9

LT1312

EN0

LT1312

EN1

VALID

SENSE

GND

LT1172

FB

GND

+

1

µF

LT1312 F4

100

µF

1N5158

13.75V

100

µH

10k

1%

1

2

4

5

3

1k

1%

TO CARD VPP PIN

0V, 5V, 12V OR HI-Z

+

22

µF

5V

+

1

µF

+

1k

Figure 7. Using a 0.33

Figure 4. Local 5V to 15V Boost Regulator for Line Operated Applications

EN0

LT1312

EN1

VALID

SENSE

GND

0.33

µF

CERAMIC

LT1312 F7

0.1

µF

2

Ω

13V TO 20V

Figure 6. Recommended >1

EN0

LT1312

EN1

VALID

SENSE

GND

+

>1

µF TANTALUM

OR ALUMINUM

LT1312 F6

0.1

µF

13V TO 20V

EN0

LT1312

EN1

VALID

SENSE

GND

SW1

LT1111CS8

SENSE

GND

SW2

+

1

µF

LT1312 F5

100

µF

1N5158

13.75V

100

µH

100k

1%

4

8

3

1

2

5

10k

1%

TO CARD VPP PIN

0V, 5V, 12V OR HI-Z

100

Ω

+

22

µF

12V

+

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

µF with an ESR of 3Ω 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

µF can be used. Extremely low ESR ceramic

capacitors with values less than 1

µF must have a 2Ω

resistor added in series with the output capacitor as shown

in shown in Figure 7.

Figure 5. Local 12V to 15V Boost Regulator for Line Operated Applications