MAX2116(2005) 데이터 시트보기 (PDF) - Maxim Integrated

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MAX2116
(Rev.:2005)

Complete DBS Direct-Conversion Tuner ICs with Monolithic VCOs

Maxim Integrated 

Complete DBS Direct-Conversion Tuner ICs

with Monolithic VCOs

PIN

34

35

36

37

38

39, 40

—

Pin Description (continued)

NAME

FUNCTION

QOUT+

Noninverting Baseband Quadrature Output

VCCBB

N.C. (MAX2116)

IOUT - (MAX2118)

IOUT/IOUT+

DC Power Supply for Baseband Circuits. Connect to a 5V ±5% low-noise supply. Bypass with a

1nF capacitor directly to GND. Do not share vias.

No Connection. Pin should be connected directly to GND.

Inverting Baseband In-Phase Output

Noninverting Baseband In-Phase Output

VCCRF2

DC Power Supply for RF Circuits and Second-Stage RF VGA Circuits. Connect to a 5V ±5% low-

noise supply. Bypass with a 1nF capacitor directly to GND. Do not share vias.

QDC+, QDC-

Exposed Pad

Q-Channel Baseband DC Offset Correction. Connect a 0.1µF ceramic chip capacitor from

QDC- to QDC+.

Ground

Detailed Description

The MAX2116/MAX2118 downconvert RF signals in the

925MHz to 2175MHz range directly to baseband I/Q sig-

nals. They are targeted for digital DBS tuner applications.

However, the MAX2116/MAX2118 are applicable to any

system requiring a broadband I/Q downconversion.

Internally, the MAX2116/MAX2118 consist of a broad-

band front-end LNA and variable gain stage, quadrature

downconverter, monolithic broadband VCOs, complete

frequency synthesizer, crystal reference oscillator and

buffer amplifier, programmable baseband lowpass fil-

ters, high-linearity I and Q baseband amplifiers, and off-

set correction amplifiers.

The MAX2116/MAX2118 feature a front-end VGA dynam-

ic range in excess of 60dB. Additionally, the baseband

VGA provides in excess of 19dB of additional gain con-

trol. The VSWR at RFIN is unaffected by the VGA setting.

The MAX2116/MAX2118 include completely monolithic

VCOs to cover the entire 925MHz to 2175MHz frequen-

cy range. The complete frequency range is covered

within a 5V tuning range, thus eliminating the need for

costly 30V supplies and varactor diodes. The VCO

architecture also eliminates problems associated with

frequency pulling with high receive input signal levels.

Applications Information

VCCVCO (Pin 13) Bypass

Adequate filtering of the VCC connection to the

VCCVCO supply pin is critical to achieve low phase noise

performance. See the Typical Operating Circuit.

Baseband LPFs

The MAX2116/MAX2118 include programmable on-

chip 7th-order Butterworth lowpass filters. The filter

bandwidth is adjusted by setting two internal registers

(M, FDAC). The M counter should be set such that the

crystal frequency divided by M is between 1MHz and

2.5MHz. The FDAC register is then used to fine tune the

bandwidth. The -3dB cutoff frequency is determined by

the following equation:

f(3dB) = fXTAL / M ✕ (4 + 0.145 ✕ FDAC)

where M and FDAC are decimals.

The filter can be adjusted from approximately 4MHz to

33MHz. Total device supply current is dependent on

the filter BW setting, with increasing current commensu-

rate with increasing 3dB BW.

I/Q Output Voltage Level

The MAX2116 I/Q outputs are single-ended and opti-

mized for a nominal output voltage drive of 800mVP-P.

Output clipping levels are typically 2VP-P.

The MAX2118 I/Q outputs are differential, with two pos-

sible nominal output voltage levels. The nominal output

voltage swing is set through the DL bit Byte 04 (see

register table description). With DL = low, the nominal

output voltage swing is 590mVP-P differential; DL = high

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