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[FAQ] TPS650250: Power loss calculation

Intellectual 2340 points
Takeshi Sasaki

Replies: 2

Views: 787

Part Number: TPS650250

Hi team,

Could you give me advise on following customer request? What document or material should the customer refer to?

<Customer request>

Could you tell me how to estimate power dissipation for TPS650250? For example, the customer found that the power dissipation estimate is described at the datasheet of TPS54340-Q1. 

Thank you for your support. 

Best regards,

Takeshi Sasaki

Intellectual 2340 points
Takeshi Sasaki
  • Genius 16055 points
    Kevin LaRosa
    Hi Sasaki-san,

    Power dissipation for TPS650250 can be calculated by using the efficiency graphs in the datasheet (page 10, starting with Table 1). They can take their Vin and Vout combination, find the closest values to those in the graphs and find their expected efficiency at a given current point. From there, power dissipation is just power in - power out = power out / efficiency - power out = power out * (1/efficiency - 1). This will give the power dissipation in the bucks. For the LDOs, power dissipation is just (Vin - Vout) * Iout since they are linear.

    Example:
    For VINDCDC1 = 5 V, VDCDC1 = 3.3 V, Iout = 1 A (for DCDC1), the efficiency is around 92%. Power out = 1 A * 3.3 V = 3.3 W, so the power dissipated should be approximately 3.3 W * (1/.92 - 1) = 0.287 W.

    For VINLDO1 = 3.3 V, VLDO1 = 1.8 V, Iout = .1 A (for LDO1), the power dissipation is (3.3 V - 1.8 V) * 0.1 A = 0.15 W.

    One advantage that TPS650250 will have over the TPS54340-Q1 is that it has synchronous bucks, so the power dissipation described in TPS54340-Q1 datasheet (equation 36) won't apply to TPS650250 since the TPS650250 has a FET for the bottom side instead of a diode, saving a lot of power dissipation at high loads.

    Thank you,
    Kevin LaRosa
    --------------------------------------------------
    For more information on Multi-Channel Power Management ICs visit www.ti.com/PMIC 

  • Intellectual 2340 points
    Takeshi Sasaki

    In reply to Kevin LaRosa:

    Hi Kevin,

    I appreciated above detail explanation how to calculate power dissipation. Thank you!

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