G576 查看數據表（PDF） - Global Mixed-mode Technology Inc
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G576 Datasheet PDF : 12 Pages
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Global Mixed-mode Technology Inc.
G576
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
G576 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 G576 during a software shutdown in
which quiescent current drops to a maximum of 3µA.
3.3V Low Voltage Mode
The G576 will operates in a 3.3V low voltage mode
when 3.3V is only available input voltage (VCC5=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
G576 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 G576 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 function is a power
reset and ensures that sensitive 3.3V circuitry is not
subjected to any residual 5V charge. The G576 offer a
selectable VCC and VPP ground state, in accordance
with PCMCIA 3.3V/5V switching specifications.
Output Ground Switches
PC Card specification requires that AVCC/BVCC 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 G576 has multiple pins for each of its 3.3V, and
5V power inputs and for switched AVCC/BVCC out-
puts. Any individual pin can conduct the rated input or
output current. Unless all pins are connected in paral-
lel, 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 G576, 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 G576 to electrostatic
discharge (ESD). Care should be taken to minimize
the inductance of PCB traces between the G576 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: 1.0
Jan 23, 2003
TEL: 886-3-5788833
http://www.gmt.com.tw
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