sm5872 Servoflo Corporation, sm5872 Datasheet - Page 2

• Manufacturer Part Number: sm5872
• Description: Sm5822/sm5872 Co-integrated Pressure Sensor
• Manufacturer: Servoflo Corporation

40SP5002.03
THEORY OF OPERATION
The operation of the signal processor is
depicted in the block diagram below. The
internal pressure sensor is a piezoresistive
bridge. This transduces the applied
pressure into an electronic signal, which
feeds into the integrating amplifier.
During the amplification step an offset
correction factor is added to allow for
maximum gain for a given pressure while
minimizing the offset error.
The signal is then processed by an 11-bit
analog to digital converter (ADC). The ADC
samples the signal multiple times and uses
the sum of those samples as a 13-bit word.
A digital signal processor (DSP) is then used
to correct and calibrate the pressure signal.
The DSP provides multi-order correction of
both pressure and temperature non-linearity
through the use of factory-programmed
coefficients. A combined total of twenty
coefficients are available for correcting
12_08
SMI Co-Integrated Multi-Order Pressure
and Temperature Correction ASIC
Piezoresistive
Internal
Bridge
Power-On
Reset
Tel: [phone] ♦ Fax: [phone] ♦ [e-mail] ♦ www.si-micro.com
Silicon Microstructures, Inc. ♦ 1701 McCarthy Blvd. ♦ Milpitas, CA 95035 USA
Integrateing
Band-gap
Capacitor
Switched
Amplifier
Oscillator
Control
Analog
Timing
V
2 MHz
Temp
Co-Integrated Pressure Sensor
+ 5 VDC
Ground
MUX
Digital Timing
11-bit ADC
Management
and Control
EEPROM
Array
pressure and temperature non-linearity. The
unique coefficients are determined during a
calibration process performed at the factory.
Factory calibration is the last step
performed, which means the effect of the
package on the pressure signal will also be
taken into account. This provides a great
advantage over conventional laser-trimming
approaches.
The DSP produces a corrected digital word,
which is transferred to a 12-bit digital to
analog converter (DAC) to provide a
calibrated analog output. In addition to the
analog output, the corrected pressure signal
is accessible through an I
See SMI application note AN05-001 for a
detailed description of how to read out the
digital corrected pressure signal using the
I2C bus interface.
pressure and
correction of
temperature
(multi-order
linearities)
non-
DSP
SM5822/SM5872
Analog Component
Digital Component
Delta DAC
I
2
Interface
Sigma-
Output
C Digital
Buffer
12-bit
2
C digital interface.
Analog
Output
SDA
SCL