TPS2231_07 Datasheet, PDF (19/35 Pages) Texas Instruments – ExpressCard TM POWER INTERFACE SWITCH

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TPS2231
TPS2236
SLVS536E – JULY 2004 – REVISED SEPTEMBER 2006
APPLICATION INFORMATION
INTRODUCTION TO ExpressCard
An ExpressCard module is an add-in card with a serial interface based on PCI Express and/or Universal Serial
Bus (USB) technologies. An ExpressCard comes in two form factors defined as ExpressCard|34 or
ExpressCard|54. The difference, as defined by the name, is the width of the module, 34 mm or 54 mm,
respectively. Host systems supporting the ExpressCard module can support either the ExpressCard|34 or
ExpressCard|54 or both.
ExpressCard POWER REQUIREMENTS
Regardless of which ExpressCard module is used, the power requirements as defined in the ExpressCard
Standard apply to both on an individual slot basis. The host system is required to supply 3.3 V, 1.5 V, and AUX
to each of the ExpressCard slots. However, the voltage is only applied after an ExpressCard is inserted into the
slot.
The ExpressCard connector has two pins, CPPE and CPUSB, that are used to signal the host when a card is
inserted. If the ExpressCard module itself connects the CPPE to ground, the logic low level on that signal
indicates to the host that a card supporting PCI Express has been inserted. If CPUSB is connected to ground,
then the ExpressCard module supports the USB interface. If both PCI Express and USB are supported by the
ExpressCard module, then both signals, CPPE and CPUSB, must be connected to ground.
In addition to the Card Present signals (CPPE and CPUSB), the host system determines when to apply power to
the ExpressCard module based on the state of the system. The state of the system is defined by the state of the
3.3 V, 1.5 V, and AUX input voltage rails. For the sake of simplicity, the 3.3-V and 1.5-V rails are defined as the
primary voltage rails as oppose to the auxiliary voltage rail, AUX.
ExpressCard POWER SWITCH OPERATION
The ExpressCard power switch resides on the host, and its main function is to control when to send power to the
ExpressCard slot. The ExpressCard power switch makes decisions based on the Card Present inputs and on
the state of the host system as defined by the primary and auxiliary voltage rails.
The following conditions define the operation of the host power controller:
1. When both primary power and auxiliary power at the input of the ExpressCard power switch are off, then all
power to the ExpressCard connector is off regardless of whether a card is present.
2. When both primary power and auxiliary power at the input of the ExpressCard power switch are on, then
power is only applied to the ExpressCard after the ExpressCard power switch detects that a card is present.
3. When primary power (either +3.3 V or +1.5 V) at the input of the ExpressCard power switch is off and
auxiliary power at the input of the ExpressCard power switch is on, then the ExpressCard power switch
behaves in the following manner:
a. If neither of the Card Present inputs is detected (no card inserted), then no power is applied to the
ExpressCard slot.
b. If the card is inserted after the system has entered this power state, then no power is applied to the
ExpressCard slot.
c. If the card is inserted prior to the removal of the primary power (either +3.3 V or +1.5 V or both) at the
input of the ExpressCard power switch, then only the primary power (both +3.3 V and +1.5 V) is
removed and the auxiliary power is sent to the ExpressCard slot.
Figure 18 through Figure 23 illustrate the timing relationships between power/logic inputs and outputs of
ExpressCard.
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