PWM Controlled, Step-up DC/DC Converter in Tiny Package

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1 PWM Controlled, Step-up DC/DC Converter in Tiny Package Description The is a high efficiency PWM DC/DC step -up converter with internally compensated current mode controller. The 250kHz switching frequency minimizes the size of external components. The output voltage is internally set and a 1A switch is built in the IC. The starts up below 1V input voltage with 1mA load. Due to built-in automatic PWM/PFM switch-over function, the is able to get high efficiency during both light and heavy load. The built-in current limit and thermal protection function protect the device in any over-load or over-temperature situation. The is available in a SOT-23-3 and SOT-23-5 packages. Features 0.9V(typ.) Low Start-up Voltage with 1mA Load Fixed 3.0V / 3.2V output Voltage 250kHz Switching Frequency Automatic PFM Mode at Light Load Low Ripple and High Efficiency Excellent Line/Load Regulation Chip Enable Control Function Current Limit Protection Thermal Overload Protection Space Saving Package : SOT-23-5 and SOT-23-3 Applications PDA MP3 DSC RF Tags Wireless Equipments Portable Equipments Pin Assignments S3 Package (SOT-23-3) Ordering Information - TR: Tape/Real G: Green Package Type S3: SOT-23-3 S5: SOT-23-5 S5 Package (SOT-23-5) Output Voltage 30: 3.0V 32: 3.2V LX VSS SOT-23-3 Marking 5 4 Part Number Product Code S3G T8= CE VOUT NC Figure 2. Pin Assignment of SOT-23-5 Marking Part Number -32S5G Product Code ax= -1.0-AUG

2 Typical Application Circuit Figure 2. Typical Application Circuit of Functional Pin Description Pin Name CE VOUT NC VSS LX Pin Function Chip Enable pin H : Normal operation (Step-up operating) L : Switch stopped (Entire circuit off) Output voltage pin and IC power supply pin No connection Ground pin External inductor connection pin -1.0-AUG

3 Block Diagram Figure 3. Block Diagram of Absolute Maximum Ratings VOUT to GND V LX, CE to GND V Power A =25 C, (P D ) SOT W SOT W Package Thermal Resistance, (θ JA ) SOT /W SOT C/W Maximum Junction Temperature C Storage Temperature Range (T STG ) C to +150 C Lead Temperature (Soldering, 10sec.) (T LEAD ) C Note1:Stresses beyond those listed under Absolute Maximum Ratings" may cause permanent damage to the device. Recommended Operating Conditions Operating Voltage ( ) V to +5.5V Operating Temperature Range (T OPR ) to AUG

4 Electrical Characteristics (T A =25 C, unless otherwise specified.) Parameter Symbol Test Conditions Min Typ Max Units Output Voltage (S) V V Start-up Voltage V START : 0 1V, =1mA V No-Load Input Current I NO_LOAD =1.5V, =3.2V 75 μa Continuous Switching Current I SWITCH =V CE = (S) * ma Shutdown Current I OFF = 3.2V, V CE =0V μa LX ON Resistance (Note2) R DS-ON =1.5V, =3.2V 0.3 Ω Max. Duty Ratio DUTY =V CE = (S) * % Oscillator Frequency f OSC =V CE = (S) * khz LX Leakage Current I LXL V LX =6V, V CE =0V, = 3.2V μa Line Regulation ΔV LINE =1.2 ~1.8V, I L =15mA mv Load Regulation ΔV LOAD =1.8V, I L =10µA~15mA mv Current Limit (Note2) I LIMIT =1.5V, =3.2V A CE High Voltage V CEH V DD =3.2V, switch ON 1.2 V CE Low Voltage V CEL V DD =3.2V, switch OFF 0.4 V CE High Current I CEH = 3.2V, V CE = 0.1 μa CE Low Current I CEL = 3.2V, V CE =0V -0.1 μa Efficiency (Note2) η 85 % Thermal Shutdown Threshold (Note2) T SD 145 ºC ΔT SD Hysteresis 30 ºC Note2: Guarantee by design -1.0-AUG

5 Typical Performance Curves CE Pin Trip Level(V) CE Pin Trip Level (V) VOUT pin Operation Voltage (V) 0.0 Temperature( O C) Figure 4. Operation Voltage vs. CE Pin Trip Level Figure 5. Temperature vs. CE Pin Trip Level =3.0V =2.5V =2.0V Efficiency (%) =1.0V =1.5V =2.0V =2.5V Efficiency (%) Output Current (ma) Figure 6. Efficiency ( =3.2V) Figure 7. Efficiency ( =3.2V) Output Voltage (V) =1.5V =2.0V =2.5V (V) =50mA =10mA =1mA Output Current (ma) (V) Figure 8. Load Regulation ( =3.2V) Figure 9. Line Regulation ( =3.2V) -1.0-AUG

