Hi Team,
My customer need a buck converter solution which efficiency performance can meet below requirement. I found performance of TPS62865 close to customer's spec. Do we have better solution?
1. VIN: TBD. 3.3V, 5Vor 19.5V are okay to use.
2. Vout: 0.75V
3. Iout: Maximum 1.5A.
4. 88% efficiency at 10mA load
5. 88% efficiency at 100mA load
6. 91% efficiency at 1.5A load
Best regards,
Hardy
Hello Hardy,
After having a look at our different device families, I came to the conclusion that the device you have now is one of the best choices you have at hand.
The limiting factor here are the low Vout of 0.75V and the 1.5A Iout Max. We have devices that are optimized for Iouts around 10m, 100m, 1A but they are not significantly better than the TPS62865 and they won't reach 1.5A.
The following curve is the Efficiency for the TPS62827, a 4A device with peak efficiencies between 1 and 2A. If you see, there is a trend of increasing efficiency for increasing Vout.
If we calculate the losses in PWM (Mode used for iout=1.5A), they stay relatively constant across Vout:
Ploss = iout^2 * L_DCR + D * HSD_Ron*iout^2 + (1-D)*LSD_Ron*iout^2 +...
Pout = iout*vout
Pin = iout*vout + Ploss
Eff = iout*vout / (iout*vout + Ploss)
For constant iout, that would mean that if Vout increases, the power dissipation becomes less important.
The following plot shows the efficiency for the TPS62865/7, and the effect of efficiency increase with increasing Vout:
I see that the TPS62865/7 offers a very good compromise between low and high current performance.
I hope this helped to clarify why it is so difficult to achieve the efficiency goals that you mentioned.
Best regards
Nelson
