SN74LVC1GX04_06 Datasheet, PDF (8/19 Pages) Texas Instruments – CRYSTAL OSCILLATOR DRIVER

SN74LVC1GX04
CRYSTAL OSCILLATOR DRIVER
SCES581B – JULY 2004 – REVISED DECEMBER 2006
APPLICATION INFORMATION
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1
NC
2
GND
6
Y
5
V_CC
C_LOAD
R_LOAD
X1
3
4
X2
R_F ≅ 2.2 MΩ
C_L = 16 pF
R_s ≅ 1 kΩ
C₁ ≅ 32 pF
C₂ ≅ 32 pF
b) Oscillator Circuit in DBV or DCK Pinout
Figure 3. Oscillator Circuit (continued)
Practical Design Tips
• The open-loop gain of the unbuffered inverter decreases as power-supply voltage decreases. This decreases
the closed-loop gain of the oscillator circuit. The value of R_s can be decreased to increase the closed-loop
gain, while maintaining the power dissipation of the crystal within the maximum limit.
• R_s and C₂ form a low-pass filter and reduce spurious oscillations. Component values can be adjusted, based
on the desired cutoff frequency.
• C₂ can be increased over C₁ to increase the phase shift and help in start-up of the oscillator. Increasing C₂
may affect the duty cycle of the output voltage.
• At high frequency, phase shift due to R_s becomes significant. In this case, R_s can be replaced by a capacitor
to reduce the phase shift.
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