MIC2562A
Micrel
If no card is inserted or the system is in sleep mode, the slot
logic controller outputs a (V
CC3
IN, V
CC5
IN) = (0,0) to the
MIC2562A, 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.
Internal device control logic and MOSFET drive and bias
voltage is powered from V
CC3
IN. The high voltage bias is
generated by an internal charge pump quadrupler. Systems
without 3.3V may connect V
CC3
IN to 5V. Input logic threshold
voltages are compatible with common PC Card logic control-
lers using either 3.3V or 5V supplies.
The PC Card Specification defines two V
PP
supply pins per
card slot. The two V
PP
supply pins may be programmed to
different voltages. V
PP
is primarily used for programming
FLASH memory cards. Implementing two independent V
PP
voltages is easily accomplished with the MIC2562A and a
MIC2557 PCMCIA V
PP
Switching Matrix. Figure 3 shows this
full configuration, supporting independent V
PP
and both 5.0V
and 3.3V V
CC
operation. However, few logic controllers
support multiple V
PP
—most systems connect V
PP1
to V
PP2
and the MIC2557 is not required. This circuit is shown in
Figure 4.
During Flash memory programming with standard (+12V)
Flash memories, the PC Card slot logic controller outputs a
(0,1) to the EN0, EN1 control pins of the MIC2562A, which
connects V
PP
IN (nominally +12V) to V
PP OUT
. The low ON
resistance of the MIC2562A switch allows using a small
bypass capacitor on the V
PP OUT
pins, with the main filtering
action performed by a large filter capacitor on V
PP
IN (usually
the main power supply filter capacitor is sufficient). Using a
small-value capacitor such as 0.1µF on the output causes
little or no timing delays. 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
MIC2562A, which then reduces V
PP OUT
to the V
CC
level.
Break-before-make switching action and controlled rise times
reduces switching transients and lowers maximum current
spikes through the switch.
Figure 5 shows MIC2562A configuration for situations where
only a single +5V V
CC
is available.
Output Current and Protection
MIC2562A output switches are capable of passing the maxi-
mum current needed by any PC Card. The MIC2562A meets
or exceeds all PCMCIA specifications. For system and card
protection, output currents are internally limited. For full
system protection, long term (millisecond or longer) output
short circuits invoke overtemperature shutdown, protecting
the MIC2562A, the system power supplies, the card socket
pins, and the PC Card. A final protective feature is the error
FLAG, which signals the PC Card slot logic controller when
a fault condition exists, allowing the controller to notify the
user that the card inserted has a problem. The open-drain
FLAG monitors the voltage level on both V
CC OUT
and V
PP
OUT
and activates (pulls low) when either output is 1V below
its programmed level or an overtemperature fault exists.
This FLAG signals output voltage transitions as well as fault
conditions. Refer to Figures 1 and 2 for details.
61
MIC2562A
Applications Information
PC Card V
CC
and V control is easily accomplished using
PP
the MIC2562A PC Card/CardBus Slot V
CC
& V
PP
Power
Controller IC. Four control bits determine V
CC OUT
and V
PP
OUT
voltage and standby/operate mode condition. V
CC
out-
puts of 3.3V and 5V at the maximum allowable PC Card
current are supported. V
PP OUT
output voltages of V
CC
(3.3V
or 5V), V
PP
, 0V, or a high impedance state are available.
When the V
CC
clamped to ground condition is selected, the
device switches into “sleep” mode and draws only nano-
amperes of leakage current. An error flag alerts the user if the
output voltage is too low because of overtemperature or
overcurrent faults. Protection from hot switching is provided
which prevents feedback from the V
CC OUT
(from 5V to 3.3V,
for example) by locking out the low voltage switch until the
initial switch’s gate voltage drops below the desired lower
V
CC
.
The MIC2562A operates from the computer system main
power supply. Device logic and internal MOSFET drive is
generated internally by charge pump voltage multipliers
powered from V
CC3
IN. Switching speeds are carefully con-
trolled to prevent damage to sensitive loads and meet all PC
Card Specification speed requirements.
Supply Bypassing
External capacitors are not required for operation. The
MIC2562A 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 1µF capacitors to improve output ripple. As all internal
device logic and comparison functions are powered from the
V
CC3
IN line, the power supply quality of this line is the most
important, and a bypass capacitor may be necessary for
some layouts. Both V
CC OUT
and V
PP OUT
pins may use
0.01µF to 0.1µF capacitors for noise reduction and electro-
static discharge (ESD) damage prevention. Larger values of
output capacitors are not necessary.
PC Card Slot Implementation
The MIC2562A is designed for full compatibility with the
Personal Computer Memory Card International Associa-
tion’s (PCMCIA) PC Card Specification, (March 1995), in-
cluding the CardBus option. One MIC2562A is required for
each PC Card slot.
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.
V
CC
switches are turned ON and OFF slowly. If commanded
to immediately switch from one V
CC
to the other (without
turning OFF and waiting 100ms first), enhancement of the
second switch begins after the first is OFF, realizing break-
before-make protection. V
PP
switches are turned ON slowly
and OFF quickly, which also prevents cross conduction.
July 1999
MICREL [ MICREL SEMICONDUCTOR ]
