Analysis of Common Interference Problems in TLV2548 Multi-channel Telemetry

VincentLee90

Analysis of Common Interference Problems in TLV2548 Multi-channel Telemetry [Copy link]

TLV2548 is an 8-channel input ADC from TI, and is commonly used for multi-channel remote measurement of analog quantities such as temperature and voltage.

The following timing is often used for multi-channel analog telemetry, setting t(Sample)=12SCLKs. The following briefly introduces some of the problems encountered. Figure 1 Timing relationship of TLV2548 used in the project 1. When TLV2548 remotely measures the thermistor, the measurement is inaccurate, but the remote measurement result changes normally with temperature. At this time, the SCLK, CS and analog input signals of TLV2548 are shown in the figure below: Figure 352008 2 Telemetry abnormalityTLV2548Related signals

Figure 3 When the telemetry is abnormalTLV2548Relative relationship of related signals

Figure1and Figure In the figure 2, probe 1 (yellow) is the SCLK signal of TLV2548, probe 3 (blue) is the CS signal of TLV2548, and probe 4 (red) is the analog channel input signal. It can be seen from the figure that the analog input signal generates periodic oscillation interference during channel selection, which leads to incorrect integration results of the analog signal during the 12 SCLKs sampling and holding process, which is manifested as abnormal telemetry DN. After determining the cause, we can make improvements in two aspects: a. Find a way to avoid the oscillation interference of TLV2548 on the analog input when channels are switched; b. Find a way to extend the sampling and holding time, and try to include the main energy of the oscillation interference in the integration process, so as to reduce the influence of the oscillation on the sampling results of the analog signal.

Since we have not yet found a way to eliminate the oscillation interference caused by channel switching on the analog input, we have temporarily adopted the second solution and set t(Sample) to 24 SCLKs. The driving result is shown in the figure below:

Figure 4 The modifiedTLV2548driving signal

Figure 5 The changedTLV2548relative relationship between drive signal and analog input

is shown in Figure5. Increaset(Sample) to24 After SCLKs, the entire sampling and holding process basically contains the main energy of the oscillation interference, so the integration result is close to the true value of the analog signal, and the telemetry DN value is normal.

2, TLV2548 input analog signal beyond the input range will cause all telemetry results to be abnormal. The oscilloscope measures the TLV2548 input analog signal and observes that when the channel is switched, the analog input signal has an irregular waveform. (Why did I forget to keep the picture at that time!)

This content is originally created by EEWORLD forum user VincentLee90. If you want to reprint or use it for commercial purposes, you must obtain the author's consent and indicate the source

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I would like to ask how to configure the internal CFR if I use a microcontroller to program it?