MIC2566

Micrel

MIC2566

8

May 2003

Applications Information

PC Card V

the MIC2566 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), 0V or a high impedance state are available. When the

V

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

example) by locking out the low voltage switch until the initial

switch’s gate voltage drops below the desired lower V

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

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

capacitors to improve output ripple. As all internal device logic

and comparison functions are powered from the V

the power supply quality of this line is the most important, and

a bypass capacitor may be necessary for some layouts. Both

V

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

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

MIC2566, which shuts down V

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

generated 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.

Figure 3 shows MIC2566 configuration for situations where

only a single +5V V

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

V

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.