MIC2568 Micrel
MIC2568 8 May 2003
Applications Information
PC Card power control for two sockets is easily accomplished
using the Micrel MIC2568 PC Card/CardBus Slot Power
Controller IC.
Output Voltage Selection
Four control bits per socket determine V
CC
and V
PP
output
voltages and standby- or operate-mode conditions. Input
logic threshold voltages are compatible with common PC
Card logic controllers using either 3.3V or 5V supplies.
The V
CC
outputs can be individually switched between 0V
(ground) or 3.3V and 5V at the maximum allowable PC Card
current. The V
PP
outputs can be individually switched be-
tween 0V (ground), 3.3V or 5V (V
CC3
or V
CC5
voltages), or
high impedance. When V
CC
= 0V (ground) is selected, the
MIC2568 goes into sleep mode and draws only nanoamperes
of leakage current.
Switching speeds are controlled to prevent damage to sensi-
tive loads and meet all PC Card Specification timing require-
ments. V
CC
switches are turned on and off slowly. If com-
manded to switch directly from one V
CC
to the other (without
first turning off and waiting 100ms), enhancement of the
second switch begins only after the first is off (break-before-
make protection).
Supply Input
The MIC2568 itself is powered from the V
CC3
IN pin (3.3V-
nominal supply input). Bias its internal MOSFETs is gener-
ated by a charge pump quadrupler. Refer to “5V-Only V
CC
Application” and Figure 4 for information on using the MIC2568
without a 3.3V supply.
Output Current and Protection
The MIC2568 meets or exceeds all PCMCIA current specifi-
cations. Its switches are capable of passing the maximum
current needed by any PC Card. For system and card
protection, output currents are internally limited. For full
system protection, long-term output short circuits (millisec-
ond or longer) invoke overtemperature shutdown, protecting
the MIC2568, system power supplies, card socket pins, and
PC Card.
Bypass Capacitors
Both V
CC3
IN and V
CC5
IN pins should be bypassed with 1µF
low-ESR surface-mount ceramic capacitors mounted near
the MIC2568 chip.
Both V
CC
OUT and V
PP
OUT pins may use 0.01µF to 0.1µF
capacitors for noise reduction and to reduce the chance of
(electrostatic discharge) ESD damage.
PC Card Slot Implementation
The MIC2568 is designed for PC Card applications, including
the CardBus option, that do not require a 12V supply.
When a memory card is initially inserted, it must receive a V
CC
voltage (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. Each card sends handshaking data to
the logic controller which determines whether that card
requires a V
PP
voltage and whether the card is designed for
dual V
CC
voltages. If the card is compatible with, and re-
quests, a different V
CC
level, the controller disables V
CC
,
waits at least 100ms, and then enables the new V
CC
voltage.
If no card is inserted, or the system is in sleep mode, the logic
controller outputs a (V
CC3
EN, V
CC5
EN) = (0, 0) to the
MIC2568, which shuts down V
CC
. This also places the switch
into its high-impedance output sleep mode.
Basic V
PP
and V
CC
Switch Application
Refer to Figure 3. A single system power supply feeds both
slot-A and slot-B supply inputs. Although the PC Card speci-
fication defines two V
PP
outputs (V
PP
1 and V
PP
2) per card,
they are usually connected together.
MIC2568-0
Power
Controller
3.3V
(
OPTIONAL)
5V
System Power Supply
Dual-Slot
PC Card
Logic Controller
A V
PP
OUT
A V
CC
OUT
B V
PP
OUT
B V
CC
OUT
PC Card
A
V
PP
1
V
PP
2
V
CC
PC Card
B
V
PP
1
V
PP
2
V
CC
Motherboard
Slot A
Slot B
Address and data lines
between logic controller and
PCMCIA cards not shown.
A EN1
A EN0
A V
CC5
EN
A V
CC3
EN
B EN1
B EN0
B V
CC5
EN
B V
CC3
EN
A
⁄BV
CC3
IN
A
⁄BV
CC5
IN
GND
V
CC
V
CC
Figure 3. Basic V
PP
and V
CC
Switch
