micrf507ymltr Micrel Semiconductor, micrf507ymltr Datasheet - Page 32

• Manufacturer Part Number: micrf507ymltr
• Description: 470mhz To 510mhz Low-power Fsk Transceiver With +10dbm Power Amplifier
• Manufacturer: Micrel Semiconductor

Figure 22 shows two waveforms with different attenuator
setting:
frequency deviation is lowered and vice versa.
The resulting frequency deviation in terms of the
parameters discussed above is given in the following
equations:
where:
Note that the constants C
Actual frequency deviation may differ by a few percent.
Modulator Filter
To reduce the high-frequency components in the
generated waveform, a filter with programmable cut-off
frequency can be enabled. This is done using Mod_F[2:0],
bit 0 being LSB. The Mod_F field should be set according
to the formula:
March 2010
Micrel, Inc.
f
f
f
Refclk_K:
Mod_clkS:
f
Mod_I:
Mod_A:
C
C
DEV
XCO
RF
MOD_CLK
1
2
f
f
:
:
DEV
:
Mod_Aa <
MOD_CLK
:
:
=
:
f
Mod_I
MOD_CLK
=
Refclk_K
Mod_F =
Mod_Ab
Single sided frequency deviation [Hz]
Crystal oscillator frequency [Hz]
Center frequency [Hz]
6 bit divider, values between 1 and 63
Modulator
between 0 and 7
Modulator clock frequency, derived
from the crystal frequency, Refclk_K
and Mod_clkS
Modulator
between 0 and 31
Modulator attenuator setting, values
between 0 and 15
-2.72 x 10
85.2
×
1
+
1
f
Mod_A
and C
XCO
×
. If Mod_A is increased, the
150x10
1
2
10
(7
−
current
Mod_clkS)
r
clock
2
b
×
are empirically derived.
3
bps
(
C
1
+
setting,
C
setting,
2
×
f
RF
)
values
values
32
in which r
modulator filter and Mod_F=7 provides the most filtering.
Figure 23 shows a waveform with and without the filter.
The modulator filter will not influence the frequency
deviation as long as the programmed cut-off frequency is
above the actual bit rate.
Figure 23. Modulator Waveform with and without Filtering
b
is the bit rate in bits/sec. Mod_F=0 disables the
M9999-032210-B
MICRF507