XR2209 Exar Corporation, XR2209 Datasheet - Page 5

• Manufacturer Part Number: XR2209
• Description: Voltage-Controlled Oscillator
• Manufacturer: Exar Corporation

PRECAUTIONS
The following precautions should be observed when
operating the XR-2209 family of integrated circuits:
1.
2.
Rev. 2.02
Pulling excessive current from the timing terminals
will adversely affect the temperature stability of the
circuit.
recommended that the total current drawn from pin 4
be limited to
to the device may occur if the total timing current
exceeds 10mA.
Terminals 2, 3, and 4 have very low internal
impedance and should, therefore, be protected from
accidental shorting to ground or the supply voltage.
To
minimize
6mA. In addition, permanent damage
1 F
this
S1
Figure 3. Test Circuit for Single Supply Operation
disturbance,
V
V
R
CC
CC
1
TR
4
I +
C1
XR-2209
2
C
it
C 2
is
I-
3
5
V
SWO
TWO
EE
BIAS
SYSTEM DESCRIPTION
The XR-2209 functional blocks are shown in the block
diagram given in Figure 1. They are a voltage controlled
oscillator (VCO), and two buffer amplifiers for triangle and
squarewave outputs. Figure 2 is a simplified XR-2209
schematic diagram that shows the circuit in greater detail.
The VCO is a modified emitter-coupled current controlled
multivibrator. Its oscillation is inversely proportional to the
value of the timing capacitor connected to pins 2 and 3,
and directly proportional to the total timing current I
current is determined by the resistor that is connected
from the timing terminals (pin 4) to ground.
The triangle output buffer has a low impedance output
(10
type. An external bias input allows the XR-2209 to be
used in either single or split supply applications.
6
7
8
5
typ.) while the squarewave is an open-collector
5.1K
R
L
Triangle Wave
Square Wave
S2
Output
Output
V
1 F
CC
5.1K
XR-2209
V
CC
T
. This