LM3553SDX-HALF

LM3553 1.2A Dual Flash LED Driver System with I2C Compatible Interface March 6, 2008 LM3553 1.2A Dual Flash LED Driver System with I2C Compatible Interface General Description The LM3553 is a fixed frequency, current mode step-up DC/ DC converter with two regulated current sinks. The device is capable of driving loads up to 1.2A from a single-cell Li-Ion battery. One or more high current flash LEDs can be driven in series either in a high power Flash mode or a lower power Torch mode controlled by either an internal register or the FEN pin. Additionally a low current (20mA) indicator mode and a fixed output voltage mode are also available. The LM3553 has 128 current levels and 16 flash safety timer durations that are user adjustable via an I2C compatible interface. Internal soft-start eliminates large inrush currents at start-up. Over-voltage protection circuitry and 1.2MHz switching frequency allow for the use of small, low-cost output capacitors with lower voltage ratings. The LM3553 includes a TX pin that forces Torch mode during a flash event allowing for synchronization between the RF power amplifier and Flash/Torch modes. It also includes a multi-function pin (M/F) that can serve as a GPIO and a hardware RESET pin. The LM3553 is available in National's 3mm by 3mm LLP12 package. Features ■ Accurate and Programmable LED Current up to 1.2A in ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 128 Steps Total Solution Size < 30mm2 90% Peak Efficiency Drives 2 LEDs in Series with 1.2A from 5V Input Drives 2 LEDs in Series with 600mA from 3.0V Input Drives 1 LED with 1.2A from 3.0V Input Adjustable Over-Voltage Protection Allows for Single or Series LED Operation Four Operating Modes: Torch, Flash, Indicator, and Voltage Mode (4.98V) Programmable Flash Pulse Safety Timer in 16 Steps TX Input Ensures Synchronization with RF Power Amplifier Pulse or Prevents LED from Overheating LED Disconnect During Shutdown Flash/Imager Synchronization via FEN Pin Active Low Hardware Reset Multi-Function Pin (RESET and GPIO) Low Profile 12-pin LLP Package (SDF12A: 3mm x 3mm x 0.8mm, 0.4mm pitch) Applications ■ Camera Phone LED Flash ■ Smartphone and PDA Flash ■ LED Backlight Typical Application Circuits 20171419 Solution Size 20171415 © 2008 National Semiconductor Corporation 201714 www.national.com LM3553 Connection Diagram 20171416 Pin Descriptions Pin 4 5 6 2, 11 DAP 1 3 8 10 9 7 12 Name VIN SW OVP D1, D2 GND ISET FEN SCL SDA VIO TX M/F Input Voltage. Input range: 2.7V to 5.5V. Switch Pin Over Voltage Protection Pin Regulated current sink inputs Ground Current sense input. Connect a 1% 16.5kΩ resistor to ground to set the full scale LED current. Flash enable pin. Serial clock pin. Serial data I/O pin. Digital Reference Voltage level input pin. RF PA synchronization control pin. High = Forced Torch mode. Hardware RESET or General purpose I/O. Function set through Multi-Function Control Register Function Ordering Information Order Number LM3553SD-NOPB LM3553SDX-NOPB LM3553SD-HALF LM3553SDX-HALF Type No Lead, NonHalogenated No Lead, NonHalogenated No Lead, Halogenated No Lead, Halogenated Package SDF12A SDF12A SDF12A SDF12A Package Marking L3553 L3553 L3553 L3553 Supplied As 1000 units, Tape-and-Reel 4500 units, Tape-and-Reel 1000 units, Tape-and-Reel 4500 units, Tape-and-Reel www.national.com 2 LM3553 Absolute Maximum Ratings (Notes 1, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN pin: Voltage to GND -0.3V to 6V SW, OVP pin: Voltage to GND -0.3V to 25V D1, D2 pins: Voltage to GND -0.3V to 25V VIO, SCL, SDA -0.3V to 6V TX, FEN, M/F -0.3V to 6V Continuous Power Dissipation (Note 3) Internally Limited Junction Temperature (TJ-MAX ) 150°C Storage Temperature Range -65°C to +150 Maximum Lead Temperature (Soldering) (Note 4) ESD Rating(Note 5) Human Body Model 2.5kV Operating Ratings Input Voltage Range Junction Temperature (TJ) Range Ambient Temperature (TA) Range (Note 6) (Notes 1, 2) 2.7V to 5.5V -30°C to +125°C -30°C to +85°C Thermal Properties Junction-to-Ambient Thermal