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TPS62740 power consumption issue

Jin Ruan
Prodigy 250 points
Other Parts Discussed in Thread: TPS62740, TPS62730

Hi

I'm using TPS62740 and found the power consumption in bypass mode without load is strange.

Applicaiton usage:

1. Set output voltage to be 3.3 V with programing setting to the input signals.

2. Without load

Current test result:

Case 1:  ramp up the VIN from 0.1 V to 3.4 V, the VOUT will follow the input, the current is about 16 uA.

Case 2: ramp up the VIN from 3.4 V to 4.5 V, the VOUT is fixed to 3.3 V and the current is 1 uA ~ 6uA.

Case 3: ramp down the VIN from 4.5 to 3.4 V, the VOUT is fixed to ~ 3.3 V and the current is 1 uA ~6 uA.

Case 4: ramp down the VIN from 3.4 V to 2.5V, the VOUT will follow the input with 0.1 V loss and the current is about 280 uA.

Why the current in case 4 is that much? Is there something wrong?

 

Regards

 

Jin

 

  • 0
    TI__Expert 7110 points
    TPS62740 has not an dedicated bypass mode. It operates in so called 100% Mode (where the high-side FET is always on) when VIN is smaller than VOUT. A device which is designed for an application with buck+bypass is TPS62730.

    First, your measured values look slightly high to me. Please be aware that the internal impedance of typical DMM's already affect your results!

    TPS62740 has a higher supply current when VIN is clearly smaller than the target VOUT. This due to the fact that there is an additional internal current limit active to protect the circuit.