MT8870D/MT8870D-1 Data Sheet
8
Zarlink Semiconductor Inc.
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.
Figure 8 - Non-Symmetric Guard Time Circuit
Parameter Unit Resonator
R1 Ohms 10.752
L1 mH .432
C1 pF 4.984
C0 pF 37.915
Qm - 896.37
∆f%±0.2%
t
GTP
=(R
P
C
1
)In[V
DD
/(V
DD
-V
TSt
)]
t
GTA
=(R
1
C
1
)In(V
DD
/V
TSt
)
R
P
=(R
1
R
2
)/(R
1
+R
2
)
V
DD
St/GT
ESt
C
1
R
2
R
1
Notes:
R
1
=368 K Ω ± 1%
R
2
=2.2 M Ω ± 1%
C
1
=100 nF ± 5%