Resistance (θJA), SDF12A Package(Note 7) 36.7°C/W ESD Caution Notice National Semiconductor recommends that all integrated circuits be handled with appropriate ESD precautions. Failure to observe proper ESD handling techniques can result in damage to the device. Electrical Characteristics Limits in standard typeface are for TA = +25°C. Limits in boldface type apply over the full operating junction temperature range (-30°C ≤ TJ ≤ +125°C). Unless otherwise noted: VIN = 3.6V, RSET = 16.5kΩ, VD1 = VD2 = 500mV, VFB bit = '0', FEN = '0', TX = '0', Flash Current Level = Full-Scale. (Notes 2, 8, 9) Symbol Parameter Conditions Flash Mode VDX = Regulation Voltage Flash Mode VDX = Regulation Voltage RSET = 13.7kΩ Indicator Mode VM = '1', EN1 = EN0 = '0' No Load VD1,D2 = 0V (Switching) Device Disabled IDx= 500mA 4.65 Min 930 Typ 1020 Max 1110 mA 1200 20 4.98 1.0 3.8 6770 1.24 VFB Bit = '0' VFB Bit = '1' VDX = Regulation Voltage OCL Bit = '0' OCL Bit = '1' Switch Off, VSW=3.6V, OVP Mode = '0' VDx = 3.5V OVP Mode = '1' OVP Mode = '0' OVP Mode = '1' OVP Mode = '0' VOVP=3.6V 18.00 5.4 2.2 1.53 450 350 2 0.25 2.5 1.70 10 10 18.90 5.6 1.6 0.6 10 V nA 19.65 5.85 2.8 1.87 5.30 1.2 6.0 mA V mA µA A/A V mV % Ω A nA nA V Units ILED-SUM Flash LED Current: ID1+ ID2 ILED-IND VMREG IQ ISD IDx / ISET VSET VD1,D2 IDx-MATCH RDSON ICL IL-SW IL-Dx VOVP Indicator Current Level Output Voltage Regulation in Voltage Mode Quiescent Supply Current Shutdown Supply Current LED Current to Set Current Ratio ISET Pin Voltage Current Sink Regulation Voltage Current Sink Matching NMOS Switch Resistance NMOS Switch Current Limit SW Pin Leakage Current D1, D2 Pin Leakage Output Over-Voltage Protection Trip Point Over-Voltage Protection Hysteresis OVP to Normal Operation OVP Pin Leakage Current OVPHyst IL-OVP 3 www.national.com LM3553 Symbol fSW tFD-MIN DMAX DMIN ThTX,F-EN Parameter Switching Frequency Conditions Min 1.0 Typ 1.2 12.8 92 6 Max 1.35 Units MHz µsec. % % Minimum Flash Duration Step tFD-MIN = 16 ÷ fSW Maximum Duty Cycle Minimum Duty Cycle TX, FEN Pin Threshold On Off Input Logic High "1" Input Logic Low "0" ILOAD = 4.2mA, GPIO Mode 1.45 VIO = 3.0V VIO = 3.0V ILOAD = 3.7mA 0 0.55 × VIO 1.0 0 0.94 0 VIN 0.6 VIN 0.64 400 V Multi-Function Pin (M/F) Voltage Specifications VM/F VOL Multi-Function Pin Threshold Voltages Output Logic Low "0" V mV I2C Compatible Voltage Specifications (SCL, SDIO, VIO) VIO VIL VIH VOL Serial Bus Voltage Level Input Logic Low "0" Input Logic High "1" Output Logic Low "0" VIN 0.38 ×VIO VIO 400 V V V mV I2C Compatible Interface Timing Specifications (SCL, SDIO, VIO) t1 t2 t3 t4 t5 SCL (Clock Period) Data In Setup Time to SCL High Data Out stable After SCL Low SDA Low Setup Time to SCL Low (Start) SDA High Hold Time After SCL High (Stop) 2.5 100 0 100 100 µs ns ns ns ns 20171411 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables. Note 2: All voltages are with respect to the potential at the GND pin. Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=140ºC (typ.) and disengages at TJ=120ºC (typ.). Note 4: For detailed soldering specifications and information, please refer to National Semiconductor Application Note: AN-1187 for Recommended Soldering Profiles. Note 5: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. (MIL-STD-883 3015.7) Note 6: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125ºC), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the part/package in the application (θJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX). Note 7: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues in board design. www.national.com 4 LM3553 Note 8: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical (Typ) numbers are not guaranteed, but do represent the most likely norm. Unless otherwise specified, conditions for Typ specifications are: VIN = 3.6V and TA = 25ºC. Note 9: All testing for the LM3553 is done open-loop. 5 www.national.com LM3553 Typical Performance Characteristics Unless otherwise specified: TA = 25°C; VIN = 3.6V; VM/F = VIN; RSET = 16.5kΩ; CIN= 