LTC1164

8

1164fa

ANALOG CONSIDERATIONS

1. Grounding and Bypassing

The LTC1164 should be used with separated analog

and digital ground planes and single point grounding

techniques.

Pin 6 (AGND) should be tied directly to the analog ground

plane.

Pin 7 (V+) should be bypassed to the ground plane with a

0.1µF ceramic disk with leads as short as possible. Pin 19

(V–) should be bypassed with a 0.1µF ceramic disk. For

single supply applications, V– can be tied to the analog

ground plane.

For good noise performance, V+ and V– must be free of

noise and ripple.

All analog inputs should be referenced directly to the

single point ground. The clock inputs should be shielded

from and/or routed away from the analog circuitry and a

separate digital ground plane used.

Figure 3 shows an example of an ideal ground plane design

for a two sided board. Of course this much ground

plane will not always be possible, but users should strive

to get as close to this as possible. Proto boards are not

recommended.

2. Buffering the Filter Output

When driving coaxial cables and 1x scope probes, the filter

output should be buffered. This is important

especially when high Qs are used to design a specific filter.

Inadequate buffering may cause errors in noise,

distortion, Q, and gain measurements. When 10x probes

are used, buffering is usually not required. A buffer is

recommended especially when THD tests are performed.

As shown in Figure 4, the buffer should be adequately

bypassed to minimize clock feedthrough.

Figure 3. Example Ground Plane Breadboard Technique for LTC1164

APPLICATIO S I FOR ATIO

LTC1164 • AI01

DIGITAL GROUND

PLANE

ANALOG

GROUND

PLANE

7.5V

–7.5V

VIN

0.1µF CERAMIC DISK

0.1µF

CERAMIC

DISK

CLOCK

(SINGLE POINT

GROUND)

NOTE: CONNECT ANALOG AND DIGITAL

GROUND PLANES AT A SINGLE POINT AT

THE BOARD EDGE

FOR BEST HIGH FREQUENCY RESPONSE

PLACE RESISTORS PARALLEL TO DOUBLE

SIDED COPPER CLAD BOARD AND LAY FLAT

(4 RESISTORS SHOWN HERE TYPICAL)

1

2

3

4

5

6

10

11

12

24

23

22

15

14

13

• PIN 1 DENT

7

21

20

18

17

8

9

16

19