DC1398A-GA Linear Technology, DC1398A-GA Datasheet - Page 14

• Manufacturer Part Number: DC1398A-GA
• Description: BOARD EVAL LTM9001-GA
• Manufacturer: Linear Technology
• Type: Baseband Receiverr

Specifications of DC1398A-GA

• Design Resources: Demo Circuit 1398A Schematic
• Frequency: 0Hz ~ 300MHz
• Kit Contents: Board, Manual
• Features: LTM9001 16bit Receiver Subsystem, DC-10MHz LPF
• Tool / Board Applications: Wireless Connectivity-ZigBee, RF, Infrared, USB
• Development Tool Type: Hardware - Eval/Demo Board
• Mcu Supported Families: LTM9001
• For Use With/related Products: LTM9001
• Lead Free Status / RoHS Status: Not applicable / Not applicable

LTM9001-GA
APPLICATIONS INFORMATION
INPUT SPAN
The LTM9001 is confi gured with a fi xed input span and
input impedance. With the amplifi er gain and the ADC
input network described above for LTM9001-GA, the full-
scale input range of the driver circuit is 1000mV
recommended ADC input span is achieved by tying the
SENSE pin to V
changed by applying a DC voltage to the SENSE pin.
Input Impedance and Matching
The differential input impedance of the LTM9001 can be
50Ω, 200Ω or 400Ω. In some applications the differential
inputs may need to be terminated to a lower value imped-
ance, e.g. 50Ω, in order to provide an impedance match
for the source. Several choices are available.
One approach is to use a differential shunt resistor
(Figure 2). Another approach is to employ a wideband
transformer (Figure 3). Both methods provide a wideband
match. The termination resistor or the transformer must
be placed close to the input pins in order to minimize the
refl ection due to input mismatch.
Table 2. Differential Amplifi er Input Termination Values
14
400Ω
200Ω
50Ω
Z
IN
DD
. However, the ADC input span can be
R
T
66.5Ω
Figure 2
None
57Ω
P-P
. The
Figure 2. Input Termination for Differential 50Ω Input Impedance
Using Shunt Resistor (See Table 2 for R
+
–
Figure 3. Input Termination for Differential 50Ω
Input Impedance Using a Wideband Transformer
V
25Ω
25Ω
IN
+
–
V
25Ω
25Ω
•
IN
•
R
IN
IN
IN
IN
T
+
–
+
–
Z
Z
Z
Z
IN
IN
IN
IN
/2
/2
/2
/2
R
R
R
R
T
F
F
F
F
LTM9001-GA
LTM9001-GA
Values)
9001-GA F02
9001-GA F03
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