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AD7485
1 MSPS, Serial 14-Bit SAR ADC
FEATURES
Fast Throughput Rate: 1 MSPS
Wide Input Bandwidth: 40 MHz
Excellent DC Accuracy Performance
Flexible Serial Interface
Low Power:
80 mW (Full Power) and 3 mW (NAP Mode)
STANDBY Mode: 2 H9262A Max
Single 5 V Supply Operation
Internal 2.5 V Reference
Full-Scale Overrange Indication
FUNCTIONAL BLOCK DIAGRAM
2.5 V
REFERENCE
BUF
T/H
AV
DD
AGND C
BIAS
DV
DD
DGND
REFSEL
REFOUT
REFIN
VIN
14-BIT
ALGORITHMIC
SAR
NAP
STBY
RESET
CONVST
MCLK
TFS
SCO
CONTROL
LOGIC AND I/O
REGISTERS
SMODE
AD7485
V
DRIVE
SDO
GENERAL DESCRIPTION
The AD7485 is a 14-bit, high speed, low power, successive-
approximation ADC. The part features a serial interface with
throughput rates up to 1 MSPS. The part contains a low noise,
wide bandwidth track-and-hold that can handle input frequencies
in excess of 40 MHz.
The conversion process is a proprietary algorithmic successive-
approximation technique. The input signal is sampled and a
conversion is initiated on the falling edge of the CONVST signal.
The conversion process is controlled by an external master
clock. Interfacing is via standard serial signal lines, making the
part directly compatible with microcontrollers and DSPs.
The AD7485 provides excellent ac and dc performance specifi-
cations. Factory trimming ensures high dc accuracy resulting in
very low INL, DNL, offset, and gain errors.
The part uses advanced design techniques to achieve very low
power dissipation at high throughput rates. Power consumption
in the normal mode of operation is 80 mW. There are two power-
saving modes: a NAP mode keeps reference circuitry alive for
quick power-up and consumes 3 mW, while a STANDBY mode
reduces power consumption to a mere 10 µW.
The AD7485 features an on-board 2.5 V reference, but the part can
also accommodate an externally provided 2.5 V reference source.
The nominal analog input range is 0 V to 2.5 V.
The AD7485 also provides the user with overrange indication via a
fifteenth bit. If the analog input range strays outside the 0 V to
2.5 V input range, the fifteenth data bit is set to a logic high.
The AD7485 is powered from a 4.75 V to 5.25 V supply. The
part also provides a V
DRIVE
pin that allows the user to set the
voltage levels for the digital interface lines. The range for this
V
DRIVE
pin is from 2.7 V to 5.25 V. The part is housed in a
48-lead LQFP package and is specified over a –40°C to +85°C
temperature range.