Sony XM-1502SX Training Manual page 15

Table 1-4 shows the normal operating voltages of IC901.
IC901/pin
1 (protect
input)
2 (ref in)
3 (latch
output)
4 (reg
input)
5 (internal)
6 (internal)
Operation
The first protection circuit monitors the temperature of the amplifier using two or more thermistors on the circuit
board (one near each heat sink). The thermal triggered oscillator stop circuit is shown in Figure 1-10a. The
other thermistor circuits are in parallel between IC901/pins 14 and 16.
There are "TH" prefixed negative temperature coefficient thernistors or "THP" positive coefficient ones depending
upon availability at the time of manufacture. The TH and THP require different circuit configurations.
TH Thermistors - The "TH" thermistor measures 24k ohms out of circuit and decrease in resistance when warm.
In the configuration of Figure 1-10a, the thermistors are connected to regulated 5Vdc from IC901/pin 14 at one
end and to the anode of an isolation diode at the other. The cathode outputs are all connected to one protection
input at IC901/pin 16.
Batt
+12V
Figure 1-10a - Thermal Stop Circuit - TH Thermistors used (simplified)
Table 1-4 - IC901 uPC494GS-F1 - Normal Operating Voltages
Voltage
0 Vdc
1.28 Vdc
0.11 Vdc
(5V = tripped)
0.6 Vdc
(1.2 V = tripped)
1.7 Vdc
3.7 Vdc
5V Reg
14
in IC901
12
Thermal LED
IC901/pin Voltage
7 (gnd) 0 Vdc
8 (Battery in) 14 Vdc
9 (osc out +) 3.5 Vdc
10 (osc out -) 3.5 Vdc
11 (Battery in) 14 Vdc
12 (Battery in) 14 Vdc
TH Thermistor Circuit
24k ohm
D1
.1V
thermistor
TH-xxx
R1
13
1. Car Power Amplifier
IC901/pin Voltage
13 (reg out) 5 Vdc
14 (reg out) 5 Vdc
15 (ref in) 1.28
Vdc
16 (thermal 0.14
input) Vdc
Protection
0.17V
Circuit in
16
IC901
3
0V