CN0411 ec: Questions

Hello. I'm interested in incorporating the CN0411 conductivity-measurement design into a circuit. (www.analog.com/.../cn0411.html)
I plan to use the analog components as listed, but with a different MCU and ADC.

1: In the flowchart that describes how to set the gain etc (Figure 12) What is V_DEF? Is it the 2.5V vref? The 0.4V default DAC output?

2: How long should the PWM 1 and 2 pulses be? (the ones that go in the middle of the V_EXC pulses. Is there a guide on configuring their on/off durations? The document provides the 2 standard frequences and a diagram (Figure 9). PWM0 is described as either 94Hz or 2.4kHz. (I assume that means cycle at these intervals), but I'm not clear on PWM 1 and 2.

3: Does this design supersede CN0349 and CN0359? The three documents don't mention each other. They were published in date that goes with their number, and all appear to accomplish the same task.

Thank you very much.

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  • I have an additional question:

    The ADG884BRMZ schematic in CN0411 shows D1 connected to S1A, and D2 connected to S2A, with a line inside the diagram. I assume this doesn't mean a trace; it just shows that's one of the two configs depending on switch setting.

    Here's my confusion: The same notation is used on the ADG1608 between S1 and D. Is there a trace wired between S1 and D? Is S1 unused? Thank you.

  • 0
    •  Analog Employees 
    on Jul 27, 2020 6:05 AM in reply to The Alchemist

    Hi,

    I assume by schematic you are referring to the block diagram in the circuit note. You can view the complete schematic in the Design Support files.

    For the block diagram representation of the two switches, yes you are correct. The line connecting the two just shows that the one connected is the default state. This means that for ADG1608 S1 and D is the default connection and there is no trace connecting them directly.

    Regards,

    Nikko

Reply
  • 0
    •  Analog Employees 
    on Jul 27, 2020 6:05 AM in reply to The Alchemist

    Hi,

    I assume by schematic you are referring to the block diagram in the circuit note. You can view the complete schematic in the Design Support files.

    For the block diagram representation of the two switches, yes you are correct. The line connecting the two just shows that the one connected is the default state. This means that for ADG1608 S1 and D is the default connection and there is no trace connecting them directly.

    Regards,

    Nikko

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