Hello,
we are using TPS62816-Q1 in one of the applications. To calculate the power dissipation certain parameters are not available like gate drive details, dead time, switching time have not been mentioned. Could you please provide the mentioned details?
The output capacitor mentioned minimum in the datasheet is 22uF. Could you please provide the equation for the same? I am not able to get that value with the general formula for output capacitor.
Thanks,
Regards,
Roopa.
Hi Roopa,
We normally collect efficiency data for many corners. (Vout, Iout, Vin). With the efficiency you'll be able to calculate the power dissipation of the device together with the inductor.
Do you have a specific set of conditions where you would like to know the power dissipation?
Have you tried our Webench software before?
Example for Vin=5V Vout=0.9 Iout=3A
https://webench.ti.com/power-designer/switching-regulator/customize/16?VinMin=5&VinMax=5.1&O1V=0.9&O1I=1&base_pn=TPS62816-Q1&AppType=None&Flavor=None&op_TA=30&origin=pf_panel&lang_chosen=en-US&optfactor=3&Topology=Buck&flavor=None&VoltageOption=None
Regarding the output capacitance. This value is dependent not only on the ripple allowed but also on the converter stability. A too low capacitance may cause stability issues. To calculate the minimum output cap you can refer to Table 9-1 on the datasheet.
Let me know if this information helps you with your design.
Best regards
Nelson
Hi Roopa,
Switching losses may depend on Vin. I could not provide a figure for that. What we can offer is the efficiency for a given condition.
For the Webench circuit I refer you to:
Vin = 5V
Vout = 0.9V
Iout = 3A
Eff = 86.5%
Eff = Pout / Pin = Vout * Iout / (Vin * Iin)
Iin = Vout * Iout / (Eff * Vin)
Iin = 0.624A
Pin = 3.12W
Pout = 2.7W
Pin - Pout = Total loss =0.42W = L_loss + Dev_loss
L_loss =L_DCloss + L_ACloss + L_Coreloss
L_DCloss= DCR*Iout^2 = 4.2mOhm * (3)^2 = 37.8mW
If we are far from saturation of the inductor, the AC loss might be negligible.
Dev_loss = 420mW - 37.8mW = 382.2mW
Let me know if this example helps you find out the losses in your application.
From my experience, I would recommend to measure the efficiency for the given condition in the lab because it is hard to have all parameters and the real measurement will be more accurate than any calculation.
Regards
Nelson
Hi Roopa,
Unfortunately we are not able to provide this data. We can assure that the dead time is optimized to minimize losses.
With this Webench link you'll be able to get the efficiency for the corner you indicated.
https://webench.ti.com/power-designer/switching-regulator/customize/18?VinMin=5&VinMax=5.1&O1V=1.05&O1I=5.15&base_pn=TPS62816-Q1&AppType=None&Flavor=None&op_TA=30&origin=pf_panel&lang_chosen=en-US&optfactor=3&Topology=Buck&flavor=None&VoltageOption=None
L=0.25nH (XFL4012-251MEB) for this Webench calculation.
We also have data for Vout=1V and L= 0.25nH (XGL4020-251MEC) in the datasheet.
At 5.15A output current, the effects that dominate the losses are mostly the RdsON of the switches and the DCR of the inductor. We recommend using ceramic capacitors, for which you can neglect the losses.
I hope this data offers you an alternative way to calculate the losses.
Regards
Nelson
