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TPS25944A: Ton(dly) and Toff (dly)

higa daisuke
Intellectual 900 points
Part Number: TPS25944A

Hi support team.

My customer is evaluating a TPS25944A at EVM.

I received a question from him about Ton(dly) and Toff(dly) which are 220us(tpy) and 2us(tpy) on datesheet.

He got the result of Ton(dly) /Toff(dly) are more longer/shorter than datesheet spec. 

(Please refer to attached .docx file.)

He thinks that his EN/UVLO setting is wrong.

His setting isthe below,

Vin=5V±10%

UVLO=4.58V

OVP=5.58V

R1=110kohm

R2=3.3kohm

R3=24.9kohm

(Above setting R1/2/3 is refered to datesheet on P22 Fig.50.)

If you can advise me, please let me know.Measured data Ton(dly)_Toff(dly) .docx

Best regards.

  • 0
    TI__Guru* 95791 points
    Hi Daisuke

    Thanks for reaching out!.
    The EN/UVLO and OVP settings are fine.
    Can you please confirm what other changes are done for TPS25944A EVM? Any capacitor is added at dVdT pin?
    Can you please also capture Vin in your Ton(dly), Toff(dly)wavefoms and provide.

    Regards,
    Rakesh
  • 0 in reply to Rakesh
    Intellectual 900 points

    Hi Rakesh-sun

    I apologize to you the late response.

    I confirmed the other changes in TPS25942AEVM-635(replaced 944A) to my customer.

    Please refer to attached word file and the below,

    R3  475k⇒110kΩ

    R9  16.9k⇒3.3kΩ

    R13  32.4k⇒24.9kΩ

    C6   DNP ⇒ 6800pF

    R10  16.9k⇒ 0Ω

    R12  24.9k⇒44.2kΩ

    R4    475k⇒110kΩ

    R11  47k⇒30.9kΩ

    C2、C3  4.7uF⇒10uF

    C4   330uF⇒47uF

    J1    1-2 Short

    J6    Open

    J4    Open

    Best Regards.

    Vin vs EN_FLT_Vout.xlsx

  • 0 in reply to higa daisuke
    TI__Guru* 95791 points
    Hi Daisuke-san,

    Thanks for the test waveforms.
    The turn-on delay with C(dVdT) capacitor is 100 + 150 x C(dVdT) us, where C(dVdT) capacitor is in nF. For 6800pF, the turn-on delay is 1.12ms.
    Regarding turn-off delay, the FLT output is asserting LOW at maximum of EN/UVLO falling threshold voltage 0.94V. The 100mV below V(ENF) is a typical case, a lower overdrive 30mV to 40mV may be sufficient to assert the FLT out.
    please let me know where this device is considered to use and how important is the delays for the customer.

    Regards,
    Rakesh
  • 0 in reply to Rakesh
    Intellectual 900 points
    Hi Rakesh-sun

    Thanks for your support.
    I will tell him your advice.

    Best regards.