NCP1523 3 MHz, 600 mA, High−Efficiency, Adjustable Output Voltage Step−down Converter The NCP1523 step−down PWM DC−DC converter is optimized for portable applications powered from 1−cell Li−ion or 3 cell Alkaline/NiCd/NiMH batteries. The device is available in an adjustable output voltage from 0.9 V to 3.3 V. It uses synchronous rectification to increase efficiency and reduce external part count. The device also has a built−in 3 MHz (nominal) oscillator which reduces component size by allowing use of a small inductor and capacitors. NCP1523 is available in automatic switching PWM/PFM (NCP1523FCT2G) improving system efficiency and in PWM mode only (NCP1523BFCT2G) offering a very efficient load transient solution. Additional features include integrated soft−start, cycle−by−cycle current limiting and thermal shutdown protection. The NCP1523 is available in a space saving, 8 pin chip scale package. http://onsemi.com MARKING DIAGRAM A1 NCPxxxxG AYWW FLIP−CHIP−8 CASE 766AE A1 NCPxxxx = Device Code xxxx = 1523 or 523B A = Assembly Location Y = Year WW = Work Week G = Pb−Free Package Features • • • • • • • Sources up to 600 mA 3 MHz Switching Frequency Up to 93% Efficiency Synchronous rectification for higher efficiency Thermal limit protection Shutdown current consumption of 0.3 A These are Pb−Free Devices PIN CONNECTIONS A1 A2 B1 B2 C1 C2 D1 D2 PIN: Special Features for NCP1523FCT2G • Auto PFM/PWM mode solution • High efficiency at light load A1 − GND A2 − VIN B1 − SW B2 − EN C1 − GND C2 − ADJ D1 − VOUT D2 − FB Top View (Bumps Below) Special Features for NCP1523BFCT2G • Load Transient Highly Efficient Solution • Very small Output Voltage Ripple • Adjustable Output Voltage from 0.9 V to 3.3 V ORDERING INFORMATION Typical Applications • • • • • Cellular Phones, Smart Phones and PDAs Digital Still Cameras MP3 Players and Portable Audio Systems Wireless and DSL Modems Portable Equipment © Semiconductor Components Industries, LLC, 2007 February, 2007 − Rev. 2 Device Package Shipping † NCP1523FCT2G (NCP1523) FLIP−CHIP−8 (Pb−Free) 3000 / Tape & Reel NCP1523BFCT2G (NCP1523B) FLIP−CHIP−8 (Pb−Free) 3000 / Tape & Reel †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. 1 Publication Order Number: NCP1523/D NCP1523 VIN A2 CIN C1 A1 L SW B1 VIN VOUT COUT VOUT D1 GND ADJ C2 GND R1 OFF B2 ON EN D2 FB R2 Figure 1. NCP1523 Typical Applications TYPICAL APPLICATIONS SW VIN VBATTERY B1 A2 Q1 2.2 H Q2 4.7 F 4.7 F Mode Control VOUT GND C1 D1 ILIMIT Comp GND A1 ADJ C2 R1 Reference Voltage Enable EN B2 Logic Control & Thermal Shutdown FB D2 R2 Figure 2. Simplified Block Diagram http://onsemi.com 2 NCP1523 PIN FUNCTION DESCRIPTION Pin Pin Name Type A1 GND Power Ground Description A2 VIN Power Input B1 SW Analog Output B2 EN Digital Input C1 GND Power Ground C2 ADJ Analog Input This pin is the compensation input. R1 is connected to this pin. D1 VOUT Analog Input This pin is connected of the converter’s output. This is the sense of the output voltage. D2 FB Analog Input Feedback voltage from the output of the power supply. This is the input to the error amplifier. Ground connection for the NFET Power Stage and the analog sections. Power Supply Input for the PFET Power Stage and the Analog Sections of the IC. Connection from Power MOSFETs to the Inductor. Enable for Switching Regulator. This pin is active high. This pin contains an internal pulldown resistor. Ground connection for the NFET Power Stage and the analog