SC605 SEMTECH | Alldatasheet
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Technical content
Features
Typical Application Circuit
Applications
The SC605 is a high-current charge pump designed spe - cifically for use with white LEDs used in camera flash ap - plications. Only two small bucket capacitors are required to develop the output drive, providing a low EMI solution compared to inductive boost regulators. The SC605 has two modes of operation: Flash mode and Spotlight mode. In Flash mode, the SC605 is capable of delivering 500mA of regulated current for a duration of 500ms or up to 700mA for a reduced duration. In Spotlight mode the SC605 can output 20%, 30%, or 40% of the Flash mode current and remain enabled continuously. An external resistor is connected in series with the LED to set the current. In Flash mode, this resistor can dissipate up to 0. 75mW, reducing the power dissipation require - ment of the SC605. The Flash input (FLASH) overrides the control inputs (CTRL0 and CTRL1) to ensure the Flash function has the highest priority. The thermally efficient MLPD-12 package and ceramic bypass and bucket capacitors help make the SC605 a high output current driver that requires a minimal amount of PCB area. Two selectable modes - Flash and Spotlight Up to 700mA output - Flash mode Up to 280mA output - Spotlight mode 500mA output over specified temperature and volt- age ranges - Flash mode Spotlight mode selectable to 20%, 30% and 40% of Flash current 3.0V to 5.25V input range Flash control pin for synchronization to a camera module or graphics controller Short circuit, over-voltage and over-temperature protection Soft-start functionality Three control inputs for maximum versatility Shutdown current < 2μA Micro-lead package MLPD-12, 3mm x 3mm VBAT 0µF µF white LED CTRL CTRL0 FLASH 0.5W SC605 VIN1 FLASH6 CTRL08 CTRL19 NC5 VOUT 11 ISET 7 C1+ 10 C1- 4 C2+ 12 C2- 2 µF µF GND3 Mobile Camera Phones Digital Cameras PDAs with Built-in Cameras
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Absolute Maximum Ratings
Electrical Characteristics
Exceeding the specifications below may result in permanent damage to the device or device malfunction. Operation outside the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability. Parameter Symbol Maximum Units Supply Voltage VIN -0.3 to 6.5 V Output Voltage VOUT -0.3 to 6.5 V Pin Voltage - FLASH, CTRL0, CTRL1, ISET, C1-, C2- -0.3 to VIN + 0.3 V Pin Voltage - C1+, C2+ -0.3 to VOUT + 0.3 V VOUT Short Circuit Duration SC Indefinite Thermal Resistance, Junction to Ambient (JESD51 Standard Method)(1) θJA 40 °C/W Operating Ambient Temperature Range TA -40 to +85 °C Junction Temperature Range TJC -40 to +150 °C Storage Temperature Range TSTG -65 to +150 °C IR Reflow Temperature TLEAD 260 °C ESD Protection Level(2) VESD 2 kV Notes: 1) Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards. 2) Tested according to JEDEC standard JESD22-A114-B Unless otherwise specified: TA = 25°C for TYP, -40°C to +60°C for MIN and MAX; CIN = 0µF, CBUCKET = COUT = 1.0µF (ESR < 0.1Ω); Parameter Symbol Conditions Min Typ Max Units Flash Mode - Output Current IOUT FLASH high, RISET = 0.357W, 3.7V < VIN < 4.2V, VOUT = 3.7V (1) 700 mA FLASH high, RISET = 0.5W, 3.3V < VIN < 4.2V, 2.8V < VOUT < 4.25V 460 500 540 FLASH low, CTRL0 high, CTRL1 high, RISET = 0.357W, 3.7V < VIN < 4.2V, VOUT = 3.4V (1) 280 Spotlight Mode - Output Current IOUT FLASH low, CTRL0 high, CTRL1 high, RISET = FLASH low, CTRL0 low, CTRL1 high, RISET = FLASH low, CTRL0 high, CTRL1 low, RISET =
