TPS560430: 5V then to output to 3.3V LDO

Dharmesh Joshi

Expert 1845 points

Part Number: TPS560430
Other Parts Discussed in Thread: TPS560200-Q1

Dear Sir/Madam

Our PCB requires 5V and 3.3V. Max Vin can be 24V

The 3.3V will be used for all the wifi and uC circuits, max 350mA

The 5V is needed as a pullup on a PWM signal to a fan, max few mA.

I intended to use this device to generate the 5V, then use a simple SOT23 LDO to generate 3.3V. Would this be the best way or can you offer any better suggestions?

Can we also use following inductor with this device?

Murata

LQH43PN100M26L

over 3 years ago

0 Victor Yu over 3 years ago

TI__Expert 4731 points

Hi,

1. If the lower efficiency caused by LDO is not a problem for you, it would be a good solution. Another choice is that you might use flybuck topology to generate a 3.3V and an isolated 5V.

2. If you use 2.1MHz version, the device is acceptable.

BR,

Victor

0 Dharmesh Joshi over 3 years ago in reply to Victor Yu

Expert 1845 points

Can you please give an example what you mean by flybuck?

5V is only used for PWM signal, but the reset is 3.3V.

I am thinking maybe use TPS560430, for 3.3V and use a simple cheap LDO for 5V,

Would there be alot of heat for 5V, when current is just few mA?

0 Denislav Petkov over 3 years ago in reply to Dharmesh Joshi

TI__Mastermind 19891 points

Hi Dharmesh,

To answer your questions:

1. Here is an example of flybuck: https://www.ti.com/lit/an/snva790/snva790.pdf

2. The TPS560430 will work well for both 3.3V and 5V with high efficiency. You can generate the 5V and use a low input voltage converter to do 5V to 3.3V. You can use the webench tool https://webench.ti.com/power-designer/switching-regulator to select a part.

3. The power dissipation in an LDO would be (VIN-VOUT) x IOUT. The heat will depend on these application conditions and the board size.

Cheers,
Denislav

0 Dharmesh Joshi over 3 years ago in reply to Denislav Petkov

Expert 1845 points

Dear Denislav

Thank You for your reply. We have changed our design to use TPS560200-Q1 to achieve 3.3V(https://e2e.ti.com/support/power-management/f/power-management-forum/998267/tps560200-q1-design-advice/3688725#3688725)

THe 5V was to going to be used for a pull up for PWM signal, therefore we will using resistor and Zener diode circuit,

0 Denislav Petkov over 3 years ago in reply to Dharmesh Joshi

TI__Mastermind 19891 points

Sounds good. Thank you.

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TPS560430: 5V then to output to 3.3V LDO