Welch Allyn Atlas Service Manual page 76

Theory of Operation – Model 622/623
1 DC/DC Power Supply
1.1 Overview:
1.2 On/Off Circuits
1.2.1 Backup Regulator and Micro-Controller
1.2.2 18V boost converter and FET ON/OFF switch
1.3 +12V Boost Converter
1.4 Battery Charger:
1.5 Linear Regulators – 5VDC and 3.3VDC
1.5.1 5V regulator
1.5.2 3.3V Regulator
2 Patient Isolated Circuits
2.1 Isolated Power
2.2 A/D Circuits
2.2.1 PWM A/D
2.2.2 A/D Multiplexer
2.3 Serial Communication
2.4 Signal Isolation
2.5 ECG Circuits
2.5.1 Overview
2.5.2 Defib Protect, RFI Filtering
2.5.3 Front End Buffer - 1st Gain Stage
2.5.4 Wilson Network - Lead Select Mux
2.5.5 Differential Amplifier and Slew rate limit
2.5.6 Right Leg Drive Amplifier
2.5.7 High Pass and Gain Stage
2.6 Temperature Amplifier
2.7 Impedance Respiration
2.7.1 Overview
2.7.2 Signal Source – Current Drive
2.7.3 Differential Amplifier and Peak Detector
2.7.4 Gain and Filtering
2.8 SpO2 Circuits
3 Non-Isolated circuits - A/D and Mux
3.1 A/D – grounded circuits
3.2 A/D Mux – grounded circuits
4 NIBP Circuits
4.1 Overview - Safety:
4.2 Primary Transducer - Amplifier:
4.3 Safety Transducer - Amplifier
4.3.1 Current Source:
4.3.2 Differential Amplifier and Offset Centering:
4.4 Hardware Overpressure:
4.5 Pump and Relay Drive:
5 CRT Deflection Board
5.1 Overview:
5.2 Vertical Amplifier:
5.2.1 Ramp Generator:
5.2.2 Vertical Amplifier:
5.2.3 Zero Adjust:
5.3 Horizontal Amplifier:
5.3.1 Horizontal Gain:
5.3.2 Grid Voltages:
5.4 Video Amplifier:
Appendix A 10/14/99