Datasheet

 
SLUS318B – APRIL 1999 – REVISED JANUARY 2002
11
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APPLICATION INFORMATION
The TACH_OUT signal can be used to close a digital velocity loop using a microcontroller, as shown in Figure 6,
or directly low-pass filtered in an analog implementation, Figure 7.
UDG–97188
5
4
14
R_TACH
C_TACH
PWM_NI
PWM_I
13
TACH_OUT
3
6CT
UCC3626
VOUT
AD558
VCE
VCS
IC1
PC0
MC68HC11
PB0–PB7
DB0–DB7
V
OUT
SENSE
V
OUT
SELECT
Figure 6. Digital Velocity Loop Implementation Using MC68HC11
two quadrant vs four quadrant control
Figure 8 illustrates the four possible quadrants of operation for a motor. Two-quadrant control refers to a system
in which operation is limited to quadrants I and III (where torque and velocity are in the same direction). With
a two-quadrant brushless dc amplifier, there are no provisions other than friction to decelerate the load, limiting
the approach to less demanding applications. Four-quadrant controllers, on the other hand, provide controlled
operation in all quadrants, including II and IV, where torque and rotation are of opposite direction.
2
5
4
14
VREF
R_TACH
C_TACH
PWM_NI
PWM_I
13
TACH_OUT
3
6CT
+
–
UCC3626
Figure 7. Simple Analog Velocity Loop
UDG–97189
I
IVIII
II
VELOCITY
CW
CCW
TORQUE
CW
CCW
UDG–01118
Figure 8. Four Quadrants of Operation