Datasheet

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12-V SUPPLY NOT REQUIRED
VOLTAGE-TRANSITIONING REQUIREMENT
SHUTDOWN MODE
POWER-SUPPLY CONSIDERATIONS
TPS2220A , TPS2223A
TPS2224A , TPS2226A
SLVS428E – MAY 2002 – REVISED MSRCH 2008
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. Excessive current
generates an error signal that limits the output current of only the affected output, preventing damage to the host.
Each xVCC output overcurrent limits from 1 A to 2.0 A, typically around 1.6 A; the xVPP outputs limit from 100
mA to 250 mA, typically around 200 mA.
Second, when an overcurrent condition is detected, the TPS2220A, TPS2223A, TPS2224A, and TPS2226A
assert an active low OC signal that can be monitored by the microprocessor or controller to initiate diagnostics
and/or send the user a warning message. If an overcurrent condition persists, causing the IC to exceed its
maximum junction temperature, thermal-protection circuitry activates, shutting down all power outputs until the
device cools to within a safe operating region, which is ensured by a thermal shutdown hysteresis. Thermal
limiting prevents destruction of the IC from overheating beyond the package power-dissipation ratings.
During power up, the devices control the rise times of the xVCC and xVPP outputs and limit the inrush current
into a large load capacitance, faulty card, or connector.
Some 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 TPS2220A, TPS2224A and TPS2226A offer considerable power
savings by using an internal charge pump to generate the required higher gate drive voltages from the 3.3-V
input. Therefore, the external 12-V supply can be disabled except when needed by the PC Card in the slot,
thereby extending battery lifetime. A special feature in the 12-V circuitry actually helps to reduce the supply
current demanded from the 3.3-V input. When 12 V is supplied and requested at the VPP output, a voltage
selection circuit draws the charge-pump drive current for the 12-V FETs from the 12-V input. This selection is
automatic and effectively reduces demand fluctuations on the normal 3.3-V VCC rail. For proper operation of this
feature, a minimum 3.3-V input capacitance of 4.7 µ F is recommended, and a minimum 12-V input ramp-up rate
of 12 V/50 ms (240 V/s) is required. Additional power savings are realized during a software shutdown in which
quiescent current drops to a maximum of 1 µ A.
PC Cards, like portables, are migrating from 5 V to 3.3 V to minimize power consumption, optimize board space,
and increase logic speeds. The TPS2220A, TPS2223A, TPS2224A, and TPS2226A meet 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 action ensures that sensitive 3.3-V circuitry is not subjected to any residual 5-V
charge and functions as a power reset. PC Card specification requires that V
CC
be discharged within 100 ms. PC
Card resistance cannot 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. The devices include discharge
transistors on all xVCC and xVPP outputs to meet the specification requirement.
In the shutdown mode, which can be controlled by SHDN or bit D8 of the input serial DATA word, each of the
xVCC and xVPP outputs is forced to a high-impedance state. In this mode, the chip quiescent current is reduced
to 1 µ A or less to conserve battery power.
These switches have multiple pins for each 3.3-V (except for TPS2220A) and 5-V power input and for the
switched xVCC outputs. Any individual pin can conduct the rated input or output current. Unless all pins are
connected in parallel, the series resistance is higher than that specified, resulting in increased voltage drops and
power loss. It is recommended that all input and output power pins be paralleled for optimum operation.
To increase the noise immunity of the TPS2220A, TPS2223A, TPS2224A, and TPS2226A, the power-supply
inputs should be bypassed with at least a 4.7- µ F electrolytic or tantalum capacitor paralleled by a 0.047- µ F to
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Product Folder Link(s): TPS2220A TPS2223A TPS2224A TPS2226A