LTC6421IUDC-20#PBF Linear Technology, LTC6421IUDC-20#PBF Datasheet - Page 10

• Manufacturer Part Number: LTC6421IUDC-20#PBF
• Description: IC ADC DRIVER DIFF 20-QFN
• Manufacturer: Linear Technology
• Type: ADC Driverr

Specifications of LTC6421IUDC-20#PBF

• Applications: Data Acquisition
• Mounting Type: Surface Mount
• Package / Case: 20-QFN
• No. Of Amplifiers: 2
• Input Offset Voltage: 2mV
• Gain Db Max: 20dB
• Bandwidth: 1.3GHz
• Slew Rate: 4500V/µs
• Supply Voltage Range: 2.85V To 3.5V
• Supply Current: 40mA
• Amplifier Case Style: QFN
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LTC6421-20
voltage with a 0.1μF bypass capacitor. When interfacing
with A/D converters such as the LTC22xx families, the
V
Driving A/D Converters
The LTC6421-20 has been specifi cally designed to interface
directly with high speed A/D converters. The back page of
this data sheet shows the LTC6421-20 driving an LTC2285,
which is a dual 14-bit, 125Msps ADC.
The V
V
level of 1.5V. Both ICs are powered from the same 3V
supply voltage.
The inputs to the LTC6421-20 can be confi gured in various
ways, as described in the Input Impedance and Matching
section of this data sheet. The outputs of the LTC6421-20
may be connected directly to the analog inputs of an ADC,
or a simple lowpass or bandpass fi lter network may be
inserted to reduce out-of-band noise.
10
OCM
CM
pins of the LTC2285, which provide a DC voltage
OCM
pin can be connected to the V
pins of the LTC6421-20 are connected to the
CM
pin of the ADC.
Test Circuits
Due to the fully-differential design of the LTC6421 and
its usefulness in applications with differing characteristic
specifi cations, two test circuits are used to generate the
information in this data sheet. Test Circuit A is DC1299, a
two-port demonstration circuit for the LTC6420/LTC6421
family. The schematic and silkscreen are shown in Fig-
ure 4. This circuit includes input and output transformers
(baluns) for single-ended-to-differential conversion and
impedance transformation, allowing direct hook-up to a
2-port network analyzer. There are also series resistors
at the output to avoid loading the amplifi er directly with a
50Ω load. Due to the input and output transformers, the
–3dB bandwidth is reduced from 1.3GHz to approximately
1.1GHz.
Test Circuit B uses a 4-port network analyzer to measure
S-parameters and gain/phase response. This removes the
effects of the wideband baluns and associated circuitry,
for a true picture of the >1GHz S-parameters and AC
characteristics.
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