5

LTC1263

The LTC1263 uses a charge pump tripler to generate 12V

internal oscillator. The oscillator frequency is not critical

and may vary from the typical value of 300kHz. When the

oscillator output is low, C1 and C2 are each connected

3). When the oscillator output goes high, C1 and C2 are

(see Figure 4). The top plate of C2 is switched to charge

gating scheme that turns the charge pump on and off

tor, then oscillator pulses are applied to the charge pump

oscillator pulses are prevented from clocking the charge

To reduce supply current, the LTC1263 may be put into

shutdown mode by “floating” the SHDN pin or connecting

tor and resistor divider are switched off to reduce the

supply current to typically 0.5

µA. At the same time an

is low, the LTC1263 exits shutdown and the charge pump

+

C1

+

C2

LTC1263 • F03

+

C1

+

C2

LTC1263 • F04

Choice of Capacitors

The LTC1263 is tested with the capacitors shown in Figure

2. C1 and C2 are 0.47

other choices are desired.

Table 1. Recommended Capacitor Types and Values

CAPACITOR

CERAMIC

TANTALUM

ALUMINUM

C1, C2

0.47

µF to 1µF

Not Recommended Not Recommended

10

µF (Min)

10

µF (Min)

10

µF (Min)

10

µF (Min)

10

µF (Min)

10

µF (Min)

C1 and C2 should be ceramic capacitors with values in the

range of 0.47

µF to 1µF. Higher values provide better load

regulation. Tantalum capacitors are not recommended as

the higher ESR of these capacitors degrades performance