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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.
Features http://onsemi.com MARKING DIAGRAM
A1 FLIP-CHIP-8 CASE 766AE NCPxxxxG AYWW A1
NCPxxxx = Device Code xxxx = 1523 or 523B A = Assembly Location Y = Year WW = Work Week G = Pb-Free Package
* * * * * * *
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 mA These are Pb-Free Devices
PIN CONNECTIONS
A1 B1 C1 D1 A2 PIN: B2 C2 D2 A1 - GND A2 - VIN B1 - SW B2 - EN C1 - GND C2 - ADJ D1 - VOUT D2 - FB
Special Features for NCP1523FCT2G
* Auto PFM/PWM mode solution * High efficiency at light load
Special Features for NCP1523BFCT2G
Top View (Bumps Below)
* Load Transient Highly Efficient Solution * Very small Output Voltage Ripple * Adjustable Output Voltage from 0.9 V to 3.3 V
Typical Applications
ORDERING INFORMATION
Device NCP1523FCT2G (NCP1523) NCP1523BFCT2G (NCP1523B) Package FLIP-CHIP-8 (Pb-Free) FLIP-CHIP-8 (Pb-Free) Shipping 3000 / Tape & Reel 3000 / Tape & Reel
* * * * *
Cellular Phones, Smart Phones and PDAs Digital Still Cameras MP3 Players and Portable Audio Systems Wireless and DSL Modems Portable Equipment
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.
(c) Semiconductor Components Industries, LLC, 2007
1
February, 2007 - Rev. 2
Publication Order Number: NCP1523/D
NCP1523
VIN CIN A2 VIN SW B1 VOUT D1 ADJ C2 R1 OFF ON B2 EN FB D2 R2 L VOUT COUT
C1
GND GND
A1
Figure 1. NCP1523 Typical Applications
TYPICAL APPLICATIONS
VIN VBATTERY A2 Q1 Q2 4.7 mF GND C1 Mode Control
SW B1 2.2 mH
4.7 mF VOUT D1
ILIMIT
GND A1
Comp
ADJ C2
R1 Reference Voltage Enable EN B2 Logic Control & Thermal Shutdown FB D2 R2
Figure 2. Simplified Block Diagram
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NCP1523
PIN FUNCTION DESCRIPTION
Pin A1 A2 B1 B2 C1 C2 D1 D2 Pin Name GND VIN SW EN GND ADJ VOUT FB Type Power Ground Power Input Analog Output Digital Input Power Ground Analog Input Analog Input Analog Input Description 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. This pin is the compensation input. R1 is connected to this pin. This pin is connected of the converter's output. This is the sense of the output voltage. Feedback voltage from the output of the power supply. This is the input to the error amplifier.
MAXIMUM RATINGS
Rating Minimum Voltage All Pins Maximum Voltage All Pins (Note 1) Maximum Voltage Enable, FB, SW Thermal Resistance, Junction-to-Air (Note 2) Operating Ambient Temperature Range Storage Temperature Range Junction Operating Temperature Latch-up Current Maximum Rating TA = 85C (Note 4) ESD Withstand Voltage (Note 3) Human Body Model Machine Model Symbol VMIN VMAX VMAX RqJA TA TSTG TJ LU VESD 2.0 200 kV V Value -0.3 7 VIN + 0.3 159 -40 to 85 -55 to 150 -40 to 125 "100 Unit V V V C/W C C C mA
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 RqJA is highly dependent of the PCB heatsink area. RqJA = 159C/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.
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NCP1523
ELECTRICAL CHARACTERISTICS FOR NCP1523
(Typical values are referenced to TA = +25C, Minimum and Maximum values are referenced -40C to +85C ambient temperature, unless otherwise noted, operating conditions VIN = 3.6 V, VOUT = 1.2 V unless otherwise noted) Symbol VIN VUVLO Iq ISTB FOSC ILIM VREF VFBtol DVFB VOUT VOUT VOUT DVOUT VLOADREG Input Voltage Range Under Voltage Lockout (VIN Falling) Quiescent Current (Light Load Mode) Standby Current, EN Low Oscillator Frequency Peak Inductor Current Feedback Reference Voltage FB Pin Tolerance Overtemperature Reference Voltage Line Regulation Output Voltage Accuracy (Note 5) Minimum Output Voltage Maximum Output Voltage Output Voltage Line Regulation (VIN from 2.7 to 5.5) IO = 100 mA Voltage Load Regulation (IO = 150 mA to 600 mA) Duty Cycle RSWH RSWL ILeakH ILeakL VENH VENL TSTART P-Channel On-Resistance N-Channel On-Resistance P-Channel Leakage Current N-Channel Leakage Current Enable Pin High Enable Pin Low Soft Start Time 350 1.2 0.4 450 300 300 0.05 0.01 -3% -3 0.1 Vnom 0.9 2.3 0.1 0.001 100 +3% 2.400 Rating Min 2.7 2.4 60 0.3 3 1200 0.6 3 95 1.2 3.600 Typ Max 5.5 Unit V V mA mA MHz mA V % % V V V % %/mA % mW mW mA mA V V ms
