G571 Ver la hoja de datos (PDF) - Unspecified

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G571

Single-Slot PCMCIA/CardBus Power Controllers

Unspecified 

Global Mixed-mode Technology Inc.

G571

Thermal limiting prevents destruction of the IC from

overheating if the package power dissipation rating

are exceeded. Thermal limiting disables power output

until the device has cooled.

12V Supply Not Required

Most PC Card switches use the externally supplied

12V to power gate drive and other chip functions,

which require that power be present at all times. The

G571 offers considerable power savings by using an

internal charge pump to generate the required higher

voltages from 5V input; Therefore, the external 12V

supply can be disable except when needed for

flash-memory functions, thereby extending battery

lifetime. Do not ground the 12V switch inputs when the

12-V input is not used. Additional power savings are

realized by the G571 during a software shutdown in

which quiescent current drops to a maximum of 3µA.

3.3V Low Voltage Mode

The G571 will operates in a 3.3V low voltage mode

when 3.3V is only available input voltage (VI(5V) = 0).

This allows host and PC Cards to be operated in

low-power 3.3V-only modes such as sleep modes or

pager modes. Note that in these operation mode, the

G571 will derive its bias current from the 3.3V input

pin and only 3.3V can be delivered to the PC Card.

Voltage Transitioning Requirement

PC Cards are migrating from 5V to 3.3V to minimize

power consumption, optimize board space, and in-

crease logic speeds. The G571 meets all combina-

tions of power delivery as currently defined in the

PCMCIA standard. The latest protocol accommodates

mixed 3.3V/5V systems by first powering the card with

5V, then polling it to determine its 3.3V compatibility.

The PCMCIA specification requires that the capacitors

on 3.3V-compatible cards be discharged to below

0.8V before applying 3.3V power. This functions as a

power reset and ensures that sensitive 3.3V circuitry is

not subjected to any residual 5V charge. The G571

offer a selectable VCC and VPP ground state, in accor-

dance with PCMCIA 3.3V/5V switching specifications.

Output Ground Switches

PC Card specification requires that VCC be discharged

within 100 ms. PC Card resistance can not 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.

Power Supply Considerations

The G571 has multiple pins for each of its 3.3V, and

5V power inputs and for switched VCC outputs. Any

individual pin can conduct the rated input or output

current. Unless all pins are connected in parallel, the

series resistance is significantly higher than that

specified, resulting in increased voltage drops and lost

power. it is recommended that all input and output

power pins be paralleled for optimum operation.

To increase the noise immunity of the G571, the

power supply inputs should be bypassed with a 1µF

electrolytic or tantalum capacitor paralleled by a

0.047µF to 0.1µF ceramic capacitor. It is strongly

recommended that the switched outputs be bypassed

with a 0.1µF or larger, ceramic capacitor; doing so

improves the immunity of the G571 to electrostatic

discharge (ESD). Care should be taken to minimize

the inductance of PCB traces between the G571 and

the load. High switching currents can produce large

negative voltage transients, which forward biases sub-

strate diodes, resulting in unpredictable performance.

Similary, no pin should be taken below -0.3V.

Ver 1.1

Jan 08, 2001

TEL: 886-3-5788833

http://www.gmt.com.tw

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