MAX8631XETI+ [MAXIM]
1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN;
| 型号： | MAX8631XETI+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN |
| 文件： | 总15页 (文件大小：266K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3688; Rev 3; 6/08
1x/1.5x/2x White LED Charge Pump with
Two LDOs in 4mm x 4mm Thin QFN
MA8631X/Y
General Description
Features
The MAX8631X/Y charge pump drives up to eight white
LEDs with regulated constant current for uniform inten-
sity. 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 cam-
era functions. The LDOs’ output voltages are pin-pro-
grammable to meet different camera-module
requirements. By utilizing adaptive 1x/1.5x/2x charge-
pump 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-fre-
quency switching allows for tiny external components,
and the regulation scheme is optimized to ensure low
EMI and low input ripple.
♦ 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
/P
) over Li+
LED BATT
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 T Derating Function
A
The MAX8631X/Y is available in a 28-pin thin QFN,
4mm x 4mm lead-free package (0.8mm max height).
♦ Low Input Ripple and EMI
♦ 2.7V to 5.5V Supply Voltage Range
Applications
Camera Phones and Smartphones
Backlighting and Flash
♦ Soft-Start, Overvoltage, and Thermal-Shutdown
Protection
♦ 28-Pin Thin QFN, 4mm x 4mm Package
PDAs, Digital Cameras, and Camcorders
Typical Operating Circuit
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
1μF
1μF
28 Thin QFN-EP*
4mm x 4mm (T2844-1)
MAX8631XETI+
-40°C to +85°C
OUTPUT
UP TO 480mA
INPUT
2.7V TO 5.5V
C1P
PIN
C1N
C2P
C2N
OUT
MAIN
FLASH
10μF
IN
28 Thin QFN-EP*
4mm x 4mm (T2844-1)
MAX8631YETI+
-40°C to +85°C
10μF
MAX8631X/Y
GND
M1
M2
*EP = Exposed pad.
+Denotes a lead-free package.
PGND
M3
M4
F1
ENM1
ENM2
MAIN ON/OFF
AND DIMMING
F2
F3
ENF
FLASH ON/OFF
F4
LDO1
LDO2
ENLDO
P1
DUAL-LDO ON/OFF
CAMERA
MODULE
DUAL-LDO
VOLTAGE
1μF
1μF
SELECTION
P2
SETM
SETF
REF
0.01μF
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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.
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
ABSOLUTE MAXIMUM RATINGS
PIN, IN, OUT, REFBP to GND................................-0.3V to +6.0V
SETF, SETM, ENLDO, ENM1, ENM2, ENF,
Continuous Power Dissipation (T = +70°C)
A
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
P1, P2, LDO1, LDO2 to GND....................-0.3V to (V + 0.3V)
IN
OUT
M1, M2, M3, M4, F1, F2, F3, F4 to GND...-0.3V to (V
+ 0.3V)
C1N, C2N to GND ......................................... -0.3V to (V + 1V)
IN
C1P, C2P
to GND.............. -0.3V to greater of (V
+ 1V) or (V + 1V)
IN
OUT
PGND to GND .......................................................-0.3V to +0.3V
OUT, LDO1, LDO2 Short-Circuit to GND ...................Continuous
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.
