# DCDC controller--TPS61030

Registered Users Posts: 1

Hello~

I want to use DCDC controller--TPS61030 to make a power circuit, the schematic diagram is as following. As we can see,the input is between 2.0V~3.3V and the output is 2.2V. What’s more,the biggest load current is 50mA. Because considering the volume,I want to choose the smaller compenents. Generally,The wire wound inductors in the DCDC circuit is big. But the load current I required is small,I don’t know if the stacked inductor is suitable for me like 0603/0805?  I have seen that the stacked inductor is about 100mA. If it’s not suitable, what problems will happen here?

Can you help me? Thank you in advance.

• Solar Expert Posts: 479 ✭✭✭✭
edited May 17 #2
Hi grass,
I can't answer your question but there are a few members here that might be able to help. In the mean time you might check out the All about circuits forum. Here's the link,
12 x 300W Renogy PV, MNE175DR-TR epanel modified, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 195AH HI Power LiFePO4 no BMS, 4000W gen.
• Super Moderators Posts: 26,873 admin
edited May 17 #3
This is a boost type switching regulator. Generally, such a regulator only "regulates" when the output voltage is higher than the input voltage. When the input voltage is equal to or higher than the output voltage, the output voltage follows the input voltage (no regulation).

If you notice on page Page 11, section 11.2.2.3, the inductor selection equation basically breaks down if Voutput is 80% of Vinput (the current through the inductor is less than the output current).

On the next page, If Vout is equal to Vin for the inductor and capacitor selection, the equations give you ZERO (0) as the answer for the component sizes--And give you a negative inductor and capacitor value if Vout<Vin.

If you need the input is between 2.0V~3.3V and the output is 2.2V, then you need a Buck-Boost type switching power supply. Basically the buck part regulates the output voltage if Vin>Vout. And the boost section regulates if Vin<Vout.

Too small of inductor current rating, the inductor will "saturate" (no longer behave as an inductor) and will not store any energy over its rated current (and may overheat). And will not be able to "boost" the Vin to Vout voltage (at your desired output current) and Vout will fall at higher current levels (no longer regulate).

Can you parallel two smaller inductors--Possibly (concerns on my part--I have not designed a switching supply in 30 years), but the circuit layout will need to be carefully done. You will need to ensure both inductors share the same amount of current (equal resistance between supply voltage and chip input PWB paths to inductors). Another issue could be magnetic coupling between the two inductors (could cause higher magnetic fields between the two inductors and cause them to saturate earily, at a lower current level). And two inductors in parallel can "ring" because of stray capacitance (LC circuit).

Check your power needs with a Texas Instruments application engineer. They should be able to help you.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 877 ✭✭✭✭
If you want tiny, take a look at the tps63036.