TPS2214A, TPS2216A

LOW-COST DUAL-SLOT PC CARD POWER SWITCH

FOR SERIAL PCMCIA CONTROLLERS

SLVS267 – DECEMBER 1999

20

POST OFFICE BOX 655303

APPLICATION INFORMATION

designing for voltage regulation (continued)

shutdown mode

In the shutdown mode, which can be controlled by 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 limited to 1

µA

or less to conserve battery power.

standby mode

The TPS2214A and TPS2216A can be put in standby mode by pulling STBY low to conserve power during

low-power operation. In this mode, all of the power outputs (xVCC and xVPP) will have a nominal current limit

of 50 mA. STBY has an internal 150-k

Ω pullup resistor. The output-switch status of the device must be set,

allowing the output capacitors to charge, prior to enabling the standby mode. Changing the setting of the output

switches with the device in standby mode may cause an overcurrent response to be generated.

mode

The mode pin programs the switches in either TPS2214A/ TPS2216A or TPS2206 mode. An internal 150-k

Ω

pulldown resistor is connected to the pin. Floating or pulling the mode pin low sets the switches in TPS2206

mode; pulling the mode pin high sets the switches in TPS2214A/ TPS2216A mode. In TPS2206 mode, xVPP

outputs are dependent on xVCC outputs. In TPS2214A/ TPS2216A mode, xVPP is programmed independent

of xVCC. Refer to TPS2214A/TPS2216A control-logic tables for more information.

power-supply considerations

The TPS2214A and TPS2216A have multiple pins for each of its 3.3-V and 5-V power inputs 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 less

power. It is recommended that all input and output power pins be paralleled for optimum operation. Because

the two 12-V pins are not internally connected, they must be tied together externally.

To increase the noise immunity of the TPS2214A and TPS2216A, the power-supply inputs should be bypassed

with a 1-

µF electrolytic or tantalum capacitor paralleled by a 0.047-µF to 0.1-µF ceramic capacitor. It is strongly

recommended that the switched outputs be bypassed with a 0.1-

µF (or larger) ceramic capacitor; doing so

improves the immunity of the IC to electrostatic discharge (ESD). Care should be taken to minimize the

inductance of PCB traces between the IC and the load. High switching currents can produce large negative

voltage transients, which forward biases substrate diodes, resulting in unpredictable performance. Similarly, no

pin should be taken, or allowed to fall, below –0.3 V.

RESET and RESET inputs

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

be reset at the same time as the host by applying low impedance paths from xVCC and xVPP terminals to

ground. A 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 active-high RESET

or active low RESET input will close internal switches S1, S4, S7, and S11 with all other switches left open. The

TPS2214A and TPS2216A remain in the low-impedance output state until the signal is deasserted and further

data is clocked in and latched. The input serial data can not be latched during reset mode. RESET and RESET

are provided for direct compatibility with systems that use either an active-low or active-high reset voltage

supervisor. The RESET pin has an internal 150-k

Ω pulldown resistor and the RESET pin has an internal 150-kΩ

pullup resistor. The device will be reset automatically when powered up.