PRELIMINARY TECHNICAL DATA
3MSPS,
a
PreliminaryTechnicalData
14-BitSARADC
AD7484
FEATURES
FUNC TIO NAL BLO C K D IAGRAM
Fast Throughput Rate: 3Msps
Wide Input Bandw idth: 50MHz
AV
AGND
C
DV
DGND
DD
BIAS DD
VREF1
VREF2
No Pipeline Delays w ith SAR ADC
Excellent DC Accuracy Perform ance
Tw o Parallel Interface Modes
VREF3
BUF
2.5V
REFERENCE
Low Pow er:
90m W (Full-Pow er) and 5m W (NAP Mode)
Standby Mode: 1µA m ax
14-Bit Error
Single +5V Supply Operation
Internal +2.5V Reference
Correcting SAR
VIN
T/H
Full-Scale Overrange Mode (using 15th bit)
System Offset Rem oval via User Access Offset Register
Nom inal 0 to +2.5V Input w ith Shifted Range Capability
Pin Com patible Upgrade of 12-Bit AD7482
AD7484
MODE1
MODE2
CLIP
D14
D13
D12
D11
D10
D9
CONTROL
LOGIC AND I/O
REGISTERS
NAP
STBY
RESET
CONVST
G E NE R AL D E S C R IP T IO N
D8
V
D7
DRIVE
T he AD7484 is a 14-bit, high speed, low power, succes-
sive-approximation ADC. T he part features a parallel
interface with throughput rates up to 3Msps. T he part
contains a low-noise, wide bandwidth track/hold amplifier
which can handle input frequencies in excess of 50MHz.
T he conversion process is a proprietary algorithmic suc-
cessive-approximation technique which results in no
pipeline delays. T he input signal is sampled and a conver-
sion is initiated on the falling edge of the CONVST
signal. T he conversion process is controlled via an inter-
nally trimmed oscillator. Interfacing is via standard
parallel signal lines making the part directly compatible
with microcontrollers and D SPs.
T he AD7484 features an on-board +2.5V reference but
the part can also accomodate an externally-provided
+2.5V reference source. T he nominal analog input range
is 0 to +2.5V but an offset shift capability allows this
nominal range to be offset by +/-200mV. T his allows the
user considerable flexibility in setting the bottom end
reference point of the signal range, a useful feature when
using single-supply op-amps.
T he AD7484 provides excellent ac and dc performance
specifications. Factory trimming ensures high dc accuracy
resulting in very low INL, offset and gain errors.
T he AD7484 also provides the user with an 8% overrange
capability via a 15th bit. T hus, if the analog input range
strays outside the nominal by up to 8%, the user can still
accurately resolve the signal by using the 15th bit.
T he part uses advanced design techniques to achieve very
low power dissipation at high throughput rates. Power
consumption in normal mode of operation is 90mW.
T here are two power-saving modes: a NAP mode, which
keeps the reference circuitry alive for a quick power up
while consuming 5mW and a ST ANDBY mode which
reduces power consumption to a mere 5µW.
T he AD7484 is powered from a +4.75V to +5.25V sup-
ply. T he part also provides a VDRIVE pin which allows the
user to set the voltage levels for the digital interface lines.
T he range for this VDRIVE pin is from +2.7V to +5.25V.
T he part is housed in a 48-pin LQFP package and is
specified over a -40°C to +85°C temperature range.
REV. PrC 7/13/01
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
otherwise under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 2001