www.icst.com/products/hiperclocks.html

Aug 02, 2002

4

Integrated

Circuit

Systems, Inc.

HiPerClockS™ Application Note

AC Coupled Termination

For AC termination, the offset level needs to be taken care of after the AC capacitors. A bias circuit might be

required. The board design engineer needs to verify what type of receiver is being driven. A few examples of AC

couple termination are shown in this section.

In Figure 6, the R3 and R4 at the driver pins provide a current path for the LVPECL driver. R1 and R2 serve as

matched load termination. The power supply V

VCMR input requirement of the receiver. Figure 7 and Figure 8 are equivalent to Figure 5. The Figure 7 is

equivalent to V

equivalent to V

shows AC termination with the offset bias voltage V

Figure 10 shows AC

termination with the offset bias voltage V

In some cases, for the receiver with

built-in bias resistors R1 and R2, the termination is shown in Figure 11.

R3

100-180

C2

nTL1

Zo = 50

Td

+

-

VCCO=3.3V

R4

100-180

VBB

R2

50

C1

TL1

Zo = 50

Td

R1

50

3v3 PECL Driver

U1

Figure 6 AC Coupled with V