QUADRATURE CLOCK CONVERTER

FEATURES:

• x1, x2 and x4 mode selection

• Up to 16 MHz output clock frequency

• INDEX input and output

• UP/DOWN indicator output

• Programmable output clock pulse width

• On-chip filtering of inputs for optical or

magnetic encoder applications.

• TTL and CMOS compatible I/Os

• LS7082 (DIP); LS7082-S (SOIC ) - See Figure 1

INPUT/OUTPUT DESCRIPTION:

Supply Voltage positive terminal.

INDX (Pin 2)

Encoder Index pulses are applied to this input.

RBIAS (Pin 3)

Input for external component connection. A resistor con-

pulse width (Tow). For proper operation, the output clock

pulse width must be less than or equal to the A,B pulse

Supply Voltage negative terminal.

A (Pin 5)

Quadrature Clock Input A. This input has a filter circuit to

validate input logic level and eliminate encoder dither.

x2 (Pin 8)

A low level applied to this input selects x2 mode of opera-

tion. See Table 1 for Mode Selection Truth Table and

Figure 2 for Input/Output timing relationship.

B (Pin 9)

Quadrature Clock Input B. This input has a filter circuit

identical to input A.

x4/x1 (Pin 10)

This input selects between x1 and x4 modes of operation.

See Table 1 for Mode Selection Truth Table and Figure 2

for Input/Output timing relationship.

UP/DN (Pin 11)

The count direction at any instant is indicated at this out-

put. An UP count direction is indicated by a high, and a

DOWN count direction is indicated by a low (See Figure 2).

DNCK (Pin 12)

This DOWN Clock output consists of low-going pulses gen-

erated when A input lags the B input (See Figure 2).

UPCK (Pin 13)

This UP Clock output consists of low-going pulses gener-

ated when A input leads the B input (See Figure 2).

INDX (Pin 14)

This output consists of low-going pulses generated by

clock transitions at the A input when INDX input is high and

B input is low (See Figure 2).

DESCRIPTION:

The LS7082 is a monolithic CMOS silicon gate quadrature

clock converter. Quadrature clocks derived from optical or

magnetic encoders, when applied to the A and B Inputs of the

LS7082, are converted to strings of Up Clocks and Down

Clocks. Pulses derived from the Index Track of an encoder,

when applied to the INDX input, produce absolute position ref-

erence pulses which are synchronized to the Up Clocks and

Down Clocks. These outputs can be interfaced directly with

standard Up/Down counters for direction and position sensing

of the encoder.

October 2000

1

2

3

4

5

6

7

INDX

UPCK

DNCK

UP/DN

x4/x1

B

x2

INDX

RBIAS

A

NC

NC

14

13

12

11

8

9

10

FIGURE 1

PIN ASSIGNMENT - TOP VIEW

7082-100600-1

TABLE 1. MODE SELECTION TRUTH TABLE

x2 Input

x4/x1 Input

MODE

0

Don’t Care

x2

1

0

x1

1

1

x4

LSI/CSI

LSI Computer Systems, Inc. 1235 Walt Whitman Road, Melville, NY 11747

(631) 271-0400 FAX (631) 271-0405

LS7082

UL

®

A3800