DM2502CM datasheet(4/8 Pages) NSC

4 / 8 page

Application Information (Continued)

SHORT CYCLE

If all bits are not required the register may be truncated and

conversion time saved by using a register output going low

rather then the QCC signal to indicate the end of conversion

If the register is truncated and operated in the continuous

conversion mode a lock-up condition may occur on power

turn-on This condition can be avoided by making the start

input the OR function of QCC and the appropriate register

output

COMPARATOR BIAS

To minimize the digital error below g

LSB the compara-

tor must be biased If a DA converter is used which re-

quires a low voltage level to turn on the comparator should

be biased a

LSB If the DA converter requires a high

logic level to turn on the comparator must be biased b

LSB

Definition of Terms

The clock input of the register

The serial data input of the register

The serial data out (The D input delayed one bit)

The register enable This input is used to expand the

length of the register and when high forces the Q7 (11)

for expansion the enable is held at a low logic level

(ground)

Qi ie7 (11) to 0 The outputs of the register

QCC The conversion complete output This output remains

high during a conversion and goes low when a conversion is

complete

Q7 (11)

The true output of the MSB of the register

Q7 (11)

The complement output of the MSB of the register

The start input If the start input is held low for at least a

clock period the register will be reset to Q7 (11) low and all

the remaining outputs high A start pulse that is low for a

shorter period of time can be used if it meets the set-up time

requirements of the S input

Truth Table

DM2502 DM2503

Time

Inputs

Outputs1

D03

QCC

XXXXXXX

HHHHHHH

HHHHHH

HHHHH

HHHH

D6D5D4

D6D5D4D3

D6D5D4D3D2

D6D5D4D3D2D1

NCNCNCNCNCNCNC

High Voltage Level

Note 1

Truth table for DM2504 is extended to include 12 outputs

Low Voltage Level

Note 2

Truth table for DM2502 does not include E column or last line in truth table shown

Don’t Care

Note 3

Truth table for DM2503 does not include D0 column

NC e No Change

Typical Applications

BCD Illegal Code Suppression

Active High

Active Low

TLF5702 – 3

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