[NTLK] eMate 300 charger

Ionos: robowerk.de m.melcher at robowerk.de
Mon Mar 1 16:06:28 PST 2021

On 3/2/2021 12:09 AM, Pawel Piotrowski wrote:
> Can anyone explain me that document, please? http://www.unna.org/unna/apple/documentation/n2platform/n2-padg.pdf

I am not a power supply guy by any means, but I have also spent some 
time over this graph. All the documents in this archive are preliminary 
and unverified. There are values that are still marked tbd, to be 
determined, so caution is in order.

> 1. Following this grap from page 2, can I power Newton from 3V power adapter and Newton will work?

I understand this, that a power supply that delivers power in the dotted 
range will not do any harm to the MP. I don't think, the MP will work 
with 3V, but it won;t be harmed either.

> 2.I can understand that Newton need current limitation to 1.3A, but why on 5V level that must be between 1.1-1.3A? Why the current at this level can’t be lower?

If the MP pulls less power, that's fine. But your power supply must have 
a current limiter set to something between 1.1 and 1.3 Amps. Meaning, 
it's ok if it limits power to 1.1A, and the MP will work. If you set it 
to less, the MP will no longer get enough power at all operational 
stages (two PCMCIA cards in the slot, charging, backlight). It's also 
must no allow more than 1.3A, or the MP will get smoked. In conclusing, 
just set the power limiter to 1.2A with an accuracy better than 8%.

> 3. Can I use constant voltage/constant current (something like this: https://ebay.us/WSPeep, set to 5V and 1.2A on output) to power Newton via power adapter socket by using USB power bank as a power source?

Under DC Output Requirements it states that the voltage must be between 
6.75V and 7.5V. I think that setting this DC/DC converter to 7V, 1.2A 
will do the job and not destroy you MessagePad. Hopefully.

You should absolutely measure the voltage when there is nothing 
connected (should still be 7V, but bad power supplies can deliver 12V 
and more if there is nothing hooked up == dead MessagePad). You can also 
check, if the power limit works by connecting the output through an 
Amp-Meter in line with a powerful variable resistor. Starting with a 
high resistance, slowly going lower, should show how the Amps go up, but 
no more than 1.2A. Instead of a resistor, you can connect one or more 
12V lightbulbs in series to the Amp-Meter, and in parallel to another.

  - Matthias

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