AD7985_17 Datasheet, PDF (1/29 Pages) Analog Devices – 16-Bit, 2.5 MSPS, PulSAR 15.5 mW ADC in LFCSP

Data Sheet
16-Bit, 2.5 MSPS, PulSAR
15.5 mW ADC in LFCSP
AD7985
FEATURES
16-bit resolution with no missing codes
Throughput: 2.5 MSPS (TURBO high), 2.0 MSPS (TURBO low)
Low power dissipation
15.5 mW at 2.5 MSPS, with external reference
28 mW at 2.5 MSPS, with internal reference
INL: ±0.7 LSB typical, ±1.5 LSB maximum
SNR
88.5 dB, with on-chip reference
90 dB, with external reference
4.096 V internal reference: typical drift of ±10 ppm/°C
Pseudo differential analog input voltage range
0 V to VREF with VREF up to 5.0 V
Allows use of any input range
No pipeline delay
Logic interface: 1.8 V/2.5 V/2.7 V
Proprietary serial interface SPI-/QSPI™-/MICROWIRE™-/DSP-
compatible¹
Ability to daisy-chain multiple ADCs with busy indicator
20-lead, 4 mm × 4 mm LFCSP
APPLICATIONS
Battery-powered equipment
Communications
ATE
Data acquisition systems
Medical instruments
0V
TO
V_REF
APPLICATION DIAGRAM
1.8V
TO
5V 2.5V 2.7V
BVDD _AVDD, VIO
DVDD _TURBO
IN+
SDI
AD7985
IN–
SCK
SDO
GND REF
CNV
10µF
VIO
3- OR 4-WIRE
INTERFACE:
SPI, CS,
DAISY CHAIN
(TURBO = LOW)
NOTES
1. GND REFERS TO REFGND, AGND, AND DGND.
Figure 1.
GENERAL DESCRIPTION
The AD7985¹ is a 16-bit, 2.5 MSPS successive approximation
analog-to-digital converter (SAR ADC). It contains a low power,
high speed, 16-bit sampling ADC, an internal conversion clock,
an internal reference (and buffer), error correction circuits, and
a versatile serial interface port. On the rising edge of CNV, the
AD7985 samples an analog input, IN+, between 0 V and REF
with respect to a ground sense, IN−. The AD7985 features a
very high sampling rate turbo mode (TURBO is high) and a
reduced power normal mode (TURBO is low) for low power
applications where the power is scaled with the throughput.
In normal mode (TURBO is low), the SPI-compatible serial inter-
face also features the ability, using the SDI input, to daisy-chain
several ADCs on a single 3-wire bus and provide an optional busy
indicator. It is compatible with 1.8 V, 2.5 V, and 2.7 V supplies
using the separate VIO supply.
The AD7985 is available in a 20-lead LFCSP with operation
specified from −40°C to +85°C.
Table 1. MSOP, LFCSP, 14-/16-/18-Bit PulSAR® ADCs¹
Type
100 kSPS
250 kSPS
14-Bit
AD7940
AD7942²
16-Bit
AD7680
AD7685²
AD7683
AD7687²
AD7684
AD7694
18-Bit
AD7691²
1 _{Protected by U. S. Patent 6,703,961.}
400 kSPS to 500 kSPS
AD7946²
AD7686²
AD7688²
AD7693²
AD7690²
≥1000 kSPS
AD7980²
AD7983²
AD7985³
AD7982²
AD7984²
AD7986³
ADC Driver
ADA4941-1
ADA4841-1
AD8021
ADA4941-1
ADA4841-1
AD8021
1 _{See www.analog.com for the latest selection of PulSAR ADCs and ADC drivers.}
2 _{Pin for pin compatible with all other devices marked with this endnote.}
3 _{The AD7985 and AD7986 are pin for pin compatible.}
Rev. C
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