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Electrical Characteristics (Cont.) Parameter Symbol Conditions Min Typ Max Units Flash Mode - ISET Reference Voltage VISET FLASH high, RISET = 0.5W, 3.3V < VIN < 4.2V, 2.8V < VOUT < 4.25V 230 250 270 mV Spotlight Mode - ISET Reference Voltage VISET FLASH low, CTRL0 high, CTRL1 high 3.0V < VIN < 4.5V, 2.8V < VOUT < 4.5V 85 100 115 FLASH low, CTRL0 low, CTRL1 high 3.0V < VIN < 4.5V, 2.8V < VOUT < 4.5V 60 75 90(3) FLASH low, CTRL0 high, CTRL1 low 3.0V < VIN < 4.5V, 2.8V < VOUT < 4.5V 35 50 65(3) Quiescent Current IQ FLASH High 3.4 5 mA FLASH low, CTRL0 and/or CTRL1 High 2.0 4.5 mA FLASH low, CTRL0 low, CTRL1 Low 0.1 2 µA Flash Mode Pulse Duration (4) tFLASH 3.3V < VIN < 4.2V IOUT = 500mA 500 ms Flash Mode Start-Up Time (4) tF-ST from t = 0 when FLASH goes high to IOUT = 90% of final value 1 ms Spotlight Mode Start-Up Time (4) tS-ST from t = 0 when CTRL0 and/or CTRL1 transi- tion high to IOUT = 90% of final value 1 ms Oscillator Frequency fOSC Device Enabled 250 kHz Oscillator Frequency Accuracy DfOSC -15 15 % Short-Circuit Ouput Current Limit ISC VOUT = 0V 465 mA Input Current Limit ILIMIT 3.3V < VIN < 4.2V 1.0 2.1 A VIN = 3.7V, VOUT = 3.7V, TA = 25°C 1.38 1.53 Over-Temperature Protection (4) TOT 150 °C Hysteresis 10 °C Logic Input High Threshold VIH FLASH, CTRL0, CTRL1 1.5 V Logic Input Low Threshold VIL FLASH, CTRL0, CTRL1 0.4 V Logic Input High Current IIH FLASH, CTRL0, CTRL1 1 20 35 µA Logic Input Low Current IIL FLASH, CTRL0, CTRL1 0.1 2 µA ISET Ripple Voltage(4) VPP Spotlight Mode, IOUT = 200mA 25 mV Flash Mode, IOUT = 500mA 100 Notes: (1) VOUT required by the typical LED at this current. (2) Values do not overlap with the next higher spotlight mode for any single device. Expect Spotlight Modes to be separated by about 50mA. (3) Values do not overlap with the next higher spotlight mode for any single device. Expect Spotlight Modes to be separated by about 25mV. (4) Guaranteed by design - not tested in production.
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Pin ConfigurationPin Configuration Ordering information Pin Descriptions DEVICE PACKAGE SC605MLTRT(1)(2) MLPD-12 3x3 SC605EVB Evaluation Board Notes: (1) Available in Tape and Reel only. A reel contains 3000 devices. (2) Available in lead-free package only. This product is fully WEEE and RoHS compliant. Pin Pin Name Pin Function (also see Suggested Layout guidelines on page 10) 1 VIN Input voltage. Decouple with a 10µF or larger ceramic capacitor near pin 1. 2 C2- Negative terminal of bucket capacitor 2 - use a 1µF ceramic capacitor. 3 GND Ground - connect through multiple vias to the ground plane. 4 C1- Negative terminal of bucket capacitor 1 - use a 1µF ceramic capacitor. 5 NC Not connected - leave this pin floating. 6 FLASH Flash mode enable pin - puts the device in active Flash mode when high. 7 ISET Current-setting reference pin - connect to the LED cathode and the current setting resistor. 8 CTRL0 Control input bit 0 - used with CTRL1 to enable and set the output current in Spotlight mode (see Table 1). 9 CTRL1 Control input bit 1 - used with CTRL0 to enable and set the output current in Spotlight mode (see Table 1). 10 C1+ Positive terminal of bucket capacitor 1 - use a 1µF ceramic capacitor. 11 VOUT Output pin - connect to LED anode. Decouple with a 1µF ceramic capacitor near pin 11. 12 C2+ Positive terminal of bucket capacitor 2 - use a 1µF ceramic capacitor. T Thermal Pad Pad for heat sinking purposes - not connected internally. Connect to ground plane using multiple vias. TOP VIEW MLPD - 12: 3X3 12 LEAD VIN C2- GND NC FLASH ISET CTRL0 CTRL VOUT C2+
