CMX972 Datasheet, PDF (23/41 Pages) CML Microcircuits – Small 32-lead VQFN Package

Quadrature Demodulator with IF PLL/VCO
CMX972
Rx Control Register b7
Writing b7 = ’1’ the output drive capability of the demodulator I/Q output is increased, this mode
allows the CMX972 to support wider bandwidth modulation and/or driver lower impedance loads;
b7 = ’0’ is the default condition with best power efficiency.
Rx Control Register b6
Writing b6 = ‘1’ enables the correction circuit in the quadrature demodulator. This will improve the
I/Q phase balance of the demodulator particularly in LO/2 mode; enabling this mode increases the
current consumption slightly. For further information see section 5.1.1.
With b6 = ‘0’ this enhanced mode is disabled for optimum current consumption.
Rx Control Register b5
Reserved, must be cleared to ‘0’ for correct operation.
Rx Control Register b4 – b2
Variable Gain (VGB) Control; these bits control the gain of the IF/RF amplifier reducing the gain
from the maximum in 6dB steps.
Bit _{b4 b3 b2}
11
1 Reserved do not use
11
0 Reserved do not use
10
1 VG = -30dB
10
0 VG = -24dB
01
1 VG = -18dB
01
0 VG = -12dB
00
1 VG = -6dB
00
0 VG = 0dB (maximum gain)
Rx Control Register b1 – b0
Variable Gain (VGA) control; this bits control the gain of the post-I/Q mixer baseband amplifiers
reducing the gain from the maximum in 6dB steps.
Bit _b1
1
1
0
0
b0
1 VG = -18dB
0 VG = -12dB
1 VG = -6dB
0 VG = 0dB (maximum gain)
6.3.2 Rx Control Register - $EC: 8-bit read
This read-only register mirrors the value in register $1C; see section 6.3.1 for details of bit
functions.
6.4 Rx Mode Register
6.4.1 Rx Mode Register - $1D: 8-bit write
This register controls operational modes of the receiver.
All bits of this register are cleared to ‘0’ by a General Reset command.
 2015 CML Microsystems Plc
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