19-3783; Rev 1; 2/07 KIT ATION EVALU LE B A IL A AV 1MHz PWM Boost Converter for 1.5A White LED Camera Flash 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 0.1µA (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). 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 ♦ 0.1µA Shutdown Mode Applications ♦ 14-Pin, 3mm x 3mm TDFN Package Ordering Information Camera Flashes/Strobes Cell Phones/Smartphones PART* PIN-PACKAGE TOP MARK MAX8607ETD+ 14 TDFN 3mm x 3mm (T1433-1) ABA PDAs and Digital Cameras +Indicates lead-free package. *The MAX8607ETD is characterized over the -40°C to +85°C temperature range. Typical Operating Circuit Pin Configuration OUT LX LX PGND PGND LED INPUT 2.7V TO 5.5V OUTS TOP VIEW 14 13 12 11 10 9 8 MAX8607 2.2µH OUTPUT LX MAX8607 OUT 10µF MODESELECT INPUTS OUTS PGND LGND COMP GND 10µF UP TO 1.5A FLASH UP TO 360mA MOVIE EN1 EN2 LED 4 5 6 7 FLSH GND LGND EN1 3 MOV 2 EN2 1 COMP + FLSH MOV TDFN 3mm x 3mm ________________________________________________________________ Maxim Integrated Products 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. 1 MAX8607 General Description MAX8607 1MHz PWM Boost Converter for 1.5A White LED Camera Flash 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 = +70°C) 14-Pin TDFN 3mm x 3mm (derate 18.2mW/°C above +70°C)..............................................................1455mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VEN1 = VEN2 = 5V, VOUT = VOUTS = 4V, COUT = 10µF, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER CONDITIONS MIN Supply Voltage IC supplied from OUTS 2.7 Undervoltage-Lockout Threshold VOUTS rising, 100mV (typ) hysteresis 2.25 OUT Quiescent Current, Flash or Movie Mode LX switching, ILED = 0mA OUT Quiescent Current, Shutdown Mode OUT Regulation Voltage EN1 = EN2 = GND TYP 2.38 MAX UNITS 5.5 V 2.65 V 4 TA = +25°C 0.1 TA = +85°C 1 mA 1 Overvoltage limit, ILED = 0mA, VLED = 0V 5.3 5.5 5.7 VLED = 0.5V 3.65 3.85 3.95 Disco mode, ILED = 80mA 4.8 5.0 5.2 TA = +25°C 0.01 1 TA = +85°C 0.5 LED Current, Shutdown Mode EN1 = EN2 = GND Current-Source Guaranteed Sink Current RMOV = 2kΩ, RFLSH = 2kΩ, VLED = 0.5V Current-Source Multiplier in MOV Mode (ILED / IMOV) IMOV up to 300µA Current-Source Accuracy in MOV Mode RMOV = 2kΩ, VLED = 0.5V MOV Current-Source Dropout Voltage RMOV = 2kΩ Disco Current-Source Current Setting VEN1 = 0V, VEN2 = 5V Current-Source Multiplier in FLSH Mode (ILED / IFLSH) IFLSH up to 300µA Current-Source Accuracy in FLSH Mode FLSH Current-Source Dropout Voltage Flash mode 1200 1500 Movie mode 338 360 Disco mode µA V µA mA 80 1200 A/A TA ≥ 0°C (Note 2) -3 ±0.5 +3 TA = -40°C -6 ±0.5 +6 48 100 mV 80 108 mA 62 % 5000 A/A RFLSH = 2kΩ, VLED = 0.5V, TA ≥ -40°C (Note 2) ±3 % RFLSH = 2kΩ 200 420 mV LX n-Channel Current Limit 4.4 A MOV Regulation Voltage 600 mV FLSH Regulation Voltage 600 mV 60 µS LED to COMP Transconductance 2 VCOMP = 1.5V _______________________________________________________________________________________ 1MHz PWM Boost Converter for 1.5A White LED Camera Flash (VEN1 = VEN2 = 5V, VOUT = VOUTS = 4V, COUT = 10µF, TA = -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) (Note 1) TYP MAX UNITS COMP Input Resistance to GND PARAMETER During shutdown or UVLO CONDITIONS MIN 140 250 Ω LED TA Derating Function Threshold Temperature when the LED current derating function begins +40 °C LED TA Derating Function Slope TA = +40°C to +85°C -1.67 %/°C EN1 and EN2 Logic-High Input Voltage VOUTS = 2.7V to 5.5V EN1 and EN2 Logic-Low Input Voltage VOUTS = 2.7V to 5.5V EN1 and EN2 Logic Input Bias Current VEN_ = 5.5V 1.4 V 0.4 TA = +25°C 0.01 TA = +85°C 0.03 1 V µA LX n-Channel On-Resistance ILX = 200mA 50 100 mΩ LX p-Channel On-Resistance ILX = 200mA 100 200 mΩ LX Leakage VLX = 5.5V TA = +25°C 0.01 1 TA = +85°C 0.03 Operating Frequency 0.8 1.0 Maximum Duty Cycle 65 75 Minimum Duty Cycle µA 1.2 MHz 8 % % 4 Note 1: All devices are production tested at TA = +25°C. 