SC635

SC635 SEMTECH | Alldatasheet

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 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Absolute Maximum Ratings Exceeding the specifications below may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Unless otherwise specified: TA = 25°C for TYP, -40°C to +60°C for MIN and MAX; (1) Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad as per JESD51 standards. (2) Tested according to JEDEC standard JESD22-A114-B. Parameter Symbol Maximum Units Input Supply Voltage VVIN -0.3 to +6.5 V Output Voltage VVOUT -0.3 to +6.5 V Pin Voltage - FLASH, CTRL, ISET, C1-, C2- -0.3 to VVIN + 0.3 V Pin Voltage - C1+, C2+ -0.3 to VVOUT + 0.3 V Thermal Resistance, Junction to Ambient (JESD51 Standard Method)(1) qJA 49 °C/W VOUT Short Circuit Duration SC Indefinite s Operating Ambient Temperature Range TA -40 to +85 °C Junction Temperature Range TJ -40 to +150 °C Storage Temperature Range TSTG -60 to +150 °C Peak IR Flow Temperature TLEAD 260 °C ESD Protection Level(2) VESD 2 kV Parameter Symbol Conditions Min Typ Max Units Output Current IOUT FLASH high, RISET = 1.25W 3.3V < VVIN < 4.2V 2.8V < VVOUT = 4.25V 184 200 216 mA FLASH low, CTRL high, RISET = 1.25W 3.0V < VVIN < 4.5V 2.8V < VVOUT < 4.5V 68 80 92 ISET Reference Voltage VISET FLASH high, RISET = 1.25W 3.3V < VVIN < 4.2V 2.8V < VVOUT < 4.25V 230 250 270 mV FLASH low, CTRL high, RISET = 1.25W 3.0V < VVIN < 4.5V 2.8V < VVOUT < 4.5V 85 100 115 Quiescent Current IQ FLASH high 3.4 5.0 mA FLASH low, CTRL high 2.0 4.5 mA FLASH low, CTRL low 0.1 2.0 µA Absolute Maximum Ratings

Electrical Characteristics

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Parameter Symbol Conditions Min Typ Max Units Flash Mode Start-up Time(1) tF-SU t = 0 when FLASH goes high to IOUT = 90% of final value 1 ms Flash Mode Pulse Duration tFLASH 3.3V < VVIN < 4.2V IOUT = 200mA, VVOUT > 2.8V indefinite s Spotlight Mode Start-up Time(1) tS-SU t = 0 when CTRL goes high to IOUT = 90% of final value 1 ms Oscillator Frequency fOSC Device enabled 250 kHz Oscillator Frequency Accuracy DfOSC -15 15 % Short-circuit Output Current Limit ISC VOUT shorted to GND 465 mA Input Current Limit ILIMIT 3.3V < VVIN < 4.2V 1.0 2.1 A Over-temperature Protection(1) TOT 150 Hysteresis 10 Logic Input High Threshold VIH FLASH, CTRL 1.5 V Logic Input Low Threshold VIL FLASH, CTRL 0.4 V Logic Input High Current IIH FLASH 1 20 35 µA CTRL 2 40 70 Logic Input High Current IIL FLASH, CTRL 0.1 2.0 µA ISET Ripple Voltage(1) VISET(P-P) Spotlight mode - IOUT = 80mA 25 mV FLASH mode - IOUT = 200mA 100 Notes: (1) Guaranteed by design - not tested in production. Electrical Characteristics (Cont.)

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 DEVICE PACKAGE(1) SC635MLTRT(2)(1) (1)(2) MLPD-10 3x3 SC635EVB Evaluation Board Notes: (1) Available in tape and reel only. A reel contains 3,000 devices. (2) Available in lead-free package only. Device is WEEE and RoHS compliant. Pin# Pin Name Pin Function 1 VIN Input voltage. 2 C2- Negative terminal of bucket capacitor 2. 3 GND Ground - connect to ground plane using multiple vias. 4 C1- Negative terminal of bucket capacitor 1.

