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Preliminary Specification
- 21 -
© Andigilog, Inc. 2006
www.andigilog.com
August 2006 - 70A04018
aMC8500
Figure 37 Simistor™ Sensing Thermostatic Temperature Regulator
Application Requirements
Closest Standard 1.0% Resistor Values
Threshold
Hysteresis
Min Speed
Speed Transition
Temperature °C
Minimum
Speed
Setting
R1
R2
R3
R4
R5
Min to Max
Max to Min
%on
Ω
Ω
Ω
Ω
Ω
30
28
35
499
1740
221000
2320
1210
35
30
35
215
715
40200
3240
1690
38
35
0
200
619
60400
-
-
40
38
30
187
562
68000
2490
1150
45
40
30
196
562
35700
2490
1150
Thermostatic control is achieved by configuring the Op Amp as a voltage comparator. The inverting input monitors the Simistor™ solid
state thermal sensor while the non-inverting input is biased to a reference level. The above table shows five different application
examples with the calculated resistor values. In applications 1, 2, 4, and 5, the motor speed switches from the programmed minimum
setting to maximum as the sensor temperature rises above the required transition temperature. A controlled amount of positive feedback
shifts the transition temperatures to provide thermal hysteresis as the sensor cools. In the third application requirement, the motor
switches between zero and full speed. In this case the minimum speed set input is not required and the comparator must be disabled by
connecting Pin 6 to Pin 14. Note that the total Reference load current must exceed 2.0 mA in order to disable the automatic power down
feature.
6
Fault Timer
Power Down
Kick Start
Reference
Hall Amplifier
Non-Overlap
Commutation
Current Limit
Comp
Motor
Drives
12 V
Op Amp
Oscillator
Min Speed
Comp
PWM Comp
Digital
Detector
R
Thermal
Shutdown
Under Voltage
Lockout
Current
Limit
Latch
R
Q
S
16
1
12
15
14
10
9
8
5
11
13
PWM
Logic
10 μA
34
R3
R2
R4
R5
R1
aSM121
H
H
H
N
S
S
N
M
2
10 nF
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