10µF, COUT = 10µF;L = 2.2µH; VFB bit = CL bit = '0'; OVP bit = '0' for 1 LED and VFB = '1' for two series LEDs;. Maximum LED Drive Current @ VIN = 3.6V 1.2A Flash Line Regulation 20171422 20171423 1.0A Flash Line Regulation Voltage Mode Line Regulation 20171424 20171420 Voltage Mode Load Regulation Input Current and LED Efficiency with 1A Flash Current 20171421 20171429 www.national.com 6 LM3553 Input Current and LED Efficiency with 1.2A Flash Current Input Current and LED Efficiency with 500mA Flash Current through 2 Series LEDs 20171430 20171432 Input Current and LED Efficiency with 600mA Flash Current through 2 Series LEDs Input Current vs VIN 1 LED @ 1.2A and 2 LEDs @ 600mA 20171431 20171435 LED Efficiency vs VIN 1 LED @ 1.2A and 2 LEDs @ 600mA Converter Efficiency vs VIN 20171440 20171436 7 www.national.com LM3553 Block Diagram 20171417 Circuit Description CIRCUIT COMPONENTS FEN Pin The flash enable pin, FEN, provides an external method (nonI2C) for starting the flash pulse. When FEN is pulled high, logic '1', the flash current level defined through the I2C interface, will be delived to the Flash LED. If the FEN pin is driven low during the flash pulse, the flash event will stop. In the event that FEN is not pulled low during the flash pulse, the LM3553 will continue to deliver the flash current until the safety timer duration (set through the I2C interface) is reached. The LM3553 does not provide a fixed off-time after the flash pulse has ended. Most flash LED manufacturers require that the flash pulse duration be 10% of the total Flash cycle. Example: If the flash pulse duration is set to be 200 milliseconds (Flash Duration Code= 0011), the recommended off time for the LED would be 1.8 seconds. Please consult the LED manufacturers datasheet for exact timing requirements. If the LM3553 is placed in indicator mode or torch mode through the I2C interface and the FEN pin is pulled high and then low, at the end of the flash event, the LM3553 will return to the mode stored in the General Purpose Register. It is recommended that an external pull-down be placed between the FEN pin and GND to prevent unwanted LED flashing during system start-up due to unknown control logic states. TX Pin The transmission pin (TX) can be used to limit the current drawn from the battery during a PA transmission. When the TX pin is driven high (logic '1') during a flash pulse, the LM3553 will switch to the programmed torch current level. Once the TX pin is driven low (logic '0'), the LM3553 will return to the flash current if this event occurs within the original flash duration. It is recommended that an external pull-down be placed between the TX pin and GND to prevent unwanted LED flashing during system start-up due to unknown control logic states. M/F Pin The multi-function pin (M/F) can be configured to provide hardware RESET or a general purpose input/output (GPIO). All functionality is programmed through the I2C compatible interface and set in the M/F pin functionality control register (address 0x20). The default function is a RESET, where a logic '1' places the part in the normal operating mode, and a logic '0' places the part into a RESET state. A reset condition will place all LM3553 registers into their default states. www.national.com 8 LM3553 Connection Diagram Typical System Configuration START AND STOP CONDITIONS START and STOP conditions classify the beginning and the end of the I2C session. A START condition is defined as SDA signal transitioning from HIGH to LOW while SCL line is HIGH. A STOP condition is defined as the SDA transitioning from LOW to HIGH while SCL is HIGH. The I2C master always generates START and STOP conditions. The I2C bus is considered to be busy after a START condition and free after a STOP condition. During data transmission, the I2C master can generate repeated START conditions. First START and repeated START conditions are equivalent, function-wise. The data on SDA line must be stable during the HIGH period of the clock signal (SCL). In other words, the state