Need 2>1 analog mux for higher-than-VCC signals
Need 2>1 analog mux for higher-than-VCC signals
(OP)
Well dang it. Didn't quite read the datasheet closely enough.
I have a car datalogger design that uses the DG333A quad 2>1 mux switch to multiplex the 16 input signals to 8 opamps for signal scaling for the ADC. The part I didn't notice was the voltage limitation on the signal inputs ...
They can only range just above/below VCC and GND. Since the datalogger is a 5V system, that kind of clobbers it for measuring vehicle 12V and above signals :( The DG333A was chosen for the nice low 25ohm R-on value, and the fact that it had 4 switches in one package.
So, before I set about redesigning the analog input section, does anyone know of a quad (or any) 2>1 mux switch that can handle higher input voltages ? Those inputs are fed via 180k resistors, so the total current is quite small.
If not, I have to rethink the analog input design strategy. The requirement are :
16 inputs
jumper selectable input ranges (0-5V, 0-14V and 9-14V)
feed to 8 ADC inputs
I suppose I could put the opamps up front, and feed their outputs to the mux switches, but that doubles the opamp footprint, along with the attendant scaling resistors etc :(
Dean.
I have a car datalogger design that uses the DG333A quad 2>1 mux switch to multiplex the 16 input signals to 8 opamps for signal scaling for the ADC. The part I didn't notice was the voltage limitation on the signal inputs ...
They can only range just above/below VCC and GND. Since the datalogger is a 5V system, that kind of clobbers it for measuring vehicle 12V and above signals :( The DG333A was chosen for the nice low 25ohm R-on value, and the fact that it had 4 switches in one package.
So, before I set about redesigning the analog input section, does anyone know of a quad (or any) 2>1 mux switch that can handle higher input voltages ? Those inputs are fed via 180k resistors, so the total current is quite small.
If not, I have to rethink the analog input design strategy. The requirement are :
16 inputs
jumper selectable input ranges (0-5V, 0-14V and 9-14V)
feed to 8 ADC inputs
I suppose I could put the opamps up front, and feed their outputs to the mux switches, but that doubles the opamp footprint, along with the attendant scaling resistors etc :(
Dean.





RE: Need 2>1 analog mux for higher-than-VCC signals
it to e.g. 4.5 V with Schottky-s or 4 V with regular
diodes.
<nbucska@pcperipherals.com>
RE: Need 2>1 analog mux for higher-than-VCC signals
RE: Need 2>1 analog mux for higher-than-VCC signals
Supertex has some high-voltage switches, but don't appear to hav ethe 2>1 muxes. I'll keep looking.
Thanks -
Dean.
RE: Need 2>1 analog mux for higher-than-VCC signals
Select R1 and R2 according the load.
<nbucska@pcperipherals.com>
RE: Need 2>1 analog mux for higher-than-VCC signals
D.
RE: Need 2>1 analog mux for higher-than-VCC signals
Try looking at the HCF4051B from STMicroelectronics.
It is an 8:1 MUX but you could easily cascade two of them together.