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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 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. The Shutdown (SHDN) pin saves power when the camera flash is not used by consuming less than 0.1A 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.
DFN10L (3x3)
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
Order code
Part number STCF01PMR Package DFN10L (3mm x 3mm) Packaging 4500 parts per reel
October 2006
Rev. 4
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www.st.com
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Contents
STCF01
Contents
1 2 3 4 5 6 7 8 9 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
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STCF01
Diagram
1
Diagram
Figure 1.
Block diagram
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Pin configuration
STCF01
2
Figure 2.
Pin configuration
Pin connections (top view)
Table 1.
Pln N 1 2 3 4 5 6 7 8 9 10
Pin description
Symbol PWRGND OVP VI HC LC SGLGND FB SEL SHDN SW 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.
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STCF01
Application information
3
Figure 3.
Application information
Application circuit
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Maximum ratings
STCF01
4
Table 2.
Maximum ratings
Absolute maximum ratings
Parameter DC Input Voltage to SGLGND Switch Voltage Voltage Range Over Voltage Protection Human Body Model Continuous Power Dissipation (at TA = 70C) Operating Junction Temperature Range Junction Temperature Storage Temperature Range Value -0.3 to 6 -0.3 to 20 -0.3 to VI + 0.3 -0.3 to 20 2 500 -40 to 85 -40 to 125 -65 to 150 Unit V V V V kV mW C C C
Symbol VI VSW FB, SEL, SHDN, LC, HC OVP ESD PTOT TOP TJ TSTG
Note:
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 Thermal Resistance Junction-Ambient Thermal Resistance Junction-Case Value 30.9 2.96 Unit C/W C/W
Table 3.
Symbol RthJA RthJC
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STCF01
Electrical characteristics
5
Table 4.
Electrical characteristics
DC Electrical characteristics (TJ = -40C to 85C, VI = 3.6V, CI = 2.2F, CO = 4.7F, L = 10H, RLC = 12k RHC = 4k , , VOVP = 8V, Typ. values @ 25C, unless otherwise specified)
Symbol General section VI VUVLO IQ fSW VOVP IPKMax VHC VLC ILED/IHC ILED/ILC RONFB IFB(LEAK) RON
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
Max Operation Supply Voltage Under Voltage lockout threshold Quiescent Current Switching Frequency Over Voltage Threshold Maximum Inductor Current HC Pin Voltage LC Pin Voltage High Level Current Multiplier Low Level Current Multiplier Resistance ON Feedback Current Feedback Leakage Internal Switch ON-Resistance VSEL= 0V, VSHDN = 0V, Min. duty cycle VSEL= 0V Shutdown Mode VSEL= 0V, VSHDN = 0V No Load VSHDN = 0V VSEL= 3V, VSHDN = 0V VSEL= 0V, VSHDN = 0V VSEL= 3V, VSHDN = 0V (25C) VSEL= 0V, VSHDN = 0V (25C) IFB = 100mA VSHDN = 3V, VFB = VI ISW = 1A Note: 1 2.3 2.45 2.3 0.1 1.5 18 1.2 VI-0.65 VI-0.65 1900 2200 VI-0.6 VI-0.6 2100 2400 1.2 0.1 0.3 0.1 90 0
5.5 2.6 3 0.5 1.8 19
V V mA A MHz V A
1.2 17
Current control VI-0.55 VI-0.55 2300 2600 1 V V A/A A/A A 1 A % %
Switch section ISW(LEAK) Internal Switch Leakage Current VSHDN = 3V, VSW= 16.5V DMAX IFB = 0mA Maximum Duty Cycle DMIN Minimum Duty Cycle IFB = 200mA; VSEL = 0V Pulse Skipping VI = 2.6V VI = 3.6V VI = 5.5V VI = 2.6V VI = 3.6V VI = 5.5V 145 15 1.2 1.4 1.6 0.4 0.5 0.6 C C V V
Control input section VH(SEL) SEL and SHDN Input High VH(SHDN) Threshold VL(SEL) VL(SHDN) SEL and SHDN Input Low Threshold
Thermal shutdown TSD THS Thermal Shutdown Thermal Shutdown Hysteresis
Note: 1 Typical value, not production tested
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Detailed description
STCF01
6
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=2.2F CO=4.7F), one inductor L=10H 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 200s (see TURN ON TIME plot). This fast turn-on time makes the device suitable for single shoot and multiple shoot operation modes.
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STCF01
Typical operating characteristics
7
Typical operating characteristics
(TJ = -40C to 85C, VI = 3.6V, CI = 2.2F, CO = 4.7F, L = 10H, RLC = 12k RHC = 4k VOVP , , = 8V, Typ. values @ 25C, 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
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Typical operating characteristics
STCF01
. 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
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STCF01
Typical operating characteristics
. Figure 16. Maximum duty cycle vs temperature Figure 17. Turn on and off response
VSHDN=pulse, FREQ.=1Hz, Tr=Tf=10s
Figure 18. Turn on time
Figure 19. Start up transient
VSHDN=pulse, FREQ.=1Hz, Tr=Tf=10s
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
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Package mechanical data
STCF01
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Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) 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.
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STCF01
Package mechanical data
DFN10 (3x3) MECHANICAL DATA
mm. DIM. MIN. A A1 A2 A3 b D D2 E E2 e L 0.45 1.29 2.21 0.18 0.80 TYP 0.90 0.02 0.70 0.20 0.23 3.00 2.26 3.00 1.34 0.50 0.55 0.65 17.7 1.39 50.8 2.31 87.0 0.30 7.1 MAX. 1.00 0.05 MIN. 31.5 TYP. 35.4 0.8 25.6 7.9 9.1 118.1 89.0 118.1 52.8 19.7 21.7 25.6 54.8 91.0 11.8 MAX. 39.4 2.0 mils
7426335A
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Package mechanical data
STCF01
Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA
mm. DIM. MIN. A C D N T Ao Bo Ko Po P 3.3 3.3 1.1 4 8 12.8 20.2 60 18.4 0.130 0.130 0.043 0.157 0.315 TYP MAX. 330 13.2 0.504 0.795 2.362 0.724 MIN. TYP. MAX. 12.992 0.519 inch
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STCF01
Revision history
9
Table 5.
Revision history
Revision history
Revision 1 2 3 4 First release. Maturity code has been changed. Change value in table 2 PTOT. Text updates. Changes
Date 10-Oct-2005 28-Apr-2006 27-Jul-2006 18-Oct-2006
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STCF01
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