of the data line can only be changed when CLK is LOW. 20171433 I2C Compatible Interface DATA VALIDITY The data on SDA line must be stable during the HIGH period of the clock signal (SCL). In other words, the state of the data line can only be changed when CLK is LOW. 20171412 FIGURE 2. Start and Stop Conditions TRANSFERRING DATA Every byte put on the SDA line must be eight bits long, with the most significant bit (MSB) being transferred first. Each byte of data has to be followed by an acknowledge bit. The acknowledge related clock pulse is generated by the master. The master releases the SDA line (HIGH) during the acknowledge clock pulse. The LM3553 pulls down the SDA line during the 9th clock pulse, signifying an acknowledge. The LM3553 generates an acknowledge after each byte has been received. After the START condition, the I2C master sends a chip address. This address is seven bits long followed by an eighth bit which is a data direction bit (R/W). The LM3553 address is 53h. For the eighth bit, a “0” indicates a WRITE and a “1” indicates a READ. The second byte selects the register to which the data will be written. The third byte contains data to write to the selected register. 20171404 FIGURE 1. Data Validity Diagram A pull-up resistor between VIO and SDA must be greater than [ (VIO-VOL) / 3.7mA] to meet the VOL requirement on SDA. Using a larger pull-up resistor results in lower switching current with slower edges, while using a smaller pull-up results in higher switching currents with faster edges. 20171413 FIGURE 3. Write Cycle w = write (SDA = "0") ack = acknowledge (SDA pulled down by the slave) id = chip address, 53h for LM3553 9 www.national.com LM3553 I2C COMPATIBLE CHIP ADDRESS The chip address for LM3553 is 1010011, or 53hex. VFB: Selects the regulation voltage for the LM3553. Setting this VFB bit to a '0' sets the regulation voltage to 450mV while setting the VFB bit to a '1' sets the regulation voltage to 350mV. Setting the VFB bit to a '1' during torch mode and/or lower current flash modes (ILED < 1A) will help improve the LED efficiency of the LM3553. M/F Pin Control Register 20171410 FIGURE 4. 20171409 INTERNAL REGISTERS OF LM3553 Register General Purpose Register Multi-Function Pin Control Register Current Step Time Register Torch Current Control Register Flash Current Control Register Flash Duration Control Register General Purpose Register Internal Hex Address 0x10 0x20 0x50 0xA0 0xB0 0xC0 Power On Value 0001 1000 1110 0000 1111 1100 1000 0000 1000 0000 1111 0000 FIGURE 6. RESET: Enables M/F as hardware RESET. '0' = Hardware RESET, .'1' = GPIO or current sink depending on the MODE bit. Default = '0' MODE: Sets M/F mode. Default for M0DE = '0'. '0' = GPI, and'1' = GPO Note: When M/F is configured as an input, data is transfered from GPI to DATA whenever an I2C write command is issued to the LM3553. When configuring M/F as a GPO, the first write needs to take the LM3553 out of RESET mode and a second write can then set the pin to the GPO. DATA: GPIO Data. When the M/F is configured as an output (GPO), DATA sets the GPO level. Example: DATA = '1', M/F is set high or logic '1'. When the M/F pin is configured as an input (GPI), DATA stores the GPI level. Example: M/F = '1', DATA will be set to a '1'. Default for DATA = '0'. OVP: Enables high-voltage OVP (OVP Bit ='1') or low-voltage OVP (OVP Bit ='0'). Default = low-voltage mode '0' OCL: SW Pin Current Limit Selector Bit: If OCL = '0', the inductor current limit is 2.5A typ. If OCL = '1', the inductor current limit is 1.7A typ. M/F Functionality Configuration Table 20171405 RESET 0 1 1 MODE X 0 1 M/F Function RESET GPI GPO FIGURE 5. EN0-EN1: Set Flash LED mode Indicator Mode sets ILED = 20mA. In this mode, D1 is enabled and D2 is disabled. VM: Enables Voltage Mode. Current sinks D1 and D2 are turned off and the LM3553 will operate in a regulated voltage boost mode. Setting the VM bit to a '1' does not override the EN0 and EN1 bits stored in the general purpose register. The default setting is '0'. If the