TPS2202AI

DUAL-SLOT PC CARD POWER-INTERFACE SWITCH

WITH RESET FOR SERIAL PCMCIA CONTROLLER

SLVS123A – SEPTEMBER 1995 – REVISED JUNE 1998

16

POST OFFICE BOX 655303

POST OFFICE BOX 1443

APPLICATION INFORMATION

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 will close

internal switches S1, S4, S7, and S10 with all other switches left open (see TPS2202AI control-logic table). The

TPS2202AI 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.

overcurrent and thermal protection

sense resistors or polyfuses, these FETs do not add to the series resistance of the switch; therefore, voltage

and power losses are reduced. Overcurrent sensing is applied to each output separately. When an overcurrent

condition is detected, only the power output affected is limited; all other power outputs continue to function

normally. The OC indicator, normally a logic high, is a logic low when any overcurrent condition is detected,

providing for initiation of system diagnostics and/or sending a warning message to the user.

a faulty card or connector. If a short circuit is applied after power is established (e.g., hot insertion of a bad card),

current is initially limited only by the impedance between the short and the power supply. In extreme cases, as

will reestablish normal operation.

The protection circuitry acts by linearly limiting the current passing through the switch rather than initiating a full

shutdown of the supply. Shutdown occurs only during thermal limiting.

Thermal limiting prevents destruction of the IC from overheating if the package power-dissipation ratings are

exceeded. Thermal limiting disables all power outputs (both A and B slots) until the device has cooled.

calculating junction temperature

16, 17, and 18 using an initial temperature estimate about 50

°C above ambient. Then calculate the power

dissipation for each switch, using the formula:

P

D +

r

DS(on)

I2

Next, sum the power dissipation and calculate the junction temperature:

T

P

D

RqJA ) TA,RqJA + 108 C W

°

Compare the calculated junction temperature with the initial temperature estimate. If the temperatures are not

within a few degrees of each other, recalculate using the calculated temperature as the initial estimate.