adc08062ciwm National Semiconductor Corporation, adc08062ciwm Datasheet - Page 14

• Manufacturer Part Number: adc08062ciwm
• Description: 500 Ns A/d Converter With S/h Function And Input Multiplexer
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Information
Note : Bypass capacitors consist of a 0.1 µF
ceramic in parallel with a 10 µF bead tantalum.
Note the multiple bypass capacitors on the reference and power supply pins. V
grounded (see Section 7.0 “Layout, Grounds, and Bypassing”). V
The ADC08061 can perform accurate conversions of
full-scale input signals at frequencies from dc to more than
300 kHz (full power bandwidth) without the need of an exter-
nal sample-and-hold (S/H).
7.0 LAYOUT, GROUNDS, AND BYPASSING
In order to ensure fast, accurate conversions from the
ADC08061/2, it is necessary to use appropriate circuit board
layout techniques. Ideally, the analog-to-digital converter’s
ground reference should be low impedance and free of noise
from other parts of the system. Digital circuits can produce a
great deal of noise on their ground returns and, therefore,
should have their own separate ground lines. Best perfor-
mance is obtained using separate ground planes for the digi-
tal and analog parts of the system.
External Reference 2.5V Full-Scale
(Standard Application)
DS011086-20
(Continued)
FIGURE 8. Analog Input Options
FIGURE 9. Typical Connection
Power Supply as Reference
IN1
is shown with an optional input protection network.
REF−
14
should be bypass to analog ground using multiple capacitors if it is not
The analog inputs should be isolated from noisy signal
traces to avoid having spurious signals couple to the input.
Any external component (e.g., an input filter capacitor) con-
nected across the inputs should be returned to a very clean
ground point. Incorrectly grounding the ADC08061/2 will re-
sult in reduced conversion accuracy.
The V
should be bypassed with a parallel combination of a 0.1 µF
ceramic capacitor and a 10 µF tantalum capacitor placed as
close as possible to the supply pin using short circuit board
traces. See Figures 8, 9 .
DS011086-21
+
supply pin, V
* Signal source driving V
of sinking 5 mA.
REF+
Input Not Referred to GND
DS011086-23
, and V
REF−
IN
(if not grounded)
(−) must be capable
DS011086-22