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Applications Information General Operation The SC605 is a powerful 2x charge pump designed to drive a high-intensity white LED with a constant current (Spotlight mode) or with a pulsed current of higher intensity (Flash mode) used for camera flash. In Flash mode the SC605 output can drive 500mA at 4.25V into an LED for up to 500ms. The FLASH pin is used to trigger Flash mode. In spotlight mode the SC605 regulates the output current to the value selected by the CTRL0 and CTRL1 inputs. Note that Flash mode has priority over Spotlight mode, i.e., the FLASH pin triggers Flash mode regardless of the state of the CTRL0 and CTRL1 pins. Output current is regulated by attaching the ISET pin to the cathode(s) of the LED package and a load sense resistor (typically 0.5W). The ISET pin monitors the voltage at the cathode and signals the charge pump to increase or de - crease the output current until the ISET voltage reaches the programmed setting. Programmed settings are shown in Table 1: CTRL1 CTRL0 FLASH VISET Mode 0 0 0 0mV Disabled 0 1 0 50mV Spotlight 1 0 0 75mV Spotlight 1 1 0 100mV Spotlight x x 1 250mV Flash Table 1 - Control State Table The resistor value is chosen to set the current through the LED based on this reference voltage. The resistor should not be less than 0.35W due to the output current limitations of the device. Note that the resistor sets both the Flash mode current and the Spotlight mode current. In Flash mode, IOUT = VISET / RISET = 250mV / RISET. In Spotlight mode, IOUT = VISET / RISET. Spotlight Mode Spotlight mode is enabled by setting the CTRL0 and CTRL1 pins as shown in Table . When in Spotlight mode, the SC605 can maintain a constant current indefinitely to drive an LED or bank of LEDs. The ISET pin voltage is the refer- ence VISET and has three different settings - 50mV, 75mV, and 100mV. These settings allow the designer the flexibility to select the output level needed to suit the application. Flash Mode Flash mode is enabled whenever the FLASH pin is pulled high and remains active until the FLASH pin is released. While in Flash mode the reference voltage on the ISET pin is set to 250mV. During Flash mode the charge pump de- velops enough output current to drive an LED with 500mA for a duration up to 500ms. The duration of the pulse is limited by the amount of power that can be dissipated in the SC605 before it exceeds the maximum operating tem- perature. Note that if an output current less than the rated 500mA is desired the duration of the pulse can increase proportionally. However, great care should be taken to in- sure the FLASH pin is not held high for an extended amount of time so that overheating does not occur. Extending flash mode beyond the 500ms pulse limit could adversely affect the long-term reliability of the SC605. Flash duration must be derated at higher currents, for example, 700mA derates to a maximum of 350ms. The plot below shows maximum Flash mode current for extended duration times. Maximum Flash Duration Protection Circuitry The SC605 also provides protection circuitry that prevents the device from operating in an unspecified state. These include Input Over-Voltage Protection (IOVP), Output Over- Voltage Protection (OVP), Over-Temperature Protection (OTP), Over-Current Protection (OCP), and Short-Circuit Current Protection (SCCP). Input Over-Voltage Protection Input over-voltage protection is included to prevent opera- tion at high input voltages that could damage the device. The IOVP circuit senses the input voltage and determines when the supply exceeds 6V. When the voltage rises above this threshold, the device is disabled until the input voltage drops to a level within the specified input range. Hysteresis is included in this circuit to avoid chattering between states. 100 200 300 400 500 600 700 800 0 500 1000 1500 2000 Flash Duration [ms] Flash Current [mA]
