MIC2560_06 Datasheet, PDF (6/8 Pages) Micrel Semiconductor – PCMCIA Card Socket VCC and VPP Switching Matrix

Micrel, Inc.
MIC2560
Application Information
PCMCIA V_CC and V_PP control is easily accomplished
using the MIC2560 voltage selector/switch IC. Four
control bits determine V_{CC OUT} and V_{PP OUT} voltage and
standby/operate mode condition. V_{PP OUT} output voltages
of V_CC (3.3V or 5V), V_PP, or a high impedance state are
available. When the V_CC high impedance condition is
selected, the device switches into “sleep” mode and
draws only nano-amperes of leakage current. An error
flag falls low if the output is improper, because of
overtemperature or overcurrent faults. Full protection
from hot switching is provided which prevents feedback
from the V_{PP OUT} to the V_CC inputs (from 12V to 5V, for
example) by locking out the low voltage switch until
V_{PP OUT} drops below V_CC. The V_CC output is similarly
protected against 5V to 3.3V shoot through.
The MIC2560 is a low-resistance power MOSFET
switching matrix that operates from the computer system
main power supply. Device logic power is obtained from
V_CC3 and internal MOSFET drive is obtained from the
V_{PP IN} pin (usually +12V) during normal operation. If
+12V is not available, the MIC2560 automatically
switches into “suspend” mode, where V_{CC OUT} can be
switched to 3.3V, but at higher switch resistance.
Internal break-before-make switches determine the
output voltage and device mode.
Matrix, and a controller. Figure 3 shows this full config-
uration, supporting both 5.0V and 3.3V V_CC operation.
Figure 3. MIC2560 Typical PCMCIA Memory Card
Application with Dual V_CC (5.0V or 3.3V)
and separate V_PP1 and V_PP2.
Supply Bypassing
External capacitors are not required for operation. The
MIC2560 is a switch and has no stability problems. For
best results however, bypass V_{CC3 IN}, V_{CC5 IN}, and V_{PP IN}
inputs with filter capacitors to improve output ripple. As
all internal device logic and voltage/current comparison
functions are powered from the V_{CC3 IN} line, supply
bypass of this line is the most critical, and may be
necessary in some cases. In the most stubborn layouts,
up to 0.47µF may be necessary. Both V_{CC OUT} and
V_{PP OUT} pins may have 0.01µF to 0.1µF capacitors for
noise reduction and electrostatic discharge (ESD)
damage prevention. Larger values of output capacitor
might create current spikes during transitions, requiring
larger bypass capacitors on the V_{CC3 IN}, V_{CC5 IN}, and V_{PP IN}
pins.
PCMCIA Implementation
Figure 4. MIC2560 Typical PCMCIA Memory Card
Application with Dual V_CC (5.0V or 3.3V).
Note that V _PP1 and V _PP2 are Driven Together.
The MIC2560 is designed for compatibility with the
Personal Computer Memory Card International
Association’s (PCMCIA) Specification, revision 2.1 as
well as the PC Card Specification, (March 1995),
including the CardBus option.
The Personal Computer Memory Card International
Association (PCMCIA) specification requires two V_PP
supply pins per PCMCIA slot. V_PP is primarily used for
programming Flash (EEPROM) memory cards. The two
V_PP supply pins may be programmed to different
voltages. Fully implementing PCMCIA specifications
requires a MIC2560, a MIC2557 PCMCIA V_PP Switching
However, many cost sensitive designs (especially
notebook/palmtop computers) connect V_PP1 to V_PP2 and
the MIC2557is not required. This circuit is shown in
Figure 4.
When a memory card is initially inserted, it should
receive V_CC — either 3.3V ± 0.3V or 5.0V ±5%. The
initial voltage is determined by a combination of
mechanical socket “keys” and voltage sense pins. The
card sends a handshaking data stream to the controller,
which then determines whether or not this card requires
V_PP and if the card is designed for dual V_CC. If the card is
September 2006
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M9999-092106