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 = +25°C, unless otherwise noted.) RFLSH = 4.02kΩ 2000 1500 RFLSH = 8.06kΩ 1000 94 400 RMOV = 3.57kΩ 200 RMOV = 6.49kΩ 92 90 88 86 84 100 500 96 RMOV = 2.00kΩ 300 INCLUDES 83mA LED CURRENT 98 EFFICIENCY (%) RFLSH = 3.01kΩ 2500 100 MAX8607toc02 RFLSH = 2kΩ 3000 500 BATTERY CURRENT (mA) BATTERY CURRENT (mA) 3500 600 MAX8607toc01 4000 BOOST CONVERTER EFFICIENCY vs. LOAD CURRENT (DISCO MODE) MOVIE-MODE BATTERY CURRENT vs. INPUT VOLTAGE MAX8607toc03 FLASH-MODE BATTERY CURRENT vs. INPUT VOLTAGE 82 0 80 0 2.7 3.1 3.5 3.9 4.7 4.3 INPUT VOLTAGE (V) 5.1 5.5 2.7 3.1 3.5 3.9 4.7 4.3 INPUT VOLTAGE (V) 5.1 5.5 10 100 1000 LOAD CURRENT (mA) _______________________________________________________________________________________ 3 MAX8607 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25°C, unless otherwise noted.) IC SUPPLY CURRENT vs. INPUT VOLTAGE 1000 MAX8607toc04 400 350 DISCO MODE 900 FLASH MODE 800 SUPPLY CURRENT (µA) 300 250 200 150 100 MAX8607toc05 LED CURRENT vs. AMBIENT TEMPERATURE LED CURRENT (mA) MAX8607 1MHz PWM Boost Converter for 1.5A White LED Camera Flash 700 600 500 MOVIE MODE 400 300 200 50 100 0 0 -40 -20 0 20 60 40 AMBIENT TEMPERATURE (°C) 80 2.7 SWITCHING WAVEFORMS (MOVIE MODE) 3.5 3.9 4.3 4.7 INPUT VOLTAGE (V) 5.1 5.5 SOFT-START RESPONSE (STANDBY TO MOVIE-MODE TRANSITION) MAX8607toc06 MAX8607toc07 20mV/div VIN 3.1 VEN1 0V 5V/div 200mA/div VOUT IL 10mV/div ILED 0A 100mA/div IIN 0A 5V/div VLX 100mA/div 2V/div VOUT 0V 400ns/div 100µs/div LOAD TRANSIENT (DISCO MODE) SOFT-START RESPONSE (MOVIE-MODE TO FLASH TRANSITION) MAX8607toc09 MAX8607toc08 700mA 5V/div VEN2 100mA IL0AD ILED 200mA/div IIN 0A 500mA/div 500mV/div VOUT(RIPPLE) 0A 2V/div VOUT 0V 400µs/div 4 2ms/div _______________________________________________________________________________________ 1MHz PWM Boost Converter for 1.5A White LED Camera Flash MOVIE-MODE LED CURRENT vs. MOV RESISTANCE 350 1400 1200 LED CURRENT (mA) 300 LED CURRENT (mA) MAX8607toc11 1600 MAX8607toc10 400 FLASH-MODE LED CURRENT vs. FLSH RESISTANCE 250 200 150 100 50 1000 800 600 400 200 0 0 1 10 1 100 RMOV (kΩ) 10 100 RFLSH (kΩ) Pin Description PIN NAME FUNCTION 1 COMP 2 EN1 Enable Input 1. EN1 and EN2 set the operating mode (see Table 1). 3 EN2 Enable Input 2. EN1 and EN2 set the operating mode (see Table 1). 4 MOV Movie Current Program Input. Connect a resistor from MOV to GND to set the LED current in movie mode. RMOV must be greater than 2kΩ. 5 FLSH Flash Current Program Input. Connect a resistor from FLSH to GND to set the LED current in flash mode. RFLSH must be greater than 2kΩ. 6 GND Analog Ground. Connect GND to the exposed paddle directly under the IC. 7 LGND 8 LED 9, 10 PGND 11, 12 LX 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. 13 OUT Regulator Output. Connect OUT to the anode of the external LED. Bypass OUT to PGND with a 10µF or larger ceramic capacitor. During shutdown, OUT is one body-diode drop below the input voltage. 14 OUTS Output Sense and IC Supply Input. Connect OUTS to OUT at the output bypass capacitor. The IC’s operating power is supplied from OUTS. — EP Compensation Input. Connect a 0.1µF ceramic capacitor from COMP to GND for regulator stability. 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. Exposed Paddle. Connect the exposed paddle to GND directly under the IC and to a large PC board ground plane for increased thermal performance. _______________________________________________________________________________________ 5 MAX8607 Typical Operating Characteristics (continued) (Circuit of Figure 2, VIN = VEN1 = 3.6V, VEN2 = 0V, TA = +25°C, unless otherwise noted.) MAX8607 1MHz PWM Boost Converter for 1.5A White LED Camera Flash LX OUT REF OUTS FORCED-PWM BOOST CONTROL PGND 1MHz CLOCK FEEDBACK SELECT COMP 1.25V EN1 SHUTDOWN AND MODE CONTROL LED EN2 LDO REGULATOR FLSH MOV 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. _______________________________________________________________________________________ 1MHz PWM Boost Converter for 1.5A White LED Camera Flash Drive EN1 and EN2 low to place the IC into a lowpower shutdown mode. See the Shutdown section for more details. 