U211B-MFPY Atmel, U211B-MFPY Datasheet - Page 8

• Manufacturer Part Number: U211B-MFPY
• Description: IC PHASE CONTROL TACHO 16SOIC
• Manufacturer: Atmel

Specifications of U211B-MFPY

• Applications: AC Motor Controller
• Number Of Outputs: 1
• Current - Output: 7.5mA
• Voltage - Supply: 14.6 V ~ 16.6 V
• Operating Temperature: -10°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

In each positive half-cycle, the circuit measures, via R
, the load current on pin 14 as a poten-
10
tial drop across R
and produces a current proportional to the voltage on pin 14. This current is
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available on pin 15 and is integrated by C
. If, following high-current amplitudes or a large
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phase angle for current flow, the voltage on C
exceeds an internally set threshold of approxi-
9
mately 7.3V (reference voltage pin 16), a latch is set and load limiting is turned on. A current
source (sink) controlled by the control voltage on pin 15 now draws current from pin 12 and
lowers the control voltage on pin 12 so that the phase angle
is increased to
.
max
The simultaneous reduction of the phase angle during which current flows causes firstly a
reduction of the rotational speed of the motor which can even drop to zero if the angular
momentum of the motor is excessively large, and secondly a reduction of the potential on C
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which in turn reduces the influence of the current sink on pin 12. The control voltage can then
increase again and bring down the phase angle. This cycle of action sets up a “balanced con-
dition” between the “current integral” on pin 15 and the control voltage on pin 12.
Apart from the amplitude of the load current and the time during which current flows, the
potential on pin 12 and hence the rotational speed also affects the function of load limiting. A
current proportional to the potential on pin 10 gives rise to a voltage drop across R
, via
10
pin 14, so that the current measured on pin 14 is smaller than the actual current through R
.
8
This means that higher rotational speeds and higher current amplitudes lead to the same cur-
rent integral. Therefore, at higher speeds, the power dissipation must be greater than that at
lower speeds before the internal threshold voltage on pin 15 is exceeded. The effect of speed
on the maximum power is determined by the resistor R
and can therefore be adjusted to suit
10
each individual application.
If, after load limiting has been turned on, the momentum of the load sinks below the
“o-momentum” set using R
, V
will be reduced. V
can then increase again so that the
10
15
12
phase angle is reduced. A smaller phase angel corresponds to a larger momentum of the
motor and hence the motor runs up, as long as this is allowed by the load momentum. For an
already rotating machine, the effect of rotation on the measured “current integral” ensures that
the power dissipation is able to increase with the rotational speed. The result is a current-con-
trolled acceleration run-up which ends in a small peak of acceleration when the set point is
reached. The load limiting latch is simultaneously reset. Then the speed of the motor is under
control again and is capable of carrying its full load. The above mentioned peak of accelera-
tion depends upon the ripple of actual speed voltage. A large amount of ripple also leads to a
large peak of acceleration.
The measuring resistor R
should have a value which ensures that the amplitude of the volt-
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age across it does not exceed 600 mV.
U211B
8
4752B–INDCO–09/05