TPS2216ADAP datasheet(18/27 Pages) TI

18 / 27 page

TPS2214A, TPS2216A

LOW-COST DUAL-SLOT PC CARD POWER SWITCH

FOR SERIAL PCMCIA CONTROLLERS

SLVS267 – DECEMBER 1999

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

overview

PC Cards were initially introduced as a means to add EEPROM (flash memory) to portable computers with

limited onboard memory. The idea of add-in cards quickly took hold; modems, wireless LANs, Global Positioning

Satellite System (GPS), multimedia, and hard-disk versions were soon available. As the number of PC Card

applications grew, the engineering community quickly recognized the need for a standard to ensure

compatibility across platforms. To this end, the PCMCIA (Personal Computer Memory Card International

Association), comprising members from leading computer, software, PC Card, and semiconductor

manufacturers, was established. One key goal was to realize the plug-and-play concept. Cards and hosts from

different vendors should be compatible or able to communicate with one another transparently.

PC Card power specification

System compatibility also means power compatibility. The most current set of specifications (PC Card Standard)

set forth by the PCMCIA committee states that power is to be transferred between the host and the card through

eight of the 68 terminals of the PC Card connector. This power interface consists of two VCC, two Vpp, and four

ground terminals. Multiple VCC and ground terminals minimize connector terminal and line resistance. The two

Vpp terminals were originally specified as separate signals, but are commonly tied together in the host to form

a single node to minimize voltage losses. Card primary power is supplied through the VCC terminals;

flash-memory programming and erase voltage is supplied through the Vpp terminals.

designing for voltage regulation

The current PCMCIA specification for output voltage regulation, VO(reg), of the 5-V output is 5% (250 mV). In

a typical PC power-system design, the power supply has an output-voltage regulation, VPS(reg), of 2% (100 mV).

Also, a voltage drop from the power supply to the PC Card will result from resistive losses, VPCB, in the PCB

traces and the PCMCIA connector. A typical design would limit the total of these resistive losses to less than

1% (50 mV) of the output voltage. Therefore, the allowable voltage drop, VDS, for the TPS2214A or TPS2216A

would be the PCMCIA voltage regulation less the power supply regulation and less the PCB and connector

resistive drops:

DS +

O(reg)

–V

PS(reg)

–V

PCB

Typically, this would leave 100 mV for the allowable voltage drop across the 5-V switch. The specification for

output voltage regulation of the 3.3-V output is 300 mV; so, using the same equation by deducting the voltage

drop percentages (2%) for power-supply regulation and PCB resistive loss (1%), the allowable voltage drop for

the 3.3-V switch is 200 mV. The voltage drop is the output current multiplied by the switch resistance of the

TPS2214A or TPS2216A. Therefore, the maximum output current, IO max, that can be delivered to the PC Card

in regulation is the allowable voltage drop across the IC, divided by the output-switch resistance.

max

DS(on)

The xVCC outputs can deliver 1 A continuously at 5 V and 3.3 V within regulation over the operating temperature

range. The xVPP outputs of the IC can deliver 200 mA continuously.

TPS2216ADAP Datasheet(PDF) 18 Page - Texas Instruments

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