–12–

AD760

REV. A

One feature that the AD760 incorporates to help the user layout

cent to help isolate analog signals from digital signals.

SUPPLY DECOUPLING

The AD760 power supplies should be well filtered, well regu-

lated, and free from high frequency noise. Switching power sup-

plies are not recommended due to their tendency to generate

spikes which can induce noise in the analog system.

Decoupling capacitors should be used in very close layout prox-

imity between all power supply pins and ground. A 10 µF tantalum

capacitor in parallel with a 0.1 µF ceramic capacitor provides ad-

An effort should be made to minimize the trace length between

the capacitor leads and the respective converter power supply

and common pins. The circuit layout should attempt to locate

the AD760, associated analog circuitry and interconnections as

far as possible from logic circuitry. A solid analog ground plane

around the AD760 will isolate large switching ground currents.

For these reasons, the use of wire wrap circuit construction is not

recommended; careful printed circuit construction is preferred.

GROUNDING

The AD760 has two pins, designated analog ground (AGND)

and digital ground (DGND.) The analog ground pin is the

“high quality” ground reference point for the device. Any exter-

nal loads on the output of the AD760 should be returned to

analog ground. If an external reference is used, this should also

be returned to the analog ground.

If a single AD760 is used with separate analog and digital

ground planes, connect the analog ground plane to AGND and

the digital ground plane to DGND keeping lead lengths as short

as possible. Then connect AGND and DGND together at the

AD760. If multiple AD760s are used or the AD760 shares ana-

log supplies with other components, connect the analog and

digital returns together once at the power supplies rather than at

each chip. This single interconnection of grounds prevents large

ground loops and consequently prevents digital currents from

flowing through the analog ground.

PACKAGE INFORMATION

28-Pin Cerdip Package (Q-28)

1.490 (37.84) MAX

28

1

15

14

GLASS SEALANT

0.18 (4.57)

MAX

0.620 (15.74)

0.590 (14.93)

15

°

0

°

0.012 (0.305)

0.008 (0.203)

0.125 (3.175)

MIN

0.02 (0.5)

0.016 (0.406)

0.06 (1.52)

0.05 (1.27)

0.11 (2.79)

0.099 (2.28)

0.22

(5.59)

MAX

0.525 (13.33)

0.515 (13.08)