sections. MAXIMUM RATINGS Symbol Value Unit Minimum Voltage All Pins Rating VMIN −0.3 V Maximum Voltage All Pins (Note 1) VMAX 7 V Maximum Voltage Enable, FB, SW VMAX VIN + 0.3 V Thermal Resistance, Junction−to−Air (Note 2) RJA 159 °C/W TA −40 to 85 °C Operating Ambient Temperature Range TSTG −55 to 150 °C Junction Operating Temperature TJ −40 to 125 °C Latch−up Current Maximum Rating TA = 85°C (Note 4) LU "100 mA 2.0 200 kV V Storage Temperature Range ESD Withstand Voltage (Note 3) Human Body Model Machine Model VESD Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. 1. According to JEDEC standard JESD22−A108B 2. For the 8−Pin Chip Scale Package, the RJA is highly dependent of the PCB heatsink area. RJA = 159°C/W with 50 mm2 PCB heatsink area. 3. This device series contains ESD protection and exceeds the following tests: Human Body Model (HBM) $2.0 kV per JEDEC standard: JESD22−A114 Machine Model (MM) $200 V per JEDEC standard: JESD22−A115 4. Latchup current maximum rating per JEDEC standard: JESD78. http://onsemi.com 3 NCP1523 ELECTRICAL CHARACTERISTICS FOR NCP1523 (Typical values are referenced to TA = +25°C, Minimum and Maximum values are referenced −40°C to +85°C ambient temperature, unless otherwise noted, operating conditions VIN = 3.6 V, VOUT = 1.2 V unless otherwise noted) Symbol Rating Min Typ 2.7 Max Unit 5.5 V VIN Input Voltage Range VUVLO Under Voltage Lockout (VIN Falling) 2.4 Iq Quiescent Current (Light Load Mode) 60 95 A ISTB Standby Current, EN Low 0.3 1.2 A FOSC Oscillator Frequency 3 3.600 MHz ILIM Peak Inductor Current VREF Feedback Reference Voltage VFBtol FB Pin Tolerance Overtemperature VFB Reference Voltage Line Regulation VOUT Output Voltage Accuracy (Note 5) VOUT Minimum Output Voltage 0.9 VOUT Maximum Output Voltage 2.3 V VOUT Output Voltage Line Regulation (VIN from 2.7 to 5.5) IO = 100 mA 0.1 % VLOADREG Voltage Load Regulation (IO = 150 mA to 600 mA) 0.001 %/mA 2.400 V 1200 mA 0.6 V −3 3 0.1 −3% Vnom Duty Cycle % % +3% V V 100 % RSWH P−Channel On−Resistance 300 m RSWL N−Channel On−Resistance 300 m ILeakH P−Channel Leakage Current 0.05 A ILeakL N−Channel Leakage Current 0.01 A VENH Enable Pin High VENL Enable Pin Low TSTART Soft Start Time 1.2 V 350 5. The overall output voltage tolerance depends upon the accuracy of the external resistor (R1, R2). http://onsemi.com 4 0.4 V 450 s NCP1523 ELECTRICAL CHARACTERISTICS FOR NCP1523B (Typical values are referenced to TA = +25°C, Minimum and Maximum values are referenced −40°C to +85°C ambient temperature, unless otherwise noted, operating conditions VIN = 3.6 V, VOUT = 1.2 V unless otherwise noted) Symbol Rating Min Typ 2.7 Max Unit 5.2 V VIN Input Voltage Range VUVLO Under voltage Lockout (VIN Falling) 2.4 Iq Quiescent Current − No Switching Quiescent Current − Oscillator Running 250 2.5 350 A mA ISTB Standby Current, EN Low 0.3 1.2 A FOSC Oscillator Frequency 3 3.600 MHz ILIM Peak Inductor Current VREF Feedback Reference Voltage VFBtol FB Pin Tolerance Overtemperature VFB Reference Voltage Line Regulation VOUT Output Voltage Accuracy (Note 6) VOUT Minimum Output Voltage (Note 7) 0.9 V VOUT Maximum Output Voltage 3.3 V VOUT Output Voltage Line Regulation (VIN = 2.7 – 5.2) IO = 100 mA (Note 7) 0.1 % VLOADREG Voltage Load Regulation (IO = 1 mA to 600 mA) (Note 7) 2.400 V 1200 mA 0.6 V −3 3 0.1 −3% Vnom % +3% 0.001 Duty Cycle % V %/mA 100 % RSWH P−Channel On−Resistance 300 m RSWL N−Channel On−Resistance 300 m ILeakH P−Channel Leakage Current 0.05 A ILeakL N−Channel Leakage Current 0.01 A VENH Enable Pin High VENL Enable Pin Low TSTART Soft−Start Time 1.2 V 350 6. The overall output voltage tolerance depends upon the accuracy of the external resistor (R1, R2). 