HDMP-1032 Datasheet, PDF (27/32 Pages) Agilent(Hewlett-Packard) – 1.4 GBd Transmitter/Receiver Chip Set with CIMT Encoder/Decoder and Variable Data Rate

connected directly into a high-
speed 50Ω oscilloscope. For opti-
mum performance, both outputs
should see the same impedance.
It is necessary that all HS_OUT
outputs be terminated into 50Ω.
Figure 15 shows various methods
of interfacing HS_OUT to HS_IN
and standard PECL logic.
Data Bus Line/Broadcast
Transmission
The GND_HS pins are normally
tied to ground to provide 50Ω in-
put impedance. For 1:N broadcast
applications, 18KΩ series resistors
can be inserted between GND_HS
and -5V to provide
an effective high impedance as
shown in Figure 16. A Port-
Bypass Circuit (PBC) can also be
used in a broadcast application as
shown in Figure 17. Each
input and output PBC is a dedi-
cated channel and impedance
matched to the transmission
line. This is a superior method of
achieving a broadcast mode com-
pared to Figure 16, but does add
an additional IC. More receivers
can be added by cascading PBC
ICs or using a PBC with more ports.
O_TTL
ESD
PROTECTION
V_CC
V_CC_TTL
ESD
PROTECTION
I_TTL
V_CC
GND
GND_TTL
Figure 13. O-TTL and I-TTL Simplified Circuit Schematic.
HS_OUT
ESD
PROTECTION
V_CC
1.4 V
GND
ESD
PROTECTION
HS_IN
0.1 µF
ZO = 50 Ω
0.1 µF
GND
GND_HS
Figure 14. HS_OUT and HS_IN Simplified Circuit Schematic.
27
50 Ω
50 Ω
V_CC
GND