LT1312 Linear Technology, LT1312 Datasheet - Page 9

• Manufacturer Part Number: LT1312
• Description: Single PCMCIA VPP Driver/Regulator
• Manufacturer: Linear Technology

This is easily accomplished by generating a local 14V
supply from a relatively “dirty” 5V or 12V supply as shown
in Figures 4 and 5. Precise voltage control (and further
filtering) is provided by the LT1312 driver/regulator. A
further advantage to this scheme is that it adds current
limit in series with the VPP pins to eliminate possible
damage to the card socket, the PC card, or the switching
power supply in the event of an accidental short circuit.
Output Capacitance
The LT1312 is designed to be stable with a wide range of
output capacitors. The minimum recommended value is a
1 F with an ESR of 3 or less. The capacitor is connected
directly between the output pin and ground as shown in
Figure 6.
For applications where space is very limited, capacitors as
low as 0.33 F can be used. Extremely low ESR ceramic
capacitors with values less than 1 F must have a 2
resistor added in series with the output capacitor as shown
in shown in Figure 7.
APPLICATIONS
12V
+
5V
U
22 F
+
INFORMATION
22 F
Figure 5. Local 12V to 15V Boost Regulator for Line Operated Applications
U
Figure 4. Local 5V to 15V Boost Regulator for Line Operated Applications
100
1
I
GND
LIM
GND
LT1111CS8
LT1172
3
W
5
V
V
IN
5
IN
2
+
SENSE
SW2
V
100 H
V
SW1
C
100 H
SW
FB
1
1k
4
1 F
4
2
3
8
U
1N5158
1N5158
10k
1%
1k
1%
100k
1%
10k
1%
+
+
100 F
100 F
13V TO 20V
Figure 6. Recommended >1 F Tantalum Output Capacitor
13V TO 20V
Figure 7. Using a 0.33 F to 1 F Output Capacitor
EN0
EN1
VALID
EN0
EN1
VALID
13.75V
13.75V
LT1312
LT1312
GND
V
GND
V
S
VPP
S
VPP
SENSE
SENSE
OUT
0.1 F
OUT
0.1 F
LT1312 F4
LT1312 F5
+
+
VALID
EN0
EN1
EN0
EN1
VALID
1 F
LT1312
1 F
GND
V
LT1312
S
TO CARD VPP PIN
0V, 5V, 12V OR HI-Z
VPP
TO CARD VPP PIN
0V, 5V, 12V OR HI-Z
GND
SENSE
V
S
VPP
OUT
SENSE
OUT
LT1312 F6
+
>1 F TANTALUM
OR ALUMINUM
2
LT1312
0.33 F
CERAMIC
LT1312 F7
9