MIC2560 Datasheet, PDF (6/12 Pages) Micrel Semiconductor – PCMCIA Card Socket VCC and VPP Switching Matrix

MIC2560
Applications 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 overcur-
rent 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 “sus-
pend” 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.
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.
Micrel
PCMCIA Implementation
The MIC2560 is designed for compatibility with the Personal
Computer Memory Card International Association’s (PCM-
CIA) Specification, revision 2.1 as well as the PC Card
Specification, (March 1995), including the CardBus option.
The Personal Computer Memory Card International Associa-
tion (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 PCM-
CIA specifications requires a MIC2560, a MIC2557 PCMCIA
V_PP Switching Matrix, and a controller. Figure 3 shows this
full configuration, supporting both 5.0V and 3.3V V_CC opera-
tion.
5V
System
Power 3.3V
Supply
12V
PCMCIA
Card Slot
Controller
VPPIN VCC3IN VCC5IN
EN0
EN1
MIC2560
VCC5_EN
VCC3_EN
VPP1
PCMCIA
Card Slot
VPP2
VCC
VPP _IN VDD VCC
EN0
VPP OUT
EN1
MIC2557
Figure 3. MIC2560 Typical PCMCIA memory card
application with dual V_CC (5.0V or 3.3V) and separate
V_PP1 and V_PP2.
MIC2560
6
November 1999