I2C controlled switch

Thread Starter

fastbike

Joined Dec 29, 2020
72
I'm looking for a solid state switch to handle 5v low current signals (mA loads)

This needs to be a single pole double throw type of arrangement. There will be 4 independent channels.

Ideally control of each channel from state A to state B will be via the I2C protocol as there is an I2C capable micro in the design.

Google has failed me again.

I'm looking for suggestions for suitable surface mount ICs (no relays etc). Note this is NOT for the multiplexing of the I2C bus.

Thanks
 

Irving

Joined Jan 30, 2016
1,496
The signals to be switched are:
- analog or digital?
- single ended or bipolar around ground level (DC v AC?)
- frequency of signals?
- maximum allowable loss, or series resistance?
- maximum allowable delay or phase shift?
- speed/rate of switching?

How far from the MCU are the switches? Must they be I2C or can simple logic levels be used? An outline schematic of the signal source/destination circuits would help too.
 

Thread Starter

fastbike

Joined Dec 29, 2020
72
The signals to be switched are:
- analog or digital?
- single ended or bipolar around ground level (DC v AC?)
- frequency of signals?
- maximum allowable loss, or series resistance?
- maximum allowable delay or phase shift?
- speed/rate of switching?

How far from the MCU are the switches? Must they be I2C or can simple logic levels be used? An outline schematic of the signal source/destination circuits would help too.
I'm switching a 5v single ended analog signal as one of the inputs to a comparator. The switch is adjacent to the mcu (within 70mm)
The switch can either route RAMP_LE which is a rising slope sawtooth, or RAMP_TE which is a falling slope sawtooth waveform.
These are slowly changing signals (100Hz)
1621576910210.png
 

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Thread Starter

fastbike

Joined Dec 29, 2020
72
Logic Level MOSFET such as 2N7000, 60V, 200mA, 400mW, 1.9V Gth, in TO-92 case?
I'm trying to avoid discretes to keep the component count down.

Given that I can't find an I2C controlled SPDT analog switch I've come up with a list of possible candidates:
The device will have 4 channels so the Maxim part looks interesting but it does not compete on cost with the other two.
I'll need to use an mcu with 4 spare output pins.

Unless there are better alternatives I'll procure samples of the first two and proceed to prototyping.
 

Thread Starter

fastbike

Joined Dec 29, 2020
72
Then I've just found the ADG729 ($5.50 ea) which is a dual single pole 4 throw switch with I2C interface.
That might be worth reading the datasheet.
 
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Thread Starter

fastbike

Joined Dec 29, 2020
72
Another option I've stumbled across is a 4 bit I2C port expander such as PCA9536 ($1.88 ea). This could be connected to the I2C bus from the mcu, and then control any of the analogue switch options above, meaning I can stay with the original pinout of the mcu.
 

Irving

Joined Jan 30, 2016
1,496
Have a look at TI part TMUX1134PWR ($3.19) quad SPDT with individual selects in a 20pin TSSOP package. 5v supply, rail-rail i/o and 3.3v logic compatible.
 

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