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Applications Information (Cont.) Output Over-Voltage Protection Output over-voltage protection is included to prevent the SC605 from generating an output voltage that could dam- age other devices connected to it such as load LEDs and bypass capacitors. When the output voltage exceeds 5.5V, the OVP circuit disables the charge pump until the voltage decreases to a level within the acceptable range. This cir- cuit allows the device to drive LEDs with high forward volt ages at a reduced level without exceeding the output volt- age limits specified for the device. This is a consequence of over-voltage protection, not the function of OVP. Over-Temperature Protection The OT circuit helps prevent the device from overheating and experiencing a catastrophic failure. When the junction temperature exceeds 150°C the device is disabled. It remains disabled until the junction temperature drops below this threshold. As with the OVP circuit, hysteresis is included to prevent toggling between states. Over-Current Protection When the SC605 is in 2X charge pump mode, the input current will be approximately double the required output. When the steady-state load requires the maximum current available in 2X mode, the OCP circuit prevents the device from overheating due to excessive power dissipation. Short-Circuit Current Protection SCCP is provided to limit the current that can be sourced when the output is shorted to ground. When the output voltage drops below 2V, the SCCP detects the condition as a short to ground and limits the output current. Resistor Selection The ISET resistor selection is critical to generating the cor- rect current. The value can be chosen to set the Spotlight mode current or the Flash mode current, but it must be noted that the two current settings are dependent on the same resistor. It is recommended that the resistor be se- lected to match the LEDs desired current for Flash mode. This will allow the designer to set the maximum current out of the SC605. The typical application circuit shown on page uses a 0.5W resistor to set a Flash mode current of 500mA and Spotlight mode options of 100mA, 150mA, and 200mA. A precision resistor should be used to ensure the specified accuracy for LED current. To avoid malfunction of the charge pump, it is recom - mended that the resistance seen at the ISET pin remain constant while the device is active (Flash or Spotlight mode). Changing the resistance value or the load current while the device is active could cause instability or voltage transients that would result in non-compliant behavior. The load current return path is from the ISET sense point through the resistor and back to the ground pin. Resistance in this path adds to the total resistance and has the effect of reducing the LED current by about 4% per 10mV of DC drop across the return copper trace in Flash mode. For this reason, it is crucial to have a low resistance return path. Place and ground the resistor as close as possible to the ground pin of the SC605. The trace from ISET has virtually no current. The ISET trace should make contact at the pad of the power sense resistor to minimize the effect of voltage drop between the LED cathode and the resistor. Capacitor Selection The SC605 is designed to use low-ESR ceramic capaci - tors for the input and output bypass capacitors as well as the charge pump bucket capacitors. Ideal performance is achieved when C1 is exactly equal to C2. It is recom - mended that X5R or X7R ceramic capacitors be used for best performance. Thermal Resistance The SC605 package is thermally efficient when the circuit board layout connects the thermal pad through multiple vias to the ground plane. The thermal resistance is rated at 0°C/W, but this rating is dependent on the connection between the thermal pad and the ground plane. A layout that is done correctly should keep the junction tempera - ture below the OT limit while operating the SC605 within the specifed electrical conditions for IOUT and VISET. A poor layout may allow the junction temperature to reach the OT limit while in Flash or Spotlight mode.