MA8631X/Y
ELECTRICAL CHARACTERISTICS
(V = 3.6V, V
IN
= V
= 0V, ENM1 = ENM2 = ENF = IN, R
= R
= 6.8kΩ, P1 = P2 = unconnected, C = 0.01µF,
REF
GND
PGND
SETM
A
SETF
T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
PARAMETER
CONDITIONS
MIN
2.7
TYP
MAX
UNITS
IN Operating Voltage
5.5
V
V
Undervoltage-Lockout Threshold
Undervoltage-Lockout Hysteresis
V
rising or falling
2.25
2.45
130
4.0
2.60
IN
mV
1MHz switching, no load, 1.5x or 2x mode
1x mode 10% setting, ENF = GND, V
5.5
mA
= V
,
IN
ENLDO
0.4
I
= I
LDO2
= 0A
Supply Current
LDO1
ENM1 = ENM2 = ENF = GND, V
= V
,
ENLDO
IN
110
µA
µA
I
= I
LDO2
= 0A
LDO1
T
T
= +25°C
= +85°C
0.01
0.1
5
A
A
Shutdown Supply Current
ENM1 = ENM2 = ENF = ENLDO = GND
EN_ High Voltage
EN_ Low Voltage
V
V
= 2.7V to 5.5V
= 2.7V to 5.5V
1.4
2.5
V
V
IN
IN
0.4
1
T
T
= +25°C
= +85°C
0.01
0.1
A
A
EN_ Input Current
V
= 0V or 5.5V
µA
ms
EN_
ENM_ or ENF Low Shutdown
See Figure 2
Delay t
SHDN
ENM_ or ENF t
ENM_ or ENF t
See Figure 2
See Figure 2
0.5
0.5
250.0
µs
µs
µs
µA
kΩ
°C
°C
LO
HI
Initial ENM_ or ENF t
Only required for first ENM_ or ENF pulse, see Figure 2
200
HI
P1, P2 Shutdown Input Current
P1, P2 Input Impedance
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
CHARGE PUMP
1
150
+160
20
Temperature rising
Overvoltage-Protection Threshold
Soft-Start Time
V
rising
5
2
V
OUT
ms
2
_______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
MA8631X/Y
ELECTRICAL CHARACTERISTICS (continued)
(V = 3.6V, V
IN
= V
= 0V, ENM1 = ENM2 = ENF = IN, R
= R
= 6.8kΩ, P1 = P2 = unconnected, C = 0.01µF,
REF
GND
PGND
SETM
SETF
T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
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
mA
Charge-Pump Maximum OUT
Current
V
≥ 3.15V, V
= 3.9V
OUT
580
IN
1x mode, (V - V
) / I
OUT
0.3
1.1
1.5
1.0
4.0
IN
OUT
Open-Loop OUT Resistance
1.5x mode, (1.5V - V
) / I
OUT OUT
Ω
IN
2x mode, (2V - V
) / I
4.14
IN
OUT
OUT
Charge-Pump Short-Circuit
Current
V
< 1.25V
500
1
mA
OUT
Switching Frequency
MHz
OUT Pulldown Resistance in
Shutdown
ENM_ = ENF = GND
5
kΩ
LED DRIVER
SET_ Bias Voltage
T
= +25°C
0.6
0.01
0.1
V
A
T
T
= +25°C
= +85°C
1
A
A
SET_ Leakage in Shutdown
ENM_ = ENF = GND
µA
µA
A/A
SET_ Current Range
10
145
SETM-to-Main LED Current Ratio
100% setting, M1–M4
100% setting, F1–F4
230
690
(I /I
M_ SETM
)
SETF-to-Flash LED Current Ratio
(I /I
A/A
%
)
F_ SETF
T
T
= +25°C
-1.25
-4
+1.25
+4
A
M_, F_ Current Accuracy
= -40°C to current derating start temperature
A
Maximum Main LED Sink Current
Maximum Flash LED Sink Current
R
SETM
R
SETF
