LM5164: LM5164DDAR schematics review

Hi Kelvin,

What is the input voltage Vin min/nom/max and load current? Kindly share for schematic review

regards

Arpita

Hi

30V~56V (TYP 48V) ， LOAD <1A

Hi Kevin,

1. recommend adding filter capacitances before ferrite bead L3, as suggested in the device EVM

2. Can add decoupling capacitor of ~100pF at input [along with the caps present in current schematic]

3. Ra [R2] needs to be decreased to ~550kohm to have sufficient ripple amplitude at FB note, especially at minimum output voltage.

3. Kindly note: 2*22uF, 25V rated output capacitors might not provide sufficient capacitance at 12V due to derating/dc bias effect. Effective capacitance would be ~2*8.8uF at 12V output. Customer might want to increase output capacitance based on allowable output voltage ripple.

4. What is the exact load current <1A??? Note that required inductor value has to be calculated so that the (load current+0.5*peak to peak inductor current ripple)< minimum value of peak current limit threshold of the device.

For load current ~1A, would recommend increasing inductor value ~120uH to avoid hitting current limit, especially at higher input voltage.

Regards

Arpita

Hi

3. Ra [R2] needs to be decreased to ~550kohm to have sufficient ripple amplitude at FB note, especially at minimum output voltage.

Ans:I have a question about this part. Your calculations suggest 909kohm, so do I still need to put <550kohm?

3. Kindly note: 2*22uF, 25V rated output capacitors might not provide sufficient capacitance at 12V due to derating/dc bias effect. Effective capacitance would be ~2*8.8uF at 12V output. Customer might want to increase output capacitance based on allowable output voltage ripple.

Ans: But the simulator calculated it to be 22uF*2

Hi Kevin

1. The required ripple injection resistor is calculated as per nominal input value. To ensure that there is sufficient ripple at min Vin also [ as minimum vin is lesser than nominal], it is recommended to take this into account. You can adjust the Ra to have sufficient margin. You can use Ra ~700kohms also that should also be fine.

2. I would like to highlight that the effective capacitance of 22uf, 25V at 12V output voltage would be ~8.9uF. You may want to adjust the required capacitance based on allowable output voltage ripple. 

Regards

Arpita

Hi Kevin,

Do you have any update?