MT8870D/MT8870D-1
Parameter
R1
L1
C1
C0
Qm
Unit
Ohms
mH
pF
pF
-
Resonator
10.752
.432
4.984
37.915
896.37
Data Sheet
∆f
%
±0.2%
Table 2 - Recommended Resonator Specifications
Note: Qm=quality factor of RLC model, i.e., 1/2ΠƒR1C1.
Applications
Receiver System for British Telecom Spec POR 1151
The circuit shown in Fig. 9 illustrates the use of MT8870D-1 device in a typical receiver system. BT Spec defines
the input signals less than -34 dBm as the non-operate level. This condition can be attained by choosing a suitable
values of R
1
and R
2
to provide 3 dB attenuation, such that -34 dBm input signal will correspond to -37 dBm at the
gain setting pin GS of MT8870D-1. As shown in the diagram, the component values of R
3
and C
2
are the guard
time requirements when the total component tolerance is 6%. For better performance, it is recommended to use the
non-symmetric guard time circuit in Fig. 8.
t
GTP
=(R
P
C
1
)In[V
DD
/(V
DD
-V
TSt
)]
t
GTA
=(R
1
C
1
)In(V
DD
/V
TSt
)
V
DD
C
1
St/GT
R
P
=(R
1
R
2
)/(R
1
+R
2
)
R
1
ESt
R
2
Notes:
R
1
=368 K
Ω ±
1%
R
2
=2.2 M
Ω ±
1%
C
1
=100 nF
±
5%
Figure 8 - Non-Symmetric Guard Time Circuit
8
Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
