LT1312CS8 Linear Technology, LT1312CS8 Datasheet - Page 8

• Manufacturer Part Number: LT1312CS8
• Description: IC DRVR/REG PCMCIA VPP SNGL8SOIC
• Manufacturer: Linear Technology

Specifications of LT1312CS8

• Applications: PCMCIA Driver/Regulator, PCMCIA Card Slot
• Voltage - Input: 13 ~ 20 V
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 5V, 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS
LT1312
inductor as shown in Figure 3. MOSFET Q4 and diode D4
have been added and diode D1 is no longer used. In the
previous circuit, power is drawn directly from the batteries
through D1, when the LTC1142 is in Burst Mode operation
and the VPP pin requires 3.3V or 5V. For these lower input
voltages this technique is no longer valid as the input will
fall below the LT1312 regulator’s dropout voltage. To
correct for this situation, the additional switch Q4 forces
the switching regulator into continuous mode operation
whenever 3.3V, 5V or 12V is selected.
LINE POWERED SUPPLIES
In line operated products such as: desktop computers,
dedicated PC card readers/writers, medical equipment,
test and measurement equipment, etc., it is possible to
derive power from a relatively “raw” source such as a 5V
or 12V power supply. The 12V supply line in a desktop
computer however, is usually too “dirty” to apply directly
to the VPP pins of a PCMCIA card socket. Power supply
switching and load transients may create voltage spikes
8
VALID
1/2 LTC1142
EN0
EN1
3.3V REG
NDRIVE
SENSE
SENSE
PDRIVE
Q4
VN7002
U
V
IN
+
–
24
23
6
1
28
INFORMATION
5.4V TO 12V
U
Figure 3. Deriving Auxiliary 14V Power from an LTC1142 3.3V Regulator
V
IN
Q1
Q2
Q3
VN7002
R3
18k
C2
1000pF
+
W
D3
MBRS130T3
*LPE-6582-A086 DALE [phone]
C1
68µF
100
100
R2
R1
+
U
R4
0.033
C3
220µF
T1
3.38T
22µH*
MBRS1100
22
D2
R4
1000pF
C4
on this line that may damage sensitive PCMCIA flash
memory cards if applied directly to the VPP pins.
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
Generating 14V from 5V or 12V
It is important that the 12V VPP supply for the two VPP
lines to the card be free of voltage spikes. There should be
little or no overshoot during transitions to and from the
12V level.
1
Intel Corporation, 1992.
D4
18V
See Application Note AP-357, “Power Supply Solutions for Flash Memory,”
+
C5
22µF
3.3V
OUTPUT
14V AUXILIARY SUPPLY
VALID
EN0
EN1
LT1312
GND
V
S
VPP
SENSE
1
.
OUT
FROM CARD
V
0V, 3.3V, 5V, 12V OR Hi-Z
CC
TO CARD VPP PIN
PIN
+
LT1312 F3
1µF