= 4.6kΩ, for each M_
30
mA
mA
= 4.12kΩ, I + I + I + I
400
F1
F2
F3
F4
Current-Derating-Function Start
Temperature
+40
°C
Current-Derating-Function Slope
Dropout Voltage
T
= +40°C to +85°C
-1.7
40
%/°C
mV
A
(Note 2)
90
1
1.5x and 2x Regulation Voltage
150
0.01
0.1
mV
T
= +25°C
= +85°C
A
A
M_, F_ Leakage in Shutdown
ENM_ = ENF = GND
µA
T
LDO_
Output Voltage Accuracy
I
= 150mA, relative to V
(Note 3)
OUT(NOM)
-1.7
0
0
+1.7
200
750
%
LDO_
Output Current Range
Current Limit
mA
mA
mA
V
= 0V
280
475
160
LDO_
Soft-Start Current Limit
_______________________________________________________________________________________
3
1x/1.5x/2x White LED Charge Pump with
Two LDOs in 4mm x 4mm Thin QFN
ELECTRICAL CHARACTERISTICS (continued)
(V = 3.6V, V
= V
= 0V, ENM1 = ENM2 = ENF = IN, R
= R
= 6.8kΩ, P1 = P2 = unconnected, C = 0.01µF,
REF
IN
GND
PGND
SETM
A
SETF
T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
PARAMETER
CONDITIONS
MIN
TYP
100
120
MAX
UNITS
µs
Soft-Start Done Time
Dropout Voltage
Load Regulation
I
= 200mA (Note 4)
320
1.3
mV
LDO_
V
= 3.7V, 100µA < I
< 200mA
%
IN
LDO_
Power-Supply Rejection
10Hz to 10kHz, C
= 1µF, I
= 10µA
LDO_
-60
40
dB
LDO_
ΔV
/ΔV
OUT IN
MA8631X/Y
Output Noise Voltage (RMS)
10Hz to 100kHz, C
= 1µF, I
= 10mA
µV
RMS
LDO_
LDO_
Note 1: All devices are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by
A
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
+ 0.5V)) ≤ V ≤ 5.5V.
IN
LDO_
Note 4: LDO dropout voltage is defined as V - V
when V
is 100mV below the value of V
measured when V
IN
=
IN
OUT
OUT
OUT
V
+ 1V. Since the minimum input voltage is 2.7V, this specification is only meaningful when V
> 2.5V.
OUT(NOM)
OUT(NOM)
Typical Operating Characteristics
(V = V
IN
= 3.6V, circuit of Figure 1, T = +25°C, unless otherwise noted.)
A
EN_
BATTERY CURRENT vs. SUPPLY VOLTAGE
DRIVING FOUR MAIN LEDs
EFFICIENCY vs. Li+ BATTERY
VOLTAGE DRIVING FOUR MAIN LEDs
EFFICIENCY vs. Li+ BATTERY
VOLTAGE DRIVING FLASH LED MODULE
120
100
80
60
40
20
0
100
90
80
70
60
50
100
90
80
70
60
50
40
V
V
FALLING
RISING
I
= 15mA
IN
IN
LED
80mA TOTAL
160mA TOTAL
15mA/LED
I
= 4.5mA
LED
I
= 1.5mA
3.9
4.5mA/LED
1.5mA/LED
LED
400mA TOTAL
40
2.7
3.0
3.3
3.6
4.2
2.7
3.0
3.3
3.6
3.9
4.2
2.7
3.0
3.3
3.6
3.9
4.2
SUPPLY VOLTAGE (V)
Li+ BATTERY VOLTAGE (V)
Li+ BATTERY VOLTAGE (V)
4
_______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with
Two LDOs in 4mm x 4mm Thin QFN
MA8631X/Y
Typical Operating Characteristics (continued)
(V = V
IN
= 3.6V, circuit of Figure 1, T = +25°C, unless otherwise noted.)
