STCF01 Step-up converter for cell phone camera flash LEDs General features ■ Supply voltage range: 2.6V to 5.5V ■ 17V Maximum output voltage ■ Two current levels up to 300mA set with external resistors ■ Dedicated pin to select the required level of current ■ Operating frequency: 1.5MHz: PWM Controller ■ Torch mode supported ■ Shutdown pin with true load disconnection ■ Efficiency: 90% at 100mA; 80% at 300mA ■ DFN10L (3mm x 3mm) Package DFN10L (3x3) to set the required current for each level. Compared to the linear current control technique, this method allows designers to achieve the best and most efficient performance possible with the selected current, thereby avoiding linear element losses. Description The STCF01 is a dedicated IC designed to drive two, three, or four white, cell phone camera flash LEDs with constant current. The step-up (boost) converter input is connected directly to the battery, and its converter output voltage is automatically determined using current feedback-based duty cycle control. The STCF01 has a dedicated pin for two levels of LED current selection. An external resistor is used The Shutdown (SHDN) pin saves power when the camera flash is not used by consuming less than 0.1µA of current. When the SHDN pin is high (logic '1'), the device is turned OFF and there is no DC current path from the supply to the white LEDs (Load Disconnect). If it is held to GND, the output current continuously flows through the LEDs (Torch mode). The SHDN pin, when it is set to low (logic '0'), is also used to set the flash function time duration. Order code Part number Package Packaging STCF01PMR DFN10L (3mm x 3mm) 4500 parts per reel October 2006 Rev. 4 1/16 www.st.com 16 STCF01 Contents Contents 1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7 Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2/16 STCF01 1 Figure 1. Diagram Diagram Block diagram 3/16 STCF01 Pin configuration 2 Pin configuration Figure 2. Pin connections (top view) Table 1. Pin description Pln N° Symbol 1 PWRGND 2 OVP 3 VI 4 HC 5 LC 6 SGLGND 7 FB 8 SEL 9 SHDN 10 SW 4/16 Note This is the application power signal reference. Connect the input and output capacitors to this pin. This pin senses step-up output voltage, which provides overvoltage protection in the event that the output voltage exceeds the OVP threshold This pin supplies the input voltage for the step-up stage as well as the supply voltage for the overall device. This pin sets the high level current for the white LEDs with a resistor that is connected between this pin and VI. This pin sets the low level current for the white LEDs with a resistor that is connected between this pin and VI. This pin is the logic signal reference for the IC. This pin senses the current flowing through the white LEDs and uses this feedback to provide current regulation. This pin is used to select the signal level of the white LEDs; a low level signal sets the low level LED current, while the high level signal sets the high level LED current. This pin enables or disables the Shutdown mode. A high level signal enables device Shutdown mode, where most of the device internal logic is turned OFF. If this pin is held to GND, the output current flows through the LEDs continuously (Torch mode). This is the switch node pin, which is connected to the internal N-channel MOSFET drain. STCF01 3 Figure 3. Application information Application information Application circuit 5/16 STCF01 Maximum ratings 4 Maximum ratings Table 2. Absolute maximum ratings Symbol Parameter VI VSW FB, SEL, SHDN, LC, HC OVP ESD PTOT TOP TJ TSTG Note: Table 3. Symbol Value Unit DC Input Voltage to SGLGND -0.3 to 6 V Switch Voltage -0.3 to 20 V Voltage Range -0.3 to VI + 0.3 V -0.3 to 20 ±2 500 V kV mW Operating Junction Temperature Range -40 to 85 °C Junction Temperature -40 to 125 °C Storage Temperature Range -65 to 150 °C Over Voltage Protection Human Body Model Continuous Power Dissipation (at TA = 70°C) Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional Operation under these conditions is not implied. Thermal data Parameter Value Unit RthJA Thermal Resistance Junction-Ambient 30.9 °C/W RthJC Thermal Resistance Junction-Case 2.96 °C/W 6/16 STCF01 5 Electrical characteristics Electrical characteristics Table 4. DC Electrical characteristics (TJ = -40°C to 85°C, VI = 3.6V, CI = 2.2µF, CO = 4.7µF, L = 10µH, RLC = 12kΩ, RHC = 4kΩ, VOVP = 8V, Typ. values @ 25°C, unless otherwise specified) Symbol Parameter Test Conditions Min. Typ. Max. Unit 5.5 V General section VI VUVLO IQ fSW Max Operation Supply Voltage Under Voltage lockout threshold Quiescent Current Switching Frequency VOVP Over Voltage Threshold IPKMax Maximum Inductor Current VSEL= 0V, VSHDN = 0V, Min. duty cycle VSEL= 0V Shutdown Mode VSEL= 0V, VSHDN = 0V No Load VSHDN = 0V 