Layout, Grounding, and Bypassing

Careful printed circuit board layout is essential for best

system performance. For best performance, use a

ground plane. To reduce crosstalk and noise injection,

keep analog and digital signals separate. Digital

ground lines can run between digital signal lines to

minimize interference. Connect analog grounds and

DGND in a star configuration to AGND. For noise-free

operation, ensure the ground return from AGND to the

supply ground is low impedance and as short as possi-

ble. Connect the logic grounds directly to the supply

to AGND to minimize high- and low-frequency fluctua-

tions. If the supply is excessively noisy, connect a 5

Ω

Figure 12.

Multirange, Single +5V, 12-Bit DAS

with 12-Bit Bus Interface

______________________________________________________________________________________

15

GND

DGND

DGND

AGND

+5V

+5V

SUPPLY

R* = 5

Ω

DIGITAL

CIRCUITRY

4.7

µF

0.1

µF

MAX196

MAX198

**

* OPTIONAL

** CONNECT AGND AND DGND WITH A GROUND PLANE OR A SHORT TRACE

Figure 12. Power-Supply Grounding Connection

_________________________________________________________Functional Diagram

T/H

THREE-STATE, BIDIRECTIONAL

I/O INTERFACE

12

10k

12

8

CHARGE REDISTRIBUTION

12-BIT DAC

CLOCK

SIGNAL

CONDITIONING

BLOCK

&

OVERVOLTAGE

TOLERANT

MUX

CONTROL LOGIC

&

LATCHES

REF

REFADJ

+2.5V

REFERENCE

D0–D11

12-BIT DATA BUS

CH5

CH4

CH3

CH2

CH1

CH0

CLK

CS

WR

RD

INT

AGND

DGND

MAX196

MAX198

1.638

COMP

SUCCESSIVE-

APPROXIMATION

REGISTER