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AM2434: ADC and thermal control guidance for a 60-channel optical measurement instrument

Danilo A.
Mastermind 34285 points

Part Number: AM2434

Hi Team,

Posting on behalf of our customer.

I will share this post with our customer so he can reply when needed.

We are developing a portable laboratory instrument that performs 60-channel fluorescence measurement with closed-loop thermal cycling, and have selected AM2434 as the production controller. Three questions:

1 — ADC configuration. We need to sample 60 optical channels from a photodiode with transimpedance amplifier, at roughly 1 sample per channel per second, requiring approximately 14-bit effective resolution. Would you recommend the integrated ADC with the sequencer and an external multiplexer, or an external delta-sigma ADC over McSPI? Any guidance on achieving stable low-noise readings at that resolution?

2 — Closed-loop thermal control. We require ±0.3 °C accuracy across a 25–95 °C cycling range, driving a heater and Peltier element via EPWM with thermistor feedback. Is there a reference design or application note for PID temperature control on the Cortex-R5F cores?

3 — Analogue and PWM coexistence. The instrument runs high-current PWM for heating while simultaneously sampling a low-level photodiode signal. Is there existing guidance on layout, grounding or timing strategies — for example synchronising ADC sampling to PWM off-periods — to keep switching noise out of the analogue front end?

Any relevant reference designs, application notes or evaluation-board recommendations would be much appreciated.

Regards,

Danilo

  • 0
    TI__Intellectual 1420 points

    Hello Danilo,

    Thank you for your question. Please allow me some time to look into this and I will get back to you with an update tomorrow.

    Regards,
    Karam

  • 0
    TI__Intellectual 1420 points

    Danilo,

    1. The AM2434 integrated ADC has a 12-bit resolution on the ALV/ANI package and 10-bit resolution on the ALX package. To meet a higher resolution, you might need to explore external ADC options over McSPI.

    2. There isn't an AM2434 specific thermal PID reference design. However, the AM243x Digital Control Library provides PI and PID controllers for implementation on the R5F Core. 

    3. TI does not have guidance on layout specific to this application. The AM2434 ePWM modules provide PWM_SOCA and PWM_SOCB start-of-conversion signals that can be used to trigger an external ADC that might be useful for your application. For more information, please refer to Section 12.4.3.3.1.3 "ADC start of conversion signals (PWM_SOCA and PWM_SOCB)" of the AM64x/AM243x Technical Reference Manual.

    Regarding signal-integrity concerns, this general guidance from TI might be useful as it goes over PCB partitioning and return current routing to prevent digital noise from coupling on analog circuitry: Grounding in mixed-signal systems demystified, Part 1 and Part 2.

    Regards,
    Karam