Datasheet MAX8645YETI+, MAX8645X Datasheet (Maxim)

EVALUATION KIT

AVAILABLE

General Description

The MAX8645X/MAX8645Y charge pumps drive up to
eight white LEDs with regulated constant current for uni­form intensity. The main group of LEDs (M1–M6) can be
driven up to 30mA per LED for backlighting. The flash
group of LEDs (F1 and F2) is independently controlled
and can be driven up to 200mA 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. The MAX8645X and MAX8645Y differ only in LDO
output voltages. By utilizing adaptive 1x/1.5x/2x charge­pump modes and very-low-dropout current regulators,
the MAX8645X/MAX8645Y achieve 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 MAX8645X/MAX8645Y are available in a 28-pin TQFN,
4mm x 4mm (0.8mm max height) lead-free package.

Applications

Camera Phones and Smartphones

Backlighting and Flash

PDAs, Digital Cameras, and Camcorders

Features

♦ Power Up to Eight 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

♦ Flexible Brightness Control

Single-Wire, Serial-Pulse Interface (32 Steps)

2-Bit Logic (Three Levels)

♦ Thermal T

A

Derating Function

♦ Low Input Ripple and EMI

♦ 2.7V to 5.5V Supply Voltage Range

♦ Soft-Start, Overvoltage, and Thermal-Shutdown

Protection

♦ 28-Pin TQFN, 4mm x 4mm Package

MAX8645X/MAX8645Y

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

Two LDOs in 4mm x 4mm TQFN

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3978; Rev 3; 12/06

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.

PART TEMP RANGE

PIN­PACKAGE

PKG

CODE

MAX8645XETI+ -40°C to +85°C

28 TQFN-EP
4mm x 4mm

T2844-1

MAX8645YETI+ -40°C to +85°C

28 TQFN-EP
4mm x 4mm

T2844-1

Pin Configuration appears at end of data sheet.

MAIN ON/OFF

AND DIMMING

MAX8645X
MAX8645Y

1μF

10μF

0.01μF

10μF

PIN

IN

PGND

GND

P1

P2

OUT

MAIN

FLASH

OUTPUT

UP TO 580mA

1μF1μF

LDO1
LDO2

C2P C2N

1μF

C1P C1N

REFSETM SETF

CAMERA
MODULE

DUAL-LDO

VOLTAGE

SELECTION

INPUT

2.7V TO 5.5V

ENM2

ENM1

ENF

ENLDO

M1
M2
M3
M4
M5
M6

F1
F2

FLASH ON/OFF

DUAL-LDO ON/OFF

Typical Operating Circuit

EP = Exposed paddle.
+Denotes a lead-free package.

MAX8645X/MAX8645Y

1x/1.5x/2x White LED Charge Pumps with Two
LDOs in 4mm x 4mm TQFN

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, M5, M6, F1,

F2 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 the 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 TQFN 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

PARAMETER CONDITIONS MIN TYP MAX UNITS

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

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

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

ENLDO

= VIN,

I

LDO1

= I

LDO2

= 0A

0.4

mA

Supply Current

ENM1 = ENM2 = ENF = GND, V

ENLDO

= VIN,

I

LDO1

= I

LDO2

= 0A

110 µA

TA = +25°C 0.01 5

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

T

A

= +85°C 0.1

µA

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

EN_ Low Voltage V

IN

= 2.7V to 5.5V 0.4 V

TA = +25°C 0.01 1

EN_ Input Current V

EN_

= 0V or 5.5V

T

A

= +85°C 0.1

µA

ENM_ or ENF Low Shutdown
Delay t

SHDN

See Figure 1 1.5 2.0 2.5 ms

ENM_ or ENF t

LO

See Figure 1 0.5 250.0 µs

ENM_ or ENF t

HI

See Figure 1 0.5 µs

Initial ENM_ or ENF t

HI

Only required for first ENM_ or ENF pulse; see Figure 1 200 µs

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

OUT

rising 5 V

Soft-Start Time 2ms

MAX8645X/MAX8645Y

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

LDOs in 4mm x 4mm TQFN

_______________________________________________________________________________________ 3

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)

