trcv012g5 ETC-unknow, trcv012g5 Datasheet - Page 18

• Manufacturer Part Number: trcv012g5
• Description: Trcv012g5 Gbits/s Trcv012g7 Gbits/s Gbits/s Limiting Amplifier, Clock Recovery, Data Demultiplexer
• Manufacturer: ETC-unknow

TRCV012G5 and TRCV012G7
Limiting Amplifier, Clock Recovery, 1:16 Data Demultiplexer
CML Output Structure (Used on Pins D2G5P/N, CK2G5P/N)
The CML architecture is essentially a current-steering mechanism combined with an amplifier. This makes the out-
put swing of the signal a function of the termination resistor and the programmable output current. The user should
connect external termination resistors from the CML output pins to V
vide a dc path when using an ac-coupled load.
The voltage swing of a CML signal is typically 400 mV, half that of ECL/PECL. The lower pulse amplitude reduces
noise transients, crosstalk, and EMI. It also uses half the amount of current through the termination resistors. The
schematic of a typical CML output structure is shown in Figure 9.
Choosing the Value of the External CML Reference Resistors (RREF1, RREF2)
The flexibility of the CML interface permits certain parameters to be customized for a particular application. The
RREF1 resistor controls the CML output driver current source. Adjusting this tail current and termination resistors
will allow signal amplitude control (see the CML output specifications for limitations, page 22 and page 24) and
flexibility in termination schemes.
With RREF2 set to 1.5 k , the equation for the CML output current is the following:
The CML outputs have on-chip 100
a 50
set RREF1 to 1.8 k . For a 600 mV voltage swing, set RREF1 to 1.2 k . In both cases, RREF2 remains fixed at a
value of 1.5 k
18
V
CC
1% load, the effective load resistance will be 33.33
RREF1
RREF2
VREF
DEVICE-INTERNAL CML OUTPUT BUFFER CIRCUIT
+
–
Figure 9. Typical CML Output Structure
load resistors to V
Iout = (18)*(1.21)/RREF1
100
18X
V
CC
CC
V
in order to accommodate capacitive ac coupling. With
CC
± 6%. For a 400 mV voltage swing into the 50
100
CC
. The on-chip, 100
EXTERNAL OUTPUT TERMINATION
Preliminary Data Sheet
I
OUT
I
OUT
Lucent Technologies Inc.
50
pull-up resistors pro-
V
CC
August 2000
V
CC
50
5-8065(F)r.2
load,