Author Topic: NDP 6020P P-Channel Mosfet Oddness  (Read 3493 times)

TomWS

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #15 on: May 09, 2017, 02:09:12 PM »
Another idea.

Power directly from a pin?  With battery backup the acquisition phase should be a few seconds at most @28mA and then drop to 20mA tracking.

I plan to add an active antenna.
I didn't check what the low power options were on this device, so I couldn't comment if you were using conventional batteries, but, if I recall correctly, you have marine SLA batteries being recharged by solar power, so, in this case, leaving the GPS on would be a nit...

Tom

gregcope

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #16 on: May 09, 2017, 02:18:34 PM »
Correct on the battery.  Solar pannels have died and need replacing, so low consumption is still key.  The battery is left unattended for long periods.

gregcope

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #17 on: May 09, 2017, 02:19:50 PM »
Antenna looks like it will consume 8ma;

http://php2.twinner.com.tw/files/onshine/ANT555-2006-NEW.pdf

I looked at the enable pin for the module, but this seems to only cut consumption to 400uA due to a 10k pull resistor on the board;

https://forums.adafruit.com/viewtopic.php?f=22&t=41452

gregcope

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #18 on: May 09, 2017, 02:45:32 PM »
TomS looking at your idea, soldering the Mosfet Drain to the 3.3V line should be easy.

I see two places to do this; See picture with Red arrows.

Would appreciate a hint/nudge as this is me guessing on Eagle.


TomWS

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #19 on: May 09, 2017, 03:17:48 PM »
TomS looking at your idea, soldering the Mosfet Drain to the 3.3V line should be easy.

I see two places to do this; See picture with Red arrows.

Would appreciate a hint/nudge as this is me guessing on Eagle.
LOL!  Just tie it to the 3.3V pin on the header...

gregcope

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #20 on: May 09, 2017, 03:38:17 PM »
Yes LOL I worked that out too ...

Oddness mind.

From the mosfet Drain to GRD I get 3.29v

Mosfet drain to the 3.3V pin I get only get 1.1V again.

Measuring the GPS draw is 28mA when searching for a fix.

gregcope

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #21 on: May 09, 2017, 04:00:05 PM »
Going a bit potty.

Made a breadboard version to rule out the Mosfet...

And it works (red LED).... GRH.

But only if I Mosfet Drain connected to 3.3V header as you suggest Tom.  Which does have the advantage of not using another regulator!

Conclusion - the mosfet on my veraboard, or the veraboard circuit is duff.

gregcope

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #22 on: May 09, 2017, 04:05:08 PM »
And this version had the battery backup powered and works like a champ - 3 secs for a warm fix.

perky

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #23 on: May 11, 2017, 06:32:40 PM »
Although a pin may be specified to drive 20mA,  this is to logic levels - you shouldn't generally use a pin to power anything that takes more than a few mA and also requires voltage close to Vcc, the MCU won't be able to supply it.
Mark.

gregcope

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Re: NDP 6020P P-Channel Mosfet Oddness
« Reply #24 on: May 12, 2017, 03:05:22 AM »
Thanks Perky.   Good to know.