5 FLASH Flash mode enable pin - puts the device in active Flash mode when high and also overrides

CTRL. 6 ISET Current-setting reference pin - connect to the LED cathode and the current setting resistor. 7 CTRL Control input bit - used to enable and set the output current in Spotlight mode when high. 8 C1+ Positive terminal of bucket capacitor 1. 9 VOUT Output pin. 10 C2+ Positive terminal of bucket capacitor 2. T Thermal Pad Pad for heat sinking purposes - not connected internally. Connect to ground plane using multiple vias. Pin Configuration Ordering Information Pin Descriptions TOP VIEW 5 6 MLP10: 3X3 10 LEAD T VIN C2- GND C1- FLASH C2+ VOUT C1+ CTRL ISET

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Pin ConfigurationApplications Information General Operation The SC635 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 inten- sity (Flash mode) used for camera flash. In Flash mode the SC635 output can drive 200mA at 4.25V into an LED for an unlimited duration under all temperature and input conditions. The FLASH pin is used to trigger this mode (active high). In Spotlight mode the SC635 regulates the output current to 40% of the Flash mode current setting when the CTRL pin is pulled high and the FLASH pin is low. Note that Flash mode has prior- ity over Spotlight mode, i.e., the FLASH pin triggers Flash mode regardless of the state of the CTRL pin. Output current is regulated by attaching the ISET pin to the cathode(s) of the LED package and a low resistance sense resistor (typically 1.25Ω). The ISET pin monitors the voltage at the cathode and signals the charge pump to increase or decrease the output current until the ISET voltage reaches the programmed setting. The resistor value is chosen to set the current through the LED based on this reference voltage. Flash Mode Flash mode is enabled whenever the FLASH pin is pulled high and remains active until the FLASH pin is released. This mode has higher priority than Spotlight mode, so the state of the CTRL pin is overridden whenever the FLASH pin is activated. While in Flash mode the reference volt age on the ISET pin is set to 250mV. Output currents other than the rated maximum of 200mA can be set by changing the RISET value. In Flash mode, IOUT = 250mV/RISET. Spotlight Mode Spotlight mode is enabled by setting the CTRL pin high and keeping the FLASH pin low. When in Spotlight mode, the SC635 can maintain a constant current indefinitely to drive an LED or bank of LEDs. The ISET reference voltage is set to 00mV so that the output current is maintained at 80mA when a 1.25Ω resistor is used. Spotlight current is always 40% of flash current for any given value of RISET. In spotlight mode, IOUT = 100mV/RISET. The resistor val- ue should not exceed 2Ω, however, to ensure the SC635 does not become unstable while in Spotlight mode due to the output current being set too low. Protection Circuitry The SC635 also provides protection circuitry that prevents the device from operating in an unspecified state. These functions include Input Over-Voltage Protection (IOVP), Output Over-Voltage Protection (OVP), Over-Temperature (OT) Protection, 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. Hysteresis is included in this circuit to avoid chattering between states. When the volt- age rises above this threshold, the device is disabled un- til the input voltage drops to a level within the specified range. Output Over-Voltage Protection Output over-voltage protection is included to prevent the SC635 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 circuit allows the device to drive LEDs with high forward voltages at a reduced level without exceeding the output voltage limits specified for the device. Note, however, that this effect is a consequence of the OVP circuit and is not its intended purpose. Over-Temperature Protection The over-temperature circuit helps prevent the device from overheating and experiencing a catastrophic fail ure. 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 UVLO and OVP circuits, hysteresis is included to prevent toggling between modes. Over-Current Protection When the SC635 is in 2X 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 over heating due to excessive power dissipation.

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Short-Circuit Current Protection Short-circuit current protection is provided to limit the cur- rent that can be sourced when the output is shorted to ground. When a short circuit forces VOUT to drop below 2V, the SCCP detects the condition and limits the output current. Resistor Selection The ISET resistor selection is critical in 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 resistance. It is recommended that the resistor be selected to match the desired LED current for Flash mode. This allows the designer to set the SC635’s maximum cur- rent and select the resistor package size necessary for the power dissipation required in Flash mode. The typical application shown on page 1 uses a 1.25Ω resistor to set a flash mode current of 200mA and spotlight mode cur- rent of 80mA. A high 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 cur- rent while the device is active could cause instability 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 pins. Resis tance in this path adds to the total resistance and has the effect of reducing the LED current by about 4% per 0mV Applications Information (Cont.) 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 SC635. The trace from the ISET pin 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 SC635 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 C is exactly equal to C2. It is recom- mended that X5R or X7R ceramic capacitors be used for best performance. Thermal Resistance The SC635 package is thermally efficient when the circuit board layout connects the thermal pad though multiple vias to the ground plane. The thermal resistance is rated at 49°C/W, and this rating is dependent on the connec- tion between the thermal pad and the ground plane. A layout that is done correctly should keep the junction tem- perature below the OT limit while operating the SC635 within the specified 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. It is critical to maintain adequate ground plane around the device to maximize heat transfer and avoid over-temperature shut- down.

