SC4560/A/B Photoflash Capacitor Charger POWER MANAGEMENT Description PRELIMINARY Features u Highly integrated IC for compact chargers u Powered by single Li-Ion cell, or any supply from The SC4560/A/B integrates a PWM controller and a power transistor into a single chip. It is designed to drive a flyback converter for charging photoflash capacitors in digital and film cameras. The SC4560/A/B adopts the Critical Current Operation Mode to improve system efficiency, simplify the control scheme, and eliminate the need of output voltage sensing circuity. The output voltage can be adjusted by simply changing the transformer turns ratio. The input current is controlled by limiting transformer primary current, which is 1.2A for SC4560, 0.55A for SC4560A, and 2.0A for SC4560B. 2.5V to 16V u Limited input current to avoid drawing too much u u u u u The SC4560/A/B provides two control pins for circuit interface. The CHG pin receives charging command and the READY pin provides an indicator when charging is complete. The SC4560/A/B is offered in a TSOT-23 package. current from battery Fast photoflash charge rate and high efficiency Adjustable output voltage No output voltage sensing divider required Charge any size photoflash capacitor TSOT-23 package Applications u Digital and film camera flash u PDA and cell phone flash Typical Application Circuit VIN 1 C1 4.7uF 2.5V to 8V U1 READY 100k 5 3 4 CHG March 3, 2005 2 SC4560 VIN SW T1 1 4 5 1:10.2 D2 320V + C2 100uF D1 READY CHG GND 1 2 www.semtech.com SC4560/A/B POWER MANAGEMENT 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. Parameter Symbol Maximum Units Input Supply Voltage VIN 16 V SW Voltage SW -0.4 to 50 V CHG Voltage VCHG 10 V VREADY 10 V +/ -1 mA READY Voltage Current into READY pin Operating Ambient Temperature Range TA -40 to 85 °C Operating Junction Temperature TJ -40 to 125 °C Thermal Resistance Junction to Ambient θJA 256 °C/W Thermal Resistance Junction to Case θJC 81 °C/W Lead Temperature (Soldering) 10s TLEAD 300 °C Storage Temperature TSTG -65 to 150 °C ESD Rating (Human Body Model) ESD 2 kV Electrical Characteristics Unless specified: VIN = 3V; TA = TJ = -40 to 85°C Parameter Symbol Conditions Min Typ Max Units 16 V General VIN Input Voltage VIN VIN Quiescent Current I QVIN Switch Current Limit (1) Switch Saturation Voltage Switch Leakage Current I SW_LIMIT 2.5 VIN = VCHG = 3.6V, TA = 25 oC 5 8 mA VIN = 3.6V, TA = 25 oC, VCHG = 0V 0 1 uA SC4560, TA = 25 oC 1.1 1.2 1.3 A SC4560A, TA = 25 oC 0.5 0.55 0.6 A SC4560B, TA = 25 oC 1.8 2.0 2.2 A VCESAT TA = 25 oC, ISW = 1A 330 430 mV I SW_LEAK VIN = VSW=5V, in shutdown mode 0.01 1 uA Note: (1). Specifications are for static test. Current limit in actual application will be slightly higher. 2003 Semtech Corp. 2 www.semtech.com SC4560/A/B POWER MANAGEMENT Electrical Characteristics Unless specified: VIN = 3V; TA = TJ = -40 to 85°C Parameter Symbol Conditions Min Typ Max Units 31 31.5 32 V 200 400 mV 36 80 mV Sensing and Control Full Comparator Trip Voltage VFULL_TRIP Full Comparator Overdrive Trigger Comparator Trip Voltage CHG Minimum Low Time Measured as V SW -VIN 300ns Pulse Width, T A = 25 oC VTRIGGER_TRIP Measured as V SW -VIN 10 High to Low to High 20 CHG Input Voltage High us 1 V CHG Input Voltage Low 0.3 V VCHG = 3V, T A = 25 oC 15 40 uA VCHG = 0V, T A = 25 oC 0 0.1 uA READY Output Voltage High 100k from VIN to READY, T A = 25 oC 3 READY Output Voltage Low 33uA into READY pin, T A = 25 oC 100 200 mV READY Leakage Current VREADY=3V, NPN Q2 off, TA =25 C 20 100 nA CHG Input Current 2003 Semtech Corp. o 3 V www.semtech.com SC4560/A/B POWER MANAGEMENT Pin Configuration TOP V IEW SW 1 5 VIN GND 2 READY 3 4 CHG TSOT-23 Ordering Information Part N umbers Top Mark P ackag e Note: SC 4560TSKTRT(1)(2) B D 00 TSOT-23 (1) Only available in tape and reel packaging. A reel contains 2500 devices. SC 4560ATSKTRT(1)(2) B D 0A TSOT-23 SC 4560BTSKTRT(1)(2) B D 0B TSOT-23 (2). Lead free product. This product is fully WEEE and RoHS compliant. SC 4560/A/B EVB Pin Descriptions Pin # Pin Name 1 SW Switch Pin. The collector of internal NPN power switch. 