tza3000 NXP Semiconductors, tza3000 Datasheet - Page 14

• Manufacturer Part Number: tza3000
• Description: Sdh/sonet Stm4/oc12 Optical Receiver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
CML outputs: OUTCML (18) and OUTQCML (19)
The output impedance of the CML output driver is 100
(see Figs 7 and 9), which doesn’t match the characteristic
impedance of the strip line. While this means that the
reflections of some incident edges will arrive at the driver
output on the PCB, this value was selected to reduce
power dissipation inside the IC. The parallel combination
of 100
200 mV peak-to-peak (single sided) with a tail current of
6 mA. If the output impedance was 50
1997 Oct 17
handbook, full pagewidth
handbook, full pagewidth
SDH/SONET STM4/OC12 optical receiver
and 50
V CC
V CC
100
100
(33
Fig.10 CML interface circuit with matched impedance; higher power dissipation.
Fig.9 CML interface circuit without matched impedance; low power dissipation.
100
100
will generate a signal swing of
inside TZA3000
inside TZA3000
generator
generator
V OQ
V OQ
V O
V O
rather than
100
interconnect
interconnect
100
Z o = 50
Z o = 50
PCB
PCB
14
Z o = 50
Z o = 50
100 , an 8 mA tail current would be needed to generate
the same voltage swing. This would increase power
dissipation by 33%.
If necessary, the output impedance of the generator can
be matched to the line impedance by connecting an
external 100
in Fig.10. The magnitude of the output voltage swing will
not change due to adaptive regulation. However, power
dissipation will increase by 33%.
V IQ
V IQ
V I
V I
resistor in parallel with the output as shown
50
50
inside TZA3004
50
50
inside TZA3004
receiver
receiver
V CC
V CC
Objective specification
MGK888
MGK889
TZA3000