TPS76933 Min Input Voltage

Chatto

The min input voltage for the TPS76933 is stated at 4.3V. If 3.3V were to be supplied to the input, what will the output of the TPS76933 be, assuming 30mA load when the chip being driven by the LDO is ON?

Thanks for helping out!

over 14 years ago

0 Jeff F over 14 years ago

TI__Guru**** 168436 points

The minimum input voltage at which the regulator can regulate its output voltage to 3.3V is actually 3.3V + Vdropout @ 50mA = 3.3V + 100mV = 3.4V. The Vin=Vo+1V specification apply to the other tested specifications.

0 Chatto over 14 years ago in reply to Jeff F

TI__Genius 12545 points

Thanks Jeff.

Therefore the TPS76933 cannot be used for this particular application as the supply voltage is lower than the 3.4V.

0 Chris Glaser over 14 years ago in reply to Chatto

TI__Guru**** 151170 points

What power specs (Vin range, Vout, Iout) do you need to meet? There is a power quick search at power.ti.com that can help you find the right part.

Also, you need to consider what minimum voltage your load requires. It won't be 3.300000V. It will likely be 3.3V +/- some %, such as 5-10 %. In this case, you could use an LDO since it meets your load's needs.

We also have buck-boost charge pumps and buck-boost switchers that will work for you.

0 Chatto over 14 years ago in reply to Chris Glaser

TI__Genius 12545 points

Chris,

The problem here is that we already have an existing board http://focus.ti.com/docs/toolsw/folders/print/cc2540usb-rd.html which uses the TPS76933. For typical applications the board was going to be driven by USB where the supply voltage is greater than 3.3V, the LDO would work perfectly fine.

However, we have a customer who wants to know if they can use it with 3.3V without having to hack the board. Unfortunately since the supply voltage of 3.3V is less than the 3.4V min for this device to function, we wont be able to use the existing board for this supply application.

0 Chris Glaser over 14 years ago in reply to Chatto

TI__Guru**** 151170 points

The device will still 'function' (be on) at 3.3V in. The issue is that Vout will be about 3.2V at a 50 mA load. You will need to see if your load can accept this lower voltage.

0 Chatto over 14 years ago in reply to Chris Glaser

TI__Genius 12545 points

Ah yes!

The control will turn on the LDO MOS as hard as possible. There will be no voltage regulation, but the circuit will work. Thanks for settling this for me.

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TPS76933 Min Input Voltage