NCP3155B ONSEMI [ON Semiconductor], NCP3155B Datasheet
NCP3155B
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NCP3155B Summary of contents
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... NCP3155A, NCP3155B 3 A Synchronous Buck Regulator The NCP3155 is a DC/DC synchronous switching regulator with fully integrated power switches and full fault protection. The switching frequency of 1 MHz and 500 kHz allows the use of small filter components, which results in smaller board space and reduced BOM cost ...
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VIN OSCILLATOR COMP REF FB PIN FUNCTION DESCRIPTION Pin Pin Name 1 PGND The PGND pin is the high current ground pin for the lower MOSFET and drivers which should be soldered to a large copper area to reduce thermal ...
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ABSOLUTE MAXIMUM RATINGS (measured vs. GND pin 8, unless otherwise noted) Rating Main Supply Voltage Input Boost to V differential voltage SW High Side Drive Boost Pin Switch Voltage Node Transconductance Amplifier Output Feedback Current Limit Set Operating Junction Temperature ...
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... NCP3155B T Ramp−Amplitude Voltage Ramp Valley Voltage PWM Minimum Duty Cycle Maximum Duty Cycle Soft Start Ramp Time NCP3155A NCP3155B ERROR AMPLIFIER (GM) Transconductance Open Loop dc Gain Output Source Current Output Sink Current FB Input Bias Current Feedback Voltage COMP High Voltage COMP Low Voltage ...
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... Figure 6. Load Regulation vs Input Voltage Input = 18 V, Output = 5.0 V, Load = 2 A, CH3 (Purple CH3: 200 mVac/div; CH2: 50 mVac/div; CH1: 5.0 V/div Time Scale: 2.0 ms/div; Figure 45 Figure 8. Switching Waveforms (NCP3155A) http://onsemi.com 5 3.3 V 1.2 V 1.5 V NCP3155B Typical Application Circuit Figure 45 1 1 OUTPUT CURRENT (A) ...
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... TYPICAL PERFORMANCE CHARACTERISTICS Input = 12 V, Output = 1.8 V, Load = 2 A, CH3 (Purple (CH2) Green = V , CH1 (Yellow) = VSW IN OUT CH3: 200 mVac/div; CH2: 50 mVac/div; CH1: 5.0 V/div Time Scale: 1.0 ms/div; Figure 46 Figure 9. Switching Waveforms (NCP3155B) 570 560 550 540 530 520 510 − ...
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... TEMPERATURE (°C) Figure 17. ISET Current vs Temperature Input = 12 V, Output = 1.8 V, Load = 2 A, CH3 (Purple (CH2) Green = V , CH1 (Yellow) = VSW IN OUT CH3: 10 V/div; CH2: 1.0 V/div; CH1: 5.0 V/div Time Scale: 0.5 ms/div; Figure 46 Figure 19. Startup Waveforms (NCP3155B) 1000 950 900 850 800 750 700 650 600 ...
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... TYPICAL PERFORMANCE CHARACTERISTICS Input = 12 V (CH2) Green = V , CH1 (Yellow) = VSW OUT CH2: 0.5 V/div; CH1: 5.0 V/div Time Scale: 2.0 ms/div; Figure 46 Figure 21. Current Limit Waveforms (NCP3155B 5 − −40 −25 − TEMPERATURE (°C) Figure 23. Low−Side MOSFET R Temperature 3 ...
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... NCP3155B 3.5 3 1.0 to 1.2 V 2.5 2 2.5 V 1.5 1 0.5 NCP3155B Figure 28. Derating Curve Input 2 5 AMBIENT TEMPERATURE (°C) A Figure 29. Derating Curve Input http://onsemi.com 9 1 5.0 V out 3 AMBIENT TEMPERATURE (° ...
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... Some overshoot may be evident at the start of each step depending on the voltage loop phase margin and bandwidth. The total soft−start time is 2.4 ms for the NCP3155A and 1.2 ms for the NCP3155B Steps 32 Voltage Steps Figure 30. Soft−Start Details http://onsemi ...
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OOV and OUV The output voltage of the buck converter is monitored at the feedback pin of the output power stage. Two comparators are placed on the feedback node of the OTA to monitor the operating window of the feedback ...
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V (vref *125%) 0.8 V (vref *100%) 0.6 V (vref *75%) FB Voltage Latch off Reinitiate Softstart Softstart Complete Figure 33. Powerup Sequence and Overvoltage Latch 1.0 V (vref *125%) 0.8 V (vref *100%) 0.6 V (vref * 75%) ...
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CURRENT LIMIT AND CURRENT LIMIT SET Overview The NCP3155 uses the voltage drop across the High Side MOSFET during the on time to sense inductor current. The Ilim Out CONTROL 6 DAC / COUNTER Itrip Ref−63 Steps, 6.51 mV/step Current ...
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No Trip: Vsense < I Itrip Ref Vsense ¾ Ton−2 1/4 1/2 3/4 Ton−1 Each switching cycle’s Ton is counted time steps. The 3/4 sample time value is held and used for the following cycle’s limit sample ...
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Reduced sampling time occurs at high duty cycles where the low side MOSFET is off for the majority of the switching period. Reduced sampling time causes errors in the regulated voltage on the boost pin. High duty cycle / input ...
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VIN VBOOST Maximum Normal VIN VBOOST Maximum Normal VIN VBOOST Figure 39. Typical Waveforms for Region 1 (top), Region 2 (middle), and Region 3 (bottom) To illustrate, a 0.1 mF boost capacitor operating at > 80% duty cycle and > ...
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Voltage Ripple Maximum Allowable Voltage 16 Maximum Boost Voltage 4.5 Inductor Selection When selecting the inductor important to know the input and output requirements. Some example conditions are listed ...
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V− V− V− 10% 15% 20% 25 (V) IN Figure 41. Ripple Current Ratio vs. Inductance To keep within the bounds of the parts ...
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... The output capacitor must be rated to handle the ripple current at full load with proper derating. The RMS ratings given in datasheets are generally for lower switching frequency than used in switch mode power supplies but a multiplier is usually given for higher frequency operation. The RMS current for the output capacitor can be calculated ...
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Compensation Type II This compensation is suitable for electrolytic capacitors. Components of the Type II (Figure 42) network can be specified by the following equations: Figure 42. Type II Compensation ...
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Output Current Derating The NCP3155 has a wide input voltage and output voltage capability. It also operates in a variety of thermal environments. These thermal conditions limit the maximum output current for a given input and output voltage. Therefore, proper ...
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... BST VIN VSW 680p PGND NCP3155A 1.5 ISET FB1 COMP AGND Figure 45. Typical Application Circuit 0.1m 4.7m BST VIN VSW 680p PGND NCP3155B 1.5 ISET FB1 COMP AGND Figure 46. Typical Application Circuit http://onsemi.com VOUT 820p 47m 47m 19.62k 649 R1 VOUT (V) R1 (kW) 1.2 39.2k 1.5 22.1k 3.3 6 ...
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... BST VIN VSW 680p PGND NCP3155B 1.5 ISET FB1 COMP AGND Figure 47. Typical Application Circuit 0.1m 4.7m BST VIN VSW 680p PGND NCP3155B 1.5 ISET FB1 COMP AGND Figure 48. Typical Application Circuit http://onsemi.com 23 3.3 V VOUT 560p 22m 22m 19.62k 270 6.19k 3.3 V VOUT 680p 220m 10m 15 ...
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−Y− −Z− 0.25 (0.010 *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference ...