SLVAEX3
October 2020
TPS8802
,
TPS8804
Trademarks
1
Introduction
2
SNR Optimization
2.1
SNR Overview
2.2
Smoke Concentration Measurement
2.3
Amplifier and LED Settings
2.3.1
Photo Amplifier Gain
2.3.2
Photo Amplifier and AMUX Speed
2.3.3
LED Current and Pulse Width
2.4
ADC Sampling and Digital Filtering
2.4.1
ADC Sampling
2.4.2
Digital Filtering
3
System Modeling
3.1
Impulse Response
3.1.1
Photodiode Input Amplifier Model
3.1.2
Photodiode Gain Amplifier and AMUX Buffer Model
3.1.3
Combined Signal Chain
3.2
Noise Modeling
3.2.1
Noise Sources
3.2.2
Output Voltage Noise Model
3.2.3
ADC Quantization Noise
3.3
SNR Calculation
3.3.1
Single ADC Sample
3.3.2
Two ADC Samples
3.3.3
Multiple Base ADC Samples
3.3.4
Multiple Top ADC Samples
3.3.5
Multiple ADC Sample Simulation
4
SNR Measurements
4.1
Measurement Procedure
4.2
Measurement Processing
4.3
Measurement Results
4.3.1
Varying Amplifier Speeds
4.3.2
Varying Digital Filter and ADC Timing
4.3.3
Varying LED Pulse Length
4.3.4
Varying ADC Sample Rate
4.3.5
Real and Ideal System Conditions
4.3.6
Number of Base Samples
4.3.7
ADC Resolution
5
Summary
6
References
3.3
SNR Calculation