7. Electrical values are guaranteed for drop between input and output voltages less than 4.0 V (Page 13). http://onsemi.com 5 0.4 V 450 s NCP1523 TABLE OF GRAPHS TYPICAL CHARACTERISTICS Efficiency vs. Load Current NCP1523FCT2G NCP1523BFCT2G 6, 7, 8 20, 21, 22 vs. Input Voltage 23 VOUT Output Voltage vs. Temperature FOSC Frequency Variation vs. Input Voltage 9, 10 19 VOUT Load Regulation vs. Load Current 11 24 VOUT Line Regulation VOUT Load Transient Response VOUT Line Transient Response Istb Iq Shutdown Current 25 vs. Output Current 26 vs. Temperature 27 15, 16 32, 33 31 vs. Input Voltage 5 vs. Temperature 3 28 vs. Temperature 4 29 PWM Mode Operation 13 18 PFM Mode Operation 14 Quiescent Current PFM/PWM Threshold Tstart vs. Temperature vs. Input Voltage Soft Start 12 17 http://onsemi.com 6 30 NCP1523 100 100 90 90 Iq, QUIESCENT CURRENT (A) Iq, QUIESCENT CURRENT (A) NCP1523 CHARACTERISTICS 80 70 60 50 40 30 20 EN = VIN IOUT = 0 mA 10 0 2.5 3.0 3.5 4.0 4.5 5.0 80 70 60 50 VIN = 5.5 V 40 30 20 10 0 −40 5.5 10 VIN, INPUT VOLTAGE (V) 110 Figure 4. Quiescent Current vs. Temperature 1.0 100 0.9 −40°C 90 0.8 0.7 EFFICIENCY (%) SHUTDOWN CURRENT (A) 60 TEMPERATURE (°C) Figure 3. Quiescent Current vs. Supply Voltage 0.6 0.5 0.4 0.3 80 25°C 105°C 70 60 50 0.2 40 EN = GND IOUT = 0 mA 0.1 0 2.5 3.0 3.5 4.0 4.5 5.0 30 5.5 1 10 100 1000 VIN, INPUT VOLTAGE (V) IOUT, OUTPUT CURRENT (mA) Figure 5. Shutdown Current vs. Supply Voltage Figure 6. Efficiency vs. Output Current (VOUT = 1.8 V, VIN = 3.6 V) 100 100 90 90 −40°C 80 70 EFFICIENCY (%) EFFICIENCY (%) VIN = 2.7 V 25°C 60 105°C 50 −40°C 80 25°C 70 105°C 60 50 40 40 30 1 10 100 1000 30 1 10 100 IOUT, OUTPUT CURRENT (mA) IOUT, OUTPUT CURRENT (mA) Figure 7. Efficiency vs. Output Current (VOUT = 0.9 V, VIN = 3.6 V) Figure 8. Efficiency vs. Output Current (VOUT = 2.0 V, VIN = 3.6 V) http://onsemi.com 7 1000 NCP1523 3.6 3.6 3.4 3.4 FREQUENCY (MHz) FREQUENCY (MHz) NCP1523 CHARACTERISTICS IOUT = 400 mA 3.2 IOUT = 600 mA 3.0 2.8 IOUT = 400 mA 3.2 3.0 IOUT = 600 mA 2.8 2.6 2.6 2.4 2.8 3.3 3.8 4.3 VIN, INPUT VOLTAGE (V) 4.8 2.4 −40 5.3 Figure 9. Frequency vs. Input Voltage 0 20 40 TEMPERATURE (°C) 60 80 Figure 10. Frequency vs. Temperature 300 3.0 IOUT, OUTPUT CURRENT (mA) 5.0 LOAD REGULATION (%) −20 VOUT = 0.9 V 1.0 −1.0 VOUT = 2.0 V −3.0 −5.0 0 100 200 300 400 500 IOUT, OUTPUT CURRENT (mA) 250 200 150 100 50 0 2.7 600 Figure 11. Load Regulation 3.2 3.7 4.2 VIN, INPUT VOLTAGE (V) 4.7 Figure 12. PFM/PWM Threshold vs. Input Voltage Figure 13. Step Down Converter PFM Mode Operation Figure 14. Step Down Converter PWM Mode Operation http://onsemi.com 8 5.2 NCP1523 NCP1523 CHARACTERISTICS Figure 15. Load Transient Response in PFM Operation (10 mA to 100 mA) Figure 16. Load Transient Response Between PFM and PWM Operation (100 mA to 200 mA) Figure 17. Soft Start Time (VIN = 3.6 V) http://onsemi.com 9 NCP1523 NCP1523B CHARACTERISTICS 3.6 3.5 FREQUENCY (MHz) VLX 2 V/Div VIN 2 V/Div VOUT 10 mV/Div IOUT 200 mA/Div 3.4 3.3 3.2 3.1 3.0 2.9 2.8 2.7 2.6 2.5 2.4 2.8 3.3 3.8 4.3 4.8 5.3 Vin, INPUT VOLTAGE (V) Figure 18. PWM Mode of Operation (VIN = 3.6 V, VOUT = 1.2 V, IOUT = 300 mA, 255C) Figure 19. Switching Frequency vs. Input Voltage (VOUT = 1.2 V, IOUT = 300 mA, 255C) 100 90 90 2.7 V 80 3.6 V EFFICIENCY (%) EFFICIENCY (%) −40°C 80 70 Vin = 5.2 V 60 50 25°C 85°C 70 60 40 30 50 0 100 200 300 400 500 600 0 200 300 400 500 IOUT, OUTPUT CURRENT (mA) IOUT, OUTPUT CURRENT (mA) Figure 20. Efficiency vs. Output Current (VOUT = 1.2 V, 255C) Figure 21. Efficiency vs. Output Current (VOUT = 1.2 V, VIN = 3.6 V) 100 600 100 90 3.3 V 90 80 1.2 V 80 70 EFFICIENCY (%) EFFICIENCY (%) 100 0.9 V 60 50 40 −40°C 70 25°C 85°C 60 50 40 30 30 0 100 200 300 400 500 600 2.5 3.0 3.5 4.0 4.5 5.0 IOUT, OUTPUT CURRENT (mA) VIN, INPUT VOLTAGE (V) Figure 22. Efficiency vs. Output Current (VIN = 3.6 V, 255C) Figure 23. Efficiency vs. Input Current (VOUT = 1.2 V, IOUT = 100 mA) http://onsemi.com 10 5.5 NCP1523 NCP1523B CHARACTERISTICS 6 4 3 LOAD REGULATION (mV) LOAD REGULATION (mV) 4 2 3.6 V 0 2.7 V −2 Vin = 5.5 V −4 2 1 0 −40°C −1 25°C −2 85°C −3 −6 −4 0 100 200 300 IOUT (mA) 400 0 600 500 Figure 24. Load Regulation vs. Input Voltage (VOUT = 1.2 V, 255C) 6 LINE REGULATION (mV) LINE REGULATION (mV) 100 mA −2 −3 −4 −5 −6 3.0 300 Iout (mA) 400 500 600 6 5 1 2.5 200 Figure 25. Load Regulation vs. Temperature (VIN = 3.6 V, VOUT = 1.2 V) 5 4 3 I OUT = 600 mA 2 1 mA 0 −1 100 3.5 4.0 Vin (V) 4.5 5.0 4 3 2 1 0 −40°C 85°C −1 −2 25°C −3 −4 −5 −6 2.5 5.5 Figure 26. Line Regulation vs. Output Current (VOUT = 1.2 V, 255C) 3.0 3.5 4.0 4.5 Vin, INPUT VOLTAGE (V) 5.0 5.5 Figure 27. Line Regulation vs. Temperature (VOUT = 1.2 V, IOUT = 100 mA) 0.50 3.9 Iq, QUIESCENT CURRENT Istb, SHUTDOWN CURRENT 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 −40 −15 10 35 TEMPERATURE (°C) 60 3.7 Vin = 4.2 V 3.5 2.7 V 3.3 3.6 V 3.1 2.9 2.7 2.5 −40 85 Figure 28. Shutdown Current vs. Temperature (VOUT = 3.6 V) −15 10 35 TEMPERATURE (°C) 60 Figure 29. Quiescent Current vs. Temperature http://onsemi.com 11 85 NCP1523 NCP1523B CHARACTERISTICS 500 mV/Div 20 mV/Div VOUT VOUT 2 V/Div EN 200 mA/Div VIN 500 mV/Div IOUT Figure 30. Soft Start Time (VIN = 3.6 V, VOUT = 1.2 V, IOUT = 600 mA) VOUT Figure 31. Line Transient Response (VIN step = 600 mV, VOUT = 1.2 V) 20 mV/Div VOUT 50 mV/Div 16 mV 45 mV IOUT IOUT 50 mA/Div Figure 32. Load Transient Response (VIN = 3.6 V, VOUT = 1.2 V, 0 mA to 95 mA step) 200 mA/Div Figure 33. Load Transient Response (VIN = 3.6 V, VOUT = 1.2 V, 0 mA to 400 mA step) http://onsemi.com 12 NCP1523 OPERATION DESCRIPTION Overview PWM Operating Mode at Light Load: NCP1523B Only The NCP1523 uses a constant frequency, voltage mode step−down architecture. Both the main (P−channel MOSFET) and synchronous (N−channel MOSFET) switches are internal. It delivers a constant voltage from either a single Li−Ion or three cell NiMH/NiCd battery to portable devices such as cell phones and PDA. The output voltage is sets by external resistor divider and has a voltage tolerance of ±3% with 90% efficiency or better. The NCP1523 sources up to 600 mA depending on external components chosen. Additional features include soft−start, under voltage protection, current overload protection, and thermal shutdown protection. As shown in Figure 1, only six external components are required for implementation. The part uses an internal reference voltage of 0.6 V. It is recommended to keep the part in shutdown until the input voltage is 2.7 V or higher. At low light conditions, NCP1523BFCT2G works also in PWM mode offering very good load transient results from light load to full charge. When there