6 Typical Performance Curves (Continued) Oscillator Start Voltage (V) Switch Current (ma) Temperature( O C) no load Tempurature ( O C) Figure 10. Temperature vs. Oscillator Start Voltage Figure 11. Temperature vs. Switch current (V) =100mA =10mA Quiescent Current (ua) Tempurature ( O C) 10 Temperture. ( O C) Figure 12. Temperature vs. Output Voltage Figure 13. Temperature vs. Quiescent Current Frequency (KHz) Tempurature ( O C) Figure 14. Temperature vs. Frequency -1.0-AUG

7 Typical Performance Curves (Continued) V LX V LX Figure 15. Output Waveform, =2.0V, =10mA Figure 16. Output Waveform, =2.0V, =50mA V LX Figure 17. Output Waveform, =2.0V, =100mA Figure 18. Power-on Response, =0 2.0V, =50mA V CE V LX -1.0-AUG-2009 Figure 19. CE Pin Enable Response =2.0V, V CE =0V 2.0V, =50mA Figure 20. Load Transient Waveform =2.0V, =0.1mA 50mA 7

8 Application Information Operation The is designed in a current mode PFM/PWM scheme which features an automatic switch PFM/PWM mode to maintain the highest efficiency and extend battery life. The quiescent current is less than 25uA at no switching status. The control loop is internally compensated reducing the amount of external components. Chip Enable The features a chip enable input pin that allows CE control the converter. When CE=Low, shutdown of the chip occurs and at that time almost no quiescent current (<1uA) flows. The chip enable input is TTL/CMOS compatible. Connect CE to battery for normal operation. Current Limit Protection The provides cycle-by-cycle over-current protection. Current limit is accomplished by sensing voltage drop across the drain to source of power switch. If the current sense amplifier output voltage is larger than current-limited threshold level (typ. 1.0A), it will be immediately turned off power MOS. Thermal Overload Protection Thermal-overload protection limits total power dissipation in the. When the junction temperature exceeds Tj = 145 C, the thermal sensor signals the shutdown logic and turns off most of the internal circuitry. The thermal sensor turns internal circuitry on again after the IC s junction temperature drops by 30 C. Inductor Selection A 3.3uH to 10uH is recommended for general used. The value of inductor depends on the operating frequency. Higher frequency allows smaller inductor and capacitor but increase internal switching loss. Two inductor parameters should be considered, current rating and DCR. The DCR of inductor affects the efficiency of the converter. The inductor with lowest DCR is chosen for highest efficiency. The inductor value can be calculated as: VIN(VOUT VIN ) L = f * ΔI * V L OUT I L : inductor ripple current, usually set 20% x I L, which defined as: Δ I L (V = V L * f OUT IN ) V ( V IN OUT The inductor should be rated for the maximum output current (I O(MAX) ) plus the inductor ripple current ( I L ) to avoid saturation. The maximum inductor current (I L(MAX) ) is given by: ΔIL IL(MAX) = IO(max) + 2 Capacitor Selection The is permissible in using ceramic capacitor for hand held instruments application. The value of capacitor depends on acceptable voltage ripple. The input capacitor can reduced peak current and noise at power source. It should have 10uF at least and can be increased for better input voltage filtering. Select the input capacitor to meet the input ripple current and voltage rating. When selecting an output capacitor, consider the output ripple voltage and the ripple current. The ESR of capacitor is a major factor to the output ripple. For best performance, a low ESR output capacitor is required. The ripple voltage is given by: 1 Δ VO = ΔIL (ESR + ) 8 * f * Co The common aluminum-electrolytic capacitors have high ESR and should be avoided. Ceramic capacitors have the lowest ESR in general. It uses 10uF ceramic output capacitors for the. Diode Selection For diode selection, both forward voltage and diode capacitance need to be considered. The output diode should be rated to the output voltage and peak switch current. Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for applications. Make sure the diode s peak current rating is at least I L(MAX) and its breakdown voltage exceeds. ) -1.0-AUG

9 Application Information (Continued) Layout Consideration Careful printed circuit layout is extremely important to avoid causing parasitical capacitance and line inductance. The following layout guidelines are recommended to achieve optimum performance. Place the boost converter diode and inductor close to the LX pin with wide and short traces. Place the ceramic bypass capacitors near the and VSS pin. Place C OUT next to Schottky diode as possible AUG

10 Outline Information SOT-23-3 Package (Unit: mm) SYMBOL DIMENSION IN MILLIMETER S UNIT MIN MAX A A A B D E E e e L SOT-23-5 Package (Unit: mm) SYMBOL DIMENSION IN MILLIMETER S UNIT MIN MAX A A A B D E E e e L Note:Followed From JEDEC MO-178-C. Life Support Policy Fitipower s products are not authorized for use as critical components in life support devices or other medical systems AUG