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19-3783; Rev 1; 2/07
KIT ATION EVALU E AILABL AV
1MHz PWM Boost Converter for 1.5A White LED Camera Flash
General Description Features
Supports Lumileds and Other High-Power White LEDs Independently Set Flash/Movie Currents Flash-Mode Current Up to 1.5A Movie-Mode Current Up to 360mA Disco Mode with Fixed 5V (Up to 1A) and 80mA LED Current 84% Efficiency (PLED / PBATT) at 1.1A TA Derating Function for LED Thermal Protection Output Overvoltage Protection (OVP) Soft-Start Eliminates Inrush Current 1MHz PWM Operation at All Loads Small External Components 2.7V to 5.5V Input Voltage Range 0.1A Shutdown Mode 14-Pin, 3mm x 3mm TDFN Package
MAX8607
The MAX8607 white LED boost converter is optimized for camera flash/strobe applications using high-current white LEDs. The MAX8607 integrates a 1MHz PWM boost converter, 1.5A low-dropout (LDO) current regulator, and logic control circuitry for a space-saving LED flash design. Two logic inputs control four modes of operation: shutdown mode reduces the quiescent current to 0.1A (typ), movie mode supplies up to 360mA of LED current for continuous lighting, flash mode supplies up to 1.5A of LED current for short-duration lighting during an exposure, and disco mode supplies +5V (at up to 1A) to external circuits while driving the LED with a fixed 80mA current. The internal 1MHz boost converter features an adaptive control scheme with an internal switching MOSFET and synchronous rectifier to improve efficiency and minimize external component count. The MAX8607 is available in a 14-pin, 3mm x 3mm TDFN package (0.8mm max height).
Applications
Camera Flashes/Strobes Cell Phones/Smartphones PDAs and Digital Cameras
Ordering Information
PART* MAX8607ETD+ PIN-PACKAGE 14 TDFN 3mm x 3mm (T1433-1) TOP MARK ABA
+Indicates lead-free package. *The MAX8607ETD is characterized over the -40C to +85C temperature range.
Pin Configuration
TOP VIEW
INPUT 2.7V TO 5.5V LED 2.2H
Typical Operating Circuit
OUTPUT LX 10F PGND COMP
PGND
PGND
OUTS
OUT
LX
LX
MAX8607 OUT
OUTS LGND GND 10F UP TO 1.5A FLASH UP TO 360mA MOVIE
14
13
12
11
10
9
8
MAX8607
+ 1 COMP 2 EN1 3 EN2 4 MOV 5 FLSH 6 GND 7 LGND
MODESELECT INPUTS
EN1 EN2 FLSH LED MOV
TDFN 3mm x 3mm
________________________________________________________________ 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.
1MHz PWM Boost Converter for 1.5A White LED Camera Flash MAX8607
ABSOLUTE MAXIMUM RATINGS
OUT, OUTS, EN1, EN2 to GND ................................-0.3V to +6V FLSH, MOV, LED, COMP, LX to GND ....-0.3V to (VOUTS + 0.3V) LGND, PGND to GND. ..........................................-0.3V to +0.3V LX Current. ........................................................................2ARMS Continuous Power Dissipation (TA = +70C) 14-Pin TDFN 3mm x 3mm (derate 18.2mW/C above +70C)..............................................................1455mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VEN1 = VEN2 = 5V, VOUT = VOUTS = 4V, COUT = 10F, TA = -40C to +85C. Typical values are at TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Supply Voltage Undervoltage-Lockout Threshold OUT Quiescent Current, Flash or Movie Mode OUT Quiescent Current, Shutdown Mode CONDITIONS IC supplied from OUTS VOUTS rising, 100mV (typ) hysteresis LX switching, ILED = 0mA EN1 = EN2 = GND TA = +25C TA = +85C 5.3 3.65 4.8 TA = +25C TA = +85C Flash mode Movie mode Disco mode 1200 338 MIN 2.7 2.25 2.38 4 0.1 1 5.5 3.85 5.0 0.01 0.5 1500 360 80 1200 TA 0C (Note 2) TA = -40C -3 -6 62 0.5 0.5 48 80 5000 3 200 4.4 600 600 VCOMP = 1.5V 60 420 +3 +6 100 108 A/A % mV mA A/A % mV A mV mV S mA 5.7 3.95 5.2 1 A V 1 TYP MAX 5.5 2.65 UNITS V V mA A