2.3 2.45 2.6 V 1.2 2.3 0.1 1.5 3 0.5 1.8 mA µA MHz 17 18 19 V 1.2 A Current control VHC HC Pin Voltage VSEL= 3V, VSHDN = 0V VI-0.65 VI-0.6 VI-0.55 V VLC LC Pin Voltage VSEL= 0V, VSHDN = 0V VI-0.65 VI-0.6 VI-0.55 V ILED/IHC High Level Current Multiplier VSEL= 3V, VSHDN = 0V (25°C) 1900 2100 2300 A/A ILED/ILC Low Level Current Multiplier VSEL= 0V, VSHDN = 0V (25°C) 2200 2400 2600 A/A Resistance ON Feedback IFB = 100mA 1.2 Current Feedback Leakage VSHDN = 3V, VFB = VI 0.1 1 µA ISW = 1A Note: 1 0.3 RONFB IFB(LEAK) Ω Switch section RON Internal Switch ON-Resistance ISW(LEAK) Internal Switch Leakage Current VSHDN = 3V, VSW= 16.5V DMAX IFB = 0mA Maximum Duty Cycle DMIN Minimum Duty Cycle 0.1 IFB = 200mA; VSEL = 0V Pulse Skipping Ω 1 µA 90 % 0 % Control input section VH(SEL) SEL and SHDN Input High VH(SHDN) Threshold VL(SEL) VL(SHDN) SEL and SHDN Input Low Threshold VI = 2.6V 1.2 VI = 3.6V 1.4 VI = 5.5V 1.6 V VI = 2.6V 0.4 VI = 3.6V 0.5 VI = 5.5V 0.6 V Thermal shutdown TSD Thermal Shutdown 145 °C THS Thermal Shutdown Hysteresis 15 °C Note: 1 Typical value, not production tested 7/16 Detailed description 6 STCF01 Detailed description The STCF01 white Led boost converter drives from two up to four white LEDs with a constant current. It needs few external components: two ceramic capacitors (CI=2.2µF CO=4.7µF), one inductor L=10µH and one schottky diode. The device works with a minimum VI=2.6V, and it has an Over Voltage Protection on the output guaranteed at minimum value equal to 17V. This value ensures proper operation with a maximum of four White LEDs in series. In the worst case of VI=2.6V at VOVP=8V (typical value of two LEDs) it is possible to obtain IO=270mA, while at VOVP=11V (typical value of three LEDs) it is possible obtain IO=180mA (Figure 4). The maximum IO current is limited by inductor peak current internally set at Typ 1.2A. This feature allows for a longer battery life as it reduces intensive use of the flash. The SEL pin allows selection of high and low current values flowing on the White LEDs. The two current values are set through external resistors RHC and RLC according to the following formula: ILED(FLASH) = 2100 * (VI - VHC) / RHC ILED(TORCH) = 2400 * (VI - VLC) / RLC A High logic level on SHDN pin puts the device in shutdown mode; if it is held at LOW the flash or torch mode is activated. When the SHDN pin is LOW the device provides the requested current in less than 200µs (see TURN ON TIME plot). This fast turn-on time makes the device suitable for single shoot and multiple shoot operation modes. 8/16 STCF01 7 Typical operating characteristics Typical operating characteristics (TJ = -40°C to 85°C, VI = 3.6V, CI = 2.2µF, CO = 4.7µF, L = 10µH, RLC = 12kΩ, RHC = 4kΩ, VOVP = 8V, Typ. values @ 25°C, unless otherwise specified). Figure 4. Maximum output current vs input Figure 5. Maximum output current vs input voltage voltage Figure 6. Efficiency vs temperature Figure 7. Efficiency vs temperature Figure 8. Efficiency vs temperature Figure 9. Quiescent current at full operation vs. temperature 9/16 STCF01 Typical operating characteristics . Figure 10. Feedback voltage vs temperature Figure 11. Current feedback leakage vs temperature Figure 12. VI-VLC vs temperature Figure 13. VI-VHC vs temperature Figure 14. Peak inductor current vs temperature Figure 15. RONFB vs temperature 10/16 STCF01 Typical operating characteristics . Figure 16. Maximum duty cycle vs temperature Figure 17. Turn on and off response VSHDN=pulse, FREQ.=1Hz, Tr=Tf=10µs Figure 18. Turn on time Figure 19. Start up transient VSHDN=pulse, FREQ.=1Hz, Tr=Tf=10µs VI=0 to 3.6V, VSEL=GND, VSHDN=GND Figure 20. Multi shoot mode Figure 21. Torch mode behavior VSEL=GND, VSHDN=pulse VSEL=GND, VSHDN=GND 11/16 Package mechanical data 8 STCF01 Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. 12/16 STCF01 Package mechanical data DFN10 (3x3) MECHANICAL DATA mm. mils DIM. MIN. TYP MAX. MIN. TYP. MAX. 0.80 0.90 1.00 31.5 35.4 39.4 A1 0.02 0.05 0.8 2.0 A2 0.70 25.6 A3 0.20 7.9 A b 0.18 D D2 2.21 7.1 2.26 1.29 1.34 2.31 87.0 0.55 11.8 89.0 91.0 118.1 1.39 50.8 0.50 0.45 9.1 118.1 3.00 e L 0.30 3.00 E E2 0.23 52.8 54.8 19.7 0.65 17.7 21.7 25.6 7426335A 13/16 STCF01 Package mechanical data Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA mm. inch DIM. MIN. TYP A MIN. TYP. 330 13.2 MAX. 12.992 C 12.8 D 20.2 0.795 N 60 2.362 T 14/16 MAX. 0.504 0.519 18.4 0.724 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 STCF01 9 Revision history Revision history Table 5. Revision history Date Revision Changes 10-Oct-2005 1 First release. 28-Apr-2006 2 Maturity code has been changed. 27-Jul-2006 3 Change value in table 2 PTOT. 18-Oct-2006 4 Text updates. 15/16 STCF01 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. 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