MC34063A DC-DC converter for 1.2V generation

Ajesh Babu

Other Parts Discussed in Thread: MC34063A, LM25085A, TPS54540

1. We are using MC34063A DC-DC converter IC for 3.3V output generation from 40Vinput, we would like to know can we generate 1.2V out put from same IC?

2. As per datasheet MC34063A can deliver maximum peak switch current of 1.5A with internal MOSFET

Currently We are using external MOSFET for driving 1.5A average current(3A peak)

but now we need output current of 2.5A average current(5A peak), our query is

Can we useexternal MOSFET of higher rating while changing current sense and Inductor to meet the requirement of 2.5 A average current?

over 10 years ago

0 Michael J Schultis over 10 years ago

TI__Mastermind 24975 points

Hello Ajesh,

1. You will not be able to generate a voltage as low as 1.2V as the internal reference voltage is 1.25V. The output voltage is dependent on the reference voltage. Please refer to the output voltage equations in the datasheet in section 9.2.1.2.

2. If you are driving an external FET, you should be alright as long as you make sure that the switching current from the MC34063A device through the Collector pin does not exceed 1.5A. Refer to Figure 5 of the datasheet.

Best,
Michael

0 Michael J Schultis over 10 years ago in reply to Michael J Schultis

TI__Mastermind 24975 points

Ajesh,

If you need to go down to 1.2V, you may want to consider a Step down controller such as the LM25085A or if you are looking for something with an integrated switch, then I would suggest looking at the TPS54540 or other similar devices in this parametric search:

http://www.ti.com/lsds/ti/power-management/converter-integrated-switch-products.page#p238max=40;60&p634min=0.8;1.2&p451max=5;6&p1498=Catalog

Best,
Michael

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MC34063A DC-DC converter for 1.2V generation