A
EN_
INPUT RIPPLE VOLTAGE vs. SUPPLY
VOLTAGE WITH FOUR MAIN LEDs
LDO GROUND PIN SUPPLY
CURRENT vs. SUPPLY VOLTAGE
BATTERY CURRENT vs. SUPPLY
VOLTAGE DRIVING FLASH
160
150
140
130
120
110
100
90
1.2
1.0
0.8
0.6
0.4
0.2
0
900
800
700
600
500
400
300
200
100
0
V
= V = 0V, V
= V
ENM
ENF
ENLDO IN
I
= 15mA
LED
I
= 400mA
= 160mA
FLASH
150mA, BOTH LDOs
NO LOAD, BOTH LDOs
I
FLASH
I
= 4.5mA
LED
I
= 80mA
FLASH
I
= 1.5mA
LED
80
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
2.7
3.0
3.3
3.6
3.9
4.2
SUPPLY VOLTAGE (V)
LED CURRENT MATCHING vs. SUPPLY
VOLTAGE WITH FOUR MAIN LEDs
LED CURRENT MATCHING vs. SUPPLY
VOLTAGE WITH FOUR FLASH LEDs
INPUT RIPPLE VOLTAGE vs. SUPPLY
VOLTAGE WITH FLASH AND MAIN LEDs
16.0
15.8
15.6
15.4
15.2
15.0
14.8
14.6
14.4
14.2
14.0
102.0
101.5
101.0
100.5
100.0
99.5
10
9
8
7
6
5
4
3
2
1
0
FOUR MAIN LEDs AT 15mA EACH
I
= 10mA
I
FLASH
= 40mA
FLASH
I
= 100mA
FLASH
99.0
98.5
98.0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
LED CURRENT vs. AMBIENT
TEMPERATURE WITH FLASH
INDIVIDUAL MAIN LED CURRENT
LED CURRENT vs. AMBIENT
TEMPERATURE WITH FOUR MAIN LEDs
vs. R
SETM
450
400
350
300
250
200
150
100
50
100
10
1
70
60
50
40
30
20
10
0
0
-40
-15
10
35
60
85
1
10
(kΩ)
100
-40
-15
10
35
60
85
AMBIENT TEMPERATURE (°C)
R
AMBIENT TEMPERATURE (°C)
SETM
_______________________________________________________________________________________
5
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
Typical Operating Characteristics (continued)
(V = V
= 3.6V, Circuit of Figure 1, T = +25°C, unless otherwise noted.)
IN
EN_ A
INDIVIDUAL FLASH LED CURRENT
vs. R
OPERATING WAVEFORMS (1x MODE)
SETF
MAX8631X toc14
1000
100
10
50mV/div
AC-COUPLED
V
OUT
20mV/div
AC-COUPLED
V
I
IN
MA8631X/Y
2mA/div
AC-COUPLED
IN
4 MAIN LEDS AT 20mA EACH
400ns/div
1
1
10
100
R
SETF
(kΩ)
OPERATING WAVEFORMS (2x MODE)
OPERATING WAVEFORMS (1.5x MODE)
MAX8631X toc16
MAX8631X toc15
50mV/div
AC-COUPLED
V
OUT
50mV/div
AC-COUPLED
V
OUT
20mV/div
AC-COUPLED
V
20mV/div
AC-COUPLED
IN
IN
V
I
IN
4 MAIN LEDS AT 20mA EACH,
FLASH AT 400mA TOTAL
2mA/div
AC-COUPLED
2mA/div
AC-COUPLED
IN
I
4 MAIN LEDS AT 20mA EACH
400ns/div
400ns/div
STARTUP AND SHUTDOWN
STARTUP AND SHUTDOWN
MAIN LED RESPONSE
FLASH LED RESPONSE
MAX8631X toc17
MAX8631X toc18
5V/div
0V
5V/div
0V
V
V
ENF
ENM_
4 MAIN LEDS AT 20mA EACH,
400mA TOTAL FLASH
4 MAIN LEDS AT 20mA EACH
100mA/div
0A
500mA/div
0A
I
OUT
I
IN
500mA/div
0A
I
OUT
V
OUT
5V/div
0V
5V/div
0V
V
OUT
1ms/div
1ms/div
6
_______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
MA8631X/Y
Typical Operating Characteristics (continued)
(V = V
= 3.6V, circuit of Figure 1, T = +25°C, unless otherwise noted.)
