TPS2211A

SINGLE-SLOT PC CARD POWER INTERFACE SWITCH

FOR PARALLEL PCMCIA CONTROLLERS

SLVS282A – SEPTEMBER 2000 – REVISED NOVEMBER 2002

14

POST OFFICE BOX 655303

APPLICATION INFORMATION

12-V supply not required

Most PC Card switches use the externally supplied 12 V to power gate drive and other chip functions, which

require that power be present at all times. The TPS2211A offers considerable power savings by using an internal

charge pump to generate the required higher voltages from the 5-V input. Therefore, the external 12-V supply

can be disabled except when needed for flash-memory functions, thereby extending battery lifetime. Do not

ground the 12-V switch inputs when the 12-V input is not used. Additional power savings are realized by the

TPS2211A during a software shutdown, in which quiescent current drops to a maximum of 1

µA.

3.3-V low-voltage mode

The TPS2211A operates in a 3.3-V low-voltage mode when 3.3 V is the only available input voltage

pager modes. Note that in these operation modes, the TPS2211A derives its bias current from the 3.3-V input

pin and only 3.3 V can be delivered to the PC Card.

voltage transitioning requirement

PC Cards are migrating from 5 V to 3.3 V to minimize power consumption, optimize board space, and increase

logic speeds. The TPS2211A meets all combinations of power delivery as currently defined in the PCMCIA

standard. The latest protocol accommodates mixed 3.3-V/5-V systems by first powering the card with 5 V, then

polling it to determine its 3.3-V compatibility. The PCMCIA specification requires that the capacitors on 3.3-V

compatible cards be discharged to below 0.8 V before applying 3.3-V power. This functions as a power reset

and ensures that sensitive 3.3-V circuitry is not subjected to any residual 5-V charge. The TPS2211A offers a

output ground switches

to provide a discharge path for voltages stored on PC Card capacitance because of possible high-impedance

isolation by power-management schemes.

power-supply considerations

The TPS2211A has multiple pins for each of its 3.3-V and 5-V power inputs and for the switched AVCC outputs.

Any individual pin can conduct the rated input or output current. Unless all pins are connected in parallel, the

series resistance is significantly higher than that specified, resulting in increased voltage drops and lost power.

It is recommended that all input and output power pins be paralleled for optimum operation.

To increase the noise immunity of the TPS2211A, the power supply inputs should be bypassed with a 4.7-

µF,

or larger, electrolytic or tantalum capacitor paralleled by a 0.1-

µF ceramic capacitor. It is strongly recommended

that the switched outputs be bypassed with a 0.1-

µF, or larger, ceramic capacitor; doing so improves the

immunity of the TPS2211A to electrostatic discharge (ESD). Care should be taken to minimize the inductance

of PCB traces between the TPS2211A and the load. High switching currents can produce large negative voltage

transients, which forward biases substrate diodes, resulting in unpredictable performance. Similarly, no pin

should be taken below – 0.3 V.