AVR-Chat

----- Original Message ----- 
From: Valerij Avrealij
To: Leon Heller
Sent: Sunday, February 13, 2005 11:53 AM
Subject: Re: [AVR-Chat] ISP problem: very high current when ISP switched ON 
(more 200mA)


Hello, Leon.

You wrote:



>> Hello 2all.

>> When I in system program my tiny15 the current    more than 200mA!!!
>> The chip and 7805 are hot. I use Altera ByteBlaster    programmer with 
>> special PC software.
>> Very interesting: when I connect    swiched ON ISP the current is normal,
>> when I OFF it and then ON the current    more than 200mA
>> How this problem can be solved?
>> P.S. Using this ISP    cable I successfull program mega8 chip.

> It sounds like the chip is going into  latch-up.

What you mean? What is  "latch-up"? Early this situation repeated with
90s2343. What it can be?
For info: Just after few seconds after new (just buyed) chip was
connected to the programmer the current ups to >200mA.


With CMOS devices, it is possible in some situations for the substrate to 
become biased so that the device behaves like an SCR, think of a 
forward-biased diode. Lots of current is drawn and the device can 
self-destruct. If power is removed quickly, they often recover.

It can be caused by applying a voltage to an I/O pin before the chip is 
supplied with power, and there are several other causes:

http://www.analog.com/library/analogDialogue/archives/35-05/latchup/

Leon 



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