Overvoltage limit, ILED = 0mA, VLED = 0V OUT Regulation Voltage VLED = 0.5V Disco mode, ILED = 80mA LED Current, Shutdown Mode EN1 = EN2 = GND RMOV = 2k, RFLSH = 2k, VLED = 0.5V IMOV up to 300A RMOV = 2k, VLED = 0.5V RMOV = 2k VEN1 = 0V, VEN2 = 5V IFLSH up to 300A RFLSH = 2k, VLED = 0.5V, TA -40C (Note 2) RFLSH = 2k
Current-Source Guaranteed Sink Current Current-Source Multiplier in MOV Mode (ILED / IMOV) Current-Source Accuracy in MOV Mode MOV Current-Source Dropout Voltage Disco Current-Source Current Setting Current-Source Multiplier in FLSH Mode (ILED / IFLSH) Current-Source Accuracy in FLSH Mode FLSH Current-Source Dropout Voltage LX n-Channel Current Limit MOV Regulation Voltage FLSH Regulation Voltage LED to COMP Transconductance
2
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1MHz PWM Boost Converter for 1.5A White LED Camera Flash
ELECTRICAL CHARACTERISTICS (continued)
(VEN1 = VEN2 = 5V, VOUT = VOUTS = 4V, COUT = 10F, TA = -40C to +85C. Typical values are at TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER COMP Input Resistance to GND LED TA Derating Function Threshold LED TA Derating Function Slope EN1 and EN2 Logic-High Input Voltage EN1 and EN2 Logic-Low Input Voltage EN1 and EN2 Logic Input Bias Current LX n-Channel On-Resistance LX p-Channel On-Resistance LX Leakage Operating Frequency Maximum Duty Cycle Minimum Duty Cycle CONDITIONS During shutdown or UVLO Temperature when the LED current derating function begins TA = +40C to +85C VOUTS = 2.7V to 5.5V VOUTS = 2.7V to 5.5V VEN_ = 5.5V ILX = 200mA ILX = 200mA VLX = 5.5V TA = +25C TA = +85C 0.8 65 TA = +25C TA = +85C 0.01 0.03 50 100 0.01 0.03 1.0 75 4 8 1.2 100 200 1 1.4 0.4 1 MIN TYP 140 +40 -1.67 MAX 250 UNITS C %/C V V A m m A MHz % %
MAX8607
Note 1: All devices are production tested at TA = +25C. Specifications over temperature are guaranteed by design and characterization and not production tested. Note 2: For temperatures below the thermal derating start point.
Typical Operating Characteristics
(Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25C, unless otherwise noted.)
FLASH-MODE BATTERY CURRENT vs. INPUT VOLTAGE
MAX8607toc01
MOVIE-MODE BATTERY CURRENT vs. INPUT VOLTAGE
MAX8607toc02
BOOST CONVERTER EFFICIENCY vs. LOAD CURRENT (DISCO MODE)
98 96 94 EFFICIENCY (%) 92 90 88 86 84 82 INCLUDES 83mA LED CURRENT
MAX8607toc03
4000 3500 BATTERY CURRENT (mA) 3000 2500 2000 1500 1000 500 0 2.7 3.1 3.5 4.7 4.3 INPUT VOLTAGE (V) 3.9 5.1 RFLSH = 3.01k RFLSH = 4.02k RFLSH = 8.06k RFLSH = 2k
600 500 BATTERY CURRENT (mA) RMOV = 2.00k 400 300 200 RMOV = 6.49k 100 0
100
RMOV = 3.57k
80 2.7 3.1 3.5 4.7 4.3 INPUT VOLTAGE (V) 3.9 5.1 5.5 10 100 LOAD CURRENT (mA) 1000
5.5
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1MHz PWM Boost Converter for 1.5A White LED Camera Flash MAX8607
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25C, unless otherwise noted.)
