6
LTC1314/LTC1315
EN0
EN1
VPP
IN
VCC
IN
VPP
OUT
GND
NOTE: 1µF CAPACITOR CONNECTED ON BOTH VPP
IN
AND V
CCIN
PINS AT TIMING TEST
t
7
LTC1314 • SW
t
5
t
2
t
4
t
1
t
6
t
3
Hi-Z
APPLICATIONS INFORMATION
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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, V
CCIN
(3.3V or 5V), VPP
IN
, 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 0.1µA of current
from the V
DD
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 V
DD
,
which is 5V ±0.5V. The gate drives for the NFETs (both
internal and external) are derived from internal charge
pumps, therefore VPP
IN
is only required when it’s switched
to VPP
OUT
. 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.
V
CC
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 V
CC
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
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