XR-2206 Datasheet, PDF (11/16 Pages) Exar Corporation – Monolithic Function Generator

XR-2206
With External Adjustment:
The harmonic content of sinusoidal output can be
reduced to -0.5% by additional adjustments as shown in
Figure 12. The potentiometer, R_A, adjusts the
sine-shaping resistor, and R_B provides the fine
adjustment for the waveform symmetry. The adjustment
procedure is as follows:
1. Set R_B at midpoint and adjust R_A for minimum
distortion.
2. With R_A set as above, adjust R_B to further reduce
distortion.
Triangle Wave Generation
The circuits of Figure 11 and Figure 12 can be converted
to triangle wave generation, by simply open-circuiting Pin
13 and 14 (i.e., S₁ open). Amplitude of the triangle is
approximately twice the sine wave output.
PRINCIPLES OF OPERATION
Description of Controls
Frequency of Operation:
The frequency of oscillation, f_o, is determined by the
external timing capacitor, C, across Pin 5 and 6, and by
the timing resistor, R, connected to either Pin 7 or 8. The
frequency is given as:
f₀ +
1
RC
Hz
and can be adjusted by varying either R or C. The
recommended values of R, for a given frequency range,
as shown in Figure 5. Temperature stability is optimum
for 4kW < R < 200kW. Recommended values of C are from
1000pF to 100mF.
Frequency Sweep and Modulation:
Frequency of oscillation is proportional to the total timing
current, I_T, drawn from Pin 7 or 8:
FSK Generation
f
+
320I_T (mA)
C(mF)
Hz
Figure 13 shows the circuit connection for sinusoidal FSK
signal operation. Mark and space frequencies can be
independently adjusted by the choice of timing resistors,
R₁ and R₂; the output is phase-continuous during
transitions. The keying signal is applied to Pin 9. The
circuit can be converted to split-supply operation by
simply replacing ground with V^-.
Pulse and Ramp Generation
Timing terminals (Pin 7 or 8) are low-impedance points,
and are internally biased at +3V, with respect to Pin 12.
Frequency varies linearly with IT, over a wide range of
current values, from 1mA to 3mA. The frequency can be
controlled by applying a control voltage, V_C, to the
activated timing pin as shown in Figure 10. The frequency
of oscillation is related to VC as:
ǒ ǒ ǓǓ f
+
1
RC
1
)
R
R_C
1
–
V_C
3
Hz
Figure 14 shows the circuit for pulse and ramp waveform
generation. In this mode of operation, the FSK keying
terminal (Pin 9) is shorted to the square-wave output (Pin
11), and the circuit automatically frequency-shift keys
itself between two separate frequencies during the
positive-going and negative-going output waveforms.
The pulse width and duty cycle can be adjusted from 1%
to 99% by the choice of R₁ and R₂. The values of R₁ and
R₂ should be in the range of 1kW to 2MW.
where V_C is in volts. The voltage-to-frequency conversion
gain, K, is given as:
K
+
ēfńēV_C
+
–
0.32
R_CC
HzńV
CAUTION: For safety operation of the circuit, I_T should be
limited to  3mA.
Rev. 1.03
11