Amphenol NPI-19 I2C Digital Pressure Sensor User Guide

June 15, 2024
Amphenol

Amphenol logo NPI-19 I2C Digital Pressure Sensor
Application Guide Amphenol NPI-19 I2C Digital Pressure
SensorAdvanced Sensors
Dec 2022

General Description

The NPI I2C digital pressure sensors combines Amphenol Advanced Sensors’ SenStable® silicon fusion bonded pressure die technology with packaged electronics to provide highly stable, amplified and calibrated pressure measurement.

Output Characteristics

2.1 Pressure Output Options
The NPI-19 I2C product is available in a range of pressure ratings, pressure configurations. The nominal output ranges for standard product ranges are detailed in Tables 1 and 2 below.
Table 1: Available Pressure Output Ranges for Standard Products

Device series Units Absolute / Gauge Excitation
NPI-19 I2C Counts 1638 14745

Table 2: Output Transfer Function

Pressure % Output Decimal Counts Hexadecimal Counts
Pmin 10 1638 0x0666
Pmid 50 8192 0x2000
Pmax 90 14746 0x399A

2.2 Pressure Output Characteristics
All NPI-19 digital pressure sensors are factory calibrated to give a defined linear change in output over a specified range of pressures. Outside this range, the output varies with pressure but with unspecified accuracy. Amphenol NPI-19 I2C Digital Pressure Sensor - Figure 1Pressure can be calculated from the sensor output using the following formula: Amphenol NPI-19 I2C Digital Pressure Sensor -
formulawhere
P = calculated pressure
Out = measured sensor output
2.3 Pressure Accuracy
The measurement accuracy of calibrated NPI-19 Digital pressure sensor is defined in terms of percentage of full scale (FS) over a specified compensated temperature range. Standard parts are specified to be ±1.0%. This accuracy figure is a total error band and includes all errors due to offset, span, linearity and temperature, as illustrated in Figure 2 below.Amphenol NPI-19
I2C Digital Pressure Sensor - Figure 2

Digital Output (I2C)

3.1 General
NPI pressure sensor provides digital output data using the industry standard I2C protocol. Bit rates up to 400 kHz are supported, compatible with the Standard-mode (Sm) and Fast-mode (Fm) standards. Devices are supplied with a slave address of 0x28 as standard.
3.2 Block DiagramAmphenol NPI-19 I2C Digital Pressure Sensor - Figure
3
3.3 I2 C Timing
Table 3: I2 C Timing Parameters

Parameter Symbol Min Max Units
SCL clock frequency fSCL 100 400 kHz
Start condition hold time relative to SCL edge tHDSTA 0.1 μs
Minimum SCL clock low width* tLOW 0.6 μs
Minimum SCL clock high width* tHIGH 0.6 μs
Start condition setup time relative to SCL edge tSUSTA 0.1 μs
Data hold time on SDA relative to SCL edge tHDDAT 0 μs
Data setup time on SDA relative to SCL edge tSUDAT 0.1 μs
Stop condition setup time on SCL tSUSTO 0.1 μs
Bus free time between stop and start condition tBUS 2 μs
  • Combined low and high widths must equal or exceed minimum SCL period.   Amphenol NPI-19 I2C Digital Pressure Sensor - Figure 4Two conditions can cause communication errors:

    • Sending a start-stop condition without any transitions on the SCL line (no clock pulses in between) creates a communication error for the following communication, even if the next start condition is correct and the clock pulse is applied.
    • Restart condition – a falling SDA edge during data transmission when the SCL line is still high will cause the next communication to fail.

In both situations, an additional start condition should be sent to restore communication.
3.4 Data Read Operations
To read data from the NPI-19 digital sensor, the I 2 C master device sends 8 bits — the 7 bit slave address (0x28 for standard devices) and the 8th bit = 1 to designate a read request. The NPI-19 digital sensor then sends acknowledge (ACK) to indicate success.
The NPI-19 digital sensor has three I2 C read commands:
Read_DF2: Pressure (2 bytes)
Read_DF3: Pressure (2 bytes) +
Temperature (1 byte) Read_DF4:
Pressure (2 bytes) + Temperature (2 bytes)
The number of data bytes returned by the NPI-19 digital sensor is determined by when the 2 IC master device sends the NACK and stop conditions as shown in Figure 5 below.

| Start Condition
---|---
| Device Slave Address (example: Bit 5)
| Data Bit(example: Bit 2)
| Read/Write Bit (example: Read=1)
| Acknowledge (ACK)
| No Acknowledge (NACK)
| Stop Condition
| Status Bit

Amphenol NPI-19 I2C Digital Pressure Sensor - Application
Guide Amphenol NPI-19 I2C Digital
Pressure Sensor - Figure 5Amphenol
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