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TPS61094: 0.5A to 1.5A boost efficiency and current limit.

Jensen Huang
Prodigy 10 points
Part Number: TPS61094

Tool/software:

Hello,

I have some questions during validation TPS61094 via TPS61094 EVB.

Test conditions:

Vin = 5.2V (makes sure Vin > target Vout+0.1V)

Vout = 5V

Charge current = 300mA

Charge voltage = 5.1V

Load current = 1A.

1. How to forecast the efficiency load current above 0.5A? We need scope of load current from 0.5A to 1.5A ,but only record to 0.5A in datasheet.

2.  The range of current limit from 1.7 to 2.6A. It's look like decided by it's made so may I might be able to change the current limit by resistor dividing?

Or I should set the current limit at 1.7A in my design.

3. The following is captured by oscilloscope, the pic. is mark 1 and 2 separately

3.1 At the mark 1. My sequence is load 1A in then turn mode to auto buck and boost, turn off Vin. When turn off Vin, Vin、Vout and Vsup all has ripples that look unusual, what is cause it?

If it is normal how could I reduce it ?

3.2 After turn off Vin, then Vsup is decrease to 2.26V then Vout is shutdown.

According to the document, UVLO is Vin and Vsup both below 1.7V, but in my test Vsup still above 2.2V , what kind of mechanism shutdown the Vout?

Thanks!

Jensen

  • 0
    Prodigy 10 points

    Hello,

    I also found that whether load is 0.5A or 1.1A, TPS61094 support 5V around 800ms. 

    It's not meet our expectations. If consider boost efficiency I think load 0.5 should above 2s.

    Does TPS61094 is locked in which mechanism so that could not support to 2s?

    Jensen

  • 0 in reply to Jensen Huang
    TI__Expert 6625 points

    Hi Jensen,

    •  How to forecast the efficiency load current above 0.5A? We need scope of load current from 0.5A to 1.5A ,but only record to 0.5A in datasheet. VIN 3.6V and 4.2V shows over 0.5A. Vin0.7V and 1.5V does not support such load. View datasheet 7.3.4 Current Limit Operation to calculate Iout capability at boost mode.
    • The range of current limit from 1.7 to 2.6A. It's look like decided by it's made so may I might be able to change the current limit by resistor dividing?No, this is just variation between different temperature and different pieces.
    • At the mark 1. My sequence is load 1A in then turn mode to auto buck and boost, turn off Vin. When turn off Vin, Vin、Vout and Vsup all has ripples that look unusual, what is cause it? This is because PFM current is not constant. this will cause some ripple on both Vsup and Vout. This is a normal behavior and will not affect usage. No need to reduce it

    • According to the document, UVLO is Vin and Vsup both below 1.7V, but in my test Vsup still above 2.2V , what kind of mechanism shutdown the Vout? The IC current limit does not support this condition.View datasheet 7.3.4 Current Limit Operation to calculate Iout capability at boost mode.

    Best Regards,

    Travis

  • 0 in reply to Travis Wang
    Prodigy 10 points

    1. Actulaly, I have calculated the output load is 1.632A close to 1.7A minimum in datasheet so TPS61094 must support output current up to 1.5A.

    So I would like to know the efficiency in output current from 0.5A to1.5A in boost mode.  

    2. If I have to set the TPS61094 solution minimum output current, the value is 1.7A in datasheet table or 1.632A after calculating  7.3.4 section equation?

    I don't understand the meaning of equation of 7.3.4 section.

    3. OK! Because ripples not alway large enough for me to notice.

    4. In the two different load current(0.5A and 1A), Vout cutoff at almost same time (800ms) but not at same Vsup(4.1V and 2.4V)  so I don't know what mechanism cause the TPS61094 shutdown.

    In normal operation, backup time should exist a linear relationship with load, but I don't find this situation on the TPS61094.

  • 0 in reply to Jensen Huang
    TI__Expert 6625 points

    Hi Jensen,

    I don't think you calculate the Iout correctly. If you cannot understand the equation, you can use Datasheet 8.2.2.2 Maximum Output Current. This one is more convenient. You can neglect ILH for rough estimate.

    The device shut down because its current limit cannot support both 0.5A and 1A with lower VSUP. 

  • 0 in reply to Travis Wang
    Prodigy 10 points

    Hello Travis,

    I think current does not touch the limitation. When shutdown occurs, Vsup is 2.2V in 1A load, Vout is 4.2V in 0.5A load. Vsup still has power support Vout.

    If it is current limit, Vout will decrease to 1.6V then shutdown, but my situation is Vout keeps 5V for a while then shutdown. It look like some interlock trigger then force to shutdown.

  • 0 in reply to Jensen Huang
    TI__Expert 6625 points

    Hi Jensen,

    I agree with your point. But our device does not have such timer logic. This shutdown is weird so I'll do similar test on EVM and see whether I can repeat this.

    Your FAE  had started another thread in e2e. So I'll update my test result to him and he will report to you.

    Best Regards,

    Travis