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參數(shù)資料
| 型號： | MAX2105 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 16-Bit Buffers/Drivers With 3-State Outputs 48-TSSOP -40 to 85 |
| 中文描述： | 直接變頻調(diào)諧器IC，適合數(shù)字DBS應(yīng)用 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 151K |
| 代理商： | MAX2105 |
M
GaAsFET can serve this function. This circuitry is usual-
ly required in order to meet system noise-figure require-
ments, may provide a buffered F-connector output, and
may also be required to meet stringent LO leakage
requirements. The PIN attenuator is typically controlled
by the same voltage as the MAX2102/MAX2105 AGC
control pin so that, overall, a single AGC line from the
baseband processor can control the entire tuner.
In some applications, a varactor-tuned preselection
bandpass filter is added between the discrete LNA and
the MAX2102/MAX2105. This is usually required only
for very high-linearity tuners, such as those designed
for single channel-per-carrier (low-data-rate) applica-
tions. The filter provides a means of broadly filtering
adjacent interferers, thus improving the tuner’s inter-
modulation performance. Additionally, the filter
removes the RF interference at twice the LO frequency,
which would otherwise add to cochannel interference
(the MAX2102/MAX2105 alone reject this carrier to typi-
cally -32.3dBc).
External Osc illator
Since the MAX2102/MAX2105 are direct-conversion
receivers, the external LO must tune to the same fre-
quencies as the desired RF input signals.
The MAX2102/MAX2105 oscillator input port (LO,
LO
)
accepts either a single-ended or differential (balanced)
LO signal. A differential LO offers reduced LO leakage
to the RFIN port, as well as lower spurious downconver-
sion levels of RF signals, which are at twice the LO fre-
quency. Refer to Figure 3 for differential LO
connections. For best performance, ensure that the LO
and
LO
traces are symmetrical.
The LO drive levels should be maintained to within the
specified limits. If the LO drive falls below the specified
range, quadrature performance may be affected.
Driving LO above the specified limits will cause a high-
er LO leakage level at RFIN; this may be acceptable in
some applications. The MAX2102/MAX2105 offset-cor-
rection loop can withstand LO leakage levels corre-
sponding to at least 0dBm of LO input power drive.
Presc aler
Typical stand-alone tuner applications will not use the
MAX2102/MAX2105 prescaler function, but instead use
a commercial synthesizer IC such as the Philips
TSA5055, which has an internal prescaler. To disable
the MAX2102/MAX2105 prescaler, disconnect the
PSGND pin (leave open). The prescaler will cause an
output spur in the baseband spectrum, to a level of
about -20dBc (referred to 500mVp-p baseband output
level) that may land within the desired signal bandwidth
in some applications.
To use the MAX2102/MAX2105 prescaler, connect the
PSGND pin to ground. In some applications, the
prescaler may be toggled on and off using a MOSFET
to switch PSGND to ground. PSGND should be forced
to within 100mV of ground, and the MOSFET must be
capable of sinking 15mA. PSOUT is capable of driving
a typical CMOS load of 10k
in parallel with 5pF. A
2k
pull-down resistor must be connected from PSOUT
to GND.
The prescaler requires a stable level at the MOD pin
12ns before the falling edge of PREOUT to assert the
desired modulus. The level at MOD must remain static
until 3ns after this falling edge.
Baseband Amplifiers
The MAX2102/MAX2105 baseband amplifiers provide
over 2Vp-p swing at IOUT and QOUT, and are capable
of driving 100
. IOUT and QOUT must be AC-coupled
to any lowpass filters. In a typical application, IOUT and
QOUT drive a 5th or 7th-order lowpass filter for ADC
anti-aliasing purposes (see the Systems Considerations:
Lowpass Filters in Direct-Conversion Tuners section).
After the filters, in some cases, additional gain may be
required. This can be accomplished with a pair of video-
speed op amps, such as the MAX4216 dual-video op
amp. Alternatively, the MAX1002/MAX1003 dual ADC
has built-in gain ahead of the ADCs, digitizing levels as
low as 125mVp-p. Contact Maxim for more information
about the MAX4216 or the MAX1002/MAX1003.
Direc t-Conversion Tuner ICs for
Digital DBS Applic ations
12
______________________________________________________________________________________
MAX2102
MAX2105
22
56
22pF
LO
22
21
22
56
22pF
LOPOWER:
-15dBmTO-5dBm
POWER INTOLO LO.
LO LODRIVEN DIFFERENTIALLY
LO
Figure 3. Differential LO Drive
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX2105CWI | Direct-Conversion Tuner ICs for Digital DBS Applications |
| MAX2104 | 16-Bit Buffers/Drivers With 3-State Outputs 48-TSSOP -40 to 85 |
| MAX2104CCM | PLASTIC ENCAPSULATED DEVICES |
| MAX2106 | 16-Bit Buffers/Drivers With 3-State Outputs 48-TVSOP -40 to 85 |
| MAX2106UCM | DBS Direct Downconverter |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX2105CWI | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX2105CWI+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX2106 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:DBS Direct Downconverter |
| MAX2106_05 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:DBS Direct Downconverter |
| MAX2106CCM | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Analog IC |
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