IN
EN_ A
LDO DROPOUT VOLTAGE
vs. OUTPUT CURRENT
SINGLE-WIRE DIMMING RESPONSE
MAX8631X toc19
140
120
100
80
5V/div
0V
V
ENM1,
V
ENM2
500mA/div
0A
I
OUT
60
40
V
OUT
2V/div
0V
20
0
0
50
100
150
200
10ms/div
OUTPUT CURRENT (mA)
LDO OUTPUT VOLTAGE
ACCURACY vs. OUTPUT CURRENT
LOAD-TRANSIENT RESPONSE
MAX8631X toc22
1.0
0.8
0.6
0.4
0.2
0
V
= 2.6V
LDO_
50mV/div
AC-COUPLED
V
LDO_
100mA
1mA
-0.2
-0.4
-0.6
-0.8
-1.0
I
LDO_
0
50
100
150
200
10μs/div
OUTPUT CURRENT (mA)
LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
MAX8631X toc23
V
IN
- V
OUT
= 77mV, V
= 2.6V
LDO_
50mV/div
AC-COUPLED
V
LDO_
100mA
1mA
I
LDO_
10μs/div
_______________________________________________________________________________________
7
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
C3
C4
1μF
1μF
INPUT
2.7V TO 5.5V
C1P C1N C2P C2N
LDO1
LDO2
PIN
IN
LOW-
DROPOUT
LINEAR
1x/1.5x/2x REGULATING
CHARGE PUMP
C6
1μF
C1
10μF
REGULATORS
GND
C7
1μF
PGND
OUTPUT
UP TO 480mA
ERROR
AMP 1
OUT
C5
10μF
MA8631X/Y
OVD
1.25V
REFBP
C8
0.01μF
CONTROL AND
REFERENCE
ENM1
ENM2
ENF
SELMIN
0.15V
FLASH CONTROL
MAIN CONTROL
0.6V
M1
M2
M3
M4
D1
D2
D3
D4
ENLDO
P1
P2
IN
+
+
+
+
–
–
–
–
ERROR
AMP 2
GND
F1
F2
F3
F4
D5
D6
D7
D8
SETM
R
SETM
6.81kΩ
IN
+
+
+
+
–
–
–
–
ERROR
AMP 3
MAX8631X
MAX8631Y
SETF
R
SETF
4.12kΩ
GND
Figure 1. Functional Diagram and Application Circuit
8
_______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
Pin Description
MA8631X/Y
PIN
NAME
FUNCTION
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.
1
PIN
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.
2
3
4
IN
Ground. Connect GND to system ground and the input bypass capacitor as close to the IC as
possible.
GND
LDO1
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.
5
6
LDO2
REFBP
Reference Filter. Bypass REFBP with a 0.01µF ceramic capacitor to GND.
Bias Current Set Input for F1–F4. The current flowing out of SETF sets the maximum (100%) bias
7
8
SETF
SETM
F4–F1
M4–M1
current into each LED. V
GND to set the flash current. R
is internally biased to 0.6V. Connect a resistor (R
) from SETF to
SETF
SETF
= 414 / I
. SETF is high impedance during shutdown.
SETF
LED(MAX)
Bias Current Set Input for M1–M4. The current flowing out of SETM sets the maximum (100%) bias
current into each LED. V is internally biased to 0.6V. Connect a resistor (R ) from SETM to GND
SETM
SETM
to set the main LED current. R
= 138 / I . SETM is high impedance during shutdown.
LED(MAX)
SETM
400mA Combined Current Flash LED Cathode Connection and Charge-Pump Feedback. Current flowing
into F_ is based on I . The charge pump regulates the lowest F_ voltage to 0.15V. Grounding any F_
9–12
13–16
SETF
input forces OUT to operate at approximately 5V. Connect F_ to OUT if this LED is not populated.