is no load on the output, the PMOS Q1 remains ON during a small pulse according to the flip−flop driven by the internal oscillator and the error comparator. If the drop between input and output voltage is higher than 4.0 V, the structure reaches the minimum ON time (TONmin). In this particular case, the part can not supply correctly the desired output voltage and shows a small output voltage deregulation. For an output voltage configured to 0.9 V, 4.9 V is the maximum input voltage which guarantees the correct output value; for an output set to 1.5 V, the maximum input is 5.5 V. Cycle−by−Cycle Current Limitation From the block diagram (Figure 3), an ILIM comparator is used to realize cycle−by−cycle current limit protection. The comparator compares the SW pin voltage with the reference voltage, which is biased by a constant current. If the inductor current reaches the limit, the ILIM comparator detects the SW voltage falling below the reference voltage and releases the signal to turn off the switch Q1. The cycle−by−cycle current limit is set at 1200 mA (nom). PWM Operating Mode: NCP1523 & NCP1523B In this mode, the output voltage of the NCP1523 is regulated by modulating the on−time pulse width of the main switch Q1 at a fixed frequency of 3 MHz. The switching of the PMOS Q1 is controlled by a flip−flop driven by the internal oscillator and a comparator that compares the error signal from an error amplifier with the PWM ramp. At the beginning of each cycle, the main switch Q1 is turned ON by the rising edge of the internal oscillator clock. The inductor current ramps up until the sum of the current sense signal and compensation ramp becomes higher than the amplifier’s error voltage. Once this has occurred, the PWM comparator resets the flip−flop, Q1 is turned OFF and the synchronous switch Q2 is turned ON. Q2 replaces the external Schottky diode to reduce the conduction loss and improve the efficiency. To avoid overall power loss, a certain amount of dead time is introduced to ensure Q1 is completely turned OFF before Q2 is being turned ON. Soft Start The NCP1523 uses soft−start to limit the inrush current when the device is initially powered up or enabled. Soft−start is implemented by gradually increasing the reference voltage until it reaches the full reference voltage. During startup, a pulsed current source charges the internal soft−start capacitor to provide gradually increasing reference voltage. When the voltage across the capacitor ramps up to the nominal reference voltage, the pulsed current source will be switched off and the reference voltage will switch to the regular reference voltage. Shutdown Mode When a voltage less than 0.4 V is applied on the EN pin, the NCP1523 will be disabled. In shutdown mode, the internal reference, oscillator and most of the control circuitries are turned off. Therefore, the typical current consumption will be 0.3 A (typical value). Applying a voltage above 1.2 V to EN pin will enable the device for normal operation. The device will go through soft−start to normal operation. EN pin should be activated after the input voltage is applied. PFM Operating Mode at Light Load: NCP1523 Only The NCP1523FCT2G works with two mode of operation PWM/PFM depending on the current required. Under light load conditions, the NCP1523FCT2G enters in low current PFM mode of operation to reduce power consumption (IQ = 60 A typ). The output regulation is implemented by