PARAMETER CONDITIONS MIN TYP MAX UNITS

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

90 100 110 mV

Input Voltage-Mode Transition
Hysteresis

150 mV

Charge-Pump Maximum OUT
Current

V

IN

≥ 3.15V, V

OUT

= 3.9V 580 mA

1x mode (VIN - V

OUT

) / I

OUT

0.3 1.0

1.5x mode (1.5VIN - V

OUT

) / I

OUT

1.1 4.0Open-Loop OUT Resistance

2x mode (2V

IN

- V

OUT

) / I

OUT

1.5 4.14

Ω

Charge-Pump Short-Circuit
Current

V

OUT

< 1.25V 500 mA

Switching Frequency 1 MHz

OUT Pulldown Resistance in
Shutdown

ENM_ = ENF = GND 5 kΩ

LED DRIVER

SET_ Bias Voltage TA = +25°C 0.6 V

TA = +25°C 0.01 1

SET_ Leakage in Shutdown ENM_ = ENF = GND

T

A

= +85°C 0.1

µA

SET_ Current Range 10 145 µA

SETM-to-Main LED Current Ratio
(I

M_

/I

SETM

)

100% setting, M1–M6 230 A/A

SETF-to-Flash LED Current Ratio
(I

F_/ISETF

)

100% setting, F1 and F2 1380 A/A

TA = +25°C -1.25 +1.25

M_, F_ Current Accuracy

T

A

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

%

Maximum Main LED Sink Current R

SETM

= 4.6kΩ, for each M_ 30 mA

Maximum Flash LED Sink Current R

SETF

= 4.12kΩ, IF1 + I

F2

400 mA

Current-Derating-Function Start
Temperature

+40 °C

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

TA = +25°C 0.01 2

M_, F_ Leakage in Shutdown ENM_ = ENF = GND

T

A

= +85°C 0.1

µA

LDO_

Output Voltage Accuracy

I

LDO_

= 150mA, relative to V

OUT(NOM)

(Note 3) -1.7 0 +1.7 %

Output Current Range 0 200 mA

Current Limit V

LDO_

= 0V 280 475 750 mA

Soft-Start Current Limit 160 mA

MAX8645X/MAX8645Y

1x/1.5x/2x White LED Charge Pumps with
Two LDOs in 4mm x 4mm TQFN

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)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Soft-Start Done Time 100 µs

Dropout Voltage I

LDO_

= 200mA (Note 4) 120 320 mV

Load Regulation VIN = 3.7V, 100µA < I

LDO_

< 200mA 1.3 %

Power-Supply Rejection
ΔV

OUT

/ΔV

IN

10Hz to 10kHz, C

LDO_

= 1µF, I

LDO_

= 10µA -60 dB

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

LDO_

= 1µF, I

LDO_

= 10mA 40 µV

RMS

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 2, TA= +25°C, unless otherwise noted.)

EFFICIENCY vs. Li+ BATTERY

VOLTAGE DRIVING SIX MAIN LEDs

MAX8645Y 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

MAX8645Y 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 SIX MAIN LEDs

MAX8645Y toc03

SUPPLY VOLTAGE (V)

BATTERY CURRENT (mA)

3.93.63.33.0

30

60

90

120

150

180

0

2.7 4.2

I

LED

= 15mA

I

LED

= 4.5mA

I

LED

= 1.5mA

V

IN

FALLING

V

IN

RISING

MAX8645X/MAX8645Y

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

Two LDOs in 4mm x 4mm TQFN

_______________________________________________________________________________________ 5

BATTERY CURRENT vs. SUPPLY

VOLTAGE DRIVING FLASH

MAX8645Y toc04

SUPPLY VOLTAGE (V)

BATTERY CURRENT (mA)

3.93.63.33.0

100

200

300

400

500

600

700

800

900

0

2.7 4.2

I

FLASH

= 400mA

I

FLASH

= 160mA

I

FLASH

= 80mA

LDO GROUND-PIN SUPPLY

CURRENT vs. SUPPLY VOLTAGE

MAX8645Y toc05

SUPPLY VOLTAGE (V)

GROUND-PIN SUPPLY CURRENT (μA)

