User manual

PmodDPG1™ Reference Manual
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Page 2 of 4
2 Specifications
Parameter
Min
Typical
1
Max
Units
Recommended Operating Voltage
3.125
3.3
3.5
V
Maximum Supply Voltage
-
-
5.5
V
Maximum Pressure
2
-
-
75
kPa
Minimum Pressure Offset
3
0.1
0.24
0.38
V
Sensor Accuracy
-0.54
0
0.54
kPa
Parameter
Value
Units
Communication Protocol
SPI Mode 0
4
Power Supply Current draw
5
10
mA
Sensor Response Time
1
mS
Sensor Bandwidth
500
Hz
Note
1
- Data in the Typical Column uses V
CC
at 3.3V unless otherwise noted
Note
2
- Where the pressure at P1 (top nozzle) is greater than the pressure at P2 (bottom nozzle)
Note
3
- Output voltage corresponding to a pressure differential of 0 kPa
Note
4
- CPOL = 0, CHPA = 0
Note
5
- Normal operation with V
CC
at 3.3V
3 Interfacing with the Pmod
The PmodDPG1 communicates with the host board via the SPI protocol with SPI Mode 0 (CPOL = 0, CHPA = 0). The
12 bits of digital data are sent to the system board in 16 clock cycles with the most significant bit first. For the
embedded ADC7476, each bit is shifted out on each falling edge of the serial clock line after the chip select line is
brought low with the first four bits as leading zeroes and the remaining bits representing the 12 bits of data.
The datasheet for the ADC7476 recommends that for faster microcontrollers or DSPs that the serial clock line is
first brought to a high state before being brought low after the fall of the chip select line to ensure that the first bit
is valid.
As a differential pressure module, it should be noted that the Pmod can only accept a certain range of pressure
differences without damaging the internal piezoresistive silicon. When the Pmod is laid on a flat surface such that
transducer is above the PCB, the top most nozzle is P1 (the receiving nozzle to detect fluctuating pressure) and the
bottom most nozzle is P2 (the pressure reference nozzle for P1). The pressure at P1 is recommended to be
between 0 and 10 kPa above the pressure present at P2. Pressures outside of this range may cause permanent
damage to the device.
To convert the serial data stream back into a corresponding pressure, users may use the following equation: