MIC2562A

Micrel

June 2004

8

M9999-062204

Applications Information

PC Card V

the MIC2562A PC Card/CardBus slot V

controller IC. Four control bits determine V

V

outputs of 3.3V and 5V at the maximum allowable PC Card

current are supported. V

or 5V), V

When the V

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

for example), by locking out the low-voltage switch until the

initial switch’s gate voltage drops below the desired lower

V

The MIC2562A operates from the computer system’s main

power supply. Device logic and internal MOSFET drive is

generated internally by charge pump voltage multipliers

powered from V

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

with 1

µF capacitors to improve output ripple. As all internal

device logic and comparison functions are powered from the

V

important, and a bypass capacitor may be necessary for

some layouts. Both V

0.01

µF 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

PCMCIA PC Card Specification (March 1995), including the

CardBus option. One MIC2562A is required for each PC Card

slot.

When a memory card is initially inserted, it should receive

V

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

V

level, the controller commands this change by disabling V

waiting at least 100ms, and then re-enabling the other V

CC

voltage.

V

to immediately switch from one V

turning OFF and waiting 100ms first), enhancement of the

second switch begins after the first is OFF, realizing break-

before-make protection. V

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

MIC2562A, which shuts down V

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, MOSFET drive and bias voltage

is powered from V

by an internal charge pump quadrupler. Systems without

3.3V may connect V

voltages are compatible with common PC Card logic control-

lers using either 3.3V or 5V supplies.

The PC Card specification defines two V

card slot. The two V

different voltages. V

Flash memory cards. Implementing two independent V

PP

voltages is easily accomplished with the MIC2562A and a

MIC2557 PCMCIA V

full configuration, supporting independent V

and 3.3V V

support multiple V

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

resistance of the MIC2562A switch allows using a small

bypass capacitor on the V

action performed by a large filter capacitor on V

the main power supply filter capacitor is sufficient). Using a

small-value capacitor such as 0.1

µF on the output causes

little or no timing delays. The V

12.0V typically takes 250

µs. After programming is com-

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

MIC2562A, which then reduces V

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

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

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.