5.14.73.9 4.33.53.1

90

100

110

120

130

140

150

160

80

2.7 5.5

V

ENM_

= V

ENF

= 0V, V

ENLDO

= VIN

150mA, BOTH LDOs

NO LOAD, BOTH LDOs

INPUT RIPPLE VOLTAGE vs. SUPPLY

VOLTAGE WITH SIX MAIN LEDs

MAX8645Y toc06

SUPPLY VOLTAGE (V)

INPUT RIPPLE (mV

RMS

)

5.14.74.33.93.53.1

0.3

0.6

0.9

1.2

1.5

1.8

0

2.7 5.5

I

LED

= 15mA

I

LED

= 4.5mA

I

LED

= 1.5mA

INPUT RIPPLE VOLTAGE vs. SUPPLY

VOLTAGE WITH FLASH AND MAIN LEDs

MAX8645Y toc07

SUPPLY VOLTAGE (V)

INPUT RIPPLE (mV

RMS

)

5.14.73.1 3.5 3.9 4.3

1

2

3

4

5

7

9

6

8

10

0

2.7 5.5

FOUR MAIN LEDs AT 15mA EACH

I

FLASH

= 40mA

I

FLASH

= 160mA

I

FLASH

= 400mA

LED CURRENT MATCHING vs. SUPPLY

VOLTAGE WITH SIX MAIN LEDs

MAX8645Y toc08

SUPPLY VOLTAGE (V)

MAIN LED CURRENT (mA)

5.14.73.9 4.33.53.1

14.2

14.4

14.6

14.8

15.0

15.2

15.4

15.6

15.8

16.0

14.0

2.7 5.5

LED CURRENT MATCHING vs. SUPPLY

VOLTAGE WITH TWO FLASH LEDs

MAX8645Y toc09

SUPPLY VOLTAGE (V)

FLASH LED CURRENT (mA)

5.14.74.33.93.53.1

99.0

98.5

99.5

100.0

100.5

101.0

101.5

102.0

98.0

2.7 5.5

LED CURRENT vs. AMBIENT

TEMPERATURE WITH SIX MAIN LEDs

MAX8645Y toc10

TA (°C)

TOTAL LED CURRENT (mA)

603510-15

15

30

45

60

75

90

105

0

-40 85

LED CURRENT vs. AMBIENT

TEMPERATURE WITH FLASH

MAX8645Y toc11

TA (°C)

TOTAL LED CURRENT (mA)

603510-15

50

100

150

200

250

300

350

400

450

0

-40 85

INDIVIDUAL MAIN LED CURRENT

vs. R

SETM

MAX8645Y toc12

R

SETM

(kΩ)

MAIN LED CURRENT (mA)

10

10

100

1

1001

Typical Operating Characteristics (continued)

(VIN= V

EN_

= 3.6V, circuit of Figure 2, TA= +25°C, unless otherwise noted.)

MAX8645X/MAX8645Y

1x/1.5x/2x White LED Charge Pumps with Two
LDOs in 4mm x 4mm TQFN

6 _______________________________________________________________________________________

INDIVIDUAL FLASH LED CURRENT

vs. R

SETF

MAX8645Y toc13

R

SETF

(kΩ)

FLASH LED CURRENT (mA)

10

20

200

2000

2

1100

OPERATING WAVEFORMS (1x MODE)

MAX8645Y toc14

50mV/div
AC-COUPLED

20mV/div
AC-COUPLED

2mA/div
AC-COUPLED

V

OUT

V

IN

I

IN

400ns/div

6 MAIN LEDS AT 20mA EACH

OPERATING WAVEFORMS (1.5x MODE)

MAX8645Y toc15

50mV/div
AC-COUPLED

20mV/div
AC-COUPLED

2mA/div
AC-COUPLED

V

OUT

V

IN

I

IN

400ns/div

6 MAIN LEDS AT 20mA EACH

OPERATING WAVEFORMS (2x MODE)

MAX8645Y toc16

50mV/div
AC-COUPLED

20mV/div
AC-COUPLED

2mA/div
AC-COUPLED

V

OUT

V

IN

I

IN

400ns/div

6 MAIN LEDS AT 20mA EACH,

FLASH AT 400mA TOTAL

STARTUP AND SHUTDOWN

MAIN LED RESPONSE

MAX8645Y toc17

5V/div
0V

100mA/div

5V/div
0V

0A

V

ENM_

I

OUT

V

OUT

1ms/div

6 MAIN LEDS AT 20mA EACH

STARTUP AND SHUTDOWN

FLASH LED RESPONSE

MAX8645Y toc18

5V/div
0V

500mA/div

500mA/div

5V/div
0V

0A

0A

V

ENF

I

IN

V

OUT

I

OUT

1ms/div

6 MAIN LEDS AT 20mA EACH,

400mA TOTAL FLASH

Typical Operating Characteristics (continued)

(VIN= V

EN_

= 3.6V, circuit of Figure 2, TA= +25°C, unless otherwise noted.)

