AN1672 데이터 시트보기 (PDF) - ON Semiconductor

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AN1672

The ECL Translator Guide PECL • LVPECL • NECL • TTL • LVTTL/LVCMOS • CMOS

ON Semiconductor 

AN1672/D

Different ECL operating supply modes are generally

considered to be as presented below in Table 1.

Table 1. ECL Operating Supply Modes

PECL

LVPECL

2.5VPECL

2.5VNECL

LVNECL

NECL

VCC = 5.0, VEE = 0.0

VCC = 3.3, VEE = 0.0

VCC = 2.5, VEE = 0.0

VCC = 0.0, VEE = −2.5

VCC = 0.0, VEE = −3.3

VCC = 0.0, VEE = −5.0

Some devices may span one or more operating modes and

each mode will allow supply tolerances. ECL signal levels

(VOL, VOH, VIL, and VIH) are referenced from the VCC pin

or positive rail. Therefore, when ECL devices are operated

from different negative power supplies, no translation is

required for interconnects. When operated in a single ended

configuration, the critical Input parameters are VIL and VIH

limits (VIHCMR and Vpp are ignored). When operation

differentially, critical limit Input parameters are VIHCMR

and Vpp (VIL and VIH are ignored). See AND8066 for

interconnect details. All supply pins, VCC, LVCC, and

GND, must be connected for proper operation. A 0.1 mF to

0.01 mF decoupling cap is recommended from VCC to GND.

VCC ripple should be minimized and may require additional

filter networks.

Standard non ECL operating modes are generally

considered (with certain supply tolerances) to be as presented

below in Table 2.

Table 2. Non ECL Operating Supply Modes

VCC = 5.0, VEE = 0.0

VCC = 3.3, VEE = 0.0

VCC = 2.5, VEE = 0.0

Most translation interface between technologies will

require a separate, dedicated translator IC device, but some

newer ECL devices offer a translation feature integrated into

certain mode control pins. Several of the GigaComm™

devices offer a programmable mode pins for selecting the

control pins translation levels. MC10EP195 offers Delay

Select pins with user programmable TTL, CMOS, or ECL

threshold levels.

An alternative translation technique, cap coupling, is

discussed in Application Note AND8020, Section 5. Cap

coupling may accommodate level shifting when the signal’s

“edge density” is sufficient. Otherwise, coding may be

required to increase ”edge density”. Certainly the risk of

erroneous levels, due to the coupling cap leakage, may not

be acceptable and system requirements may demand the

hard levels found with active device translation.

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