ltm9005v Linear Technology Corporation, ltm9005v Datasheet - Page 12

• Manufacturer Part Number: ltm9005v
• Description: Ltm9005 - If Sampling Receiver Subsystem
• Manufacturer: Linear Technology Corporation

operaTion
LTM9005
DESCRIPTION
The LTM9005 is an integrated System in a Package (SiP)
that includes a high-speed 14-bit A/D converter, two low-
distortion fixed-gain amplifiers, a SAW filter, a continuously
variable attenuator and an active mixer. The LTM9005 is
designed for very compact IF sampling applications with
RF input frequencies up to 3.8GHz. Typical applications
include wireless base stations, remote radio heads and
communications test instrumentation.
All of the supply bypassing and passive filtering has been
included inside the LTM9005 making the total solution size
extremely small. Furthermore, the tight coupling makes
the performance more consistent and less dependent on
board layout. Great care has been taken to protect sensi-
tive signals from noise within the µModule package and
isolate the RF section from the digital section.
The overall gain is optimized for the dynamic range of the
ADC relative to the RF input level allowed by the mixer. The
equivalent cascaded noise figure is 16dB. The RF input
level for –1dBFs is typically –19dBm.
The following sections describe the operation of each
functional element. The SiP technology allows the
LTM9005 to be customized and this is described in the
Semi-Custom Options section. The outline of the remaining
sections follows the basic functional elements as shown
in Figure 2.
RF
The Applications section describes the design consider-
ations and recommendations for interfacing to the key
ports and functions as well as board layout in the follow-
ing order:
12
MIXER
V
LO
CC1
GAIN CONTROL
ATTENUATOR
Figure 2. Basic Functional Elements
AMPLIFIER
V
1ST
CC2
SAW
AMPLIFIER
V
2ND
CC3
GND
BPF
ADC
ADC CLK
V
DD
LTM9005
9005 F02
OV
OGND
DD
• RF Input Port
• LO Input Port
• ADC Clock Input Port
• GAIN Control Input
• SENSE and Reference Input
• Digital Outputs
• Shutdown Control
• Power Supplies
• Layout
SEMI-CUSTOM OPTIONS
The µModule construction affords a new level of flexibility
in application-specific standard products. Standard mixed-
signal, IF and RF components can be integrated regardless
of their process technology and matched with passive
components to a particular application. The LTM9005-AA,
as the first example, is configured with a 14-bit ADC
sampling at rates up to 125Msps. The total system gain
is 22dB of which 20dB is variable. The IF is fixed by the
SAW filter at 140MHz with 16MHz bandwidth. The RF range
is matched for 1.6GHz to 2.3GHz with external matching
required to achieve 400MHz to 3.8GHz.
However, other options are possible through Linear
Technology’s semi-custom development program. Linear
Technology has in place a program to deliver other speed,
resolution, RF/IF range, gain and filter configurations for
nearly any specified application. ADC resolution and speed
options range from 14-bits and 125Msps to 10-bits and
10Msps. The IF can be set from 70MHz to about 270MHz
with bandwidths from a few MHz to about 60MHz. These
semi-custom designs are based on existing ADCs, am-
plifiers, filters and mixers with appropriately modified
matching networks. The final subsystem is then tested
to the exact parameters defined for the application. The
final result is a fully integrated, accurately tested and
optimized solution in the same package. For more details
on the semi-custom receiver subsystem program, contact
Linear Technology.
9005p