tza3030 NXP Semiconductors, tza3030 Datasheet - Page 14

• Manufacturer Part Number: tza3030
• Description: Sdh/sonet Stm1/oc3 Optical Receiver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
CML outputs: OUTCML and OUTQCML
The output impedance of the CML output driver is 100
(see Fig.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 value, single-sided) with a tail
current of 6 mA.
1998 Aug 24
handbook, full pagewidth
handbook, full pagewidth
SDH/SONET STM1/OC3 optical receiver
and 50
V CC
V CC
100
100
(33 ) will generate a signal swing of
Fig.9 CML interface circuit without matched impedance; low power dissipation.
100
100
Fig.10 CML interface circuit with matched impedance; high power dissipation.
inside TZA3030
inside TZA3030
generator
generator
V OQ
V OQ
V O
V O
100
interconnect
interconnect
100
Z o = 50
Z o = 50
PCB
PCB
14
Z o = 50
Z o = 50
If the output impedance was 50
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
50
50
inside TZA3004
inside TZA3004
receiver
receiver
V CC
V CC
rather than 100 ,
Objective specification
MBK862
MBK861
TZA3030