TPS2201IDFR Datasheet, PDF (17/25 Pages) Texas Instruments – DUAL-SLOT PC CARD POWER-INTERFACE SWITCHES FOR PARALLEL PCMCIA CONTROLLERS

TPS2201
DUAL-SLOT PC CARD POWER-INTERFACE SWITCHES
FOR PARALLEL PCMCIA CONTROLLERS
SLVS094C – AUGUST 1994 – REVISED JANUARY 2001
APPLICATION INFORMATION
overcurrent and thermal protection
The TPS2201 uses sense FETs to check for overcurrent conditions in each of the V_CC and V_pp outputs. Unlike
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.
During power up, the TPS2201 controls the rise time of the V_CC and V_pp outputs and limits the current into 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
much as 10 A to 15 A may flow into the short before the current limiting of the TPS2201 engages. If the V_CC
or V_pp outputs are driven below ground, the TPS2201 may latch nondestructively in an off state. Cycling power
will reestablish normal operation.
Overcurrent limiting for the V_CC outputs is designed to engage if powered up into a short in the range of
0.75 A to 1.9 A, typically at about 1.3 A; the V_pp outputs limit from 120 mA to 400 mA, typically around 200 mA.
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 when 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
The switch resistance, r_DS(on), is dependent on the junction temperature, T_J, of the die. The junction temperature
is dependent on both r_DS(on) and the current through the switch. To calculate T_J, first find r_DS(on) from Figures
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:
+ @ PD rDS(on) I2
+ ǒ @ Ǔ ) + ń Next, sum the power dissipation and calculate the junction temperature:
TJ S PD R_qJA TA, R_qJA 108°C W
Compare the calculated junction temperature with the initial temperature estimate. If they are not within a few
degrees of each other, reiterate using the calculated temperature as the initial estimate.
logic input and outputs
The TPS2201 was designed to be compatible with most popular PCMCIA controllers and current PCMCIA and
JEIDA standards. However, some controllers require slightly counterintuitive connections to achieve desired
output states. The TPS2201 control logic inputs A_VCC3, A_VCC5, B_VCC3 and B_VCC5 are defined active
low (see Figure 23 and control-logic table). As such, they are directly compatible with the logic outputs of the
Cirrus Logic CL-PD6720 controller (see Figure 24). The separate V_pp power-good indicators of the TPS2201
can be ORed together to provide a single input to the Cirrus controller.
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