5. The overall output voltage tolerance depends upon the accuracy of the external resistor (R1, R2).
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NCP1523
ELECTRICAL CHARACTERISTICS FOR NCP1523B
(Typical values are referenced to TA = +25C, Minimum and Maximum values are referenced -40C to +85C ambient temperature, unless otherwise noted, operating conditions VIN = 3.6 V, VOUT = 1.2 V unless otherwise noted) Symbol VIN VUVLO Iq ISTB FOSC ILIM VREF VFBtol DVFB VOUT VOUT VOUT DVOUT VLOADREG Input Voltage Range Under voltage Lockout (VIN Falling) Quiescent Current - No Switching Quiescent Current - Oscillator Running Standby Current, EN Low Oscillator Frequency Peak Inductor Current Feedback Reference Voltage FB Pin Tolerance Overtemperature Reference Voltage Line Regulation Output Voltage Accuracy (Note 6) Minimum Output Voltage (Note 7) Maximum Output Voltage Output Voltage Line Regulation (VIN = 2.7 - 5.2) IO = 100 mA (Note 7) Voltage Load Regulation (IO = 1 mA to 600 mA) (Note 7) Duty Cycle RSWH RSWL ILeakH ILeakL VENH VENL TSTART P-Channel On-Resistance N-Channel On-Resistance P-Channel Leakage Current N-Channel Leakage Current Enable Pin High Enable Pin Low Soft-Start Time 350 1.2 0.4 450 300 300 0.05 0.01 -3% -3 0.1 Vnom 0.9 3.3 0.1 0.001 100 +3% 2.400 Rating Min 2.7 2.4 250 2.5 0.3 3 1200 0.6 3 350 1.2 3.600 Typ Max 5.2 Unit V V mA mA mA MHz mA V % % V V V % %/mA % mW mW mA mA V V ms
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).
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NCP1523
TABLE OF GRAPHS
TYPICAL CHARACTERISTICS h Efficiency vs. Load Current vs. Input Voltage VOUT FOSC VOUT Output Voltage Frequency Variation Load Regulation vs. Temperature vs. Input Voltage vs. Load Current vs. Temperature VOUT Line Regulation vs. Output Current vs. Temperature VOUT VOUT Istb Load Transient Response Line Transient Response Shutdown Current vs. Input Voltage vs. Temperature Iq Quiescent Current PWM Mode Operation PFM Mode Operation PFM/PWM Threshold Tstart Soft Start vs. Input Voltage vs. Temperature 5 3 4 13 14 12 17 30 28 29 18 15, 16 9, 10 11 19 24 25 26 27 32, 33 31 NCP1523FCT2G 6, 7, 8 NCP1523BFCT2G 20, 21, 22 23
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NCP1523
NCP1523 CHARACTERISTICS
100 Iq, QUIESCENT CURRENT (mA) Iq, QUIESCENT CURRENT (mA) 90 80 70 60 50 40 30 20 10 0 2.5 3.0 3.5 4.0 4.5 EN = VIN IOUT = 0 mA 5.0 5.5 100 90 80 70 60 50 40 30 20 10 0 -40 10 60 110 VIN = 5.5 V VIN = 2.7 V
VIN, INPUT VOLTAGE (V)
TEMPERATURE (C)
Figure 3. Quiescent Current vs. Supply Voltage
Figure 4. Quiescent Current vs. Temperature
1.0 0.9 SHUTDOWN CURRENT (mA) 0.8 EFFICIENCY (%) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 2.5 3.0 3.5 4.0 4.5 EN = GND IOUT = 0 mA 5.0 5.5
100 90 80 25C 70 60 50 40 30 1 10 100 1000 IOUT, OUTPUT CURRENT (mA) 105C -40C
VIN, INPUT VOLTAGE (V)
Figure 5. Shutdown Current vs. Supply Voltage
100 90 EFFICIENCY (%) 80 70 60 50 40 30 1 10 100 1000 IOUT, OUTPUT CURRENT (mA) 105C 25C -40C EFFICIENCY (%) 100 90 80 70 60 50 40 30 1
Figure 6. Efficiency vs. Output Current (VOUT = 1.8 V, VIN = 3.6 V)
-40C
25C 105C
10
100
1000
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)
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NCP1523
NCP1523 CHARACTERISTICS
3.6 3.4 FREQUENCY (MHz) 3.2 3.0 2.8 2.6 2.4 2.8 IOUT = 400 mA IOUT = 600 mA FREQUENCY (MHz) 3.6 3.4 IOUT = 400 mA 3.2 3.0 IOUT = 600 mA 2.8 2.6 2.4 -40
