TPS2206

DUALSLOT PC CARD POWERINTERFACE SWITCH

WITH RESET FOR SERIAL PCMCIA CONTROLLER

SLVS138D − MAY 1996 − REVISED JANUARY 2001

19

POST OFFICE BOX 655303

APPLICATION INFORMATION

output ground switches

Several PCMCIA power-distribution switches on the market do not have an active-grounding FET switch. These

can not be relied on to provide a discharge path for voltages stored on PC Card capacitance because of possible

high-impedance isolation by power-management schemes. A method commonly shown to alleviate this

problem is to add to the switch output an external 100-k

Ω resistor in parallel with the PC Card. Considering that

this is the only discharge path to ground, a timing analysis shows that the RC time constant delays the required

discharge time to more than 2 seconds. The only way to ensure timing compatibility with PC Card standards

is to use a power-distribution switch that has an internal ground switch, like that of the TPS22xx family, or add

an external ground FET to each of the output lines with the control logic necessary to select it.

In summary, the TPS2206 is a complete single-chip dual-slot PC Card power interface. It meets all currently

defined PCMCIA specifications for power delivery in 5-V, 3.3-V, and mixed systems, and offers a serial control

interface. The TPS2206 offers functionality, power savings, overcurrent and thermal protection, and fault

reporting in one 30-pin SSOP surface-mount package for maximum value added to new portable designs.

power-supply considerations

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

output power pins be paralleled for optimum operation.

Although the TPS2206 is fairly immune to power input fluctuations and noise, it is generally considered good

design practice to bypass power supplies typically with a 1-

µF electrolytic or tantalum capacitor paralleled by

a 0.047-

bypassed with a 0.1-

µF or larger capacitor; doing so improves the immunity of the TPS2206 to electrostatic

discharge (ESD). Care should be taken to minimize the inductance of PCB traces between the TPS2206 and

the load. High switching currents can produce large negative-voltage transients, which forward biases substrate

diodes, resulting in unpredictable performance. Similary, no pin should be taken below − 0.3 V.

RESET or RESET inputs

To ensure that cards are in a known state after power brownouts or system initialization, the PC Cards should

low-impedance output state allows discharging of residual voltage remaining on PC Card filter capacitance,

permitting the system (host and PC Cards) to be powered up concurrently. The RESET or RESET input closes

internal switches S1, S4, S7, and S10 with all other switches left open (see TPS2206 control-logic table). The

TPS2206 remains in the low-impedance output state until the signal is deasserted and further data is clocked

in and latched. RESET or RESET is provided for direct compatibility with systems that use either an active-low

or active-high reset voltage supervisor. The unused pin is internally pulled up or down and should be left

unconnected.