ISL267440_14 Datasheet, PDF (16/18 Pages) Intersil Corporation – 10-Bit and 12-Bit, 1MSPS SAR ADCs

ISL267440, ISL267450A
Track and Hold Acquisition Time
The track and hold acquisition time is the minimum time
required for the track and hold amplifier to remain in track mode
for its output to reach and settle to within 0.5 LSB of the applied
input signal.
Power Supply Rejection Ratio (PSRR)
The power supply rejection ratio is defined as the ratio of the
power in the ADC output at full-scale frequency, f, to ADC VDD
supply of frequency f_S. The frequency of this input varies from
1kHz to 1MHz.
PSRR(dB) = 10log (Pf ⁄ Pfs)
(EQ. 4)
Pf is the power at frequency f in the ADC output; Pfs is the power
at frequency f_s in the ADC output.
Application Hints
Grounding and Layout
The printed circuit board that houses the ISL267440,
ISL267450A should be designed so that the analog and digital
sections are separated and confined to certain areas of the
board. This facilitates the use of ground planes that can be easily
separated. A minimum etch technique is generally best for
ground planes since it gives the best shielding. Digital and analog
ground planes should be joined in only one place, and the
connection should be a star ground point established as close to
the GND pin on the ISL267440, ISL267450A as possible. Avoid
running digital lines under the device, as this will couple noise
onto the die. The analog ground plane should be allowed to run
under the ISL267440, ISL267450A to avoid noise coupling.
The power supply lines to the device should use as large a trace
as possible to provide low impedance paths and reduce the
effects of glitches on the power supply line.
Fast switching signals, such as clocks, should be shielded with
digital ground to avoid radiating noise to other sections of the
board, and clock signals should never run near the analog inputs.
Avoid crossover of digital and analog signals. Traces on opposite
sides of the board should run at right angles to each other. This
reduces the effects of feedthrough through the board. A
microstrip technique is by far the best but is not always possible
with a double-sided board.
In this technique, the component side of the board is dedicated
to ground planes, while signals are placed on the solder side.
Good decoupling is also important. All analog supplies should be
decoupled with μF tantalum capacitors in parallel with 0.1μF
capacitors to GND. To achieve the best from these decoupling
components, they must be placed as close as possible to the
device.
Revision History
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to web to make sure you
have the latest revision.
DATE
REVISION
CHANGE
June 15, 2012
FN7708.2
Page 2- Typical Connection Diagram: Added value to cap 0.1µF and removed ‘+’ from the 0.1 capacitor.
Page 3, Ordering Information Table: “Removed coming soon on all the SOT23’s.”
Page11- Figure22, Ideal Transfer Characteristics: replaced the diagram for clarity.
March 22, 2012
FN7708.1
Page 12 - Updated Voltage Reference Input section
Page 13 - Removed Applications Information section
Pages 13, 14 - Replaced/updated the following sections: Power-Down/Standby Modes, Dynamic Mode, Static
Mode, Short Cycling, Power-on Reset, Power vs Throughput Rate, and Serial Digital Interface with:
Converter Operation, Power-On Reset, Acquisition Time, Short Cycling, Power vs Throughput Rate, and Serial
Digital Interface setions.
Page 18 - Added package outline drawing P8.064
December 5, 2011 FN7708.0 Initial release.
Products
Intersil Corporation is a leader in the design and manufacture of high-performance analog semiconductors. The Company's products
address some of the industry's fastest growing markets, such as, flat panel displays, cell phones, handheld products, and notebooks.
Intersil's product families address power management and analog signal processing functions. Go to www.intersil.com/products for a
complete list of Intersil product families.
For a complete listing of Applications, Related Documentation and Related Parts, please see the respective device information page on
intersil.com: ISL267440, ISL267450A
To report errors or suggestions for this datasheet, please go to: www.intersil.com/askourstaff
FITs are available from our website at: http://rel.intersil.com/reports/search.php
16
FN7708.2
June 28, 2012