30mA Main LED Cathode Connection and Charge-Pump Feedback. Current flowing into M_ is based on the
EN_ configuration and I
. The charge pump regulates the lowest M_ input voltage to 0.15V. Grounding
SETM
any M_ forces OUT to operate at approximately 5V. Connect M_ to OUT if this LED is not populated.
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.
17
18
P2
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.
ENLDO
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.
19
20
ENM2
ENM1
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.
21
22
ENF
C1N
Transfer Capacitor 1 Negative Connection. Connect a 1µF ceramic capacitor between C1P and C1N.
C1N is internally shorted to IN during shutdown.
_______________________________________________________________________________________
9
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
Pin Description (continued)
PIN
NAME
FUNCTION
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.
23
C1P
24
PGND
OUT
Power Ground. Connect PGND to system ground. PGND is used for charge-pump switching currents.
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.
25
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.
26
27
C2P
C2N
MA8631X/Y
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.
28
—
P1
EP
Exposed Paddle. Connect to GND and PGND.
Soft-Start
Detailed Description
The MAX8631X/Y includes soft-start circuitry to limit
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 reg-
ulators, it achieves high efficiency over the 1-cell lithi-
um-battery input voltage range. 1MHz fixed-frequency
switching allows for tiny external components and low
input ripple. Two on-board 200mA programmable-out-
put-voltage LDOs are provided to meet camera-module
requirements.
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 charge-
pump 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 termi-
nated 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.
1x to 1.5x Switchover
When V is higher than V
, the MAX8631X/Y oper-
IN
OUT
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.
ates in 1x mode and V
is pulled up to V . The
IN
OUT
internal current regulators regulate the LED current. As
V
drops, V (or V ) eventually falls below the
IN
M_
F_
switchover threshold of 100mV and the MAX8631X/Y
starts switching in 1.5x mode. When the input voltage
rises above V
by approximately 50mV, the
OUT
MAX8631X/Y switches back to 1x mode.
Thermal Derating
The MAX8631X/Y limits the maximum LED current
depending on the die temperature. The maximum LED
1.5x to 2x Switchover
When V is less than V
OUT
but greater than two-thirds
IN
OUT
current is set by the R
and R
resistors. Once
SETM
SETF
V
, the MAX8631X/Y operates in 1.5x mode. The
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.
internal current regulators regulate the LED current. As
V
drops, V (or V ) eventually falls below the
IN
M_
F_
switchover threshold of 100mV, and the MAX8631X/Y
starts switching in 2x mode. When the input voltage
The temperature derating function allows the LED cur-
rent to be safely set higher at normal operating temper-
atures, thereby allowing either a brighter display or
fewer LEDs to be used for normal display brightness.
rises above two-thirds V
by approximately 50mV,
OUT
the MAX8631X/Y switches back to 1.5x mode.
True Shutdown is a trademark of Maxim Integrated Products, Inc.
10 ______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
MA8631X/Y
INITIAL t
HI
≥ 200μs
0
1
2
3
4
5
27
28
29
30
31
32
ENM1 AND ENM2
OR
ENF
t
SOFT-START
t
SHDN
t
t
LO
HI
(2.5ms)
32/32
32/32
≥500ns
500ns TO 250μs
31/32
31/32
30/32
29/32
28/32
27/32
I
OR I
F_
M_
5/32
4/32
3/32
2/32
1/32
SHUTDOWN
SHUTDOWN
Figure 2. ENM_ and ENF Timing Diagram
(500ns to 250µs pulse width) reduces the LED current
by 3.125% (1/32), so after one pulse the LED current is
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.
