Conditioning the bridge

Texas Instruments has introduced a digitally programmable analog signal conditioner designed for pressure bridge sensors.

‘The PGA309 offers bridge sensor customers an off-the-shelf signal conditioner, with digital calibration, that will solve the problem of conditioning non-linear sensors over a wide temperature range,’ said Tim Green, strategic marketing engineer for TI’s high-performance linear products.

‘An integral part of the PGA309 solution is a Designer’s Kit (PGA309DK). With this tool, a designer can evaluate and calibrate their sensor over temperature.’

The chip amplifies a low level bridge sensor signal and provides digital calibration for sensor zero, zero drift, span, span drift and linearity errors with applied pressure. The calibration is performed via a One-Wire or Two-Wire serial interface. Calibration parameters – up to 17 different temperature calibration points with linear interpolation – are stored in an external non-volatile memory (typically a low-cost, SOT23-5 EEPROM). This eliminates manual trimming and assures long-term stability.

The PGA309 consists of amplification signal path (low-noise, low-drift, auto-zero programmable gain instrumentation amplifier), offset and offset drift adjustment, span and span drift adjustment, integrated temperature sensor, voltage reference, bridge excitation and linearisation, sensor fault detection, power-on reset and digital interface. The PGA309 features a wide operating temperature range (-40C to +125C), internal/external temperature sense select, over/under limit scaling, internal/external reference selection and +2.7V to +5.5V supply operation.

The device is packaged in a TSSOP-16 and is priced from $2.95 in 1,000 piece quantities.

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