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MIC2561 Datasheet(PDF) 6 Page - Micrel Semiconductor |
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MIC2561 Datasheet(HTML) 6 Page - Micrel Semiconductor |
6 / 8 page MIC2561 Micrel 1997 2-35 2 Applications Information PCMCIA VCC and VPP control is easily accomplished using the MIC2561 voltage selector/switch IC. Four control bits determine VCC OUT and VPP OUT voltage and standby/ operate mode condition. VPP OUT output voltages of VCC (3.3V or 5V), VPP, or a high impedance state are available. When the VCC high impedance condition is selected, the 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 prevents feedback from the VPP OUT to the VCC inputs (from 12V to 5V, for example) by locking out the low voltage switch until VPP OUT drops below VCC. The VCC output is similarly 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 supply. Device logic power is obtained from VCC3 and internal MOSFET drive is obtained from the VPP IN pin (usually +12V) during normal operation. If +12V is not avail- able, the MIC2561 automatically switches into “suspend” mode, where VCC OUT can be switched to 3.3V, but at higher 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 results however, bypass VCC3 IN, VCC5 IN, and VPP IN inputs with filter capacitors to improve output ripple. As all internal device logic and voltage/current comparison func- tions are powered from the VCC3 IN line, supply bypass of this 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. Both VCC OUT and VPP OUT pins may have 0.01µF to 0.1µF capacitors for noise reduction and electrostatic discharge (ESD) damage prevention. Larger values of output capacitor might create current spikes during transitions, requiring larger bypass capacitors on the VCC3 IN, VCC5 IN, and VPP IN pins. PCMCIA Implementation The Personal Computer Memory Card International Associa- tion (PCMCIA) specification requires two VPP supply pins per PCMCIA slot. VPP is primarily used for programming Flash (EEPROM) memory cards. The two VPP supply pins may be programmed to different voltages. Fully implementing PCM- CIA specifications requires a MIC2561, a MIC2557 PCMCIA VPP Switching Matrix, and a controller. Figure 3 shows this full configuration, supporting both 5.0V and 3.3V VCC opera- tion. Figure 3. MIC2561 Typical PCMCIA memory card application with dual V CC (5.0V or 3.3V) and separate VPP1 and VPP2. 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 |
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