AD7484 Datasheet, PDF (1/12 Pages) Analog Devices – 3MSPS, 14-Bit SAR ADC

PRELIMINARY TECHNICAL DATA
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3MSPS,
14-Bit SAR ADC
Preliminary Technical Data
AD7484
FEATURES
Fast Throughput Rate: 3Msps
Wide Input Bandwidth: 50MHz
No Pipeline Delays with SAR ADC
Excellent DC Accuracy Performance
Two Parallel Interface Modes
Low Power:
90mW (Full-Power) and 5mW (NAP Mode)
Standby Mode: 1µA max
Single +5V Supply Operation
Internal +2.5V Reference
Full-Scale Overrange Mode (using 15th bit)
System Offset Removal via User Access Offset Register
Nominal 0 to +2.5V Input with Shifted Range Capability
Pin Compatible Upgrade of 12-Bit AD7482
GENERAL DESCRIPTION
The AD7484 is a 14-bit, high speed, low power, succes-
sive-approximation ADC. The part features a parallel
interface with throughput rates up to 3Msps. The part
contains a low-noise, wide bandwidth track/hold amplifier
which can handle input frequencies in excess of 50MHz.
The conversion process is a proprietary algorithmic suc-
cessive-approximation technique which results in no
pipeline delays. The input signal is sampled and a conver-
sion is initiated on the falling edge of the CONVST
signal. The 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 DSPs.
The AD7484 provides excellent ac and dc performance
specifications. Factory trimming ensures high dc accuracy
resulting in very low INL, offset and gain errors.
The part uses advanced design techniques to achieve very
low power dissipation at high throughput rates. Power
consumption in normal mode of operation is 90mW.
There are two power-saving modes: a NAP mode, which
keeps the reference circuitry alive for a quick power up
while consuming 5mW and a STANDBY mode which
reduces power consumption to a mere 5µW.
FUNCTIONAL BLOCK DIAGRAM
VREF3
AVDD AGND CBIAS DVDD DGND
BUF
2.5 V
REFERENCE
VREF1
VREF2
VIN
T/H
14-Bit Error
Correcting SAR
AD7484
MODE1
D14
MODE2
D13
CLIP
D12
NAP
CONTROL
D11
STBY
LOGIC AND I/O
REGISTERS
D10
RESET
D9
CONVST
D8
VDRIVE
D7
The AD7484 features an on-board +2.5V reference but
the part can also accomodate an externally-provided
+2.5V reference source. The nominal analog input range
is 0 to +2.5V but an offset shift capability allows this
nominal range to be offset by +/-200mV. This 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.
The AD7484 also provides the user with an 8% overrange
capability via a 15th bit. Thus, 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.
The AD7484 is powered from a +4.75V to +5.25V sup-
ply. The part also provides a V_DRIVE pin which allows the
user to set the voltage levels for the digital interface lines.
The range for this V_DRIVE pin is from +2.7V to +5.25V.
The 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
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© Analog Devices, Inc., 2001