pulse frequency modulation. If the output voltage drops below the threshold of PM comparator (typically Vnom−2%), a new cycle will be initiated by the PM comparator to turn on the switch Q1. Q1 remains ON until the peak inductor current reaches 200 mA (nom). Then ILIM comparator goes high to switch OFF Q1. After a short dead time delay, switch rectifier Q2 is turn ON. The Negative current detector (NCD) will detect when the inductor current drops below zero and the output voltage decreases through discharging the output capacitor. When the output voltage falls below the threshold of the PFM comparator, a new cycle starts immediately. Thermal Shutdown Internal Thermal Shutdown circuitry is provided to protect the integrated circuit in the event that the maximum junction Temperature is exceeded. If the junction temperature exceeds 160_C, the device shuts down. In this mode switch Q1 and Q2 and the control circuits are all turned off. The device restarts in soft start after the temperature drops below 135°C. This feature is provided to prevent catastrophic failures from accidental device overheating. http://onsemi.com 13 NCP1523 APPLICATION INFORMATION The device operates with inductance value between 1 H and maximum of 4.7 H. If the corner frequency is moved, it is recommended to check the loop stability depending of the output ripple voltage accepted and output current required. For lower frequency, the stability will be increase; a larger output capacitor value could be chosen without critical effect on the system. On the other hand, a smaller capacitor value increases the corner frequency and it should be critical for the system stability. Take care to check the loop stability. The phase margin is usually higher than 45°. Output Voltage Selection The output voltage is programmed through an external resistor divider connected from ADJ to FB then to GND. For low power consumption and noise immunity, the resistor from FB to GND (R2) should be in the [100 k − 600 k] range. If R2 is 200 k given the VFB is 0.6 V, the current through the divider will be 3 A. The formula below gives the value of VOUT, given the desired R1 and the R1 value, VOUT + VFB • • • • ǒ1 ) R1 Ǔ R2 VOUT: output voltage (volts) VFB: feedback voltage = 0.6 V R1: feedback resistor from VOUT to FB R2: feedback resistor from FB to GND Table 2. L−C FILTER EXAMPLE Inductance (L) Input Capacitor Selection In PWM operating mode, the input current is pulsating with large switching noise. Using an input bypass capacitor can reduce the peak current transients drawn from the input supply source, thereby reducing switching noise significantly. The capacitance needed for the input bypass capacitor depends on the source impedance of the input supply. The maximum RMS current occurs at 50% duty cycle with maximum output current, which is IO, max/2. For NCP1523, a low profile ceramic capacitor of 4.7 F should be used for most of the cases. For effective bypass results, the input capacitor should be placed as close as possible to the VIN Pin. 1 H 10 F 2.2 H 4.7 F 4.7 H 2.2 F Inductor Selection The inductor parameters directly related to device performances are saturation current and DC resistance and inductance value. The inductor ripple current (IL) decreases with higher inductance: IL + GRM188R60J475KE TDK JMK212BY475MG Output L−C Filter Design Considerations: The NCP1523 is built in 3 MHz frequency and uses voltage mode architecture. The