MAX1215N Datasheet, PDF (10/21 Pages) Maxim Integrated Products – 1.8V, Low-Power, 12-Bit, 250Msps ADC for Broadband Applications

1.8V, Low-Power, 12-Bit, 250Msps
ADC for Broadband Applications
AV_CC
OV_CC
INP
INN
REFIO
REFADJ
CLKP
CLKN
CLKDIV
T/H
900Ω
900Ω
COMMON-
MODE BUFFER
REFERENCE
DIV1/DIV2
AGND
12-BIT PIPELINE
ADC
CLOCK
MANAGEMENT
MAX1215N
LVDS
DATA
PORT
OGND
DCLKP
DCLKN
D0P/N
D1P/N
D2P/N
D11P/N
ORP/ORN
T/B
Figure 1. Block Diagram
Detailed Description—
Theory of Operation
The MAX1215N uses a fully differential pipelined archi-
tecture that allows for high-speed conversion, opti-
mized accuracy, and linearity while minimizing power
consumption.
Both positive (INP) and negative analog input terminals
(INN) are centered around a 0.7V common-mode volt-
age, and accept a differential analog input voltage
swing of ±V_FS / 4 each, resulting in a typical 1.385V_P-P
differential full-scale signal swing. Inputs INP and INN
are sampled when the differential sampling clock sig-
nal transitions high. When using the clock-divide
mode, the analog inputs are sampled at every other
high transition of the differential sampling clock.
Each pipeline converter stage converts its input voltage
to a digital output code. At every stage, except the last,
the error between the input voltage and the digital out-
put code is multiplied and passed along to the next
pipeline stage. Digital error correction compensates for
ADC comparator offsets in each pipeline stage and
ensures no missing codes. The result is a 12-bit parallel
digital output word in user-selectable two’s-complement
or offset binary output formats with LVDS-compatible
output levels. See Figure 1 for a more detailed view of
the MAX1215N architecture.
Analog Inputs (INP, INN)
INP and INN are the fully differential inputs of the
MAX1215N. Differential inputs usually feature good
rejection of even-order harmonics, which allows for
enhanced AC performance as the signals are progress-
ing through the analog stages. The MAX1215N analog
inputs are self-biased at a 0.7V common-mode voltage
and allow a 1.385V_P-P differential input voltage swing
(Figure 2). Both inputs are self-biased through 900Ω
resistors, resulting in a typical differential input resis-
tance of 1.8kΩ. Drive the analog inputs of the
MAX1215N in AC-coupled configuration to achieve
best dynamic performance. See the Transformer-
Coupled, Differential Analog Input Drive section.
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