Welch Allyn Atlas Service Manual page 85

f+5V
14
11 10 U604-10
A/D-sync
7
U604E
74HCT04
E
Integrator
Input
(U604-10)
Comparator
Inputs
PWM-Out
(U604-8)
2.2.2 A/D Multiplexer
A 16-channel multiplexer (formed by two 8-channel multiplexers) is used to select the analog signal to be
digitized. Control of the multiplexer is through a serial communication channel from the main CPU. The
following signals are digitized:
1. Ground
2. f1.24V
3. ECG
4. V Buffer
5. LL Buffer
6. LA Buffer
7. RA Buffer
8. RL Output
9. Patient Temp
10. Respiration
11. Resp Leads Off
Appendix A
R601 fVcc
10K
U601-3
f+5V
R602 3
+
73.2K 1
2
-
U601A
R603 MC34072
E
46.4K
U601-2
C601 fVee
R604 1000pF
10K
D601-2 2 1
D601
MMBD1503A
52uSec
833uSec
+5V
Analog In
-5V
PWM-timer
Ground Reference for digitized signals, used in calibrating the A/D converter
Reference Voltage, used in calibrating the A/D converter
Amplified ECG signal
Output of the V-lead buffer, used to determine leads off
Output of the LL-lead buffer, used to determine leads off
Output of the LA-lead buffer, used to determine leads off
Output of the RA-lead buffer, used to determine leads off
Output of the RL amplifier
Analog voltage representing patient Temperature
Amplified Respiration signal
DC impedance for respiration, used to determine respiration Leads off.
R605 R607
3.48K 464K
Analog In
fVcc
C603
680pF
2
+
U602-3
U601-1 3
-
R606
3.48K
fVee
PWM
E
A/D
Converter
10/14/99
iso+5Vdig
f+5V
R608
1K
14
7 9 8
PWM-Out
U602 7
LM311 U604D
74HCT04
E