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Johnny_B_Goode 17/11/2019
The module that was shipped out to me, although physically similar in layout, used a similar 8 pin (but umarked and with a different pin out) to the MP1584 shown in the product photos. The trimpot was faulty, causing great difficulty in setting the output to 5.15 volts and prone to generating excessive voltage at random points of the adjustment range. I replaced the trimpot with a 33KR smd resistor and added a 200KR across the 6K2R smd resistor between ground and the Vref pin to trim it to 5.2v. Having modified it to give a reliable 5.2v output, I then discovered that it had excessive ripple, 400mVp-p no load rising to 800mV or more with a 1A test load. I gave up on this module and tried another one which had option solder bridge jumper links for 3.3, 5, 9 and 12 volt outputs along with an adj option where I discovered the pot had been replaced with a 39KR to preset it to 5 volts, saving the need to bridge any of the voltage option jumpers. This had much less voltage ripple but unfortunately I managed to burn out its very tiny IC when probing with a DMM to track down why it had suddenly taken a dislike to my add on LC filter. It had worked ok until then but now it was back to this variable voltage converter module where I discovered that the shottky diode had been left disconnected from the inductor via an open solder bridge jumper which I bridged with a blob of solder and saw a 6dB reduction in output ripple voltage. Still not marvellous but with the additional LC filtering, it was down to a p-p of 24 to 90mV (rms of 2.5 to 4mV). I'm fully aware of all the pitfalls in using a 'scope to examine ripple voltage waveforms hence my use of a 12v SLA to power it to minimise ground loop interference from other smpsu sources (including the 'scope's own psu). To say I was unimpressed by the example I'd received would be an understatement! I suspect the one actually pictured will be a lot better (just make sure the pot isn't a "timebomb in waiting" before using it).
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  • valbuz hi.i have some problems with the product: Mini DC-DC1.3A Voltage Converter Step Down Module 12V 24V to 5V 3.3V 9V with Integrated Inductor for 360 RCfor all settings the output will still be 2.8V. what going wrong here?thanks for helppat

    Ответить 11/12/2019
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