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TPS2212IDBRG4 Datasheet(PDF) 14 Page - Texas Instruments
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TPS2212IDBRG4 Datasheet(HTML) 14 Page - Texas Instruments
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SINGLE-SLOT, PARALLEL INTERFACE POWER SWITCH
FOR LOW POWER PC CARD SLOTS
SLVS193A – APRIL 1999 – REVISED JANUARY 2001
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
overcurrent and overtemperature protection
PC Cards are inherently subject to damage from mishandling. Host systems require protection against
short-circuited cards that could lead to power supply or PCB trace damage. Even systems sufficiently robust
to withstand a short circuit would still undergo rapid battery discharge into the damaged PC Card, resulting in
a sudden loss of system power. Most hosts include fuses for protection. The reliability of fused systems is poor
and requires troubleshooting and repair, usually by the manufacturer, when fuses are blown.
The TPS2212 uses sense FETs to check for overcurrent conditions in each of the VCC and VPP 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 an overcurrent condition is detected
providing for initiation of system diagnostics and/or sending a warning message to the user.
During power up, the TPS2212 controls the rise time of the VCC and VPP 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 5 A to 10 A may flow into the short before the current limiting of the TPS2212 engages. If the VCC or
VPP outputs are driven below ground, the TPS2212 may latch nondestructively in an off state. Cycling power
will reestablish normal operation.
Overcurrent limiting for the VCC outputs is designed to activate if powered up into a short in the range of
300 mA to 600 mA, typically at about 450 mA. The VPP outputs limit from 120 mA to 400 mA, typically around
280 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 if the package power dissipation ratings are
exceeded. Thermal limiting disables power output until the device has cooled.
12-V supply not required
Most PC Card switches use the externally supplied 12 V to power gate drive and other chip functions, which
requires that power be present at all times. The TPS2212 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 VPPI switch input when the VPPI input is not used. Additional power savings are realized by the
TPS2212 during a software shutdown in which quiescent current drops to a maximum of 1
3.3-V low-voltage mode
The TPS2212 will operate in a 3.3-V low-voltage mode when 3.3 V is the only available input voltage
= 0). This allows host and PC Cards to be operated in low-power 3.3-volts-only modes such as sleep or
pager modes. Note that in these operation modes, the TPS2212 will derive its bias current from the 3.3-V input
pin and only 3.3 V can be delivered to the PC Card.
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