5

LTC1520

SWITCHI G TI E WAVEFOR S

3.3V

≥18k

≥18k

A

B

3.3V

≥18k

A

B

1520 F05

≥18k

Figure 5. Input Thevenin Equivalent

EQUIVALE T I PUT NETWORKS

Theory of Operation

Unlike typical line receivers whose propagation delay can

vary by as much as 500% from package to package and

show significant temperature drift, the LTC1520 employs

a novel architecture that produces a tightly controlled and

temperature compensated propagation delay. The differ-

ential timing skew is also minimized between rising and

3V

B1, B2 = 2.5V

2V

CH1 OUT

INPUT

A1, A2

CH2 OUT

1520 F03

Figure 3. Any Channel to Any Channel Skew, Same Package

Figure 4. Package-to-Package Propagation Delay Skew

falling output edges, and the propagation delays of any

two receivers within a package are very tightly matched.

The precision timing features of the LTC1520 reduce

overall system timing constraints by providing a narrow

6ns window during which valid data appears at the re-

ceiver output. This output timing window applies to all

receivers in all packages over all operating temperatures

Figure 2. Receiver Enable and Disable Timing

Test Circuit and Waveforms

1.5V

1.5V

1.5V

1k

1k

S1

S2

1.5V

0.2V

0.2V

OUTPUT

NORMALLY LOW

OUTPUT

NORMALLY HIGH

0V

3V

ENABLE

5V

0V

RECEIVER

OUTPUT

OUT 1

OUT 1

1520 F02

SAME INPUT FOR BOTH PACKAGES

INPUT

A1, B1

PACKAGE 1

OUT 1

1520 F04

PACKAGE 2

OUT 1