96.9% (or 31/32) x I
. The 31st pulse reduces the
. The 32nd pulse sets the LED
LED
current to 0.03125 x I
LED
current back to I
. Figure 2 shows a timing diagram
LED
Applications Information
for single-wire pulse dimming. Because soft-start is
longer than the initial t , apply dimming pulses quickly
HI
Setting the Main Output Current
SETM controls M1–M4 regulation current. Current flow-
ing into M1, M2, M3, and M4 is a multiple of the current
flowing out of SETM:
upon startup (after initial t ) to avoid LED current tran-
HI
sitioning 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
I
= I = I = I = K x (0.6V / R
)
M1
M2
M3
M4
SETM
where K = 230, and R
is the resistor connected
SETM
between SETM and GND (see the Typical Operating
Circuit).
Table 1. ENM1/ENM2 States
the values of R
and R
.
SETM
SETF
M1–M4
CURRENT
ENM1/ENM2 STATES
BRIGHTNESS
Driving Fewer than 8 LEDs
ENM1 = low, ENM2 = low
Shutdown
0
When driving fewer than 8 LEDs, two different connec-
tion 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
ENM1 = high, ENM2 = high Full brightness
230 x I
SETM
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 cur-
rent flowing out of SETF.
and effectively allows total LED current to be I
multi-
LED
plied by the number of connected drivers. The second
method of connection is shown in Figure 5 where stan-
dard white LEDs are used and fewer than 8 are con-
nected. This scheme does not alter current through
each LED but ensures that the unused LED driver is
properly disabled.
I
F1
= I = I = I = N x (0.6V / R
)
F2
F3
F4
SETF
where N = 690.
Single-Wire Pulse Dimming
Input Ripple
For LED drivers, input ripple is more important than out-
put ripple. Input ripple is highly dependent on the
source supply’s impedance. Adding a lowpass filter to
the input further reduces input ripple. Alternately,
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
increasing C to 22µF cuts input ripple in half with only
IN
a small increase in footprint. The 1x mode always has
very low input ripple.
______________________________________________________________________________________ 11
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
1μF
1μF
INPUT
2.7V TO 5.5V
C1P
C1N
C2P
C2N
LDO1
PIN
1μF
LDO2
IN
10μF
1μF
GND
OUTPUT
UP TO 480mA
OUT
MAX8631X
MAX8631Y
MAIN
FLASH
10μF
ENM2
ENM1
ENF
MAIN ON/OFF
AND DIMMING
MA8631X/Y
M1
M2
FLASH ON/OFF
AND DIMMING
M3
M4
F1
ENLDO
ON/OFF
P1
P2
F2
F3
VOLTAGE
SELECTION
F4
SETM
SETF REFBP
PGND
0.01μF
6.81kΩ
4.12kΩ
Figure 3. Dimming Using Single-Wire, Serial-Pulse Interface
1μF
1μF
INPUT
2.7V TO 5.5V
C1P
C1N
C2P
C2N
LDO1
PIN
1μF
LDO2
IN
10μF
1μF
GND
OUTPUT
UP TO 480mA
OUT
MAX8631X
MAIN FLASH
10μF
ENM2
ENM1
ENF
MAX8631Y
M1
M2
ON/OFF AND
VOLTAGE
SELECTION
M3
M4
F1
ENLDO
P1
F2
F3
P2
F4
SETM
SETF REFBP
PGND
0.01μF
6.81kΩ
4.12kΩ
Figure 4. Providing Increased LED Current per LED
12 ______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with Two
LDOs in 4mm x 4mm Thin QFN
MA8631X/Y
1μF
1μF
INPUT
2.7V TO 5.5V
C1P
C1N
C2P
C2N
LDO1
PIN
1μF
LDO2
IN
10μF
1μF
GND
OUTPUT
UP TO 240mA
OUT
MAX8631X
MAX8631Y
MAIN
FLASH
10μF
ENM2
ENM1
ENF
M1
M2
ON/OFF AND
VOLTAGE
SELECTION
M3
M4
F1
ENLDO
P1
F2
F3
P2
F4
SETM
SETF REFBP
PGND
0.01μF
6.81kΩ
4.12kΩ
Figure 5. Schematic for When Fewer than 8 LEDs Is Acceptable
Typical operating waveforms shown in the Typical
Operating Characteristics show input ripple current in
1x, 1.5x, and 2x mode.
