[sdiy] SSM2164 last time buys

[Steve Lenham]

I would instinctively shy away from putting a non-negligible value of 
resistance in the supply to any IC - it converts the naturally varying 
supply current into voltage modulation, which may or may not cause 
problems or feed through to outputs. But I think you are on the right 
lines...other options would be:

1. Put in the resistor but add a largish decoupling cap at the supply 
pin to reduce the impedance at the frequencies of interest (yuk)

2. Replace the resistor with a simple constant-current source set above 
the maximum normal operating current but below that which causes damage. 
The source would operate in saturation most of the time (because the 
current drawn by the 2164 would be less than the set current of the 
source) but, under fault conditions, would limit the supply current and 
protect the 2164.

3. Give each 2164 considered to be vulnerable its own supply voltage 
regulator, choosing regs with a low enough current limit to protect the 
chip.

I have seen option 3 used in pro audio equipment where balanced line 
drivers are prone to latch up and release the smoke from the output 
device (SSM2142 or similar) - rather than power all the outputs from a 
single pair of 1A 7815/7915s, they were divided into groups each fed by 
100mA-rated 78L15/79L15s.

In this application I would go for option 2 though.

Cheers,

Steve L.
Benden Sound Technology
www.bendensound.co.uk


On 01/03/2011 00:51, Oscar Salas wrote:
> Hey Tim thanks,
> Yes I have the same question, it would be great the solution just with one resistor. If not the other solution would be the resettable fuse. Lets see more opinions!
>
> --- On Tue, 3/1/11, Tim Ressel<madhun2001 at yahoo.com>  wrote:
>
>> From: Tim Ressel<madhun2001 at yahoo.com>

>> Excellent work Oscar! This will be a
>> relief to many I'm sure. The only question
>> I have is does the current limiting resistor affect normal
>> operation?
>>
>> --TimR
>>
>>
>> ----- Original Message ----
>> From: Oscar Salas<osaiber at yahoo.es>
>> To: Synth DIY<synth-diy at dropmix.xs4all.nl>;
>>
>> As a summary I would say:
>>
>> A) With a resistor in series with the positive supply the
>> chip is protected
>> restricting the current. I would say that a value about
>> 510Ω or 1K would do the
>> job.
>>
>> Question: There is any inconvenient in use a resistor?
>> could it affect the
>> performance of the VCAs
>>
>> B) I didn't test it but another solution would be a
>> resettable fuse but in this
>> case stay within 10mA or 50mA per chip. Maybe better one
>> fuse per chip.