LM3553 is in Voltage Mode and an indicator, torch or flash command is issued, the LM3553 will turn on the D1 and D2 current sources and begin regulating the output voltage to a value equal to VFB (350mV or 450mV) + VLED. VM 0 0 0 0 1 1 1 1 www.national.com Current Step Time Register 20171418 FIGURE 7. ST1-ST0: Sets current level stepping time for D1 and D2 during the beginning and end of the flash or torch current waveform. '00' = 25µs, '01' = 50µs, '10' = 100µs, '11' = 200µs. The current ramp-up/ramp-down times can be approximated by the following equation: TRAMPUP/RAMPDOWN = (NFLASH - NSTART + 1) × tSTEP where N is equal to the decimal value of the brightness level (0 ≤ NFLASH ≤ 127 and 0 ≤ NSTART ≤ 31). NSTART = NTORCH if Torch is enabled before going into a flash. If going straight into a flash from an off-state, NSTART = 0 EN1 0 0 1 1 0 0 1 1 EN0 0 1 0 1 0 1 0 1 Function Shutdown Indicator Mode Torch Mode Flash Mode Voltage Mode Indicator Mode Torch Mode Flash Mode 10 LM3553 Torch Current Control Register Safety Timer Duration Code (Binary) 0000 0001 20171406 Typical Safety Timer Duration (milliseconds) 50 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 3200 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 FIGURE 8. TC6-TC0: Sets Torch current level for D1 and D2. xxx1 1111 = Fullscale Flash Current Control Register 20171407 1101 1110 1111 FIGURE 9. FC6-FC0: Sets Flash current level for D1 and D2. x111 1111 = Fullscale Current Level Equation The Full-Scale Flash Current Level is set through the use of an external resistor (RSET) connected to the ISET pin. The RSET selection equation can be used to set the current through each of the two current sinks, D1 and D2. RSET = 6770 × 1.24V ÷ IDx RSET Selection Table IFlash = ID1 + ID2 500mA 600mA 1A 1.2A RSET 33.6kΩ 28kΩ 16.8kΩ 14kΩ EN1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 LM3553 Functionality Truth Table EN0 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 FEN 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 TX 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Result Shutdown Shutdown Flash Torch Indicator Indicator Flash Torch Torch Torch Flash Torch Flash Torch Flash Torch The current through each current sink, D1 and D2, can be approximated by the following equation using the values stored in either the Torch or Flash Current Control registers. IFLASH≊ (N + 1) × ILED_TOTAL ÷ 128 where N is the decimal equivalent number (0 ≤ N ≤ 127 for Flash and 0 ≤ N ≤ 31 for Torch) stored in the Torch or Flash Current control registers and ILED_TOTAL = ID1 + ID2 @ Fullscale. Brightness codes 0 through 4 are repeated and each sets the total LED current to approximately 40mA. Flash Safety Timer Control Register FEN Terminated Pulse 20171408 FIGURE 10. FD3-FD0: Sets Flash Duration for D1 and D2. 1111 = Fullscale 20171426 11 www.national.com LM3553 Safety Timer Terminated Pulse 20171427 TX Terminated Pulse 20171428 Application Information INDUCTOR SELECTION The LM3553 is designed to use a 2.2µH inductor. When the device is boosting (VOUT > VIN) the inductor is one of the biggest sources of efficiency loss in the circuit. Therefore, choosing an inductor with the lowest possible series resistance is important. Additionally, the saturation rating of the inductor should be greater than the maximum operating peak current of the LM3553. This prevents excess efficiency loss that can occur with inductors that operate in saturation and prevents over heating of the inductor and possible damage. For proper inductor operation and circuit performance ensure that the inductor saturation and the peak current limit setting of the LM3553 (2.6A or 1.8A) is greater than IPEAK. IPEAK can be calculated by: CAPACITOR SELECTION The LM3553 requires 2 external capacitors for proper operation (CIN = 10µF recommended (4.7µF min.) and COUT = 10µF (single LED) or 4.7µF (series LEDs)). Surface-mount multilayer ceramic capacitors are recommended. These capacitors are small, inexpensive and have very low equivalent series resistance (ESR