Features
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Internal Frequency-to-voltage Converter
Externally Controlled Integrated Amplifier
Automatic Soft Start with Minimized “Dead Time”
Voltage and Current Synchronization
Retriggering
Triggering Pulse Typically 155 mA
Internal Supply-voltage Monitoring
Temperature-compensated Reference Source
Current Requirement
≤
3 mA
1. Description
The integrated circuit U209B is designed as a phase-control circuit in bipolar technol-
ogy with an internal frequency-to-voltage converter. The device includes an internal
open-loop amplifier, which means it can be used for motor speed control with tacho
feedback.
The U209B is a 14-pin shrink version of the U211B with reduced features. Using the
U209B, the designer is able to realize sophisticated as well as economic motor control
systems.
Figure 1-1.
Block Diagram
14(16)
Voltage/Current
detector
1(1)
Automatic
retriggering
Output
pulse
4(4)
Phase Control
IC for Tacho
Applications
U209B
5(5)
Control
amplifier
6(6)
Phase
control unit
9(9)
-
ϕ
= f (V
11
)
Supply
voltage
limitation
Reference
voltage
Voltage
monitoring
3(3)
-V
S
2(2)
GND
10(10)
+
13(15)
Soft start
-V
S
11(11)
Pin numbers in brackets refer to SO16 Package
12(12)
Frequency-
to-voltage
converter
U209B
7(7)
8(8)
4765C–INDCO–02/07
U209B
3. Description
3.1
Mains Supply
The U209B 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
Calculations for Mains Supply” on page 9.
The reference voltage source on pin 13 of typically
-8.9 V is derived from the supply voltage and represents the reference level of the control unit.
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
~
U209B
24 V~
1
2
3
4
5
R
1
C
1
3.2
Phase Control
The function of the phase control is largely identical to that of the well known integrated circuit
U2008B. 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 4. The
slope of the ramp is determined by C
2
and its charging current. The charging current can be var-
ied using R
2
on pin 5. The maximum phase angle
α
max
can also be adjusted by using R
2
.
When the potential on pin 6 reaches the nominal value predetermined at pin 11, 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).
The current sensor on pin 1 ensures that, for operation with inductive loads, no pulse is gener-
ated 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 11 can be in the range 0 V to -7 V (reference point pin 2).
If V
11
= -7 V, the phase angle is at maximum =
α
max
, i.e., the current flow angle is at minimum.
The minimum phase angle
α
min
is when
V
11
= V
pin 2
.
5
4765C–INDCO–02/07
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