MAX8645X/MAX8645Y

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

LDOs in 4mm x 4mm TQFN

_______________________________________________________________________________________ 7

SINGLE-WIRE DIMMING RESPONSE

MAX8645Y toc19

5V/div
0V

500mA/div

2V/div

0A

0V

V

ENM1,

V

ENM2

I

OUT

V

OUT

10ms/div

LDO DROPOUT VOLTAGE

vs. OUTPUT CURRENT

MAX8645Y toc20

OUTPUT CURRENT (mA)

DROPOUT VOLTAGE (mV)

15010050

20

40

60

80

100

120

140

0

0200

LDO OUTPUT VOLTAGE

ACCURACY vs. OUTPUT CURRENT

MAX8645Y toc21

OUTPUT CURRENT (mA)

OUTPUT VOLTAGE ACCURACY (%)

15010050

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1.0

-1.0
0200

LOAD-TRANSIENT RESPONSE

MAX8645Y toc22

50mV/div
AC-COUPLED

100mA

1mA

V

LDO_

I

LDO_

10μs/div

V

LDO_

= 2.6V

LOAD-TRANSIENT RESPONSE

NEAR DROPOUT

MAX8645Y toc23

50mV/div
AC-COUPLED

100mA

1mA

V

LDO_

I

LDO_

10μs/div

VIN - V

OUT

= 77mV, V

LDO_

= 2.6V

Typical Operating Characteristics (continued)

(VIN= V

EN_

= 3.6V, circuit of Figure 2, TA= +25°C, unless otherwise noted.)

MAX8645X/MAX8645Y

1x/1.5x/2x White LED Charge Pumps with Two
LDOs in 4mm x 4mm TQFN

8 _______________________________________________________________________________________

Pin Description

PIN NAME FUNCTION

1 PIN

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.

2IN

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

3 GND G r ound . C onnect G N D to system g r ound and the i np ut b yp ass cap aci tor as cl ose as p ossi b l e to the IC .

4 LDO1

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

5 LDO2

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

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

7 SETF

Bias Current Set Input for F1, F2. The current flowing out of SETF sets the maximum (100%) bias
current into each LED. V

SETF

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

SETF

) from SETF to

GND to set the flash current. R

SETF

= 82.8 / I

LED(MAX)

. SETF is high impedance during shutdown.

8 SETM

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

S E T M

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

S E T M

) fr om S E TM to GN D

to set the m ai n LE D cur r ent. R

S E T M

= 138 / I

L E D ( M AX )

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

9, 10 F2, F1

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

S E T F

. 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_

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 .

11–16 M6–M1

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

S E TM

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

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 L E D i s not p op ul ated .

17 P2

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.

18 ENLDO

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.

19 ENM2

Enable and Dimming Control for M1–M6. 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. Alternate
dimming techniques are discussed in the Applications Information section.

20 ENM1

Enable and Dimming Control for M1–M6. 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. Alternate
dimming techniques are discussed in the Applications Information section.

21 ENF

Enable and Dimming Control for F1, F2. 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. Dimming techniques are discussed in the
Applications Information section.

22 C1N

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

MAX8645X/MAX8645Y

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

LDOs in 4mm x 4mm TQFN

_______________________________________________________________________________________ 9

Detailed Description

The MAX8645X/MAX8645Y charge pumps drive up to
six white LEDs in the main display for backlighting and
up to two 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, they achieve high efficiency over the
1-cell lithium-battery input voltage range. 1MHz fixed­frequency 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 MAX8645X/

MAX8645Y operate in 1x mode and V

OUT

is pulled up
to VIN. The internal current regulators regulate the LED
current. As VINdrops, VM_(or VF_) eventually falls
below the switchover threshold of 100mV and the
MAX8645X/MAX8645Y start switching in 1.5x mode.
When the input voltage rises above V

OUT

by approxi­mately 50mV, the MAX8645X/MAX8645Y switch back to
1x mode.

