MIC2557
Micrel
MIC2557
PCMCIA Card Socket V
PP
Switching Matrix
General Description
The MIC2557 switches the four voltages required by PCMCIA
(Personal Computer Memory Card International Association)
card V
PP
Pins. The MIC2557 provides selectable 0V, 3.3V,
5.0V, or 12.0V (±5%) from the system power supply to V
PP1
or V
PP2
. Output voltage is selected by two digital inputs.
Output current ranges up to 120mA. Four control states, V
PP
,
V
CC
, high impedance, and active logic low are available. An
auxiliary control input determines whether the high imped-
ance (open) state or low logic state is asserted.
In either quiescent mode or full operation, the device draws
very little current, typically less than 1µA.
The MIC2557 is available in an 8-pin SOIC and an 8-pin
plastic DIP.
Features
•
•
•
•
•
•
•
•
•
•
Complete PCMCIA V Switch Matrix in a Single IC
PP
No External Components Required
Digital Selection of 0V, V
CC
, V
PP
, or High Imped–
ance Output
No V
PP OUT
Overshoot or Switching Transients
Break-Before-Make Switching
Low Power Consumption
120mA V (12V) Output Current
PP
Optional Active Source Clamp for Zero Volt Condition
3.3V or 5V Supply Operation
8-Pin SOIC Package
Applications
•
•
•
PCMCIA V
PP
Ordering Information
Part Number
MIC2557BM
MIC2557BM T&R
Temperature Range
–40°C to +85°C
–40°C to +85°C
Package
8-pin SOIC
8-SOIC Tape & Reel*
Pin Voltage Switch
Power Supply Management
Power Analog Switch
* 2,500 Parts per reel.
Typical Application
VCC
+3.3V or +5V
VPP IN
+12V
VDD
+5V
Pin Configuration
VPP IN
VPP OUT
+VCC
0.1µF
8
8
2
7
MIC2557
3
6
4
5
VDD
Hi-Z/Low
EN0
EN1
GND
Hi-Z/ Low Control
EN0
EN1
VPP(n) OUT
0.1µF
1µF
1µF
2
7
MIC2557
3
6
4
5
Simplified Block Diagram
VDD
VPP IN
VCC
EN1
0
0
0
1
1
EN0 Hi-Z/Low V
PP OUT
0
0
1
0
1
0
1
x
x
x
0V, (Sink current)
Hi-Z (No Connect)
V
CC
(3.3V or 5.0V)
V
PP
Hi-Z (No Connect)
Hi-Z/Low
EN0
EN1
Decoder,
Driver &
Bias Control
High
Impedance or
Pull Down
Select
VPP OUT
For a dual PCMCIA Card Socket V
PP
Switching Matrix, see the MIC2558.
For a V
PP
and V
CC
Switching Matrix, see the MIC2560.
2-4
1997
MIC2557
Micrel
Applications Information
PCMCIA V
PP
control is easily accomplished using the
MIC2557 voltage selector/switch IC. Two control bits deter-
mine output voltage and standby/operate mode condition.
Output voltages of 0V (defined as less than 0.4V), V
CC
(3.3V
or 5V), V
PP
, or a high impedance state, are available. When
either the high impedance or low voltage conditions are
selected, the device switches into "sleep" mode, and draws
only nanoamperes of leakage current.
The MIC2557 is a low-resistance power MOSFET switching
matrix that operates from the computer system main power
supply. Device power is obtained from V
DD
, which may be
either 3.3V or 5V, and FET drive is obtained from V
PP IN
(usually +12V). Internal break-before-make switches deter-
mine the output voltage and device mode.
Supply Bypassing
For best results, bypass V
CC
and V
PP IN
at their inputs with
1µF capacitors. V
PP OUT
should have a 0.01µF to 0.1µF
capacitor for noise reduction and electrostatic discharge
(ESD) damage prevention. Larger values of output capacitor
will create large current spikes during transitions, requiring
larger bypass capacitors on the V
CC
and V
PP IN
pins.
PCMCIA
Card Slot
Controller
VCC
5V
System
Power
Supply
12V
EN0
EN1
VPP IN
VCC
VCC Switch
VCC
VPP1
PCMCIA
Card Slot
A
MIC2557
EN0
EN1
VPP IN
VCC
VPP2
MIC2557
EN0
EN1
VPP IN
VCC
VPP1
PCMCIA
Card Slot
B
MIC2557
5V
System
Power 3.3V
Supply
12V
EN0
EN1
VPP IN
VCC
VCC Select and
Switch
VCC
EN0
EN1
VPP IN
VCC
VPP2
MIC2557
VPP1
PCMCIA
Card Slot
A
MIC2557
Figure 3. MIC2557 Typical two slot PCMCIA applica-
tion with single 5.0V V
CC
.
PCMCIA Implementation
EN0
EN1
VPP IN
VCC
VPP2
MIC2557
PCMCIA
Card Slot
Controller
VCC Select and
Switch
VCC
EN0
EN1
VPP IN
VCC
VPP1
PCMCIA
Card Slot
B
MIC2557
The Personal Computer Memory Card International Asso-
ciation (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 implement-
ing PCMCIA specifications requires two MIC2557, and a
controller. Figure 2 shows this full configuration, supporting
both 5.0V and 3.3V V
CC
operation. Figure 3 is a simplified
design with fixed V
CC
= 5V. Palmtop computers, where size
and battery life are tantamount, can sometimes use a com-
promise implementation, with V
PP1
tied to V
PP2
(see Figure
4).
When a memory card is initially inserted, it should receive
V
CC
, usually 5.0V
±5%.
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 5.0V
or 3.3V V
CC
. If the card uses 3.3V V
CC
, the controller
commands this change, which is reflected on the V
CC
pins of
both the PCMCIA slot and the MIC2557.
During Flash memory programming, the PCMCIA controller
outputs a (1,0) to the MIC2557, which connects V
PP IN
to
2-8
1997
EN0
EN1
VPP IN
VCC
VPP2
MIC2557
Figure 2. MIC2557 Typical two slot PCMCIA applica-
tion with dual V
CC
(5.0V or 3.3V).
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