MIC2561

Micrel

January 2005

7

MIC2561

However, many cost sensitive designs (especially notebook/

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

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 MIC2561, which connects

switches allow using small bypass capacitors (in some cases,

filtering action performed by a large filter capacitor on the

completed, the controller outputs a (EN1, EN0) = (0,1) to the

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

level selected. The lockout delay time varies with the load

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 MIC2561.

Output Current and Protection

MIC2561 output switches are capable of more current than

needed in PCMCIA applications 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 MIC2561,

the system power supplies, the card socket pins, and the

memory card. The MIC2561 overtemperature shutdown oc-

curs at a die temperature of 110°C.

Suspend Mode

An additional feature in the MIC2561 is a pseudo power-down

mode, Suspend Mode, which allows operation without a V

PP

IN supply. In Suspend Mode, the MIC2561 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

receives V

CC

at reduced capacity during Suspend Mode, as

the switch resistance rises to approximately 4.5Ω.

High Current V

+12V Supply

Figure 5 shows the MIC2561 with V

CC

switch bias provided

by a simple charge pump. This enables the system designer

to achieve full V

CC

performance without a +12V supply,

which is often helpful in battery powered systems that only

provide +12V when it is needed. These on-demand +12V

System

Power

Supply

PCMCIA

Card Slot

Controller

MIC2561

PCMCIA

Card Slot

5V

3.3V

12V

EN0

EN1

VPP1

VCC

VPPIN

VCC5IN

VCC3IN

VCC5_EN

VCC3_EN

VPP2

Figure 4. MIC2561 Typical PCMCIA memory card application with dual V

driven together.