Features
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Internal Frequency-to-voltage Converter
Externally Controlled Integrated Amplifier
Overload Limitation with “Fold Back” Characteristic
Optimized Soft-start Function
Tacho Monitoring for Shorted and Open Loop
Automatic Retriggering Switchable
Triggering Pulse Typically 155 mA
Voltage and Current Synchronization
Internal Supply-voltage Monitoring
Temperature Reference Source
Current Requirement
≤
3 mA
1. Description
The integrated circuit U211B is designed as a phase-control circuit in bipolar technol-
ogy with an internal frequency-to-voltage converter. The device includes an internal
control amplifier which means it can be used for speed-regulated motor applications.
Amongst others, the device features integrated load limitation, tacho monitoring and
soft-start functions, to realize sophisticated motor control systems.
Figure 1-1.
Block Diagram
17(16)
1(1)
5*
Automatic
retriggering
Output
pulse
4(4)
Phase Control
IC with
Overload
Limitation
for Tacho
Applications
U211B
Voltage/current
detector
Control
amplifier
11(10)
+
10(9)
-
6(5)
7(6)
Phase-
control unit
ϕ
= f (V12)
3(3)
Supply
voltage
limitation
Reference
voltage
Voltage
monitoring
2(2)
-VS
GND
14(13)
Load limitation
speed/time
controlled
16(15)
15(14)
Controlled
current sink
-V
Ref
12(11)
Pin numbers in brackets refer to SO16
* Pins 5 and 18 connected internally
Soft start
Frequency-
to-voltage
converter
9(8)
8(7)
Pulse-blocking
tacho
monitoring
18*
13(12)
Rev. 4752B–INDCO–09/05
2. Pin Configuration
Figure 2-1.
Pinning DIP18
I
sync
1
18 PB/TM
17 V
sync
16 V
Ref
15 OVL
GND 2
V
S
3
Output 4
Retr 5
V
RP
6
C
P
7
F/V 8
C
RV
9
U211B
14 I
sense
13 C
soft
12 CTR/OPO
11 OP+
10 OP-
Table 2-1.
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Pin Description
Symbol
I
sync
GND
V
S
Output
Retr
V
RP
C
P
F/V
C
RV
OP-
OP+
CTR/OPO
C
soft
I
sense
OVL
V
Ref
V
sync
PB/TM
Function
Current synchronization
Ground
Supply voltage
Trigger pulse output
Retrigger programming
Ramp current adjust
Ramp voltage
Frequency-to-voltage converter
Charge pump
OP inverting input
OP non-inverting input
Control input/OP output
Soft start
Load-current sensing
Overload adjust
Reference voltage
Voltage synchronization
Pulse blocking/tacho monitoring
2
U211B
4752B–INDCO–09/05
U211B
Figure 2-2.
Pinning SO16
I
sync
GND
V
S
Output
V
RP
C
P
F/V
C
RV
1
2
3
4
16 V
sync
15 V
Ref
14 OVL
13 I
sense
U211B
5
6
7
8
12 C
soft
11 CTR/OPO
10 OP+
9
OP-
Table 2-2.
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Pin Description
Symbol
I
sync
GND
V
S
Output
V
RP
C
P
F/V
C
RV
OP-
OP+
CTR/OPO
C
soft
I
sense
OVL
V
Ref
V
sync
Function
Current synchronization
Ground
Supply voltage
Trigger pulse output
Ramp current adjust
Ramp voltage
Frequency-to-voltage converter
Charge pump
OP inverting input
OP non-inverting input
Control input/OP output
Soft start
Load-current sensing
Overload adjust
Reference voltage
Voltage synchronization
3
4752B–INDCO–09/05
3. Mains Supply
The U211B is equipped with voltage limiting and can therefore be supplied directly from the
mains. The supply voltage between pin 2 (+ pol/_|_) and pin 3 builds up across D
1
and R
1
and is
smoothed by C
1
. The value of the series resistance can be approximated using:
V
M
–
V
S
-
R
1
= --------------------
2 I
S
Further information regarding the design of the mains supply can be found in the section
“Design
Hints” on page 9.
The reference voltage source on pin 16 of typically -8.9 V is derived from the
supply voltage and is used for regulation.
Operation using an externally stabilized DC voltage is not recommended.
If the supply cannot be taken directly from the mains because the power dissipation in R
1
would
be too large, the circuit as shown in
Figure 3-1
should be used.
Figure 3-1.
Supply Voltage for High Current Requirements
~
24 V~
1
2
3
4
5
R
1
C
1
4. Phase Control
The phase angle of the trigger pulse is derived by comparing the ramp voltage (which is mains
synchronized by the voltage detector) with the set value on the control input pin 12. The slope of
the ramp is determined by C
2
and its charging current. The charging current can be varied using
R
2
on pin 6. The maximum phase angle
α
max
can also be adjusted by using R
2
.
When the potential on pin 7 reaches the nominal value predetermined at pin 12, a trigger pulse
is generated whose width t
p
is determined by the value of C
2
(the value of C
2
and hence the
pulse width can be evaluated by assuming 8 µs/nF). At the same time, a latch is set, so that as
long as the automatic retriggering has not been activated, no more pulses can be generated in
that half cycle.
The current sensor on pin 1 ensures that, for operations with inductive loads, no pulse will be
generated in a new half cycle as long as a current from the previous half cycle is still flowing in
the opposite direction to the supply voltage at that instant. This makes sure that “gaps” in the
load current are prevented.
The control signal on pin 12 can be in the range of 0 V to -7 V (reference point pin 2).
If V
12
= -7 V, the phase angle is at maximum (α
max
),
i.e., the current flow angle, is at minimum.
The phase angle is minimum (
α
min
)
when V
12
= V
2
.
4
U211B
4752B–INDCO–09/05
U211B
5. Voltage Monitoring
As the voltage is built up, uncontrolled output pulses are avoided by internal voltage surveil-
lance. At the same time, all latches in the circuit (phase control, load limit regulation, soft start)
are reset and the soft-start capacitor is short circuited. Used with a switching hysteresis of
300 mV, this system guarantees defined start-up behavior each time the supply voltage is
switched on or after short interruptions of the mains supply.
6. Soft Start
As soon as the supply voltage builds up (t
1
), the integrated soft start is initiated.
Figure 6-1
shows the behavior of the voltage across the soft-start capacitor, which is identical with the volt-
age on the phase-control input on pin 12. This behavior guarantees a gentle start-up for the
motor and automatically ensures the optimum run-up time.
Figure 6-1.
Soft Start
V
C3
V
12
V
0
t
1
t
2
t
tot
t
3
t
t
1
= Build-up of supply voltage
t
2
= Charging of C
3
to starting voltage
t
1
+ t
2
= Dead time
t
3
= Run-up time
t
tot
= Total start-up time to required speed
C
3
is first charged up to the starting voltage V
0
with a current of typically 45 µA (t
2
). By reducing
the charging current to approximately 4 µA, the slope of the charging function is also substan-
tially reduced, so that the rotational speed of the motor only slowly increases. The charging
current then increases as the voltage across C
3
increases, resulting in a progressively rising
charging function which accelerates the motor more and more with increasing rotational speed.
The charging function determines the acceleration up to the set point. The charging current can
have a maximum value of 55 µA.
5
4752B–INDCO–09/05
Microchip MCU
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