I had design a product according to the TIDA 00663.And now I'm debugging the calibration function.However,when I give TPS22968 the start signal,and it do output the 3.3V VOUT at the rate of 3.3V/120us,but I could not detect the pulse signal at the position of R5 or R6,let alone between C8 and C10.Is there anything I mistake?
For the debug of the calibration function I suggest to power the board externally with 3.3V. Then you should see the pulse signal between R5 and R6.
In reply to Giovanni Campanella:
Hello,Giovanni Thanks for your timely reply .Well,in my design, 3.3V power com from the TPS73701 .Does it work for this function? And in addition, I use the Multisim to stimulate this circuit, I could see a pulse signal about 30 mV between R5 and R6 ,but for there is R14 of 0.01 after the R6, the laser ON signal will be too small to detect.Does my stimulation make an error?
In reply to user4289837:
Please ensure that your TPS73701 is providing 3.3V and enough current for your circuit.
30mV pulse between R5 and R6 is too few. How are you measuring the 30mV? Could you please add a series resistance to your scope probe to isolate the probe capacitance from the circuit?
Also the input of the OPA857 should be biased around 2.1 to 2.5V.
Please make sure the node is discharged before you perform the measurement between C8 and C9.
This TI design reuses the TDC7200EVM firmware source code. The complete TDC7200EVM firmware source code zip is part of the TDC7200EVM-GUI install folder C:\Program Files (x86)\Texas Instruments\TDC720xEVM\Firmware.
Simulations have been done with TINA TI. Attached the simulation of the part of the circuit you are referring at. Do you get the same thing with multisim?
node is discharged before you can try again.
Thanks very much for your patient instructions ,but I'm confused more.Does not I understand this shcematic?Why I built up a different simulation model comparing 'tprop_calibration_pulse_laser_fire'.Am I totally wrong?
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