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PGA309: PGA309AIPW

jean-françois chesneau
Prodigy 10 points
Part Number: PGA309

Hi

I am representing a major sensors provider for applications in the aerospace industry.

We have already assessed the behavior component in our environment and its accuracy performance and we would like to introduce it in our production.

We have a DO254 specification requirement and that standard defines some components families: simple, complex and highly complex.

When the component can be considered as simple, the DO254 is not applicable.
For example, if i choose a Texas analog to digital converter, it is considered as simple, the DO254 is not applicable and I can use it in an application where the DO254 is a requirement.

I understand that the component has not been designed to be DO254 compliant for avionics HW and SW. You have not the evidences which are requested when you follow a DO254 development.

Nevertheless, if I can prove that the PGA309 is simple, that would be possible to choose it and go ahead.

If the component was based on a microprocessor, the DO178 would be applicable (rejected for the application)
If the component was a FPGA, the DO254 would be applicable (rejected for the application)

Here, the component is a SOC and i haven’t details on the hardware of the PGA309, so i can’t classify it.

A first analysis regarding the PGA309 simple aspect could be based on its hardware architecture.

An important point is the table operating principle.

I can imagine that Texas has created a multiplier/adder to calculate the right gain and offset for a temperature measured (difficulty to create a divider).

Can you share something about the hardware structure ?

Thanks for your support

Chesneau Jean-françois

 

 

  • 0
    TI__Guru 54576 points

    Hi Chesneau,

    As you have mentioned, the PGA309 is not certified for aerospace certifications such as DO254 as the PGA309 adheres to the semiconductor industry standards.  The PGA309 was qualified per JEDEC industry standards defined for a catalog commercial integrated circuit at the time of release. For details on the qualification please refer to the following link: PGA309 Qual Summary. There is also an extended temperature range version of the device, the PGA309-HT specified for the extended temperature range -55C to +150C.  For details on the qualification please refer to the following link: PGA309-HT Qual Summary.

    The PGA309 User Guide, on the introduction section and section 1.1 PGA309 Functional Description p11-p14 provides  provides a detailed functional diagram description of the device.  PGA309 development is supported via the PGA309EVM-USB evaluation board.  The GUI software includes a "Block Diagram" section to exercise the hardware.  The "Auto-Cal"  on the EVM software routine performs the calibration over temperature for a bridge sensor. A built in sensor emulator allows you to calibrate using an emulated sensor before connecting your real world sensor.  The hardware also allows to connect external bridge sensors.

    Thank you and Regards,

    Luis

    From Section 1.1, Functional Description, page 12 of the PGA309 User Guide:

    From Section 1.1

  • 0 in reply to Luis Chioye
    Prodigy 10 points

    Hello, Luis

    Thanks

    What means SOC concerning the PGA309 ?

    In particular, could you confirm that there is not any embedded software, buried code ?

    Rgds

    Jean-françois

  • 0 in reply to jean-françois chesneau
    TI__Guru 54576 points

    HI Jean,

    The PGA309 is in essence a programmable gain instrumentation amplifier with offset, gain/span adjustment and sensor linearization, offering temperature calibration of span/offset. It offers internal/external temperature measurement capability, fault detection, and digital calibration.  The device relies on a separate external memory EEPROM IC to store the device settings and the calibration coefficients look-up table. 

    As shown on the block diagram of the PGA309 User Guide Section 1-1, the device incorporates internal programmable gain instrumentation amplifiers and operational amplifiers, internal DACs for gain and offset adjustment, multiplexers, an ADC for temperature sensing, an internal temperature sensor, a voltage reference, and supports two digital interfaces: One-Wire UART-compatible interface and a standard Two-Wire interface.  The device incorporates digital control circuitry for the internal state machine and digital circuitry to support the calibration look-up table.

    The device operates under the internal state machine and RAM control where the PGA309 lookup logic contains a linear interpolation algorithm for accurate DAC adjustments between stored temperature indexes.  The device relies on the external EEPROM to store the desired PGA309 settings and corresponding temperature coefficients for the Fine Gain adjust and the Fine Offset adjustment. Each time a temperature is read by the temp ADC, the lookup table logic reads the coefficients stored on the external EEPROM to provide the appropriate values to the Fine Gain and Offset DACs to remove the effects of the sensor non-ideal temperature characteristics.  However, the PGA309 does not incorporate a programmable processor and does not incorporate embedded software. 

    Thank you and Regards,

    Luis