[sdiy] DG408 issues

mark verbos markverbos at gmail.com
Fri Aug 11 11:30:19 CEST 2017


I don’t know about this guys. I use DG409’s in a production module and DG212 in most modules and I always send them +12v logic signals with no problems.  I even do PWM between two of them with a a comparator going into the EN pins. On DG212’s I tie the VL or “logic level” pin to the V+ which is right next to it at +12. Everything works fine, thousands of them out in the field, not getting hot or blowing up. 
I did once use the low voltage DG409’s on a prototype and all hell broke loose. I think that was your only problem. 

Mark




> On Aug 11, 2017, at 10:14 AM, Tom Bugs <admin at bugbrand.co.uk> wrote:
> 
> Where is this max +5V reading coming from for the Dig line?
> 
> Both Intersil & Maxim datasheets say "(V-) - 2 to (V+) + 2,or 20 mA, whichever occurs first"
> 
> Only a quick reading by me at the moment, but I couldn't see anything else obvious that suggested otherwise.
> As long as the digital control goes over 2.4V it registers HI.
> 
> I think the original issue is the Low Voltage chip variant - I had that issue once DG4xxLDY rather than DG4xxDY
> 
> Tom
> 
> 
> On 11/08/2017 05:14, Ben Bradley wrote:
>> "I had tied the enable pin directly to the +15 supply, but hacked in a
>> resistor to tie it to a divider that was already in use, after seeing
>> a comment online that the chip doesn't like large voltages on the
>> digital pins.  There's about 8V on the pin with 120k to +15."
>> 
>> The way I read the data sheet(s) for this DG series, there's a +V
>> input (+15v), -V (-15V) and GND, and these are for the analog switch
>> section. All digital inputs should be at least at GND pin and at most
>> +5V above GND pin. There's internal level translation for the
>> switches. 8V sounds way too high for a digital input, even if it's got
>> little current going into it through a high value resistor. I think
>> it's turning on something that shouldn't be turning on, and pulling
>> lots of current through the +15V and/or -15V power inputs, and that's
>> what's causing heating.
>> 
>> Make the resistive dividers so the digital inputs are at most +5V, and
>> at lowest, the potential of the DG's GND pin. Both Vishay and Intersil
>> say a digital input over 2.4V is a Logic 1, and below 0.8V is a logic
>> 0. I might make the 1 voltage 3.3V
>> 
>> On Thu, Aug 10, 2017 at 11:55 PM, Tim Ressel <timr at circuitabbey.com> wrote:
>>> Check the datasheet for the exact DG408 you have. Some have narrower voltage
>>> maximums.
>>> 
>>> --timbo
>>> 
>>> 
>>> 
>>> On 8/10/2017 8:47 PM, David Moylan wrote:
>>>> As mentioned in my other thread I'm using a DG408 to switch modes on a
>>>> Roland IR3109 filter.  Can't quite figure out why the DG408 is so hot. The
>>>> digital inputs are rather large as they're coming from the outputs of 3
>>>> opamps set up as a 3-bit ADC.  However, I'm sending them through large
>>>> resistors (220k) and they don't appear to be drawing much current,
>>>> approximately .13 mA.
>>>> 
>>>> Datasheet suggests that anything within the supply range is ok. However,
>>>> I'm not sure if the negative supply should be considered ground for the
>>>> digital inputs.  Even so, if I set the ADC to all positive outputs so
>>>> there's no negative voltage on the digital pins the chip is still just as
>>>> hot.
>>>> 
>>>> I had tied the enable pin directly to the +15 supply, but hacked in a
>>>> resistor to tie it to a divider that was already in use, after seeing a
>>>> comment online that the chip doesn't like large voltages on the digital
>>>> pins.  There's about 8V on the pin with 120k to +15.
>>>> 
>>>> Voltages at all pins appear normal, but the chip is very hot. Can't keep
>>>> my finger on it for more than a few seconds.  Other than that symptom
>>>> everything works correctly.
>>>> 
>>>> Anyone experienced problems with this chip?
>>>> 
>>>> Thanks.
>>>> 
>>>> Dave
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>> 
>>> --
>>> --Tim Ressel
>>> Circuit Abbey
>>> timr at circuitabbey.com
>>> 
>>> 
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at synth-diy.org
>>> http://synth-diy.org/mailman/listinfo/synth-diy
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>> 
> 
> -- 
> BugBrand LTD
> UK company No. 07199808
> VAT No. GB 988 2629 57
> 1 Ninetree Hill
> BRISTOL BS1 3SB
> United Kingdom
> www.bugbrand.co.uk
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy




More information about the Synth-diy mailing list