LTC1314CS datasheet(6/12 Pages) LINER

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LTC1314/LTC1315

EN0

EN1

VPPIN

VCCIN

VPPOUT

GND

NOTE: 1

µF CAPACITOR CONNECTED ON BOTH VPPIN AND VCCIN PINS AT TIMING TEST

LTC1314 • SW

Hi-Z

APPLICATIONS INFORMATION

PCMCIA VPP control is easily accomplished using the

LTC1314 or LTC1315 switching matrix. Two control bits

(LTC1314) or four control bits (LTC1315) determine the

output voltage and standby/operate mode conditions. Out-

put voltages of 0V, VCCIN (3.3V or 5V), VPPIN, or a high

impedance state are available. When either the high imped-

ance or low voltage (0V) conditions are selected, the device

switches into “sleep” mode and draws 0.1

µA of current

from the VDD supply.

The LTC1314/LTC1315 are low resistance power MOSFET

switching matrices that operate from the computer system

main power supply. Device power is obtained from VDD,

which is 5V

±0.5V. The gate drives for the NFETs (both

internal and external) are derived from internal charge

pumps, therefore VPPIN is only required when it’s switched

to VPPOUT. Internal break-before-make switches deter-

mine the output voltage and device mode.

Flash Memory Card VPP Power Considerations

PCMCIA compatible flash memory cards require tight

regulation of the 12V VPP programming supply to ensure

that the internal flash memory circuits are never subjected

to damaging conditions. Flash memory circuits are typi-

cally rated with an absolute maximum of 13.5V and VPP

must be maintained at 12V

±5% under all possible load

conditions during erase and program cycles. Undervoltage

can decrease specified flash memory reliability and over-

voltage can damage the device.

VCC Switch Driver and VPP Switch Matrix

Figures 1 and 2 show the approach that is very space and

power efficient. The LTC1314/LTC1315 used in conjunc-

tion with the LT1301 DC/DC converter, provide complete

power management for a PCMCIA card slot. The LTC1314/

LTC1315 and LT1301 combination provides a highly effi-

cient, minimal parts count solution. These circuits are

especially good for applications that are adding a PCMCIA

socket to existing systems that currently have only 5V or

3.3V available.

The LTC1314 drives three N-channel (LTC1315 six

N-channel) MOSFETs that provide VCC pin power switch-

ing. On-chip charge pumps provide the necessary voltage

to fully enhance the switches. With the charge pumps on-

chip, the MOSFET drive is available without the need for a

12V supply. The LTC1314/LTC1315 provide a natural

break-before-make action and smooth transitions due to

SWITCHI G TI E WAVEFOR S

LTC1314CS Datasheet(PDF) 6 Page - Linear Technology

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