LED CURRENT vs. AMBIENT TEMPERATURE
MAX8607toc04
IC SUPPLY CURRENT vs. INPUT VOLTAGE
DISCO MODE FLASH MODE 900 800 SUPPLY CURRENT (A) 700 600 500 400 300 200 100 0 MOVIE MODE
MAX8607toc05
400 350 300 LED CURRENT (mA) 250 200 150 100 50 0 -40 -20 60 40 AMBIENT TEMPERATURE (C) 0 20 80
1000
2.7
3.1
3.5
3.9 4.3 4.7 INPUT VOLTAGE (V)
5.1
5.5
SWITCHING WAVEFORMS (MOVIE MODE)
MAX8607toc06
SOFT-START RESPONSE (STANDBY TO MOVIE-MODE TRANSITION)
MAX8607toc07
VIN
20mV/div
VEN1
0V 5V/div 200mA/div
VOUT
10mV/div
ILED
0A
IL
100mA/div
IIN
0A
100mA/div
VLX
5V/div
VOUT 0V
2V/div
400ns/div
100s/div
SOFT-START RESPONSE (MOVIE-MODE TO FLASH TRANSITION)
MAX8607toc08
LOAD TRANSIENT (DISCO MODE)
MAX8607toc09
VEN2
5V/div IL0AD
700mA 100mA
ILED
200mA/div
IIN
0A 500mA/div 0A 2V/div
VOUT(RIPPLE)
500mV/div
VOUT 0V 400s/div 2ms/div
4
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1MHz PWM Boost Converter for 1.5A White LED Camera Flash MAX8607
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25C, unless otherwise noted.)
MOVIE-MODE LED CURRENT vs. MOV RESISTANCE
MAX8607toc10
FLASH-MODE LED CURRENT vs. FLSH RESISTANCE
1400 1200 LED CURRENT (mA) 1000 800 600 400 200 0
MAX8607toc11
400 350 300 LED CURRENT (mA) 250 200 150 100 50 0 1 10 RMOV (k)
1600
100
1
10 RFLSH (k)
100
Pin Description
PIN 1 2 3 4 5 6 7 8 9, 10 11, 12 13 14 -- NAME COMP EN1 EN2 MOV FLSH GND LGND LED PGND LX OUT OUTS EP FUNCTION Compensation Input. Connect a 0.1F ceramic capacitor from COMP to GND for regulator stability. Enable Input 1. EN1 and EN2 set the operating mode (see Table 1). Enable Input 2. EN1 and EN2 set the operating mode (see Table 1). Movie Current Program Input. Connect a resistor from MOV to GND to set the LED current in movie mode. RMOV must be greater than 2k. Flash Current Program Input. Connect a resistor from FLSH to GND to set the LED current in flash mode. RFLSH must be greater than 2k. Analog Ground. Connect GND to the exposed paddle directly under the IC. LED Current Regulator Ground. Connect LGND to the ground plane on the PC board. LED Current Regulator. Connect LED to the cathode of the external LED. LED is high impedance during shutdown. Power Ground. Connect PGND to the input capacitor ground. Also, connect PGND to the PC board ground plane. Inductor Connection. Connect LX to the switched side of the inductor. LX is internally connected to the drains of the internal MOSFETs. Both MOSFETs are off during shutdown. Regulator Output. Connect OUT to the anode of the external LED. Bypass OUT to PGND with a 10F or larger ceramic capacitor. During shutdown, OUT is one body-diode drop below the input voltage. Output Sense and IC Supply Input. Connect OUTS to OUT at the output bypass capacitor. The IC's operating power is supplied from OUTS. Exposed Paddle. Connect the exposed paddle to GND directly under the IC and to a large PC board ground plane for increased thermal performance.
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1MHz PWM Boost Converter for 1.5A White LED Camera Flash MAX8607
LX
OUT
REF
OUTS
FORCED-PWM BOOST CONTROL
PGND 1MHz CLOCK COMP 1.25V
FEEDBACK SELECT
EN1 EN2
SHUTDOWN AND MODE CONTROL
LED
FLSH MOV
LDO REGULATOR
GND
MAX8607
LGND
Figure 1. Functional Diagram
Detailed Description
Boost Converter
The MAX8607 includes a fixed-frequency, PWM boost converter that supplies the LED current. The output voltage is adaptively controlled to provide adequate headroom with varying LED forward voltage. The boost converter switches an internal power MOSFET and synchronous rectifier at a constant 1MHz frequency with varying duty cycle up to 75% to maintain constant LED current over the 2.7V to 5.5V input range. Internal special circuits prevent any unwanted subharmonic switching in the critical buck/boost region.
