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PDF LTC6605-10 Data sheet ( Hoja de datos )
| Número de pieza | LTC6605-10 | |
| Descripción | Dual Matched 10MHz Filter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC6605-10www.DataSheet4U.com
Dual Matched 10MHz Filter
with Low Noise, Low Distortion
Differential Amplifier
FEATURES
DESCRIPTION
n Two Matched 10MHz 2nd Order Lowpass Filters
with Differential Amplifiers
Gain Match: ±0.35dB Max, Passband
Phase Match: ±1.2° Max, Passband
Single-Ended or Differential Inputs
n < –90dBc Distortion in Passband
n 2.1nV/√Hz Op Amp Noise Density
n Pin-Selectable Gain (0dB/12dB/14dB)
n Pin-Selectable Power Consumption (0.35mA/
16.2mA/33.1mA)
n Rail-to-Rail Output Swing
Adjustable Output Common Mode Voltage Control
Buffered, Low Impedance Outputs
n 2.7V to 5.25V Supply Voltage
n Small 22-Pin 6mm × 3mm × 0.75mm DFN Package
APPLICATIONS
n Broadband Wireless ADC Driver/Filter
n Antialiasing Filter
n Single-Ended to Differential Conversion
n DAC Smoothing Filter
n Zero-IF Direct Conversion Receivers
The LTC®6605-10 contains two independent, fully differ-
ential amplifiers configured as matched 2nd order 10MHz
lowpass filters. The f–3dB of the filters is adjustable in the
range of 9.7MHz to 14MHz.
The internal op amps are fully differential, feature very
low noise and distortion, and are compatible with 16-bit
dynamic range systems. The inputs can accept single-
ended or differential signals. An input pin is provided
for each amplifier to set the common mode level of the
differential outputs.
Internal laser-trimmed resistors and capacitors determine
a precise, very well matched (in gain and phase) 10MHz
2nd order filter response. A single optional external re-
sistor per channel can tailor the frequency response for
each amplifier.
Three-state BIAS pins determine each amplifier’s power
consumption, allowing a choice between shutdown, me-
dium power or full power.
The LTC6605-10 is available in a compact 6mm × 3mm
22-pin leadless DFN package and operates over a –40°C
to 85°C temperature range.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual, Matched 9.7MHz Lowpass Filter
+
VINA 3V
–
+
VINB 3V
–
1
2+
3
4–
5
6 LTC6605-10
7
8+
9
10 –
11
22
21 3V
0.1μF
20
0.1μF
19
18
17
16
15 3V
0.1μF
14
0.1μF
13
12
660510 TA01
–
VOUTA
+
–
VOUTB
+
Channel to Channel Phase Matching
120
352 TYPICAL UNITS
TA = 25°C
100 fIN = 10MHz
80
60
40
20
0
–1.0 –0.8–0.6 –0.4–0.2 0 0.2 0.4 0.6 0.8 1.0
PHASE MATCH (DEG)
660510 TA01b
660510f
1
1 page  
ELECTRICAL CHARACTERISTICS
Note 8: See the Applications Information section for a detailed
discussion of input and output common mode range. Input common
mode range is tested by measuring the differential DC gain with VINCM
= mid-supply, and again with VINCM at the input common mode range
limits listed in the Electrical Characteristics table, with ΔVIN = ±0.25V,
verifying that the differential gain has not deviated from the mid-supply
common mode input case by more than 0.5%, and that the common
mode offset (VOSCM) has not deviated from the mid-supply common
mode offset by more than ±10mV.
Output common mode range is tested by measuring the differential
DC gain with VOCM = mid-supply, and again with voltage set on the
VOCM pin at the output common range limits listed in the Electrical
LTC6605-10www.DataSheet4U.com
Characteristics table verifying that the differential gain has not
deviated from the mid-supply common mode input case by more than
0.5%, and that the common mode offset (VOSCM) has not deviated by
more than ±10mV from the mid-supply case.
Note 9: CMRR is defined as the ratio of the change in the input common
mode voltage at the internal amplifier inputs to the change in differential
input referred voltage offset (VOS).
Note 10: Power supply rejection ratio (PSRR) is defined as the ratio of
the change in supply voltage to the change in differential input referred
voltage offset (VOS).
