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Original question:

LDC1614: Switching sensors on channel 0 using analog MUX - TMUX1136

LDC1612: status register does not change (stays on 0)

alon vain
Prodigy 10 points
Part Number: LDC1612
Other Parts Discussed in Thread: TMUX1136, LDC1614, LDC1312

greetings!

We are currently working on a device that uses the ldc1612 to measure 2 coils with an inductance about 200nH.

due to a low Q factor we use the "high current" mod (on channel 0) and an analog mux - TMUX1136 in order to switch between the 2 coils.

when running, we get nice a steady oscillation; a picture can be seen here:

  

with freq of 13.6Mhz and max steady voltage if 1.73V

despite that status register (0x18) stays 0 forever (not even ERR_WD changes).

some information that I found while testing:

   1. I have tried on different ldc1612 and I got the same problem 

   2. I tried the same code but with ldc1614 and I got results (status register changed from 0).

   3. I tried other coils with with ldc1612 and still the status did not changed from 0.

any ideas why and how can I fix it?

my configurations are as below:

mux_config = 0x020F;  [20F = single cannel. deglich config 33 MHz] 

sensor_config = (0x3EC1); [3EC1 = channel 0 is selected. sleep mode on. RP Override on. full current off. auto amplitude off. external clk. INTB off. high sensor drive on] 

stabilize_time = 0xffff ; // For starters set the max time

conversion_time 0xffff; // For starters set the max time

driver_current 0xF800) //full current on channel 0

external reference clock of 40Mhz

target distance is about 90mm 

thanks for helping and have a lovely day!

Alon

  • 0
    TI__Mastermind 43470 points

    Hello Alon,

    Can you describe your hardware and provide a schematic?  You mention that the same coil works properly with LDC1614.  Is this using the EVM or some other hardware?  Does this also use the TMUX device?  

    When using single channel operation, please note that the reference clock must be 35MHz or lower.

    Also, please note that the max sensor frequency of the LDC1312 is 10MHz.  

    You may also consider adding a series inductor to increase your Rp and Q.  This could also help get your resonant frequency within the datasheet specifications.

    Last, your target distance is fairly long.  I would assume that your coil is also small since the inductance value is so low.  Typical sensing range is about 1/2 of the diameter of the coil.