1.5x to 2x Switchover

When VINis less than V

OUT

but greater than 2/3 V

OUT

,
the MAX8645X/MAX8645Y operate 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 MAX8645X/
MAX8645Y start switching in 2x mode. When the input
voltage rises above 2/3 V

OUT

by approximately 50mV,

the MAX8645X/MAX8645Y switch back to 1.5x mode.

Soft-Start

The MAX8645X/MAX8645Y include 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–M6 and F1, F2 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 2ms or longer, the MAX8645X/MAX8645Y are
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 MAX8645X/MAX8645Y limit 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 +40°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
PCB 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)

PIN NAME FUNCTION

23 C1P

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

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

25 OUT

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

shutdown.

26 C2P

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

27 C2N

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

28 P1

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 in an on condition.

— EP Exposed Paddle. Connect to GND and PGND.

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

MAX8645X/MAX8645Y

1x/1.5x/2x White LED Charge Pumps with Two
LDOs in 4mm x 4mm TQFN

10 ______________________________________________________________________________________

Thermal Shutdown

The MAX8645X/MAX8645Y include a thermal-limit circuit
that shuts down the IC at approximately +160°C. Turn­on occurs after the IC cools by approximately 20°C.

Applications Information

Setting the Main Output Current

SETM controls M1–M6 regulation current. Current flow­ing into M1, M2, M3, M4, M5, and M6 is a multiple of
the current flowing out of SETM:

IM1= IM2= IM3= IM4= IM5= IM6= K x (0.6V / R

SETM

)

where K = 23, 69, or 230 (depending upon the state of
ENM1 and ENM2; see Table 1), 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, F2 regulation current. Current
flowing into F1 and F2 is a multiple of the current flow­ing out of SETF:

IF1= IF2= N x (0.6V / R

SETF

)

where N = 1380.

Single-Wire Pulse Dimming

For more dimming flexibility or to reduce the number of
control traces, the MAX8645X/MAX8645Y support 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). 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 1 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

.

Dimming Using PWM into ENM1

Use ENM2 for shutdown and drive ENM1 with a PWM
signal. LED brightness can be varied from 10% to full
brightness based upon the duty cycle of the PWM sig­nal. Drive ENM2 high to keep the IC on, eliminating any
soft-start delay that would impede PWM control and
allowing a PWM frequency up to 5kHz (Figure 2).

Driving Fewer than Eight LEDs

When driving fewer than eight LEDs, two connection
schemes can be used. The first scheme is shown in
Figure 3 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 4 where stan­dard white LEDs are used and fewer than eight are
connected. This scheme does not alter current through
each LED but ensures that the unused LED driver is
properly disabled.

10243 5 27 28 29 30 31 32

SHUTDOWN

t

SHDN

2ms (typ)

