m28333-3x Mindspeed Technologies, m28333-3x Datasheet - Page 51

• Manufacturer Part Number: m28333-3x
• Description: Single/dual/triple E3/ds3/sts-1 Line Interface Unit
• Manufacturer: Mindspeed Technologies

3.1.1 Power Supply and Ground Plane
3.1.2 Component Placement
28333-DSH-003-A
3.1.2.1 RBIAS Resistor
3.0 Applications
The M28331/M28332/M28333 can be used in a variety of applications.
M28333. The data and clock are extracted and passed on to the framer chip for
further data manipulation and user interface.
board layout.
3.1 PCB Design Considerations for the M2833i
The M28333 is a mixed signal triple-port LIU device operating at frequencies up
to 51.84 MHz. This calls for a careful design of the PCB layout.
Some design considerations are outlined below.
A single power plane with bulk capacitors (typically 10 µf) distributed throughout
the board will mitigate most power rail-related voltage transients. A bulk
capacitor should also be placed where the power enters the board. It is
recommended that decoupling capacitors be routed directly to each of the power
pins. It is recommended that 0.1 µf, 0.01 µf, and 0.001 µf decoupling capacitors
be used. All three values are not required on each pin, but values should be
dispersed uniformly to filter different frequencies of noise. 10 µf tantalum
capacitors should be placed on all four corners of the chip.
A continuous ground plane is the best way to minimize ground impedance. Most
ground noise is produced by the return currents and power supply transients
during switching. This effect is minimized by reducing the ground plane
impedance.
It is important to keep the RBAIS pins quiet, as any noise coupled to these pins
affect the internal references. The RBIAS resistors should be placed as close as
possible to the RBIAS pins and no digital signals should be routed near the pins
or the resistors. It is recommended to guard the pin, resistor, and traces with
ground vias.
It is important to employ high-frequency design techniques for the printed
Figure 3-1
Mindspeed Technologies
illustrates an example of three DS3 lines being terminated by the
3
™
3-1