Datasheet

ZADCS146 / ZADCS147

Copyright © 2008, ZMD AG, Rev. 1.1

All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The

Information furnished in this publication is preliminary and subject to changes without notice.

11/19

CH0

CH1

CH2

CH3

CH4

CH5

CH6

CH7

COM

IN-

IN+

Converter

SGL/DIF = HIGH

See Table 3 & Table 4

for Coding Schemes

Shown configuration

A2 … A0 = 0x000

input voltage is clamped at VDD + 0.2V by ESD protec-

tion devices.

out limiting the Code Range, assuming the fore men-

tioned VDD condition is true. See also Figure 5 for input

voltage ranges in unipolar conversion mode.

+ Vref/2) keeping the converter out of code saturation.

the output code at the minimum or maximum code value.

Figure 6 shows the input voltage ranges in bipolar mode

As explained before, ZADCS146 / ZADCS147 can also

be used to convert fully differential input signals that

change around a common mode input voltage.

The bipolar mode is best used for such purposes since it

allows the input signals to be positive or negative in rela-

tion to each other.

The common mode level of a differential input signal is

ping or over steering of the converter, the common mode

level can change from ¼ Vref … ¾ Vref. Within this range

the peak to peak amplitude of the differential input signal

can be ± Vref/2.

The average input current on the analog inputs depends

on the conversion rate. The signal source must be capa-

ble of charging the internal sampling capacitors (typically

equivalent input circuit in sampling mode is shown in

Figure 7.

The following equation provides a rough hand calculation

DC input signal referenced to AGND with 12 bit accuracy

in a given acquisition time

Figure 4: Block diagram of input multiplexer

0V

Code Range

0xFFF

0x000

Figure 5: Input voltage range in unipolar mode

0V

Figure 6: Input voltage range for fully differen-

tial signals in bipolar mode

0V

16pF

4pF

AGND

16pF

4pF

AGND

CH0

CH1

CH2

CH3

CH4

CH5

CH6

CH7

COM

Channel

Multiplexer

3kΩ

3kΩ

Figure 7: Equivalent input circuit during sampling