AMC8500 Datasheet, PDF (24/27 Pages) List of Unclassifed Manufacturers – TWO PHASE VARIABLE SPEED FAN MOTOR CONTROLLER

Preliminary Specification
aMC8500
Figure 43- Dual Fan Redundancy
12 V
R1
R2
5
1.0 M 590
C1
7
1.0
8
9
6
R3 ₁₀
787
12
Ref
UVLO
Op Amp
3
4
Hall Amp
Commutation
Timers
Power Down
H
M
16
1
Drives
15
TSD
Min Spd
Osc
PWM
Digital
Detector
PWM
Logic
Latch
R
Q
S
Current Limit
10 μA
13
2
10 nF
11
14
12 V
H
M
1
16
Drives
15
TSD
4
3
Hall Amp
Commutation
Timers
Power Down
12
UVLO
Ref
Op Amp
13
2
10 nF
Latch
R
Q
S
Current Limit
10 μA
PWM
Logic
Min Spd
PWM
Osc
Digital
Detector
5 R2 R1
590 1.0 M
7
C1
1.0
8
9
6
10 ^R3
787
14
11
In applications that require increased system reliability, multiple cooling fans can be employed for redundancy. In this example two
aMC8500s are cross coupled so that each device drives a fan while monitoring operation of the other. Resistors R2 and R3 program the
Speed Control inputs to operate each fan at a 50% speed. During normal operation, the Frequency Generator / Rotor Lock outputs,
Pin 15, continuously discharges their respective C1 capacitors. In the event that one fan should fail, Pin 15 will allow R1 to charge C1
above 2.0 V. This causes the Op Amp output to drive the Minimum Speed Set input above 3.0 V for maximum speed on the remaining
fan. The values for resistors R2 and R3 are chosen so that each Reference Output is loaded in excess of 2.0 mA in order to disable the
automatic power down feature.
© Andigilog, Inc. 2006
- 24 -
www.andigilog.com
August 2006 - 70A04018