2 GND Ground Pin. 3 READY When charging is complete, this pin will be pulled low. Open collector output of NPN, pullup resistor is needed externally. 4 CHG Charge Command Pin. Logic high enables the part and starts to charge the output, logic low halts the charging and shuts down the part. 5 VIN 2003 Semtech Corp. Pin Function Input Supply Pin. 4 www.semtech.com SC4560/A/B POWER MANAGEMENT Block Diagram V IN SW Chip Supply REA DY Full Co mparator Q2 CHG Qb R Q S 1.25V Bias & Bandgap Trigger Comparator 1-shot S Q Q1 R Current Limit 2003 Semtech Corp. 5 GND www.semtech.com SC4560/A/B POWER MANAGEMENT Applications Information THEOR Y OF OPERA TION THEORY OPERATION COMPONENT SELECTION The SC4560/A/B integrates a PWM controller and a power transistor into a single chip. It is designed to drive a flyback converter for charging photoflash capacitors in digital and film cameras. The SC4560/A/B adopts the Critical Current Operation Mode to improve system efficiency, simplify the control scheme, and eliminate the need of output voltage sensing circuitry. The primary peak current of flyback transformer is limited to avoid drawing too much current from the battery that may pull down the battery voltage and affect system operation. General design guideline of flyback converters can be applied to the component selection for the SC4560/A/ B. Transf ormer ransformer The transformer is most critical part for SC4560/A/B circuit design. The flyback transformer performs as an inductor for storing energy and as a booster for high output voltages. The main transformer parameters that need to be designed are turns ratio N, primary inductance Lpri, and primary leakage inductance Lleak. As shown in the Block Diagram and Application Circuit, when the CHG pin is pulled high, a one shot sets both SR latches. The power NPN transistor, Q1, turns on and current begins building up in the primary of transformer. The Current Limit Comparator monitors Q1 current and when the peak current reaches the limit, the SR latch resets and Q1 turns off. The energy stored in the transformer is delivered to charge the photoflash capacitor via the secondary and diode D2. As the secondary current decreases to zero, the SW pin voltage will begin to collapse. When the voltage between SW and VIN drops to 36mV or lower, the output of Trigger Comparator will go low. This fires a one shot that turns Q1 back on. This completes one switching cycle. The cycle will repeat until the output is fully charged. The transformer turns ratio N is determined by target output voltage. The SC4560/A/B detects output voltage by monitoring the flyback waveform on the primary between SW pin and VIN pin during discharging. When the SW voltage reaches 31.5V higher than the VIN voltage, the part will halt power delivery. Thus, choose turns ratio N according to the equation: N= Vout + 2 31.5 where Vout is the desired output voltage. 2V is added to Vout to offset the effect of the output diode voltage drop. The transformer primary inductance Lpri, or magnetizing inductance, has to be chosen to ensure the SC4560/A/ B has enough time to sense output voltage during discharging when the output is almost fully charged. It is recommended to set the monitoring time as 200ns or higher. Then, the Lpri can be calculated by: During the discharge of the transformer in every switching cycle, the voltage across SW and VIN reflects the output voltage. This voltage is used to determine the completion of the charge. Therefore no output voltage divider is required to sense the output voltage. When the SW voltage is 31.5V above VIN, the output of Full Comparator goes high which resets the master latch. This disables Q1 and halts power delivery. NPN transistor Q2 is turned on pulling the READY pin low, indicating that the part has finished charging. L pri ³ Vout × 200 × 10 -9 N × I pk where Vout is the desired output