SN74LVC1GX04_06 Datasheet, PDF (7/19 Pages) Texas Instruments – CRYSTAL OSCILLATOR DRIVER

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SN74LVC1GX04
CRYSTAL OSCILLATOR DRIVER
SCES581B – JULY 2004 – REVISED DECEMBER 2006
APPLICATION INFORMATION
Figure 3 shows a typical application of the SN74LVC1GX04 in a Pierce oscillator circuit. The buffered inverter
(SN74LVC1G04 portion) produces a rail-to-rail voltage waveform. The recommended load for the crystal shown
in this example is 16 pF. The value of the recommended load (C_L) can be found in the crystal manufacturer's
data sheet.
Values
of
C₁
and
C₂
are
chosen
so
that
C_L
+
C₁C₂
C₁ ) C₂
and
C₁
≡
C₂.
R_s
is
the
current-limiting
resistor,
and
the
value depends on the maximum power dissipation of the crystal. Generally, the recommended value of R_s is
specified in the crystal manufacturer's data sheet and, usually, this value is approximately equal to the reactance
of C₂ at resonance frequency, i.e.,^{Rs + XC2}. R_F is the feedback resistor that is used to bias the inverter in the
linear region of operation. Usually, the value is chosen to be within 1 MΩ to 10 MΩ.
SN74LVC1GU04
SN74LVC1G04
Portion
Portion
Y
X2
X1
C_LOAD
R_LOAD
R_F ≅ 2.2 MΩ
C_L ≅ 16 pF
R_s ≅ 1 kΩ
C₁ ≅ 32 pF
C₂ ≅ 32 pF
a) Logic Diagram View
Figure 3. Oscillator Circuit
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