zl10354 Zarlink Semiconductor, zl10354 Datasheet - Page 29

• Manufacturer Part Number: zl10354
• Description: Diversity Enabled Nordig Unified Dvb-t Cofdm Terrestrial Demodulator For Pc-tv And Hand-held Digital Tv Dtv
• Manufacturer: Zarlink Semiconductor

5.4.1
The capacitor values used must ensure correct operation of the Pierce oscillator such that the total loop gain is
greater than unity. Correct selection of the two capacitors is very important and the following method is
recommended to obtain values for C1 and C2.
5.4.1.1
Although oscillation may still occur if the loop gain is just above 1, a loop gain of between 5 and 25 is optimum to
ensure that oscillations will occur across all variations in temperature, process and supply voltage, and that the
circuit will exhibit good start-up characteristics.
Equation 1 -
Equation 2 -
5.4.1.2
A
Cin
Cout
Cpar
Zo
gm
Rf
ESR
f
Selection of External Components
total loop gain (between 5 and 25)
C1 + Cpar
C2 + Cpar
parasitic capacitance associated with each oscillator pin (XTI and XTO). It consists of track
capacitances, package capacitance and cell input capacitance. Normally Cpar
9.143 k
8.736 mA/V - transconductance of amplifier at 1.8 V operation -typical
2.3 M
maximum equivalent series resistance of crystal - given by crystal manufacturer ( )
fundamental frequency of crystal (Hz)
Loop Gain Equation
List of Equation Parameters
- A =
- Z
- internal feedback resistor
in
- output impedance of amplifier at 1.8 V operation - typical
=
(2. .f.C
C
out
C
in
.g
m
out
1
)
2
.ESR
C
C1
out
R
f
.C
Figure 14 - Crystal Oscillator Circuit
XTI
+ C
in
in
XTI
Zarlink Semiconductor Inc.
+
Z
1
in
ZL10354
+
Z
29
1
o
XT0
-1
C2
OSCMODE
4pF.
Data Sheet