Question, MC34704 VIN current

Aemj — Wed, 26 Aug 2015 03:10:55 GMT

Hello team,

I have a customer who is using MC34704 with i.MX25.

And 5V is supplied into VIN of MC34704, and REG2,3,4 are used on his board.

In that case, where can I find the description which can be helpful to estimate the current flowing into PVIN2,3,4(VIN)?

Thanks,

Miyamoto

Re: Question, MC34704 VIN current

art — Thu, 27 Aug 2015 08:56:40 GMT

The estimation is quite simple in that case. Let's consider it on "per regulator" basis.

1. First, calculate the power that the regulator 'x' provides to a load: Pout_x = Vout_x * Iout_x, where Pout_x is the output power of a regulator 'x', Vout_x and Iout_x - its output voltage and current, respectively.

2. Then, assuming the typical conversion efficiency of regulator as 80% (denoted in the data sheet), multiply the Pout_x by 1.25 (1/0.8) to calculate the power that the regulator 'x' consumes on its input: Pin_x = Pout_x *1.25 .

3. Now, knowing the input power and input voltage, we can calculate the input current: Iin_x = Pin_x / Vin_x .

Assuming the input voltage of 5V, the final calculation for a regulator 'x' is as follows:

Iin_x = (Vout_x * Iout_x * 1.25) / 5 = (Vout_x * Iout_x) / 4 .

Have a great day,
Artur

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