MIC2566 Micrel
MIC2566 8 May 2003
Applications Information
PC Card V
CC
and V
PP
control is easily accomplished using
the MIC2566 PC Card/CardBus Slot V
CC
and V
PP
Power
Controller IC. Four control bits determine V
CC OUT
and
V
PP OUT
voltage and standby/operate mode condition. V
CC
outputs 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), 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 nanoamperes 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 pre-
vents 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 MIC2566 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
MIC2566 is a switch and has no stability problems. For best
results however, bypass V
CC3
IN and V
CC5
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 capaci-
tors for noise reduction and electrostatic discharge (ESD)
damage prevention. Larger values of output capacitors are
not necessary.
PC Card Slot Implementation
The MIC2566 is designed for PC Card applications, including
the CardBus option, that do not require a 12V bias. One
MIC2566 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.
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
MIC2566, 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.
Figure 3 shows MIC2566 configuration for situations where
only a single +5V V
CC
is available.
Output Current and Protection
MIC2566 output switches are capable of passing the maxi-
mum current needed by any PC Card. 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 MIC2566, 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.