6
LDO Current Regulator (LED)
A low-dropout (LDO) linear current regulator from LED to LGND sinks current from the external LED's cathode terminal. The LED current is regulated to a user-programmable level. In movie mode, the current into LED is regulated to 1200 times the current set by the MOV resistor (RMOV). In flash mode, the current into LED is regulated to 5000 times the current set by the FLSH resistor (RFLSH). In disco mode, the current into LED is regulated to 80mA.
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1MHz PWM Boost Converter for 1.5A White LED Camera Flash
Mode-Select Inputs (EN1, EN2)
Drive EN1 high and EN2 low to enable movie mode. In this mode, the current regulator regulates the current through the LED to 1200 times the current set by the MOV resistor. See the Setting the Movie-Mode Current section for details on setting the movie-mode current. Drive EN1 and EN2 high to enable flash mode. In this mode, the current through the LED is regulated to 5000 times the current set by the FLSH resistor. See the Setting the Flash-Mode Current section for details on setting the flash-mode current. The time duration of the flash mode must be set using external circuitry or software. Drive EN1 low and EN2 high to enable disco mode. In this mode, the output of the boost converter provides a regulated +5V at up to 1A for external circuitry, while the LED current is regulated to 80mA. The LED current is not adjustable in this mode. Drive EN1 and EN2 low to place the IC into a lowpower shutdown mode. See the Shutdown section for more details.
MAX8607
Table 1. EN1 and EN2 Mode Selection
EN1 0 0 1 1 EN2 0 1 0 1 Shutdown Disco Mode Movie Mode Flash Mode MODE
Shutdown
Drive EN1 and EN2 low to place the MAX8607 into a low-power shutdown mode. In shutdown, supply current is reduced to 0.1A (typ). CCOMP is discharged during shutdown, allowing the device to reinitiate softstart when it is enabled. The internal MOSFET and synchronous rectifier are turned off during shutdown; however, OUT is one body-diode drop below the input. LED is high impedance so the external LED is off, but any external circuitry on OUT is not disconnected and, therefore, should include its own shutdown capability. Typical shutdown timing characteristics are shown in the Typical Operating Characteristics.
Overvoltage Protection
The output voltage of the MAX8607 is limited by internal overvoltage-protection (OVP) circuitry, which prevents the output from exceeding 5.7V under any conditions. In flash and movie modes, if the output voltage nears 5.5V, the LED current is smoothly reduced through proprietary means to prevent overvoltage without sudden termination of the output current. In case of an LED with very high forward voltage (V F), this circuit provides more reliable and repeatable flash than would a simple on/off comparator. In disco mode, the output is limited by the internal 5.0V regulation.
Ambient Temperature Derating Function
The MAX8607 limits the maximum LED current depending on its die temperature. Once the die temperature reaches +40C, the LED current decreases by 1.67% per C. This corresponds to approximately 0mA of LED current at +100C. Due to the package's exposed paddle, the die temperature is 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 flash or movie light to be used for normal ambient temperatures. See the Typical Operating Characteristics for a graph of LED Current vs. Ambient Temperature.
Undervoltage Lockout
The MAX8607 contains undervoltage-lockout (UVLO) circuitry that disables the IC until VOUTS is greater than 2.38V. Prior to startup, VOUTS is one diode drop below the input voltage. This ensures a great enough input voltage for startup.
Applications Information
Setting the Movie-Mode Current
To set the LED current during movie mode, connect a resistor from MOV to GND (RMOV). VMOV is regulated to 0.6V and the current through RMOV is mirrored to LED with a gain of 1200. RMOV is calculated as: RMOV = (0.6V x 1200) / ILED(MOV)
Soft-Start
The MAX8607 attains soft-start by charging C COMP with a 100A current source. During this time, the internal MOSFET is switching at the minimum duty cycle. Once VCOMP rises above 1V, the duty cycle increases until output reaches the desired regulation level. COMP is pulled to GND with a 140 internal resistor during UVLO, OVP, or shutdown. See the Typical Operating Characteristics for an example of soft-start operation.
