EVDO PC Embedded Datasheet

Product Datasheet
V001R006
Issue 2 (2009-01-20)
Confidencein Commercial
Page 27 of 60
Design guide
The RUIM signals are connected to the Mini PCI Express card connector (the card
edge connector) and pass through an EMI filtering and ESD protection circuit on the
module board before entering the EM660 processor. There is also an EMI filtering
and ESD protection circuit between UIM card interface and Mini PCI interface on the
user’s board.
1. Power supply
The UIM interface is powered by an LDO regulator. The default value of this regulator
is 2.85 V. The power of the regulator is programmable in the range of 1.5 V to 3.05 V
and is expected to be set to 2.85 V or 1.8 V.
2. Modem signals
After a power-on or reset, the RUIM signals are activated to detect if a UIM card is
present and to initialize it if it exists. Once a card has been detected and initialized,
the interface is always on. However, the clock signal is only activated when data is
actually being transferred. The RUIM signals from the MSM are connected to the
level translators and then to the Mini Card host connector.
These levels exceed those required in ISO/IEC 7816-3.
3. ESD protection
Since the UIM is a CMOS device, ESD protection devices should be placed near to
the UIM connector to provide protection. In addition, all the UIM interface signals
should be bypassed with a 33 pF capacitor.
4. Routing recommendations
The UIM interface signals consist of four signals that are Vcc, RST, CLK, and IO (Vpp
is also connected but not used in many applications). Due to the relatively low clock
frequencies involved, the concern is not the degradation of the UIM signals
themselves. The main concern is routing of the UIM interface signals through areas
considered to be of high risk for RF noise coupling (crosstalk and RF contamination)
which can desensitize the radio circuitry. The general guidelines that should be
followed are listed as follows:
l
It is recommended that these signals should be routed over a contiguous ground
plane.
l
UIM interface signals should not be routed near high transient signals (power
supply chokes and DC/DC switching FETs).
l
Avoid routing of these signals near output connectors.
l
Keep UIM interface signals isolated from other signals. 2x width spacing (1.5x
min) between UIM interface signals and all other signal routing is recommended.