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. 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. Soft-Start The MAX8607 attains soft-start by charging C COMP with a 100µA 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 140Ω internal resistor during UVLO, OVP, or shutdown. See the Typical Operating Characteristics for an example of soft-start operation. Table 1. EN1 and EN2 Mode Selection EN1 EN2 0 0 Shutdown MODE 0 1 Disco Mode 1 0 Movie Mode 1 1 Flash Mode Shutdown Drive EN1 and EN2 low to place the MAX8607 into a low-power shutdown mode. In shutdown, supply current is reduced to 0.1µA (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. Ambient Temperature Derating Function The MAX8607 limits the maximum LED current depending on its die temperature. Once the die temperature reaches +40°C, the LED current decreases by 1.67% per °C. This corresponds to approximately 0mA of LED current at +100°C. 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. 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) 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) _______________________________________________________________________________________ 7 MAX8607 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. 1MHz PWM Boost Converter for 1.5A White LED Camera Flash MAX8607 Capacitor Selection L1 INPUT 2.7V TO 5.5V 2.2µH C1 10µF 11, 12 9, 10 C3 0.1µF LX MAX8607 U1 OUTS 3 C2 10µF 14 D1 1 2 13 PGND COMP MODESELECT INPUTS OUT LGND GND EN1 EN2 FLSH 5 R1 MOV 4 LED EP 7 6 8 PC Board Layout R2 Figure 2. Typical Application Circuit Inductor Selection The MAX8607 is designed to use a 2.2µH 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 × ILED(MAX) 0.9 × VIN(MIN) + 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 10µF; 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 10µF ceramic capacitor works well in most situations, but a 4.7µF capacitor is acceptable for load current below 300mA. 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. VIN(MIN) × 0.5µs 2 × 2.2µH Chip Information PROCESS: BiCMOS Table 2 provides a list of suggested inductors. Table 2. Suggested Inductors MANUFACTURER Coilcraft Cooper (Coiltronics) FDK TOKO 8 SERIES INDUCTANCE (µH) DCR (mΩ) ISAT (A) DIMENSIONS (LTYP x WTYP x HMAX = Volume) LPO3310 2.2 150 1.1 3.3 x 3.3 x 1.0 = 11mm3 SD3114 2.2 83 1.48 3.0 x 3.0 x 1.45 = 13mm3 MIPF2520 2.2 80 0.7 2.5 x 2.0 x 1.0 = 5mm3 MIPW3226 2.2 100 1.1 3.2 x 2.6 x 1.0 = 8mm3 DE2812C 2.2 70 1.6 3.0 x 2.8 x 1.2 = 10mm3 FDSE0312 2.2 160 2.3 3.0 x 3.0 x 1.2 = 11mm3 _______________________________________________________________________________________ 1MHz PWM Boost Converter for 1.5A White LED Camera Flash 6, 8, &10L, DFN THIN.EPS _______________________________________________________________________________________ 9 MAX8607 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.) MAX8607 1MHz PWM Boost Converter for 1.5A White LED Camera Flash 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 PACKAGE VARIATIONS SYMBOL MIN. MAX. PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e A 0.70 0.80 T633-2 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF D 2.90 3.10 T833-2 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF E 2.90 3.10 T833-3 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF A1 0.00 0.05 T1033-1 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 2.00 REF L 0.20 0.40 T1033-2 10 1.50±0.10 2.30±0.10 0.50 BSC MO229 / WEED-3 0.25±0.05 2.00 REF k 0.25 MIN. T1433-1 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.05 2.40 REF A2 0.20 REF. T1433-2 14 1.70±0.10 2.30±0.10 0.40 BSC ---- 0.20±0.05 2.40 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 © 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.