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TPS57140-Q1: About tON(Max) and switching frequency error of TPS57140-Q1

Noritomo Harukawa
Intellectual 990 points
Part Number: TPS57140-Q1

Customers are considering switching frequency of TPS 57140-Q1.

The switching frequency was calculated from Equation 8 on page 18 of the TPS57140-Q1 datasheet.
The values in Equation 8 are as follows.

　tON：130ns (From TPS57140-Q1 data sheet 8.2.2.1)
　VIN：16V (From customer specification)
　VOUT：3.3V (Setting value)
　IL：1.2A (Assumed max current of 3.3 V system)
　Rdc：0.05Ω (From coil data sheet)
　Vd：0.69V (From the diode data sheet)
　RDS(on)：410mΩ (From TPS57140-Q1 datasheet 6.5)

The calculation result was about 1.9 MHz.
Datasheet From Equation 7 on page 17, the customer is planning to make 1.88 MHz using a 56 kΩ resistor.

Q1.
I want to confirm if pulse skipping can be avoided with this switching frequency(1.88MHz).
To that end,
(1)Max value of Minimum on time
(2)Switching frequency error value
I need these information.

Would you please provide me with the information on (1) and (2)?

-Harukawa

  • 0
    TI__Expert 4100 points
    Hello Harukawa-san,
    We will need few days to get this information from responsible manufacturing group.
    I will get back to you as soon as i have the information you requested.
    Regards
    Brani
  • 0
    TI__Expert 4100 points

    Hello Harukawa-san,

    Regarding your questions, here are the answers form our manufacturing team:

    1. Maximum min On time is 152ns
    2. Switching frequency is not measured directly, but jitter is measured. Maximum jitter variation for 2MHz switching frequency is +/- 40ns (or +/- 8%).

    I hope this helps.

    Regards

    Brani