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TPS61378-Q1: TPS61378-Q1

Srijesh Kumar
Prodigy 160 points
Part Number: TPS61378-Q1
Other Parts Discussed in Thread: TPS61033-Q1

Hi Team,

Kindly Review the attached Schematic circuit for TPS61378-Q1 and provide the feedback 

Below mentioning the design details,

Input Voltage  - 4.1V(Max) and 2.3V (Min)

Output Voltage  -5.25V

Maximum load current - 1.5A

Continous Load current  - 1A

Inductor Value (L22)  -0.47uH

Switching Frequency  - 2.2MHz

TPS61378_TI_Review.pdf

  • 0
    TI__Expert 8615 points

    Hi Srijesh,

    There is China National Day this week, so the responsible team is out of the office. Please be patient until next week.

    Best regards,

    Moritz

  • 0
    TI__Genius 12655 points

    Hi Srijesh,

    Sorry for reply late.

    The input current seems too large for TPS61378-Q1, as the device has a minimum peak current limit of 4A.

    please see the calculation tool.

    3704.TPS61378 Calculation Tool V1.1.xlsx

    Iin=5.25*1.5/2.3/0.9=3.8A, neglecting the ripple current.

    that means the device cannot output 5.25V1.5A at 2.3Vin.

    It is recommended to use TPS61033-Q1.

    adjustment should be made on the condition if you insist with the device.

    Best Regards

    Fergus

  • 0 in reply to Fergus He
    Prodigy 160 points

    Hi Fergus,

    Thanks for reply.

    Q1)Is there any impact on TPS61378 IC under above condition("the device cannot output 5.25V1.5A at 2.3Vin")?

    Q2)From Calculation sheet Current limit can be set between 1A and 4.8A.

    At 2.3V,Iin =3.8A,which falls between 1A and 4.8A .under this condition can the device output 5.25V ,1.5A at 2.3V input. Please confirm?

    Kindly reply

  • 0 in reply to Srijesh Kumar
    TI__Genius 12655 points

    Hi Srijensh,

    for your questions.

    1. the device will limit its input current thus the output voltage will drop to maintain the output current.(input power is limited)

    2. the 4.8A is typical value and it can vary to 4A in all cases.

    Srijesh Kumar said:
    At 2.3V,Iin =3.8A,which falls between 1A and 4.8A

    the peak current is not 3.8A but 4.57A due to the calculation tool.

    it is higher than the minimum spec 4A and the device cannot ensure the output capacity in all cases.

    Best Regards

    Fergus

  • 0 in reply to Fergus He
    Prodigy 160 points

    Hi Fergus,

    While checking with TPS61378 EVM Board,Following points were observed,

    When the input current is above 1.8A  @3.3V input voltage, Output voltage starts fluctuating, so input current and load current also start fluctuating.

    Mentioning below Testing parameters, 

    Input Voltage = 4.1V to 2.3V

    Ilim =4.8A

    Continous load current  =0.65A

    Output Voltage = 5.25V

    Inductor -0.47uH 

    Please see Inductor Specification

    Please see recommendation from Calculation sheet.

    Q)Even after setting Current limit to 4.8A, @1.8A input current ,Output voltage is getting fluctuate. Please Clarify.

  • 0 in reply to Srijesh Kumar
    TI__Genius 12655 points

    Hi Srijensh,

    The fluctuate could result from the loop unstable or simply the limit of the source.

    Please double check the current limit of your source and make the input wire as short as possible to avoid much voltage drop.

    On the other hand, please check the loop of the circuit, it can be seen in the calculation tool, please ensure the stability. 

    It is easy to mislead that the output capacitance is the effective capacitance of the output capacitors.

    It will be better that you provide more clues like tested waveforms for me to check if you still have questions.

    Waveforms with SW, Vin, Vout and IL in one picture would be preferred.

    Best Regards

    Fergus