ADC122S655 Datasheet, PDF (1/20 Pages) National Semiconductor (TI) – Dual 12-Bit, 200 kSPS to 500 kSPS, Simultaneous Sampling A/D Converter

February 25, 2008
ADC122S655
Dual 12-Bit, 200 kSPS to 500 kSPS, Simultaneous Sampling
A/D Converter
General Description
The ADC122S655 is a dual 12-bit, 200 kSPS to 500 kSPS
simultaneous sampling Analog-to-Digital (A/D) converter.
The analog inputs on both channels are sampled simultane-
ously to preserve their relative phase information to each
other. The converter is based on a successive-approximation
register architecture where the differential nature of the ana-
log inputs is maintained from the internal track-and-hold cir-
cuits throughout the A/D converter to provide excellent
common-mode signal rejection. The ADC122S655 features
an external reference that can be varied from 1.0V to V_A.
The ADC122S655's serial data output is binary 2's comple-
ment and is compatible with several standards, such as
SPI™, QSPI™, MICROWIRE™, and many common DSP se-
rial interfaces. The serial clock (SCLK) and chip select bar
(CS) are shared by both channels.
Operating from a single 5V analog supply and a reference
voltage of 2.5V, the total power consumption while operating
at 500 kSPS is typically 11 mW. With the ADC122S655 op-
erating in power-down mode, the power consumption re-
duces to 3 µW. The differential input, low power consumption,
and small size make the ADC122S655 ideal for direct con-
nection to sensors in motor control applications.
Operation is guaranteed over the industrial temperature
range of −40°C to +105°C and clock rates of 6.4 MHz to 16
MHz. The ADC122S655 is available in a 10-lead MSOP pack-
age.
Features
■ ^{True Simultaneous Sampling Differential Inputs}
■ ^{Guaranteed performance from 200 kSPS to 500 kSPS}
■ ^{External Reference}
■ ^{Wide Input Common-Mode Voltage Range}
■ ^{Single High-Speed Serial Data Output}
■ ^{Operating Temperature Range of −40°C to +105°C}
■ ^{SPI™/QSPI™/MICROWIRE™/DSP compatible Serial}
Interface
Key Specifications
■ ^{Conversion Rate}
200 kSPS to 500 kSPS
■ ^INL
±1 LSB (max)
■ ^DNL
±0.95 LSB (max)
■ ^SNR
71 dBc (min)
■ ^THD
-72 dBc (min)
■ ^ENOB
11.25 bits (min)
■ ^{Power Consumption at 500 kSPS}
— Converting, V_A = 5V, V_REF = 2.5V
11 mW (typ)
— Power-Down, V_A = 5V, V_REF = 2.5V
3 µW (typ)
Applications
■ ^{Motor Control}
■ ^{Power Meters/Monitors}
■ ^{Multi-Axis Positioning Systems}
■ ^{Instrumentation and Control Systems}
■ ^{Data Acquisition Systems}
■ ^{Medical Instruments}
■ ^{Direct Sensor Interface}
Connection Diagram
TRI-STATE® is a trademark of National Semiconductor Corporation.
MICROWIRE™ is a trademark of National Semiconductor Corporation.
QSPI™ and SPI™ are trademarks of Motorola, Inc.
© 2008 National Semiconductor Corporation 300519
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