD PITCH

ENLDO

MAX8631XETI
MAX8631YETI

GND

LDO1

THIN QFN

P2

LDO2

M1

REFBP

M2

SETF

14

M3

M4

13

12

F1

11

F2

10

F3

9

F4

8

SETM

MAX8631X/Y

1x/1.5x/2x White LED Charge Pump with

Two LDOs in 4mm x 4mm Thin QFN

Revision History

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.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________

15

© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

REVISION

NUMBER

3 6/08

REVISION

DATE

DESCRIPTION

Removed PWM dimming control feature and updated ENM_ and ENF low
shutdown delay EC values

PAGES

CHANGED

1, 2, 9–12, 14