Dear sir or madam,
I would like to ask you to check the schematic for the TPS61033.
Please check the following and give me your advice.
1. Application : TPS61033 supply 4.9V to the TDD based Power amplifier (Max TX duty : > 75%, Typ. 12.5%, Time duration : Typ. 5 mS)
2. Max I(OUT) : 2A @ 4.9V
3. schematic
There are more capacitors such as the 100uF, 22uF, 100nF, 1nF near the power amplifier module.
4. Questions
(1) Inductor
In accordance with your datasheet page 17, It's written as "Nomally, it is advisable to work with an inductor peak to peak current of less than 40% of the average inductor current for maximum output current.".
And you recommended the inductors as follows.- If want to cover up to 2A current, recommended to use the XGL4020-471MEC - 0.47uH inductor in your datasheet.
But, in Our schematic, I will try to use the XGL4012-451MEC because of the placement issue on our terminal.
It has a poor DCR and lower ISAT than XGL4020-471MEC.
What i am worried about with this inductor is the poor DCR and Higher peak to peak current across the inductor.
I'd love to hear your thoughts about using this inductor.
Please refer to the following table.
A1. Is there any problem despite the high inductor peak-to-peak current being close to 60% of the average output current?
A2. Do you have any recommendation for DCR of Inductor when it's supplied 2A?
(2) Feedforward Capacitor
In your Evaluation Board, when I set and tested the dynamic constant current 2A (cycle : 50ms ->2A, 350ms -> 0A ) by using electrical load, i could find out the voltage drop at Vout.
The voltage drop fluctuation(voltage drop and rise) is about 1.2Vpp.
I want to use a feedforward capacitor to get a more stable output voltage.
In your EVM schematic, it seems that you tried to use the 100pF series with 4.75kohm, although there is no use at last.
I also tried using the feedforward 100pF capacitor as you did, but it rather tended to make the output voltage and current unstable.
In my previous experience, It's found that feedforward capacitor could only be used near a 10pF. And it only helped to reduce the fluctuation around 300mVpp.
A3. Do you have any recommencdations for feedforward capacitor to reduce the voltage drop at the output?
Thank you,
Best Regards,
