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TPS62843: several questions

Given Ding
Expert 8365 points
Part Number: TPS62843

Hi Team, 

below are several questions. 

1. can TPS62843x support 2.2uH inductor? Or it can only support 1uH as datasheet mentioned.  If it can support 2.2uH, will eff be improved? 

2. If Vout is higher than Vin, that is, there is power supply on Vout, can TPS62843x support reverse block? I see the block that the body diode of HS FET should be from Vout to Vin, so it cannot block reverse current, right? 

3. in datasheet, there is only Vout dc accuracy at PWM mode, what's the accuracy of PFM mode? 

4. in datasheet, typical Iq is 275nA but max is 1500nA, my customer think it will be better to be below 1000nA max, just want to check how much margin of the max value in datasheet? 

5. datasheet shows ripple @ 0.7V from light load to full load, is there test results for 1.8V @ 0- full load? Or if there is any test result on 1.8V on your hand, please kindly share. 

Thanks. 

BRs

Given 

  • +1
    TI__Genius 15440 points

    Hi Given,

    Here are my answers to the questions:

    1. The max inductor that can be supported is 1.2uH

    2. If VOUT is higher than VIN, there will be current flow from VOUT to VIN through the body diode of the high side FET. The max SW voltage spec is VIN+0.3V

    3. The PFM mode accuracy is not a spec parameter, so I can't provide you limits for that.  Below is the VOUT accuracy data for 1.8V VOUT for VIN range from 2.3V to 5.5V. X axis is Iout and different columns correspond to different ambient temperatures.

    4. I think it should be possible to have IQ below 1000nA. Below is characterization data for IQ in a histogram form. Y axis is the number of units. X axis is IQ and different colors correspond to different VINs. Rows correspond to different ambient temperatures. The pink dotted lines show the 6 sigma values.

    5. We don't have scope shots of ripple at 1.8V VOUT. Webench should be able to determine this for the BOM the customer has.

    Best regards,

    Varun

  • 0 in reply to Varun John
    TI__Expert 8365 points

    Hi Varun,

    Thanks. 

    one more question, when thermal shutdown, will output discharge function works, that is, is output discharge circuit works when OTP happens and before it recover ? Thanks. 

    BRS

    Given 

  • +1 in reply to Given Ding
    TI__Genius 15440 points

    Hi Given,

    That is correct, output discharge will be active during thermal shutdown.

    Best regards,

    Varun