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
37.5
35.0
32.5
30.0
VS = 2.7V, BIAS = FLOAT
27.5 VS = 3V, BIAS = FLOAT
25.0
22.5
VS
VS
VS
VS
=
=
=
=
5V, BIAS =
2.7V, BIAS
3V, BIAS =
5V, BIAS =
FLOAT
= V+
V+
V+
20.0
17.5
15.0
VINCM = VOCM = MID-SUPPLY
12.5
–60 –40 –20 0 20 40 60 80 100
TEMPERATURE (°C)
660510 G01
–3dB Frequency vs Temperature
2.5
VS = 3V
2.0 VINCM = VOCM = 1.5V
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
BIAS = FLOAT
–2.0 BIAS = V+
–2.5
–60 –40 –20 0 20 40 60 80 100
TEMPERATURE (°C)
660510 G03
Filter Gain vs Temperature
1.010
1.005
1.000
0.995
VS = 3V, BIAS = V+
VINCM = VOCM = MID-SUPPLY
5 RANDOM UNITS
0.990
–60 –40 –20 0 20 40
60
TEMPERATURE (°C)
80 100
660510 G02
Filter Frequency Response
0
–10
–20
–30
BIAS = V+
BIAS PIN FLOATING
–40
VS = 3V
VINCM = VOCM = MID SUPPLY
–50
0.1 1.0 10
100
FREQUENCY (MHz)
1000
660514 G04
660510f
5
5 Page 
LTC6605-10www.DataSheet4U.com
APPLICATIONS INFORMATION
Setting the passband gain (GAIN = R2/R1) only requires
choosing a value for R1, since R2 is a fixed internal 400Ω.
Therefore, the following three gains can be easily configured
without external components:
Table 1. Configuring the Passband Gain Without External
Components
GAIN GAIN (dB) R1 (Ω)
(V/ V)
INPUT PINS TO USE
1 0 400 Drive the 400Ω Resistors. Tie
the 100Ω Resisters Together.
4 12 100 Drive the 100Ω Resistors.
5 14 80 Drive the 400Ω and 100Ω
Resistors in Parallel.
Figure 4 shows three filter configurations with an
f–3dB = 9.7MHz, without any external components. These
filters have a Q = 0.61, which is an almost ideal Bessel
characteristic with linear phase.
Figure 5 shows three filter configurations that use some
external resistors, and are tailored for a very flat ±0.7dB
11.2MHz passband.
Many other configurations are possible by using the equa-
tions in Figure 3. For example, external resistors can be
added to modify the value of R1 to configure GAIN ≠ 1. For
an even more flexible filter IC with similar performance,
consider the LTC6601.
The resonant frequency, fO, is independent of R1, and
therefore independent of the gain. For any LTC6605-10
filter configuration that conforms to Figure 3, the fO is
fixed at 11.36MHz. The f–3dB frequency depends on the
combination of fO and Q. For any specific gain, Q is adjusted
by the selection of R4.
Setting the f–3dB Frequency
Using an external resistor (REXT), the f–3dB frequency is ad-
justable in the range of 9.7MHz to 14.0MHz (see Figure 3).
The minimum f–3dB is set for REXT equal to 0Ω and the
maximum f–3dB is arbitrarily set for a maximum passband
gain peak less than 1dB.
Table 2. REXT Selection GAIN = 1,
R1 = 400Ω, R4A = R4B = 100Ω
f–3dB (MHz)
REXT Ω
9.7 0
10 5.11
10.5 13.3
11 22.1
11.5 31.6
12 41.2
12.5 52.3
13 64.9
13.5 80.6
14 97.6
BIAS Pin
Each channel of the LTC6605-10 has a BIAS pin whose
function is to tailor both performance and power. The BIAS
pin can be modeled as a voltage source whose potential
is 1.15V above the V– supply and that has a Thevenin
equivalent resistance of 150k. This three-state pin has fixed
logic levels relative to V– (see the Electrical Characteristics
table), and can be driven by any external source that can
drive the BIAS pin’s equivalent input impedance.
If the BIAS pin is tied to the positive supply, the part is
in a fully active state configured for highest performance
(lowest noise and lowest distortion).
If the BIAS pin is floated (left unconnected), the part is in a
fully active state, but with amplifier currents reduced and
performance scaled back to preserve power consumption.
Care should be taken to limit external leakage currents
to this pin to under 1μA to avoid putting the part in an
unexpected state.
If the BIAS pin is tied to the most negative supply (V–),
the part is in a low power shutdown mode with amplifier
outputs disabled. In shutdown, all internal biasing current
sources are shut off, and the output pins each appear as
open collectors with a non-linear capacitor in parallel and
steering diodes to either supply. Because of the non-linear
capacitance, the outputs can still sink and source small
amounts of transient current if exposed to significant
voltage transients. Using this function to wire-OR outputs
together is not recommended.
660510f
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC6605-10.PDF ] | |
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