Setting the Flash-Mode Current
To set the LED current during flash mode, connect a resistor from FLSH to GND (RFLSH). VFLSH is regulated to 0.6V and the current through RFLSH is mirrored to LED with a gain of 5000. RFLSH is calculated as: RFLSH = (0.6V x 5000) / ILED(FLSH)
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7
1MHz PWM Boost Converter for 1.5A White LED Camera Flash MAX8607
Capacitor Selection
L1 INPUT 2.7V TO 5.5V 2.2H C1 10F 11, 12 13 14 C2 10F
LX
MAX8607 U1
OUT OUTS
9, 10 C3 0.1F 1
PGND D1 COMP LGND GND 7 6
MODESELECT INPUTS
2 3
EN1 EN2 FLSH 5 R1
Bypass the input to PGND using a ceramic capacitor. Place the capacitor as close to the IC as possible. The exact value of the input capacitor is not critical. The typical value for the input capacitor is 10F; however, larger value capacitors can be used to reduce input ripple at the expense of size and higher cost. The output capacitance required depends on the required LED current. A 10F ceramic capacitor works well in most situations, but a 4.7F capacitor is acceptable for load current below 300mA.
MOV 4
LED EP R2
8
PC Board Layout
Due to fast switching waveforms and high-current paths, careful PC board layout is required. Connect GND directly to the exposed paddle underneath the IC; connect the exposed paddle to the PC board ground plane. Connect LGND and PGND to the ground plane. The output bypass capacitor should be placed as close to the IC as possible. C COMP should be connected from COMP to GND as close to the IC as possible. Minimize trace lengths between the IC and the inductor, the input capacitor, and the output capacitor; keep these traces short, direct, and wide. The ground connections of CIN and COUT should be as close together as possible and connected to PGND. The traces from the input to the inductor and from the output capacitor to the LED may be longer. A sample layout is available in the MAX8607 evaluation kit (MAX8607EVKIT) to speed design.
Figure 2. Typical Application Circuit
Inductor Selection
The MAX8607 is designed to use a 2.2H inductor. To prevent core saturation, ensure that the inductor-saturation current rating exceeds the peak inductor current for the application. Calculate the worst-case peak inductor current with the following formula: IPEAK = 5V x ILED(MAX) 0.9 x VIN(MIN) + VIN(MIN) x 0.5s 2 x 2.2H
Chip Information
PROCESS: BiCMOS
Table 2 provides a list of suggested inductors.
Table 2. Suggested Inductors
MANUFACTURER Coilcraft Cooper (Coiltronics) FDK TOKO SERIES LPO3310 SD3114 MIPF2520 MIPW3226 DE2812C FDSE0312 INDUCTANCE (H) 2.2 2.2 2.2 2.2 2.2 2.2 DCR (m) 150 83 80 100 70 160 ISAT (A) 1.1 1.48 0.7 1.1 1.6 2.3 DIMENSIONS (LTYP x WTYP x HMAX = Volume) 3.3 x 3.3 x 1.0 = 11mm3 3.0 x 3.0 x 1.45 = 13mm3 2.5 x 2.0 x 1.0 = 5mm3 3.2 x 2.6 x 1.0 = 8mm3 3.0 x 2.8 x 1.2 = 10mm3 3.0 x 3.0 x 1.2 = 11mm3
8
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1MHz PWM Boost Converter for 1.5A White LED Camera Flash
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.)
6, 8, &10L, DFN THIN.EPS
MAX8607 MAX8607
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1MHz PWM Boost Converter for 1.5A White LED Camera Flash MAX8607
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.)
COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 0.20 MAX. 0.80 3.10 3.10 0.05 0.40
PACKAGE VARIATIONS PKG. CODE T633-2 T833-2 T833-3 T1033-1 T1033-2 T1433-1 T1433-2 N 6 8 8 10 10 14 14 D2 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.700.10 1.700.10 E2 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 e 0.95 BSC 0.65 BSC 0.65 BSC 0.50 BSC 0.50 BSC 0.40 BSC 0.40 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEC MO229 / WEEC MO229 / WEED-3 MO229 / WEED-3 ------b 0.400.05 0.300.05 0.300.05 0.250.05 0.250.05 0.200.05 0.200.05 [(N/2)-1] x e 1.90 REF 1.95 REF 1.95 REF 2.00 REF 2.00 REF 2.40 REF 2.40 REF
0.25 MIN. 0.20 REF.
Revision History
Pages changed at Rev 1: 1, 2, 9, 10
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.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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