RFID Reader Documentation

David - 

you really can't do a PCB coil design for the TMS3705 unless you do a conversion ckt...that part is expecting between 400-700uH, which means you need a wirewound or ferrite + wirewound coil. 

see attached if you are interested...this would allow you to make a 47uH PCB antenna coil.

8424.TMS3705_Inductance_Translator.pdf

which you can use any L calculator to figure out ==> this one is pretty good. 

http://emclab.mst.edu/inductance/

First of all I would like to thank you about your response.

How can I place TMS3705 in CW Mode?

Does exist a newer revision for "scba020" application note, because this document does not mention anything about it?

Thank you for your attention.

Regards.

The TMS3705 can be placed into CW mode by lowering the TXCT line.

these may help you out, too...

1460.Notes on TMS3705A1DRG4 & Read.pdf

www.ti.com/litv/pdf/scbu052‎

David and Josh ... Refering to your 8424.TMS3705_Inductance_Translator.PDF ...which enables you to "see" the actual Tag reply.

We use a simple made, inductance pick-up probe and can also "see" the actual Tag emission, without being blinded by the incoming "Charge Flux".

A very small ThroughHole inductor (or SMD) typically 47uH in parallel with a 100 ohm "damping resistor" are soldered across a 50 ohm cable with a BNC at the other end.(into the oscilloscope).

Position the "pick-up probe" close against the rim of the RFID tag ensuring it is aligned 90 degrees to the incoming Reader flux ...now the pick-up inductor is best aligned to "see" the "close Tag" Telegram and worst aligned to see the "distant" incoming, but large,  charge flux. The pickup inductor is too small to have any significant effect on the tag  performance.

We use this in a simple jig to compare actual output emissions from suspect tags, and it is instructive!

While simple, and CRO sync is a bit vague, with cardboard and hotmelt glue, it is perhaps a good learning tool

Thanks for your other help Josh

Ray

the purpose of the inductance translator was simply to be able to use lower inductance antennas with the TMS3705...as you cannot use PCB to make 400 to 700uH...we have another transmitter module called the RI-STU-MRD1 (now MRD2) which uses 47uH coil...which can be etched on circuit board material....because of this experience and whatnot, that was why we chose this value for the coil and what performance we aimed at duplicating. this was not just for diagnostics or pickup this was just to avoid a wire-wound coil.  

Thanks Josh ... I have a MRD2EVM Microreader here. I see your 47uH PCB coil.

Out of curiosity, I cannot see the surface mount version of the TMS3705 on the MRD2 PCB,

Does it not use this HDX Reader chip, or have I missed something?

Ray

observant you are

the MRD1 used the RI-RFM-001A (which has EOL'ed), the MRD2 uses a discrete ckt. driven by MCU.

David, Josh ... if you were to accept a PCB say 300mmx300mm , I think you can get somewhere near 400uH using PCB concentric etching about 10 turns at 250mm Diameter and "nest" the TMS3705 etc in one corner.(will check it out if you wish).

Depends what you want to do... if you want 400uh on say 5cmx5cm pcb then might be difficult, though you could surely invoke the second layer of a double sided pcb and come close?

Seems like a lot of extra components needed to enable use of 47uH to be comparable with MRD2EVM evaluation pcb.... just interesting... Josh, where can I learn more about what's on the MRD2EVM that does not use a TMS3705? seems like a good way to go even for us!

Ray 

MRD2 product page ==> http://www.ti.com/product/ri-stu-mrd2

----

background on the translator...this was compared (performance wise) to the MRD1 at the time, because we we had made the S4100 module, which was dual freq/multi-protocol reader...the thought was that anyone using the MRD1 who wanted to add HF capability could use the S4100 module as is, and add the extra ckt, which would allow them to keep their existing LF antenna and end users in the field would not see any change in the way they used their LF tags...that's the entire reason for the translator ckt existence. 

Hi Josh, I appreciate your attention.

Now I´m working on hardware design for RFID reader based on TMS3705A, and for this reason I can´t validate RFID signals yet.

I need hardware design guide in order to implement my own circuit board.

I found “LF Technical Training TMS3705A Transceiver IC” document (attached), which depicts a circuit evaluation board on page 3, and I would like to have these circuit schematic.

6366.1016.LF TMS3705A ASIC.pdf

Please, could you provide me part number for coil and circuit schematic for circuit on page 3?

Regards.

you won't be able to buy that - its a handmade sample - you will have to wind your own coil and measure it, then do the simple calculation for resonance ==> fc = 1/2pi * sqrt LC 

the schematic is on page 16 here ==> http://www.ti.com/lit/ds/symlink/tms3705.pdf

4 outside connections and 8 parts - will it work for you?

Hi Josh, I really don´t understand how to write MCR register on TMS3705A, that is,

Also pin TXCT, is It necessary to set high or low another additional pin in order to indicate value to be written on MCR?

Do TMS3705 can read 125KHz RFID tags?

Regards. 

you don't need to write the MCR register - i found this older document which has the flow in it where you see if TXCT stay low long enough, it will skip over that 

6431.TMS3705_manual.pdf

5444.LF TMS3705A ASIC.pdf

no the TMS3705 will not read 125kHz tags as the frequency divider won't reach down that far.

the newer TRF4140, however, will.