PGA309: provide I2C output?

Hi Art,

This is technically possible. The PGA309 datasheet states "An additional function provided through the Temp ADC is the ability to read the VOUT pin back through the Temp ADC input mux. This provides flexibility for a digital output through either One-Wire or Two-Wire interface, as well as the possibility for an external microcontroller to perform real-time custom calibration of the PGA309." The Temp ADC input mux is shown in the block diagram.

To read Vout from the ADC, they will need to set the Temp ADC input to Vout (see section 6.2.7 in the user guide, specifically Table 6-15 and Figure 6-5) and then read register 0 (see section 6.2.1 of the user guide) using the two-wire interface.

However, the issue is that the PGA between the Temp ADC Input Mux and the ADC itself is not calibrated, and will likely exhibit some drift/offset errors (see page 5 of the datasheet). Thus, the benefits of tuning the main PGA will be undermined by the comparatively imprecise nature of the Temp ADC circuit. Therefore, while this could be used for diagnostic purposes, the customer should not rely on it for actual operation. They would be better off using a peripheral, I2C capable ADC to read the Vout of the device externally.

Cheers,

Jon

Hi Art,

The PGA309 is an analog voltage output programmable amplifier sensor conditioner used to measure bridge sensors, offering sensor error compensation for span, offset and temperature drift.  The PGA309 analog voltage output can easily be used to drive a two-wire current transmitter like the XTR117 to implement a current output sensor module as featured on the PGA309EVM-USB. 

The PGA309 offers a 1-wire UART or 2-wire digital interface to program and access the registers of the device.  The digital interface is only used to program or modify the PGA309 internal register settings controlling gain/offset/reference settings during the calibration procedure, or to access the external EEPROM that stores the calibration coefficients.  As Jon has mentioned, the device incorporates an ADC as part of the temperature sense function in order to apply the correct temperature gain/offset temperature calibration coefficients, and the user may be able to access the internal ADC temperature reading through the 2-wire or 1-wire interface. 

However, the PGA309 is primarily an analog voltage output Programmable Gain amplifier conditioner offering a calibrated analog bridge voltage output sensor reading.

Thank you and Regards,

Luis 

Thanks a lot Guys!

I might forward the customer directly to this link in case of further inquiries.

Best regards,

Art

Hello Guys,

Do we have something similar to PGA309 for pressure sensor with I2C output? Customer need accuracy like PGA309 but only with I2C output.

Thanks and regards,

Art

Hi Art,

The PGA900 is a programmable signal conditioner for pressure sensors and transducers that offers user-programmable temperature and nonlinearity compensation incorporating a precision ADC.   I believe the device offers both analog and digital outputs, where the data and configuration settings can be accessed through UART, I2C and SPI. 

The PGA900 is supported by the Data Converters group, so you may want to submit a new E2E query on the data converters forum for additional information on the PGA900.

Thank you and Regards,

Luis

Hi Art,

One approach would be to interface an I2C capable, external delta-sigma ADC with the PGA309. Which specific device would be best depends on the sampling requirements and desired resolution of the customer's application.

Alternatively, the PGA305 has an internal 24-bit ADC that you can read the values from over I2C. It allows you to compensate for temperature effects, integrates nonlinearity correction, and allows control of the gain/offset but does not have the same level of calibration and extra fault/limit features that the PGA309 has. As Luis mentioned, there is also the PGA900, which is more fully featured and has a comparable price point. The PGA900, PGA305, and PGA300 actually all come from the same family, and there is an app note on their usage (PGA900, PGA300 and PGA305 Use Case for the Pressure Transmitter Applications) that might prove useful as a reference.

In either case, as Luis said the Data Converters folks will be your best option for further support, so feel free to reach out to them.

Cheers,

Jon