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PGA305: Termination for unused pins etc

Oba
Genius 16035 points
Part Number: PGA305
Other Parts Discussed in Thread: PGA300, PGA900

Hello,

 

I have some questions for PGA305.

 

Q1) When using only I2C for output, can DACCAP pin be left open?

Q2) When not using INT+/INT- pins, how should these pins be terminated?

Q3) When using only I2C for output, how should FB+/FB-/COMP/OUT pins be terminated?

 

Q4) The below questions are for using Voltage output mode case.

Q4-A) How should FB- be terminated. Is it OK to be left open?

Q4-B) 100nF is put on FB- pin in Figure 49 in the datasheet. Is this capacitance absolutely required?

Q4-C) Regarding COMP pin, the datasheet recommend to put capacitance on this pin when driving large capacitive loads with the OUT pin.

          If the load capacitance is not so large, Is it OK to be left open this pin?

 

Regards,

Oba

  • 0
    TI__Mastermind 31655 points

    Hello Oba-san,

    1. Yes, you can leave the DACCAP open.

    2. These pins can be left floating.If the external inputs are not used, I would make sure that the internal temperature sensor is connected to the temperature ADC

    3. These pins can all be left floating if the DAC output stage is not used

    4a. For voltage output, FB- is connected to the output circuitry. Do you mean FB+? FB+ can be left open/floating

    4b. The capacitor is there to reduce high frequency noise that might be coupled onto the feedback into the amplifier. I do recommend some capacitance there, but the value could be adjusted if desired. I would still keep the value between 10nF and 100nF

    4c. Please refer to this application note regarding how to achieve output stability with different types of loads. It is written for the PGA900, but the PGA300 shares the same output stage: https://www.ti.com/lit/an/slda020/slda020.pdf?ts=1594848527931&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FPGA900

    Regards,