MAX3761 Maxim, MAX3761 Datasheet - Page 10

• Manufacturer Part Number: MAX3761
• Description: Low-Power / 622Mbps Limiting Amplifiers with Chatter-Free Power Detect for LANs
• Manufacturer: Maxim

For LOS assert at -35dBm, select R1 = 100kΩ and R2 =
22kΩ, which programs the LOS assert at input
With this selection, LOS assert time will typically be less
than 85µs.
In Fibre Channel applications, the desired LOS assert
time is typically 25µs maximum, and data-dependent
jitter is reduced by 8B10B coding techniques. The fol-
lowing are recommended in a Fibre Channel system
where preamp gain is 2000V/W, LOS assert is set for
-24dBm (13mV MAX3761/MAX3762 input), and the
maximum input to the MAX3761/MAX3762 is 1Vp-p:
C
C
C
R1 = 100kΩ, R2 = 50kΩ (to set LOS assert at -24dBm)
The standard PECL termination (50Ω to V
recommended for best performance and output char-
acteristics. The data outputs operate at high speed,
and should always drive transmission lines with
50Ω to 75Ω terminations. Balanced termination is rec-
ommended for all outputs.
Figure 5 shows an alternative method for terminating
the data outputs. The technique provides approximate-
ly 8mA DC bias current, with a 50Ω AC load, for the
output termination. This technique is useful for viewing
the output on an oscilloscope or changing the PECL
reference voltage.
The MAX3762’s PECL LOS outputs are relatively slow
and do not need 50Ω terminations (although they are
capable of driving them). To reduce power, the
MAX3762’s LOS outputs can be terminated with 500Ω.
Figure 6 shows a typical operating circuit for the
MAX3762.
Low-Power, 622Mbps Limiting Amplifiers
with Chatter-Free Power Detect for LANs
10
IN
AZ
FILTER
= 3.3nF (to provide LOS assert in 25µs)
= 82pF (to provide f
______________________________________________________________________________________
= 100pF (for a 3MHz integration constant)
Fibre Channel Component Selection
OC
= 1/10 f
PECL Terminations
C
for stability)
CC
- 2V) is
3mV.
For high current density and reliable operation, the
MAX3761/MAX3762 use gold metalization. Make con-
nections to the dice with gold wire only, and use ball-
bonding techniques (wedge bonding is not
recommended). Die-pad size is 4 mils square, with a
6 mil pitch. Die thickness is 12 mils (0.3mm).
The MAX3761/MAX3762 are high-frequency, high-
bandwidth circuits. To ensure stability, use good high-
frequency layout techniques. Filter voltage supplies,
and keep ground connections short. Use multiple vias
where possible. Use controlled-impedance transmis-
sion lines to connect the MAX3761/MAX3762 data out-
puts to other circuits.
Figure 5. Alternative PECL Termination
DRIVING 50
MAX3761
TO GROUND
OUT+
OUT-
470
470
Layout Techniques
Wire Bonding
50
50