correct selection of the output filter ensures good stability and fast transient response. Due to the nature of the buck converter, the output L−C filter must be selected to work with internal compensation. For NCP1523, the internal compensation is internally fixed and it is optimized for an output filter of L = 2.2 H and COUT = 4.7 F The corner frequency is given by: fc + 2 ǸL 1 + 2 Ǹ2.2 H COUT 4.7 F Ǔ IL 2 IL(MAX) Maximum inductor current IO(MAX) Maximum Output current The inductor’s resistance will factor into the overall efficiency of the converter. For best performances, the DC resistance should be less than 0.3 for good efficiency. C2012X5R0J475KT C1608X5R0J475KT 1 ǒ VOUT V 1− OUT VIN fSW IL(MAX) + IO(MAX) ) GRM21BR71C475KA Taiyo Yuden L IL = peak to peak inductor ripple current L = inductor value fSW = Switching frequency The Saturation current of the inductor should be rated higher than the maximum load current plus half the ripple current: Table 1. LIST OF INPUT CAPACITOR Murata Output Capacitor (COUT) Table 3. LIST OF INDUCTOR FDK MIPW3226 Series TDK VLF3010AT Series TFC252005 Series Taiyo Yuden Coil Craft LQ CBL2012 DO1605−T Series LPO3010 + 49.5 KHz http://onsemi.com 14 NCP1523 Output Capacitor Selection Table 4. LIST OF OUTPUT CAPACITOR ROHS Selecting the proper output capacitor is based on the desired output ripple voltage. Ceramic capacitors with low ESR values will have the lowest output ripple voltage and are strongly recommended. The output capacitor requires either an X7R or X5R dielectric. The output ripple voltage in PWM mode is given by: VOUT + IL ǒ4 Murata GRM188R60J475KE 4.7 F GRM21BR71C475KA Taiyo Yuden Ǔ 1 ) ESR fSW COUT TDK In PFM mode (at light load), the output voltage is regulated by pulse frequency modulation. The output voltage ripple is independent of the output capacitor value. It is set by the threshold of PM comparator. GRM188R60OJ106ME 10 F JMK212BY475MG 4.7 F JMK212BJ106MG 10 F C2012X5R0J475KT 4.7 F C1608X5R0J475KT C2012X5R0J106KT http://onsemi.com 15 10 F NCP1523 PACKAGE DIMENSIONS 8 PIN FLIP−CHIP, 2.05x1.05, 0.5P CASE 766AE−01 ISSUE C D 0.10 C 2X TERMINAL A1 LOCATOR NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994. 2. CONTROLLING DIMENSION: MILLIMETERS. 3. COPLANARITY APPLIES TO SPHERICAL CROWNS OF SOLDER BALLS. A B È È E MILLIMETERS DIM MIN MAX A −−− 0.655 A1 0.210 0.270 A2 0.335 0.385 b 0.290 0.340 D 2.050 BSC D1 1.500 BSC E 1.050 BSC e 0.500 BSC 0.10 C TOP VIEW 2X A2 A1 0.10 C C A SEATING PLANE 0.05 C 8X SIDE VIEW NOTE 3 D1 b 0.05 C A B 8X 0.03 C e e/2 1 2 A B C D e BOTTOM VIEW ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. 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This literature is subject to all applicable copyright laws and is not for resale in any manner. PUBLICATION ORDERING INFORMATION LITERATURE FULFILLMENT: Literature Distribution Center for ON Semiconductor P.O. Box 5163, Denver, Colorado 80217 USA Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada Fax: 303−675−2176 or 800−344−3867 Toll Free USA/Canada Email: [email protected] N. American Technical Support: 800−282−9855 Toll Free USA/Canada Europe, Middle East and Africa Technical Support: Phone: 421 33 790 2910 Japan Customer Focus Center Phone: 81−3−5773−3850 http://onsemi.com 16 ON Semiconductor Website: www.onsemi.com Order Literature: http://www.onsemi.com/orderlit For additional information, please contact your local Sales Representative NCP1523/D