EP4CE40 datasheet(140/488 Pages) ALTERA

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Chapter 6: I/O Features in Cyclone IV Devices

High-Speed I/O Standards Support

Cyclone IV Device Handbook,

May 2013

Altera Corporation

Volume 1

LVPECL I/O Support in Cyclone IV Devices

The LVPECL I/O standard is a differential interface standard that requires a 2.5-V

VCCIO. This standard is used in applications involving video graphics,

telecommunications, data communications, and clock distribution. Cyclone IV

devices support the LVPECL input standard at the dedicated clock input pins only.

The LVPECL receiver requires an external 100-

Ω termination resistor between the two

signals at the input buffer.

f For the LVPECL I/O standard electrical specification, refer to the Cyclone IV Device

Datasheet chapter.

AC coupling is required when the LVPECL common mode voltage of the output

buffer is higher than the Cyclone IV devices LVPECL input common mode voltage.

Figure 6–18 shows the AC-coupled termination scheme. The 50-

Ω resistors used at the

receiver are external to the device. DC-coupled LVPECL is supported if the LVPECL

output common mode voltage is in the Cyclone IV devices LVPECL input buffer

specification (refer to Figure 6–19).

Figure 6–19 shows the LVPECL DC-coupled termination.

Figure 6–18. LVPECL AC-Coupled Termination (1)

Note to Figure 6–18:

(1) The LVPECL AC-coupled termination is applicable only when an Altera FPGA transmitter is used.

Figure 6–19. LVPECL DC-Coupled Termination (1)

Note to Figure 6–19:

(1) The LVPECL DC-coupled termination is applicable only when an Altera FPGA transmitter is used.

Cyclone IV Device

LVPECL Receiver

VICM

Z0 = 50 Ω

LVPECL

Transmitter

0.1 µF

Cyclone IV Device

LVPECL Receiver

100

LVPECL Transmitter

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