www.ti.com

APPLICATION INFORMATION

INTRODUCTION TO ExpressCard

ExpressCard POWER REQUIREMENTS

ExpressCard POWER SWITCH OPERATION

TPS2231

TPS2236

SLVS536B – JULY 2004 – REVISED JANUARY 2005

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.

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.

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.

19