voltage. N is the transformer turns ratio, and Ipk is 1.3A for SC4560, 0.6A for SC4560A, and 2.2A for SC4560B. The charging can be halted at any time by pulling the CHG pin low. Only when the final output voltage is reached will the READY pin go low. The transformer primary leakage inductance Lleak will cause a voltage spike to occur on the SW pin when the power transistor Q1 turns off. The leakage value must be controlled so that the spike does not exceed 40V with the absolute maximum rating of the SW Pin at 50V. Table 1 lists all parameters of the flyback transformer that need to meet or exceed the recommended limits. The transformer must be carefully designed and checked 2003 Semtech Corp. 6 www.semtech.com SC4560/A/B POWER MANAGEMENT Applications Information (Cont.) that it does not cause excessive current or voltage on any pin of the SC4560/A/B. Table 1. Recom mended Transformer Pa rameters Param eter Name Typical Range N Secondary / Prim ary Turn Ratio Lpri Primary Inductance Lleak Primary Leakage Inductance Vis o 8 to 12 >5 uH 100 to 300 nH Secondary to Prim ary Is olation Voltage >500 V Is at Primary Saturation Current >1.6 A Rpri Primary Winding Resis tance <300 m -OHM Rsec Secondary Winding Resis tance <40 OH M Input Capacitor A high quality X5R or X7R type ceramic capacitor with sufficient voltage capability is recommended for the input bypass capacitor. LA Y OUT GUIDELINES LAY The switching regulator is a high di/dt power circuit. Its Printed Circuit Board (PCB) layout is critical. A good layout can achieve optimum circuit performance while minimizing the component stress, resulting in better system reliability. Output Diode A low capacitance diode with adequate reverse voltage and forward current characteristics is recommended for the output rectifier. The peak reverse voltage of the diode is approximately: The following guidelines are typically recommended for using the SC4560/A/B controller. (1) Place the SC4560/A/B over a quiet ground plane to avoid pulsing current noise. V pk _ R = Vout + ( N × Vin ) (2) Place the transformer close to VIN pin and SW pin. The loop formed by the VIN pin, transformer primary, and SW pin must be as small as possible to reduce the leakage inductance. The peak current of the diode is: I pk _ SEC = Units 1 .4 N (3) Place the input ceramic capacitor close to the VIN pin and GND pin for the high frequency and high current decoupling. SW Pin Clamp Diode During a switch cycle, the SW node may go below ground due to the transformer leakage inductance. A Schottky diode between the GND pin to the SW pin is required to prevent the SW node from going too far below ground. It is recommended to select the Schottky diode with at least a 500mA peak forward current capability, and 600mV or less forward voltage drop at 500mA forward current. The diode reverse voltage rating should be 40V or higher. 2003 Semtech Corp. 7 www.semtech.com SC4560/A/B POWER MANAGEMENT Outline Drawing - TSOT-23 DIM A e1 2X N E/2 E1 1 E 2 ccc C 2X N/2 TIPS e B D aaa C A2 SEATING PLANE - A A1 A2 b c D E1 E e e1 L L1 N 01 aaa bbb ccc D DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX .000 .028 .012 .003 .110 .060 bxN bbb .043 .004 .039 .020 .008 .118 .067 .114 .063 .110 BSC .037 BSC .075 BSC .012 .018 .024 (.024) 5 0° 8° .004 .008 .010 - 0.00 0.70 0.30 0.08 2.80 1.50 - 0.90 - 1.10 0.10 1.00 0.50 0.20 3.00 1.70 2.90 1.60 2.80 BSC 0.95 BSC 1.90 BSC 0.30 0.45 0.60 (0.60) 5 0° 8° 0.10 0.20 0.25 A H A1 C - .035 - C A-B D c GAGE PLANE 0.25 L 01 (L1) DETAIL SEE DETAIL A A SIDE VIEW NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS 3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 4. REFERENCE JEDEC STD MO-193, VARIATION AB. -A- AND -B- TO BE DETERMINED AT DATUM PLANE -H- Land Pattern - TSOT-23 X DIM (C) G C G P X Y Z Z Y P DIMENSIONS INCHES MILLIMETERS (.087) .031 .037 .024 .055 .141 (2.20) 0.80 0.95 0.60 1.40 3.60 NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 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