3.3
3.8 4.3 VIN, INPUT VOLTAGE (V)
4.8
5.3
-20
0 20 40 TEMPERATURE (C)
60
80
Figure 9. Frequency vs. Input Voltage
Figure 10. Frequency vs. Temperature
5.0 IOUT, OUTPUT CURRENT (mA) 600
300 250 200 150 100 50 0 2.7
LOAD REGULATION (%)
3.0
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)
3.2
3.7 4.2 VIN, INPUT VOLTAGE (V)
4.7
5.2
Figure 11. Load Regulation
Figure 12. PFM/PWM Threshold vs. Input Voltage
Figure 13. Step Down Converter PFM Mode Operation
Figure 14. Step Down Converter PWM Mode Operation
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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)
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NCP1523
NCP1523B CHARACTERISTICS
3.6 3.5 FREQUENCY (MHz) 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)
VLX 2 V/Div
VIN 2 V/Div VOUT 10 mV/Div IOUT 200 mA/Div
Figure 18. PWM Mode of Operation (VIN = 3.6 V, VOUT = 1.2 V, IOUT = 300 mA, 255C)
100 90 EFFICIENCY (%) 80 70 60 50 40 30 0 100 200 300 400 500 600 IOUT, OUTPUT CURRENT (mA) 50 0 Vin = 5.2 V 2.7 V
Figure 19. Switching Frequency vs. Input Voltage (VOUT = 1.2 V, IOUT = 300 mA, 255C)
90
-40C EFFICIENCY (%) 3.6 V 80 25C 70
85C
60
100
200
300
400
500
600
IOUT, OUTPUT CURRENT (mA)
Figure 20. Efficiency vs. Output Current (VOUT = 1.2 V, 255C)
100 90 EFFICIENCY (%) 80 70 60 50 40 30 0 100 200 300 400 500 600 IOUT, OUTPUT CURRENT (mA) 3.3 V EFFICIENCY (%) 1.2 V 0.9 V 100 90 80 70
Figure 21. Efficiency vs. Output Current (VOUT = 1.2 V, VIN = 3.6 V)
-40C 25C
60 50 40 30 2.5 3.0 3.5 4.0 4.5
85C
5.0
5.5
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)
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NCP1523
NCP1523B CHARACTERISTICS
6 4 2 0 -2 Vin = 5.5 V -4 -6 0 100 200 300 IOUT (mA) 400 500 600 3.6 V 2.7 V 4 3 LOAD REGULATION (mV) 2 1 0 -1 -2 -3 -4 0 100 200 300 Iout (mA) 400 500 600 -40C 25C 85C
LOAD REGULATION (mV)
Figure 24. Load Regulation vs. Input Voltage (VOUT = 1.2 V, 255C)
6 5 4 3I OUT = 600 mA 2 1 mA 1 0 -1 -2 -3 -4 -5 -6 2.5 3.0 3.5 4.0 Vin (V) 4.5 5.0 5.5 100 mA 6 5 LINE REGULATION (mV) 4 3 2 1 0 -1 -2 -3 -4 -5 -6
Figure 25. Load Regulation vs. Temperature (VIN = 3.6 V, VOUT = 1.2 V)
LINE REGULATION (mV)
-40C 85C 25C
2.5
3.0
3.5 4.0 4.5 Vin, INPUT VOLTAGE (V)
5.0
5.5
Figure 26. Line Regulation vs. Output Current (VOUT = 1.2 V, 255C)
0.50 0.45 Istb, SHUTDOWN CURRENT 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 -40 -15 10 35 TEMPERATURE (C) 60 85 Iq, QUIESCENT CURRENT 3.9 3.7 3.5 3.3 3.1 2.9 2.7
Figure 27. Line Regulation vs. Temperature (VOUT = 1.2 V, IOUT = 100 mA)
Vin = 4.2 V
2.7 V 3.6 V
2.5 -40
-15
10 35 TEMPERATURE (C)
60
85
Figure 28. Shutdown Current vs. Temperature (VOUT = 3.6 V)
Figure 29. Quiescent Current vs. Temperature
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NCP1523
NCP1523B CHARACTERISTICS
500 mV/Div 20 mV/Div VOUT 2 V/Div EN 200 mA/Div VIN IOUT 500 mV/Div VOUT
Figure 30. Soft Start Time (VIN = 3.6 V, VOUT = 1.2 V, IOUT = 600 mA)
Figure 31. Line Transient Response (VIN step = 600 mV, VOUT = 1.2 V)
VOUT
20 mV/Div 16 mV
VOUT
50 mV/Div 45 mV
IOUT
50 mA/Div
IOUT
200 mA/Div
Figure 32. Load Transient Response (VIN = 3.6 V, VOUT = 1.2 V, 0 mA to 95 mA step)
Figure 33. Load Transient Response (VIN = 3.6 V, VOUT = 1.2 V, 0 mA to 400 mA step)
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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.
