MIC2551A-2.5 Datasheet, PDF (9/10 Pages) Micrel Semiconductor – USB Transceiver

MIC2551A-2.5
Configuration Mode
Normal
Disconnect (D+/D-
sharing)
Disconnect
Disable Mode
Unpowered
VBUS/VTRM
Connected
Open
Ground
Connected
Connected
Micrel, Inc.
VIF
Connected
Notes
Normal supply configuration and operation.
Connected
Connected
Open
VP/VM are HIGH outputs, RCV is LOW.
With OE# = 0 and SUS = 1, data lines may be driven with external
devices up to 3.6V.
With D+, D- floating, I_IF draws less than 1µA.
VP/VM are HIGH outputs, RCV is LOW.
With D+, D- floating, I_IF draws less than 1µA.
Logic controlled input pins are Hi-Z. No communication is possible
until interface voltage is restored.
Ground
Inoperative
Table 1. Power Supply Configuration
PCB Layout Recommendations
Although the USB standard and applications are not based in
an impedance-controlled environment, a properly designed
PCB layout is recommended for optimal transceiver perfor-
mance. The suggested PCB layout hints are as follows:
• Match signal line traces (VP/VM, D+, D–) to
40ps, approximately one-third inch if possible.
FR-4 PCB material propagation is about 150ps/
inch, so to minimize skew try to keep VP/VM,
D+/D– traces as short as possible.
• For every signal line trace width (w), separate
the signal lines by 1.5 – 2 widths. Place all other
traces at >2 widths from all signal line traces.
• Maintain the same number of vias on each dif-
ferential trace, keeping traces approximately at
same separation distance along the line.
• Control signal line impedances to ±10%.
• Keep R_S as close to the IC as possible, with
equal distance between R_S and the IC for both
D+ and D–.
March 2006
9
M9999-031306