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SP505_00_08308

Phase 2 (±10V)

— V

connects the negative terminal of C

the V

terminal of C

generated –l0V or the generated –5V to C

Simultaneously,thepositivesideofcapacitor

C

is connected to ground.

Phase 2 (±5V)

— V

+

is recon-

nected to V

C

2

+

isswitchedtogroundandC

2

–

isconnected

to C

transferred to the V

receives a continuous charge from either C



or C

the cycle begins again.

Phase 3

— V

of the clock is identical to the first phase

— the charge transferred in C

–5V in the negative terminal of C

is applied to the negative side of capacitor

C

+

is at +5V, the voltage potential

across C

+

is

connected to ground so that the potential

on C

Phase 4

— V

clock connects the negative terminal of C

2

to ground and transfers the generated l0V

or the generated 5V across C

storage capacitor. Again, simultaneously

with this, the positive side of capacitor C



is switched to +5V and the negative side is

connected to ground, and the cycle begins

again.

Since both V

erated from V

and V

inefficiencies in the design.

The clock rate for the charge pump typically

operates at 5kHz. The external capacitors

must be a minimum of 22µF with a 6V

breakdown rating.

External Power Supplies

For applications that do not require +5V

only, external supplies can be applied at the

supply voltages must be no greater than

+l0.5V. The tolerance should be +5% from

+0V. The current drain for the supplies is

used for RS-232 and RS-423 drivers. For

the RS-232 driver, the current requirement

will be 3.5mA per driver. The RS-423 driver

worst case current drain will be mA per

driver. Power sequencing is required for the

SP505. The supplies must be sequenced

accordingly: +0V, +5V and –0V. It is

important to prevent V

before V

Figure 47. Charge Pump Phase 2 for +0V.

Figure 49. Charge Pump Phase 3.

–1 0V

+

+

+

–

–

–

+

–

–5 V

–5 V

+5V

+

+

+

–

–

–

+

–

Figure 50. Charge Pump Phase 4.

Figure 48. Charge Pump Phase 2 for +5V.

+

+

+

–

–

–

+

–

–5 V

+10V

+

+

+

–

–

–

+

–