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Typical Characteristics 80mA Spotlight Current, RISET = 1.25W, VOUT = 2.96V 195.0 197.0 199.0 201.0 203.0 205.0 0 100 200 300 400 500 Pulse Duration [ms] LED Current [mA] VIN = 4.2V VIN = 3.7V VIN = 3.3V 200mA Flash Duration, RISET = 1.25W, VOUT = 3.30V(start) to 3.25V(LED heated 500ms) 195.0 197.0 199.0 201.0 203.0 205.0 VIN [V] LED Current [mA] Flash Current at 10ms, RISET = 1.25W, VOUT = 3.30V 195.0 197.0 199.0 201.0 203.0 205.0 VIN [V] LED Current [mA] Flash Current at 100ms, RISET = 1.25W, VOUT = 3.28V 195.0 197.0 199.0 201.0 203.0 205.0 VIN [V] LED Current [mA] Flash Current at 500ms, RISET = 1.25W, VOUT = 3.25V 75.0 77.0 79.0 81.0 83.0 85.0 VIN [V] LED Current [mA]

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Ch1 50mV/div Ch2 200mV/div Ch3 200mV/div 4us/div Flash Mode Ripple, RISET = 1.25W Spotlight Mode Ripple, RISET = 1.25W Ch1 50mV/div Ch2 100mV/div Ch3 100mV/div 4us/div Typical Characteristics (Cont.) Startup Flash Mode 200mA Ch1 100mV/div Ch2 2V/div Ch3 2V/div Ch4 2V/div 40us/div

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Suggested Layout The sense trace between Pin 6 and R is routed around the ground vias, allowing the shortest ground return path possible. The sense trace is connected to R at the posi- tive terminal pad for the most accurate output possible. The bottom copper layer is mostly a ground plane with no obstructions between the ground vias. The smaller rect- angle to the left connects the input power to VIN pin 1 and input capacitor C4. The two traces at the lower left are for logic inputs FLASH and CTRL. The trace to the right is the ISET pin “sense” trace. The sense trace is routed out of the path of the returning ground current. Layout Guidelines The following layout is suggested for a two-layer design. The capacitors C and C2 are the bucket capacitors and each conducts the full load current of up to 200mA pulsed for one half clock cycle. C3 is the output decoupling ca- pacitor placed near the SC635 VOUT pin. C4 is the in- put decoupling capacitor placed near the SC635 VIN pin. Multiple vias should be used whenever it is necessary to change layers on nets connecting to pins VIN, VOUT, GND, C1-, C1+, C2- and C2+. Resistor R1 is routed with a very low resistance connection between R1 and GND pin 3. Bottom Copper Top Copper

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Block Diagram CHARGE PUMP 250kHz Logic Control Reference Voltage Generator LDO C+ C2+ C2- VOUT ISET VIN CTRL FLASH GND

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Marking Information 635 yyww xxxx Top Mark yyww = Datecode (Example = 0552) xxxx = Semtech Lot Number Outline Drawing - MLPD-0 MIN aaa bbb b e L N D C E A DIM MILLIMETERS NOM DIMENSIONS MAXNOM INCHES MIN MAX (LASER MARK) INDICATOR PIN 1 N NOTES: CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS.2. .003 .007 .042 .009 .048 .000 .031 (.008) 0.08 0.23 .011 .052 0.18 1.06 .039 .002 0.00 0.80 1.31 0.30 1.21 0.05 1.00 (0.20) .004 0.10 0.50 BSC.020 BSC A aaa C SEATING PLANE A bxN bbb C A B B e C C D LxN E E

 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC635 Semtech Corporation Power Management Products Division

200 Flynn Road, Camarillo, CA 302

Phone: (805) 498-2111 FAX: (805) 498-3804 Contact Information .087 .055 2.20 1.40 .150 .020 .012 .037 3.80 0.30 0.95 0.50 (.112) .075 1.90 (2.85) K H X THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. NOTES: INCHES DIMENSIONS G K H X Y P Z C DIM MILLIMETERS Y ZG(C) P Land Pattern - MLPD-0