• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 31 subscribers
  • Views 125 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMCS1101: Power on Time delay

Kinjarapu Jairam
Prodigy 10 points
Part Number: TMCS1101
Other Parts Discussed in Thread: TLV272,

Hi all ,

I am using the TMCS1101A2BQDR IC in our 3 Phase Inverter for motor control application for phase current sensing. I am facing an issue regarding the IC power on time. I have observed a varying delay time between the instant the IC supply voltage appears to the instant the IC offset voltage appears at the IC output terminals. In the datasheet it was mentioned the power on time as 25msec but I am observing a variable delay time with maximum of 3 seconds. In the image uploaded one can see a delay of 1second. Blue is the IC supply voltage and Pink is the IC output voltage. Can someone through some light on why exactly this is happening

Fig 1 : Delay of 1 second between Vcc(Blue) and Vo (Pink)

The IC output is driving one of the channels of the 2 channel opamp IC TLV272. I have removed the connection between these two ICs but still the issue persists. The issue is not consistent, sometimes there is only 25msec delay between the IC supply voltage and IC output like it was mentioned in the datasheet.

Fig 2 : Delay of 25msec (matching with datasheet ) between Vcc ( Blue) and Vo( Pink)

  • 0
    TI__Mastermind 18780 points

    Kinjarapu, 

    Thanks for using E2E. The 25ms is set internally via digital logic once a valid power supply is provided to the device. My theory is that the noisy nature of the supply may be resetting or holding up this flag. Looking at the waveforms, the supply voltage seems quite noisy, and it also looks like there is some large HF ripple on the DC. I'm assuming this is coming off of a switching converter. Have you tried tightening up the ripple, or filtering this voltage prior to energizing the TMCS1101? Do you have a bypass capacitor installed on Vs by the pin?

  • 0 in reply to Carolus Andrews
    Prodigy 10 points

    Hi Carolus,

    Thanks for the reply.

    Regarding the power supply , earlier the measuring probe was  having bigger ground loop. Now we have measured with the spring probe with AC coupling and the noise magnitude is around 100mV peak to peak and it is coming at the instant of flyback mosfet switching which will be having fast dv/dts . The flyback converter is used to generate the power supplies to all the subsystems. So this noise of 100mV will effect the IC operation ? Even when we kept 10uF bypass capacitor, we got 1 second delay but the issue is not consistent. It is coming once in 5 to 6 attempts.

    fig: power supply noise in ac coupling

  • 0 in reply to Kinjarapu Jairam
    TI__Mastermind 18780 points

    Kinjarapu, 

    I dont think 100mV would cause the issue, no, but the power supply is the main variable pertaining to turn on time. May I ask how/where you are capturing this waveform? Also, how is the TMCS1101 configured here? Is this on an EVM, on your own PCB? Where are you capturing this measurement with the tip and barrel?