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Application Information (Continued)

External Reference 2.5V Full-Scale

(Standard Application)

TL/H/11086–20

Power Supply as Reference

TL/H/11086–21

Input Not Referred to GND

TL/H/11086–22

*Signal source driving V

(

) must be capable of

sinking 5 mA.

Note: Bypass capacitors consist of a 0.1 mF ceramic in parallel with a 10 mF bead tantalum.

FIGURE 7. Analog Input Options

TL/H/11086–23

Note the multiple bypass capacitors on the reference and power supply pins. V

REF

should be bypass to analog ground using multiple capacitors if it is not

grounded (see Section 7.0 ‘‘Layout, Grounds, and Bypassing’’). V

IN1

is shown with an optional input protection network.

FIGURE 8. Typical Connection

the WR

signal. The WR input signal allows the A/D to be

synchronized to a DSP system’s sampling rate or to other

ADC08061 and ADC08062s.

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 con-

verter’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 performance is obtained using separate ground planes

for the digital and analog parts of the system.

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

supply pin, V

REF

, and V

REF

(if not grounded)

should be bypassed with a parallel combination of a 0.1 mF

ceramic capacitor and a 10 mF tantalum capacitor placed as

close as possible to the supply pin using short circuit board

traces. See

Figures 7

and

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