MIC2561

Micrel

1997

2-35

2

Applications Information

the MIC2561 voltage selector/switch IC. Four control bits

device switches into “sleep” mode and draws only nano-

amperes of leakage current. An error flag falls low if the output

is improper, because of overtemperature or overcurrent

faults. Full protection from hot switching is provided which

12V to 5V, for example) by locking out the low voltage switch

protected against 5V to 3.3V shoot through.

The MIC2561 is a low-resistance power MOSFET switching

matrix that operates from the computer system main power

(usually +12V) during normal operation. If +12V is not avail-

able, the MIC2561 automatically switches into “suspend”

switch resistance. Internal break-before-make switches de-

termine the output voltage and device mode.

Supply Bypassing

External capacitors are not required for operation. The

MIC2561 is a switch and has no stability problems. For best

inputs with filter capacitors to improve output ripple. As all

internal device logic and voltage/current comparison func-

line is the most critical, and may be necessary in some cases.

In the most stubborn layouts, up to 0.47

µF may be necessary.

capacitors for noise reduction and electrostatic discharge

(ESD) damage prevention. Larger values of output capacitor

might create current spikes during transitions, requiring larger

PCMCIA Implementation

The Personal Computer Memory Card International Associa-

programmed to different voltages. Fully implementing PCM-

CIA specifications requires a MIC2561, a MIC2557 PCMCIA

tion.

Figure 3. MIC2561 Typical PCMCIA memory card application with dual V

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

MIC2557

EN0

EN1

VPP IN VDD

VPP OUT

VCC