2/32

1/32

3/32

4/32

5/32

27/32

28/32

29/32

30/32

31/32

31/32

32/32

32/32

SHUTDOWN

I

M_

OR I

F_

ENM1 AND ENM2

OR

ENF

t

SOFT-START

INITIAL t

HI

t

LO

t

HI

≥ 200μs

≥ 500ns

500ns TO 250μs

Figure 1. ENM_ and ENF Timing Diagram

ENM1/ENM2 STATES BRIGHTNESS

M1–M6

CURRENT

ENM1 = low, ENM2 = low Shutdown 0

ENM1 = low, ENM2 = high 1/10 brightness 23 x I

SETM

ENM1 = high, ENM2 = low 3/10 brightness 69 x I

SETM

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

SETM

Table 1. ENM1/ENM2 States

MAX8645X/MAX8645Y

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

LDOs in 4mm x 4mm TQFN

______________________________________________________________________________________ 11

MAX8645X
MAX8645Y

1μF

10μF

0.01μF

10μF

PIN

IN

GND

P1

P2

OUT

MAIN FLASH

OUTPUT

UP TO 480mA

1μF

1μF

LDO1

LDO2

C2P C2N

1μF

C1P C1N

REFBPSETM SETF PGND

ON/OFF AND

VOLTAGE

SELECTION

INPUT

2.7V TO 5.5V

ENM2

ENM1

ENF

ENLDO

M1
M2
M3
M4
M5
M6

F1
F2

4.12kΩ

6.81kΩ

Figure 3. Providing Increased LED Current per LED

MAX8645X
MAX8645Y

C4

1μF

C8

0.01μF

C1

10μF

PIN

IN

ON

OFF

GND

P1

P2

OUT

MAIN FLASH

OUTPUT

UP TO 480mA

C6

1μF
C7
1μF

C5
10μF

LDO1

LDO2

C2P C2N

C3

1μF

C1P C1N

REFBPSETM SETF PGND

VOLTAGE

SELECTION

INPUT

2.7V TO 5.5V

ENM2

ENM1

ENF

ENLDO

M1
M2
M3
M4
M5
M6

F1
F2

R

SETF

4.12kΩ

PWM INPUT

ON/OFF

ON/OFF

R

SETM

6.81kΩ

Figure 2. Dimming Using PWM Signal into ENM1

MAX8645X/MAX8645Y

1x/1.5x/2x White LED Charge Pumps with Two
LDOs in 4mm x 4mm TQFN

12 ______________________________________________________________________________________

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.

Typical operating waveforms shown in the Typical
Operating Characteristics show input ripple current in
1x, 1.5x, and 2x modes.

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 as possible to the MAX8645X/MAX8645Y to mini­mize the impact of PCB trace inductance.

MAX8645X
MAX8645Y

1μF

10μF

0.01μF

10μF

PIN

IN

GND

P1

P2

OUT

MAIN FLASH

OUTPUT

UP TO 240mA

1μF

1μF

LDO1

LDO2

C2P C2N

1μF

C1P C1N

REFBPSETM SETF PGND

ON/OFF AND

VOLTAGE

SELECTION

INPUT

2.7V TO 5.5V

ENM2

ENM1

ENF

ENLDO

M1
M2
M3
M4
M5
M6

F1
F2

4.12kΩ

6.81kΩ

Figure 4. Schematic for When Fewer than 8 LEDs Are Acceptable

MAX8645X MAX8645Y

P1 P2

LDO1 (V) LDO2 (V)

LDO1 (V) LDO2 (V)

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

Table 2. P1 and P2, LDO Output Voltage
Selection

MAX8645X/MAX8645Y

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

Two LDOs in 4mm x 4mm TQFN

______________________________________________________________________________________ 13

MAX8645YETI

PCB Layout and Routing

The MAX8645X/MAX8645Y are high-frequency,
switched-capacitor voltage regulators. For best circuit
performance, use a solid ground plane and place CIN,
C

OUT

, C3, and C4 as close as possible to the IC. There
should be no vias on CIN. Connect GND and PGND to
the exposed paddle directly under the IC. Refer to the
MAX8645Y evaluation kit for an example.

DESIGNATION VALUE MANUFACTURER PART 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

Panasonic

R

SETM

, R

SETF

As

required

Vishay

— 1% resistors

Table 3. Recommended Components for Figure 2

Chip Information

PROCESS: BiCMOS

9

8

11

12

13

14

10

23

22

25

26

27

28

24

21 20 19 18 17 16 15

1234567

MAX8645X
MAX8645Y

THIN QFN

(4mm x 4mm, 0.4mm LEAD PITCH)

TOP VIEW

PGND

C1P

ENF

ENM2

P2

M1

M2

M3

M4

M5

M6

F1

F2

SETM

REFBP

LDO2

LDO1

GND

IN

PIN

ENM1

ENLDO

C2P

C1N

C2N

+ DENOTES A LEAD-FREE PACKAGE.

OUT

P1

SETF

Pin Configuration

MAX8645X/MAX8645Y

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

14 ______________________________________________________________________________________

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

24L QFN THIN.EPS

PACKAGE OUTLINE,

21-0139

2

1

E

12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm

MAX8645X/MAX8645Y

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

LDOs in 4mm x 4mm TQFN

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.

15 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

PACKAGE OUTLINE,

21-0139

2

2

E

12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm