AD9864 Analog Devices, AD9864 Datasheet - Page 41

• Manufacturer Part Number: AD9864
• Description: IF Digitizing Subsystem
• Manufacturer: Analog Devices

Specifications of AD9864

• Resolution (bits): 24bit
• # Chan: 1
• Sample Rate: 18MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni,SE-Uni
• Adc Architecture: Sigma-Delta
• Pkg Type: CSP

Hung Mixer Mode
The AD9864 can operate in hung mixer mode by tying one of
the LO’s self-biasing inputs to ground, i.e., GNDI, or the
positive supply (VDDI). In this mode, the AD9864 acts as a
narrow-band, band-pass Σ-∆ ADC, since its mixer passes the
IFIN signal without any frequency translation. The IFIN signal
must be centered about the resonant frequency of the Σ-∆ ADC
(i.e., f
be selected to accommodate the bandwidth of the desired input
signal. Note that the LO synthesizer can be disabled because it
is no longer required.
GAIN = –2dB
NF = 2dB
CLK
DUPLEXER PRESELECT
/8) and the clock rate, f
LNA
GAIN = 22dB
NF = 1dB
GAIN = –3dB
NF = 3dB
Figure 73. Example of Split Path Rx Architecture to Increase Receiver Dynamic Range Capabilities
MIXER
CLK
, and decimation factors must
GAIN = 5dB
NF = 12dB
IF SAW 1I
ATTENUATED PATH WITH
CLIP POINT = 7.0dBm
GAIN = 15dB
NF = 2dB
IF
AMP
CLIP POINT = –17dBm
DIRECT PATH WITH
F SAW 2
Rev. 0 | Page 41 of 44
GAIN = –9dB
NF = –9dB
0.1 µ F
36dB
PAD
Since the mixer does not have any losses associated with the mix-
ing operation, the conversion gain through the LNA and mixer is
higher resulting in a nominal input clip point of –24 dBm. The
SNR performance is dependent on the VGA attenuation setting,
I/Q data resolution, and output bandwidth as shown in Figure 74.
Applications requiring the highest instantaneous dynamic range
should set the VGA for maximum attenuation. Also, several extra
decibels in SNR performance can be gained at lower signal band-
widths by using 24-bit I/Q data.
VDDC
R
L
BIAS
OSC
C
OSC
VCO
C
R
VAR
D
47
43
42
19
20
19
20
47
43
42
IFIN
LON
CLKP
CLKN
LOP
CLKN
IFIN
LOP
LON
FILTER
CLKP
LOOP
C
C
P
Z
AD9864
R
AD9864
MASTER
SLAVE
F
IO
IOUTL
IO
15
38
15
FILTER
LOOP
CLKOUT
CLKOUT
DOUTA
DOUTA
SYNCB
SYNCB
FREF
FREF
FS
PC
PD
PC
FS
PE
PD
PE
35
25
24
23
33
31
29
28
35
31
29
28
25
24
23
33
13MHz
ASIC
AD9864
DSP
OR