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Block Diagram 0.5W µF µF µF0µF CHARGE PUMP VBAT 250kHz Logic Control Reference Voltage Generator LDO C+ C2+ C2- VOUT ISET VIN CTRL0 CTRL FLASH GND NC white LEDCTRL0 FLASH CTRL Figure 1 - SC605 Block Diagram with Support Components
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 675 695 715 735 755 0 100 200 300 400 500 Time [ms] Current [mA] VIN=4.2V VIN=3.7V VIN=3.3V 490 495 500 505 510 0 100 200 300 400 500 Pulse Duration [ms] LED Current [mA] VIN=4.2V VIN=3.7VVIN=3.3V Typical Characteristics Flash Duration, RISET=500mW, VOUT=3.52V(start) to 3.38V(LED heated 500ms) Flash Duration, RISET=350mW, VOUT=3.62V (start) to 3.40V(LED heated 500ms) 200mA Spotlight Current, RISET=500mW, VOUT=3.0V 187.5 192.5 197.5 202.5 207.5 212.5 VIN [V] Current [mA] Flash Current at 500ms, RISET= 500mW, VOUT=3.38V 460 480 500 520 540 VIN [V] Current [mA] Flash Current at 100ms, RISET=500mW, VOUT=3.46V 460 480 500 520 540 VIN [V] Current [mA] Flash Current at 10ms, RISET=500mW, VOUT=3.52V 460 480 500 520 540 VIN [V] Current [mA]
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Typical Characteristics (Cont.) Flash Current at 350ms, RISET=350mW, VOUT=3.45V 675 695 715 735 755 VIN [V] Current [mA] Flash Current at 100ms, RISET=350mW, VOUT=3.53V 675 695 715 735 755 VIN [V] Current [mA] Flash Current at 10ms, RISET=350mW, VOUT=3.62V 675 695 715 735 755 VIN [V] Current [mA] Flash Mode VISET Ripple Ch 00mV/div Ch2 2V/div Ch3 2V/div us/div Startup Flash Mode 500mA Ch 00mV/div Ch2 2V/div Ch3 2V/div 0us/div 100mA Spotlight Current, RISET=500m W, VOUT=2.92V 85.0 90.0 95.0 100.0 105.0 110.0 115.0 VIN [V] Current [mA]
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Suggested Layout The following layout is suggested for a two layer design with one component side. The capacitors C and C2 are the bucket capacitors and each of these capacitors conducts the full load current of up to 700mA pulsed on for one half clock cycle per capacitor. C3 is the output decoupling ca- pacitor, placed near the SC605. C is the input decoupling capacitor, placed near the SC605. Multiple vias should be used whenever it is necessary to change layers on nets connecting to pins VIN, VOUT, GND, C1-, C1+, C2-, C2+. Resistor R1 is routed with a very low resistance connection between ISET and GND pin 3. The sense trace between pin 7 and R1 is connected to R1 at the terminal pad for the most accurate sensing possible. The bottom copper layer is primarily a ground plane provid- ing a return path between the ground vias at R1 and the ground vias connecting pin 3 to the ground plane. The SC605’s center thermal pad is tied to the ground plane through a heat spreading copper shape with multiple vias. There are 0 vias shown in this layout connecting the ther mal pad and pin 3 together to the ground plane. All 0 vias help spread heat and conduct ground current. Note that the thermal pad does not conduct current. Pin 3 conducts the full ground current. Four signal traces routed on the bottom layer are CTRL1, CTRL0, FLASH and ISET. These traces are routed horizon- tally on the bottom layer. Carefully route these traces so they do no block the ground path from R1 to the ground pin 3. Top Copper Bottom Copper
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Outline Drawing - MLPD-12 Pin Marking Information NOTES: CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS.2. .003 .006 .042 .008 .048 .000 .031 (.008) 0.08 0.20 .010 .052 0.15 1.06 .039 .002 0.00 0.80 1.31 0.25 1.21 0.05 1.00 (0.20) .004 0.10 0.45 BSC.018 BSC aaa C SEATING PLANE A bbb C A B B e C (LASER MARK) INDICATOR PIN 1 N MIN aaa bbb b e L N E A DIM MILLIMETERS NOM DIMENSIONS MAXNOM INCHES MIN MAX LxN A e/2 bxN D E E/2 D/2 Top Marking yyww = Datecode (Example: 0552) xxxxx = Semtech lot number 605 yyww xxxxx
2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC605 Land Pattern - MLPD-12 Pin .087 .055 2.20 1.40 .150 .018 .010 .037 3.80 0.25 0.95 0.45 (.112) .075 1.90 (2.85) THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. NOTES: THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FUNCTIONAL PERFORMANCE OF THE DEVICE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR INCHES DIMENSIONS G K H X Y P Z C DIM MILLIMETERS H K G Y Z P (C) X Semtech Corporation Power Management Products Division
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