FCM8201 Fairchild Semiconductor, FCM8201 Datasheet - Page 13

• Manufacturer Part Number: FCM8201
• Description: FCM8201 is a three-phase sinusoidal brushless DC (BLDC) motor controller
• Manufacturer: Fairchild Semiconductor

© 2011 Fairchild Semiconductor Corporation
FCM8201 • Rev. 1.0.2
Sine Wave Generator
FCM8201 includes space vector modulation (SVM) for
the sine-wave PWM. An angle-detect circuit phase-locks
the rotor position by using the Hall signals of the motor.
The resolution is 32 steps per 60 degrees. Through the
PWM operation, the motor current of each phase is
sine-wave. The angle shift between phases is 120
degrees.
Figure 19.
Figure 18. Sine Wave Output at CW=1
Sine Wave Output at CW=0
13
Current Feedback and Protections
The current feedback circuit provides two major
functions: (1) generating a current feedback signal for
the motor control, and (2) supporting over-current
protections. The I_IN pin outputs 50µA current to
provide a DC bias on the I_IN terminal to prevent a
negative voltage, shown in Equation (1) for the I_FB and
the I_IN. A 0.5V DC bias on I_IN is recommended. The
maximum average current signal is 1V. Using these
parameters, the maximum I_FB signal swing is
0.5V~4.5V.
FCM8201 provides three different levels of over-current
(OC) protections. The first level is 1.4V, used for over-
load current protection with OC timer delay. If the I_IN is
higher than 1.4V, the OC timer is triggered. The
OC_Latch is enabled once the timer exceeds its time-
out limit. The second level is 1.5V, used for the cycle-by-
cycle current limit. The PWM signal is turned off
immediately when the I_IN is > 1.5V. The third level is
2.5V, designed for the short-circuit protection. If the I_IN
is > 2.5V for over three PWM pulses, all PWM outputs
(U, V, W, X, Y, Z pins) are turned off.
Protections and Faults
Table 3. Faults Table
Watch Dog
OC_Latch
V
Hall Error
V
SHORT
_ I
V
V
HOVP
Type
OUT
PP
PP
FB
OS
R
T
OV
UV
UV

(
V
Figure 20.
S

State
Reset
) 8
Free,
Free
Free
Free
Free
Free
Free
Free
Free
Free

I (
BIAS
Hall=000 or 111
_
Current Feedback Flow
WDT Time Out
V
_ I
Open & Short
I_IN > 1.4V
I_IN > 2.5V
SENSE
V
V
R
IN
Trigger
V
PP
OUT
T
PP

< 1.0V
R
> 18V
< 8V
< 4V
> 4.5V
BIAS
)
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R
Release
Register
T
↑Run
↑Run
↑Run
> 1.2V
(1)