PWM Operating Mode: NCP1523 & NCP1523B
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
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.
PFM Operating Mode at Light Load: NCP1523 Only
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).
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
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 mA 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.
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 mA (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.
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 135C. This feature is provided to prevent catastrophic failures from accidental device overheating.
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NCP1523
APPLICATION INFORMATION
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 kW - 600 kW] range. If R2 is 200 kW given the VFB is 0.6 V, the current through the divider will be 3 mA. The formula below gives the value of VOUT, given the desired R1 and the R1 value,
VOUT + VFB 1 ) R1 R2
The device operates with inductance value between 1 mH and maximum of 4.7 mH. 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.
Table 2. L-C FILTER EXAMPLE
Inductance (L) 1 mH 2.2 mH 4.7 mH Output Capacitor (COUT) 10 mF 4.7 mF 2.2 mF
* * * *
VOUT: output voltage (volts) VFB: feedback voltage = 0.6 V R1: feedback resistor from VOUT to FB R2: feedback resistor from FB to GND
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 mF 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.
Table 1. LIST OF INPUT CAPACITOR
Murata GRM188R60J475KE GRM21BR71C475KA Taiyo Yuden TDK JMK212BY475MG C2012X5R0J475KT C1608X5R0J475KT
Inductor Selection
The inductor parameters directly related to device performances are saturation current and DC resistance and inductance value. The inductor ripple current (DIL) decreases with higher inductance:
DIL + L VOUT V 1- OUT VIN fSW
DIL = 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:
IL(MAX) + IO(MAX) ) DIL 2
Output L-C Filter Design Considerations:
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 W for good efficiency.
Table 3. LIST OF INDUCTOR
FDK TDK MIPW3226 Series VLF3010AT Series TFC252005 Series Taiyo Yuden Coil Craft LQ CBL2012 DO1605-T Series LPO3010
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 mH and COUT = 4.7 mF The corner frequency is given by:
fc + 1 2p L 1 + 2 p 2.2 mH COUT 4.7 mF + 49.5 KHz
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NCP1523
Output Capacitor Selection
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:
DVOUT + DIL 4 1 ) ESR fSW COUT
Table 4. LIST OF OUTPUT CAPACITOR ROHS
Murata GRM188R60J475KE GRM21BR71C475KA GRM188R60OJ106ME Taiyo Yuden JMK212BY475MG JMK212BJ106MG TDK C2012X5R0J475KT C1608X5R0J475KT C2012X5R0J106KT 10 mF 10 mF 4.7 mF 10 mF 4.7 mF 4.7 mF
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.
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NCP1523
PACKAGE DIMENSIONS
8 PIN FLIP-CHIP, 2.05x1.05, 0.5P CASE 766AE-01 ISSUE C
D
2X
AB
0.10 C E
TERMINAL A1 LOCATOR 2X
NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994. 2. CONTROLLING DIMENSION: MILLIMETERS. 3. COPLANARITY APPLIES TO SPHERICAL CROWNS OF SOLDER BALLS. 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 A2 A1 0.10 C A C
SEATING PLANE
8X
0.05 C
NOTE 3
b 0.05 C A B
8X
0.03 C
1 2 A B C D
BOTTOM VIEW
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NCP1523/D

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Price & Availability of NCP1523BFCT2G

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