MAX1182ECM+TD Maxim Integrated Products, MAX1182ECM+TD Datasheet - Page 15

• Manufacturer Part Number: MAX1182ECM+TD
• Description: IC ADC 10BIT 65MSPS DL 48-TQFP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1182ECM+TD

• Number Of Bits: 10
• Sampling Rate (per Second): 65M
• Data Interface: Parallel
• Number Of Converters: 2
• Power Dissipation (max): 240mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP Exposed Pad, 48-eTQFP, 48-HTQFP, 48-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 7 shows an AC-coupled, single-ended applica-
tion. Amplifiers like the MAX4108 provide high-speed,
high-bandwidth, low noise, and low distortion to main-
tain the integrity of the input signal.
The most frequently used modulation technique for digi-
tal communications applications is probably the
Quadrature Amplitude Modulation (QAM). Typically
found in spread-spectrum based systems, a QAM signal
represents a carrier frequency modulated in both ampli-
tude and phase. At the transmitter, modulating the base-
band signal with quadrature outputs, a local oscillator
followed by subsequent up-conversion can generate the
QAM signal. The result is an in-phase (I) and a quadra-
ture (Q) carrier component, where the Q component is
90 degree phase-shifted with respect to the in-phase
component. At the receiver, the QAM signal is divided
down into it’s I and Q components, essentially repre-
senting the modulation process reversed. Figure 8 dis-
plays the demodulation process performed in the
analog domain, using the dual matched 3V, 10-bit ADC
MAX1182 and the MAX2451 quadrature demodulator to
recover and digitize the I and Q baseband signals.
Before being digitized by the MAX1182, the mixed-down
signal components may be filtered by matched analog
filters, such as Nyquist or pulse-shaping filters which
remove any unwanted images from the mixing process,
thereby enhancing the overall signal-to-noise (SNR) per-
formance and minimizing inter-symbol interference.
Table 1. MAX1182 Output Codes For Differential Inputs
*V
REF
DIFFERENTIAL INPUT
Typical QAM Demodulation Application
= V
Single-Ended AC-Coupled Input Signal
with Internal Reference and Parallel Outputs
-V
-V
V
-V
REFP
V
REF
REF
VOLTAGE*
REF
REF
REF
x 511/512
x 511/512
x 512/512
- V
x 1/512
0
x 1/512
REFN
Dual 10-Bit, 65Msps, 3V, Low-Power ADC
______________________________________________________________________________________
+FULL SCALE - 1 LSB
-FULL SCALE + 1 LSB
DIFFERENTIAL
-FULL SCALE
Bipolar Zero
+1 LSB
INPUT
-1 LSB
The MAX1182 requires high-speed board layout design
techniques. Locate all bypass capacitors as close to
the device as possible, preferably on the same side as
the ADC, using surface-mount devices for minimum
inductance. Bypass V
two parallel 0.1µF ceramic capacitors and a 2.2µF
bipolar capacitor to GND. Follow the same rules to
bypass the digital supply (OV
boards with separated ground and power planes pro-
duce the highest level of signal integrity. Consider the
use of a split ground plane arranged to match the
physical location of the analog ground (GND) and the
digital output driver ground (OGND) on the ADCs pack-
age. The two ground planes should be joined at a sin-
gle point such that the noisy digital ground currents do
not interfere with the analog ground plane. The ideal
location of this connection can be determined experi-
mentally at a point along the gap between the two
ground planes, which produces optimum results. Make
this connection with a low-value, surface-mount resistor
(1Ω to 5Ω), a ferrite bead or a direct short. Alternatively,
all ground pins could share the same ground plane, if
the ground plane is sufficiently isolated from any noisy,
digital systems ground plane (e.g., downstream output
buffer or DSP ground plane). Route high-speed digital
signal traces away from the sensitive analog traces of
either channel. Make sure to isolate the analog input
lines to each respective converter to minimize channel-
to-channel crosstalk. Keep all signal lines short and
free of 90 degree turns.
STRAIGHT OFFSET
11 1111 1111
10 0000 0001
10 0000 0000
01 1111 1111
00 0000 0001
00 0000 0000
BINARY
T/B = 0
Grounding, Bypassing, and
DD
, REFP, REFN, and COM with
DD
TWO’S COMPLEMENT
) to OGND. Multilayer
Board Layout
01 1111 1111
00 0000 0001
00 0000 0000
11 1111 1111
10 0000 0001
10 0000 0000
T/B = 1
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