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TPS76901-HT Current Output Specification VDO Requirement, Can't reach specified current in design.

Michael Drake78
Prodigy 10 points
Other Parts Discussed in Thread: TPS76901-HT, TPS7H1201-HT

TPS76901-HT Specification is for 100ma output. I am having dropout at about 30 ma. My input voltage is 5 volts. Output 3.3V.

This regulator should perform at this output level from what I can tell from the datasheet. I am looking for a solution for this problem which will allow me to use my current board, with this regulator. I have a high temperature requirement to run at least up to 175C. I am testing at room temperature.

At about 35ma my voltage output drops to about 2.6 volts.

At 30 ma it may be around 2.8 or 2.9 Volts.

I see in the specification, data sheet, that to calculate the voltage overhead required for input to output voltage drop I should use a formula including VDO, specifically VI(min) = VO(max) + VDO(max load), but I can find no specification for VDO. I need the VDO specification to find out.

Perhaps there are some tech tips for getting a little more out of the chip such as more or less output capacitance. Any recommendations would be appreciated. I may have to parallel two regulators to get what I need.

I want to be confident that with the regulator I can have 50 ma. 5% of the time 10% and 20ma in normal operation.

Cannot replace device with TPS7H1201-HT because of the ground current spec.

Summary:

1. I need the VDO specification.

2. Suggestions for getting more current out of device. My Vi is limited to about 5 Volts, out of my control.

3. Parallel operation of two of the devices. Join outputs with small resistors?

  • 0
    TI__Expert 7445 points

    Michael,

        

    For TPS76901-HT  typical dropout voltage at 100mA is indicated to be 71mV  as highlighted in the datasheet.  Figure 1 shows the variation on the output voltage thus Rds_on of the internal PMOS will increase with temperature, thus typical curve shown per figure 1 highlights variation of approx. 350mV   i.e. (3.75V - 3.4V) over temprature.

      In your application with Vin = 5V and Vout = 3.3V  I do not see an issue in that configuration.   Can you confirm using a scope that there is no oscillation issue that you see on the output.