Author Topic: MT494MT  (Read 1320 times)

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Offline csaba911Topic starter

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MT494MT
« on: July 27, 2021, 02:24:25 pm »
Hi everyone, first post  8) need help  ;D
Looking for pinout/datasheet/schematic for MT494FP (not Ti's 494)
Want to increase over voltage shut down from 15.5V to 16.5V hopping its not internally determined and some external voltage divider values can be changed to achieve it.
The chip used in a DC-AC (12v-120v) 150W inverter, the battery bank 16.4V fully charged so the inverter shut down seconds after power up.
 
Thanks in advance..
Steve
 

Offline csaba911Topic starter

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Re: MT494MT
« Reply #1 on: July 27, 2021, 02:29:33 pm »
Some pictures might help, pin 1&16 output to the Fet’s, pin5 GND, pin12 VCC (from 7805)
 

Online Zero999

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Re: MT494MT
« Reply #2 on: July 27, 2021, 03:35:51 pm »
Are you sure all of the components can tolerate 16.5V, without smoking?

It's possible the over/under-voltage circuit is elsewhere. Are there any comparator ICs on the board?
 

Offline csaba911Topic starter

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Re: MT494MT
« Reply #3 on: July 27, 2021, 07:51:30 pm »
Yes, input caps are 25V, 78L05 30V
Tried up to 24V nothing smoking or overheating but output shuts down at 16.5V
 

Offline csaba911Topic starter

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Re: MT494MT
« Reply #4 on: July 27, 2021, 07:53:11 pm »
Some transition for the gate driver, 431 ref and 1 8.3V zener diode
 

Offline csaba911Topic starter

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Re: MT494MT
« Reply #5 on: July 27, 2021, 08:09:28 pm »
Top right dot-8 is a buck converter for the USB charger. I don’t think that’s shutting down the ac output
 

Offline fourtytwo42

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Re: MT494MT
« Reply #6 on: July 27, 2021, 08:19:28 pm »
What's the product data sheet say ?
Something external like a silicon diode might work, OK it's a power loss.
Usually these things blow up before stopping working so that's unusual.
Cannot find any chip data so could be custom or re-marked.
 

Offline fzabkar

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Re: MT494MT
« Reply #7 on: July 27, 2021, 08:39:42 pm »
This chip is very old ...

https://mirrorservice.org/sites/www.bitsavers.org/components/mitsubishi/_dataBooks/1987_General_Purpose_ICs.pdf

There is an M5T494P,FP on page 218.

Also https://www.semiee.com/file/EOL2/Mitsumi-M5T494.pdf  (M5T494P,FP,GP -- Mitsubishi, not Mitsumi)
« Last Edit: July 27, 2021, 08:52:55 pm by fzabkar »
 
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Offline csaba911Topic starter

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Re: MT494MT
« Reply #8 on: July 27, 2021, 10:26:40 pm »
Unfortunately that data sheets not for this chip, my pin 5 is definitely ground 0.1ohm to input wire negative.
The output is pin 1 & 16, pin 4 goes low during shutdown but pulling high (100 ohm) will not starting it up again, pin 11 probably over current protection (latching, need power down before recovery)
 

Offline csaba911Topic starter

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Re: MT494MT
« Reply #9 on: July 27, 2021, 10:35:25 pm »
The buck converter for the USB use TMI2243B, doesn't have over voltage shut down output pin.
 

Offline fourtytwo42

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Re: MT494MT
« Reply #10 on: July 28, 2021, 01:48:10 am »
This chip is very old ...

https://mirrorservice.org/sites/www.bitsavers.org/components/mitsubishi/_dataBooks/1987_General_Purpose_ICs.pdf

There is an M5T494P,FP on page 218.

Also https://www.semiee.com/file/EOL2/Mitsumi-M5T494.pdf  (M5T494P,FP,GP -- Mitsubishi, not Mitsumi)

Well done  :) A copy of a TL494 no less and certainly no overvoltage lockout, nor does any other SMPS control chip that I have ever come across.

P.S. OP Once more can you identify the product please (weblink or make/model etc).
« Last Edit: July 28, 2021, 01:50:09 am by fourtytwo42 »
 

Offline csaba911Topic starter

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Re: MT494MT
« Reply #11 on: July 28, 2021, 04:57:09 am »
Not much information from the vendor.
 
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Offline perieanuo

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Re: MT494MT
« Reply #12 on: July 28, 2021, 05:09:55 am »
hi, if tl431 magic word appeared, did you try to play a little bit with his output? this would definitively allow you to modify output voltage
 

Offline csaba911Topic starter

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Re: MT494MT
« Reply #13 on: July 28, 2021, 06:08:50 am »
pin13  ;D, 320mv for normal operation, shut down at 400mv
added 33k across the original res and now its operational all the way to 17.3V, prefect for the 16.8 fresh fully charged battery, the under voltage cutoff raised from 9.6V to 11.02V what is ok with me as the bottom end of the battery doesn't have much capacity.
 
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Offline fourtytwo42

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Re: MT494MT
« Reply #14 on: July 28, 2021, 10:45:17 am »
pin13  ;D, 320mv for normal operation, shut down at 400mv
added 33k across the original res and now its operational all the way to 17.3V, prefect for the 16.8 fresh fully charged battery, the under voltage cutoff raised from 9.6V to 11.02V what is ok with me as the bottom end of the battery doesn't have much capacity.
Well done, result! Good bit of detective work & reverse engineering  :clap: :-+
 

Offline fourtytwo42

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Re: MT494MT
« Reply #15 on: July 28, 2021, 10:47:38 am »
Not much information from the vendor.
OMG nothing to go on there  :horse: , good job you persevered with the RE  :-+
 
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Online Zero999

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Re: MT494MT
« Reply #16 on: July 28, 2021, 11:09:53 am »
pin13  ;D, 320mv for normal operation, shut down at 400mv
added 33k across the original res and now its operational all the way to 17.3V, prefect for the 16.8 fresh fully charged battery, the under voltage cutoff raised from 9.6V to 11.02V what is ok with me as the bottom end of the battery doesn't have much capacity.
Well done, result! Good bit of detective work & reverse engineering  :clap: :-+
It's a shame the identity of the IC is still a mystery.
 


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