Table 2. P1 and P2, LDO Output Voltage
Selection
MAX8631X
MAX8631Y
P1
P2
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
LDO1 (V) LDO2 (V) LDO1 (V) LDO2 (V)
IN
IN
IN
OPEN
GND
IN
3.3
3.0
2.8
3.3
2.6
2.6
3.0
2.8
2.5
1.8
1.5
1.5
1.5
1.8
1.5
1.8
1.8
1.8
2.8
2.8
2.9
2.6
2.6
2.8
2.9
2.9
2.9
2.6
2.8
1.5
1.9
2.6
1.9
1.8
1.9
2.9
GND. The input voltage, V , must be greater than the
IN
IN
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.
OPEN
OPEN OPEN
OPEN GND
GND
IN
GND OPEN
GND GND
Component Selection
Use only ceramic capacitors with an X5R, X7R, or better
dielectric. See Table 3 for a list of recommended parts.
PC Board Layout and Routing
The MAX8631X/Y is a high-frequency switched-capaci-
tor voltage regulator. For best circuit performance, use
Connect a 1µF ceramic capacitor between LDO1 and
GND, and a second 1µF ceramic capacitor between
LDO2 and GND for 200mA applications. The LDO out-
a solid ground plane and place C , C
, C3, and C4
IN OUT
put capacitor’s (C
) equivalent series resistance
LDO
as close to the MAX8631X/Y as possible. There should
(ESR) affects stability and output noise. Use output
be no vias on C . Connect GND and PGND to the
IN
capacitors with an ESR of 0.1Ω or less to ensure stability
exposed paddle directly under the IC. Refer to the
MAX8631X/Y evaluation kit for an example.
and optimum transient response. Connect C
as
LDO_
close to the MAX8631X/Y as possible to minimize the
impact of PC board trace inductance.
______________________________________________________________________________________ 13
1x/1.5x/2x White LED Charge Pump with
Two LDOs in 4mm x 4mm Thin QFN
Table 3. Recommended Components for Figure 1
DESIGNATION
VALUE
10µF
1µF
MANUFACTURER
PART NUMBER
C2012X5R0J106M
C1005X5R0J105M
C1005X7R1E103K
NSCW215T
DESCRIPTION
10µF 20%, 6.3V X5R ceramic capacitors (0805)
1µF 20%, 6.3V X5R ceramic capacitors (0402)
0.01µF 10%, 25V X7R ceramic capacitor (0402)
White LEDs
C1, C5
TDK
C3, C4, C6, C7
C8
TDK
0.01µF
—
TDK
D1–D4
Nichia
D5 (D5–D8)
—
Nichia
NBCW011T
White LEDs, 4 LEDs in one package
Panasonic
Vishay
As
Required
R
, R
—
1% resistor
SETM SETF
MA8631X/Y
Pin Configuration
Chip Information
PROCESS: BiCMOS
TOP VIEW
21 20 19 18 17 16 15
C1N
C1P
22
23
14
M3
13 M4
12
F1
PGND 24
Package Information
11
F2
25
26
27
28
OUT
C2P
MAX8631XETI
MAX8631YETI
For the latest package outline information and land patterns, go
10
F3
to www.maxim-ic.com/packages.
9
C2N
P1
F4
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
28 TQFN-EP
T2844-1
21-0139
+
8
SETM
1
2
3
4
5
6
7
THIN QFN
4mm x 4mm, 0.4mm LEAD PITCH
14 ______________________________________________________________________________________
1x/1.5x/2x White LED Charge Pump with
Two LDOs in 4mm x 4mm Thin QFN
Revision History
MA8631X/Y
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
Removed PWM dimming control feature and updated ENM_ and ENF low
shutdown delay EC values
3
6/08
1, 2, 9–12, 14
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.
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