¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. SoftwareControlledHamRadio
  2. Topics

DDS VFO Mini-360 Buck Regulator

[email protected]
 

Wondering if there are any specs on the Mini-360 buck regulator that comes with the DDS VFO board. I've been looking at similar Mini-360s on eBay (although different design) and the specs for those units say that they can handle anywhere from 4.2v to 40v vDC input. I'm thinking about various sources of power for the 40m QRP transceiver - anything from wall-warts, to batteries, to large switching power supplies and I want to be sure that the mini-360 supplied with the DDS board can take the same type of input without going up in smoke.?

73s,


Aaron - N2HTL
Gary White
 

¿ªÔÆÌåÓý

I found this re the Mini 360 on the web. With respect to using Wall Warts, or any switching power supply I have found the AD 9850 boards from China will generate some serious spurs and really like a well regulated and filtered power source. ?I use a non-switching PS and step down the 12 VDC to 5 or 3.3 for any of my Arduino or AD 9850 projects. Now, having said that. The DDS-VFO has some good filtering and the use of a switcher (remember the Mini 360 is a switching device) has resulted in minimal spurs. They are there, but about 40 dB or more down form the fundamental.

Specifications

  • Chipset: MP2307DN
  • Input voltage: 4.75V-23V
  • Output voltage: 1V-17V
  • Output current: peak 3A, continuous 1.8A
  • Efficiency: up to 95% (@ Vin=5V, Vout=3.3V, Iout=300mA)
  • Switching frequency: 340KHz
  • Output ripple: 30mV (no load)
  • Supply current: 1.5mA (no load)
  • Working temperature: -40¡æ ~ +85¡æ
  • Module Size: 17*11*4mm
  • Mounting: 15.24 x 8.9mm (0.6 x 0.35in)

Notes

Looking at zoomed picture, this looks like typical application from datasheet - except R1 has been replaced by trimpot. Soft-start is enabled.

Internal Resistance

Despite it's tiny size this step-down DC regulator is no pushover. We tested one unit at 12.00Vin and 5.00Vout, with 4.6¦¸ load, voltage dropped to 4.98V and input current went to 0.5A. That is approx 90% efficiency and less than 20m¦¸ internal resistance.

Regulation

When set to 5.00V and input dropped to 5.00V, the output had 4.05V. Input range 6V to 20V, output voltage moved 5.00 - 5.02V.

Short Protection

This module can take some abuse too: when shorted, the input current went to 0.99A first and then slowly dropped to 0.3A as chip and inductor were heating up. After removing the short, the circuit worked as expected.

No-load Consumption

With input at 12V and output set to 5V, the module took 48mA without load. The 100uF/25V electrolytic capacitor lowered this to 21mA. With 47¦¸ output load, the input current was 82mA without 100uF, and 72mA with 100uF.

Other Notes

Built-in trim-pot is very sensitive and for fixed output applications we recommend to hold it's position by drop of glue or cut it out and replace with fixed value resistor. See the MP2307 datasheet for the math.

Conclusion

I would not recommend this module under 50mA load as linear regulator will do a better job in that range, but going over 50mA this regulator will work excellent. Also recommending additional electrolytic at least 100uF/25V at the input.

1 - 2 of 2