MIC2560 Datasheet, PDF (7/12 Pages) Micrel Semiconductor – PCMCIA Card Socket VCC and VPP Switching Matrix

MIC2560
5V
System
Power 3.3V
Supply
12V
PCMCIA
Card Slot
Controller
VPPIN VCC3IN VCC5IN
EN0
EN1
MIC2560
VCC5_EN
VCC3_EN
VPP1
VPP2 PCMCIA
Card Slot
VCC
Micrel
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.
However, many cost sensitive designs (especially notebook/
palmtop computers) connect V_PP1 to V_PP2 and the MIC2557
is 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 compatible with and desires a different V_CC
level, the controller commands this change by disabling V_CC,
waiting at least 100ms, and then re-enabling the other V_CC
voltage.
If no card is inserted or the system is in sleep mode, the
controller outputs a (V_CC3 IN, V_CC5 IN) = (0,0) to the MIC2560,
which shuts down V_CC. This also places the switch into a high
impedance output shutdown (sleep) mode, where current
consumption drops to nearly zero, with only tiny CMOS
leakage currents flowing.
During Flash memory programming with standard (+12V)
Flash memories, the PCMCIA controller outputs a (1,0) to the
EN0, EN1 control pins of the MIC2560, which connects
V_PP IN to V_{PP OUT}. The low ON resistance of the MIC2560
switches allow using small bypass capacitors (in some cases,
none at all) on the V_{CC OUT} and V_{PP OUT} pins, with the main
filtering action performed by a large filter capacitor on the
input supply voltage to V_PP IN (usually the main power supply
filter capacitor is sufficient). The V_{PP OUT} transition from V_CC
to 12.0V typically takes 250µs. After programming is com-
pleted, the controller outputs a (EN1, EN0) = (0,1) to the
MIC2560, which then reduces V_{PP OUT} to the V_CC level for
read verification. Break-before-make switching action re-
duces switching transients and lowers maximum current
spikes through the switch from the output capacitor. The flag
comparator prevents having high voltage on the V_{PP OUT}
capacitor from contaminating the V_CC inputs, by disabling the
low voltage V_PP switches until V_{PP OUT} drops below the V_CC
level selected. The lockout delay time varies with the load
current and the capacitor on V_{PP OUT}. With a 0.1µF capacitor
and nominal I_{PP OUT}, the delay is approximately 250µs.
Internal drive and bias voltage is derived from V_PP IN. Internal
device control logic is powered from V_CC3 IN. Input logic
threshold voltages are compatible with common PCMCIA
controllers using either 3.3V or 5V supplies. No pull-up
resistors are required at the control inputs of the MIC2560.
Output Current and Protection
MIC2560 output switches are capable of more current than
needed in PC Card applications (1A) and meet or exceed all
PCMCIA specifications. For system and card protection,
output currents are internally limited. For full system protec-
tion, long term (millisecond or longer) output short circuits
invoke overtemperature shutdown, protecting the MIC2560,
the system power supplies, the card socket pins, and the
memory card. Overtemperature shutdown typically occurs at
a die temperature of 115°C.
Single V_CC Operation
For PC Card slots requiring only a single V_CC, connect
V_{CC3 IN} and V_{CC5 IN} together and to the system V_CC supply
(i.e., Pins 1, 3, and 15 are all connected to system V_CC).
Either the V_CC5 switch or the V_CC3 switch may be used to
enable the card slot V_CC; generally the V_CC3 switch is
preferred because of its lower ON resistance.
Suspend Mode
An additional feature in the MIC2560 is a pseudo power-down
mode, Suspend Mode, which allows operation without a V_PP
IN supply. In Suspend Mode, the MIC2560 supplies 3.3V to
V_CC OUT whenever a V_CC output of 3.3V is enabled by the
PCMCIA controller. This mode allows the system designer
the ability to turn OFF the V_PP supply generator to save power
when it is not specifically required. The PCMCIA card re-
ceives V_CC at reduced capacity during Suspend Mode, as the
switch resistance rises to approximately 4.5Ω.
November 1999
7
MIC2560