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Dear TI Engineers,
can you advice me to design the loop power for analog input with 12 channel total number, it' mean analog input connected with 4-20 mA 2 wire system with system power (2 wire analog input has 24v power).
what TI product you can suggest to me?
Fullilove,
Thanks for the TI attention, i will wait for the answer.
Regards
Mansur. H
Hi Mansur,
sorry for the delay!
I assume you plan a 12ch 4-20mA analog input module with integrated power to power the field transmitters.
Some questions:
- Is the 24V (green box in your drawing) provided to the module from the field side (a 24V PSU is connected to isolated side of the module)?
- Do you need to control the power sources (able to turn on/off) of the channels individually (or global sufficient)?
- Do you want to limit the power of each channel (or global sufficient)?
- Are the 12ch channel-to-channel isolated or group isolated?
You may also be interested in this blog.
Thanks,
Lars
Hi Lars,
for the power supply is 24VDC inside the analog module, so, the analog input 2 wire already has 24V dc without external power supply.
control enable or disable is more advantage if possible, the maximum current for each channel is not more 50 mA.
for 12 channerl we eant to design it for isolated and non isolated mode.
Regards
Mansur. H
Hi Mansur,
does it mean that the 24V are coming from the backplane side and are isolated? This means you have a isolated 24V*50mA*12 = 14.4W DC/DC PSU in the module...
For channel-to-channel isolated modules you would need to add an isolated DC/DC for each channel.
Maybe can can provide a drawing of the system power tree?
Have you seen the Analog Input End-Equipment Reference Diagram already?
For per channel control I suggest to use a high-side switch such as TPS4H000-Q1 with Rdson=1Ohm @ 25C.
Thanks,
Lars
Hi Mansur,
A boost converter with integrated FET can be used to get from 12VDC to 24VDC. Examples are LM5001 and TPS71175 for the given output current of min 400mA. This are non-isolated solutions.
If you need channel-to-channel isolated solution you need ~30mA output current per power supply. I suggest a LM25017 in fly-buck configuration. A good example how a fly-buck works is shown in TIDA-00129 with LM5107. See also application note AN-2292 to learn about fly-buck technology.
Regards,
Lars