Other Parts Discussed in Thread: CSD18504Q5A, CSD18540Q5B
Tool/software: WEBENCH® Design Tools
I built a power supply on a WEBENCH Build It prototype board based on the schematic provided by the WEBENCH utility. The power supply is designed for 5V out at 15Amax from 24V in. I am currently using a 12V supply for Vin while I wait for my 24V source to arrive. I am only able to get about 1A out of the supply. When I increase the load above 1A, the voltage begins to drop. At 1A, my supply regulates at 5.33V. At 1.5A, my output voltage drops to 5.2. At 1.9A, the output drops to 4.1V.
When I first built the prototype, I noticed that the switching frequency was higher than specified by WEBENCH, approx. 600KHz. I have tried changing Cout from the 68uF ceramic to 150uF aluminum electrolytic with negligible affect. I doubled the Ron resistor, from 84.5K to 169K, and improved the performance slightly. The above measurements are from the 169K Ron. I tried removing Cff, as I had read in other threads, but this had little to no affect.
I used all of the parts that were recommended by WEBENCH. Can you help me get the circuit figured out? I need to get at least 8-10A from this supply.
Part,Manufacturer,Part Number,Quantity,Price ($),Footprint (mm²),Description
Cbst,Panasonic,ECPU1C474MA5,1,0.2,10.92,Cap: 470 nF Total Derated Cap: 470 nF VDC: 16 V ESR: 0 Ω Package: 1206
Cbyp,Kemet,C0805C104M5RACTU,1,0.01,6.75,Cap: 100 nF Total Derated Cap: 100 nF VDC: 50 V ESR: 64 mΩ Package: 0805
Cin,TDK,C3216X5R1H106K160AB,2,0.3,10.92,Cap: 10 µF Total Derated Cap: 4.2 µF VDC: 50 V ESR: 1 mΩ Package: 1206_180
Cout,TDK,C5750X5R1A686M230KA,2,1.26,53.9,Cap: 68 µF Total Derated Cap: 120 µF VDC: 10 V ESR: 6.83 mΩ Package: 2220
Css,TDK,CGA4F2C0G1H153J085AA,1,0.07,6.75,Cap: 15 nF Total Derated Cap: 15 nF VDC: 50 V ESR: 0 Ω Package: 0805
Cvcc,Taiyo Yuden,LMK212B7225KG-T,1,0.03,6.75,Cap: 2.2 µF Total Derated Cap: 2.2 µF VDC: 10 V ESR: 1 mΩ Package: 0805
L1,Coilcraft,XAL1010-222MEB,1,1.71,159.6,L: 2.2 µH DCR: 2.6 mΩ IDC: 32 A
M1,Texas Instruments,CSD18504Q5A,1,0.33,55.2,VdsMax: 40 V IdsMax: 50 Amps
M2,Texas Instruments,CSD18540Q5B,1,0.86,56,VdsMax: 60 V IdsMax: 100 Amps
Rfb1,Vishay-Dale,CRCW080510K0FKEA,1,0.01,6.75,Resistance: 10 kΩ Tolerance: 1.0% Power: 125 mW
Rfb2,Panasonic,ERJ-6ENF7322V,1,0.01,6.75,Resistance: 73.2 kΩ Tolerance: 1.0% Power: 125 mW
Rilim,Panasonic,ERJ-6ENF1371V,1,0.01,6.75,Resistance: 1.37 kΩ Tolerance: 1.0% Power: 125 mW
Ron,Vishay-Dale,CRCW080584K5FKEA,1,0.01,6.75,Resistance: 84.5 kΩ Tolerance: 1.0% Power: 125 mW
U1,Texas Instruments,LM3150MH/NOPB,1,1.62,58.8,
Cff,Samsung Electro-Mechanics,CL21C471KBANNNC,1,0.01,6.75,Cap: 470 pF Total Derated Cap: 470 pF VDC: 50 V ESR: 0 Ω Package: 0805
