SP312ECT datasheet(7/15 Pages) SIPEX

7 / 15 page

Rev. 06/20/02

SP202E Series High Performance RS232 Transceivers

Figure 6. Charge Pump Waveforms

+10V

a) C

GND

b) C

–

–10V

Figure 7. Charge Pump — Phase 3

VCC = +5V

–5V

+5V

–5V

VSS Storage Capacitor

VDD Storage Capacitor

–

Figure 8. Charge Pump — Phase 4

VCC = +5V

+10V

VSS Storage Capacitor

VDD Storage Capacitor

–

be symmetrical. Older charge pump approaches

that generate V– from V+ will show a decrease in

the magnitude of V– compared to V+ due to the

inherent inefficiencies in the design.

The clock rate for the charge pump typically

operates at 15kHz. The external capacitors can

be as low as 0.1

µF with a 16V breakdown

voltage rating.

Shutdown (SD) and Enable (EN) for the

SP310E and SP312E

Both the SP310E and SP312E have a shutdown/

standby mode to conserve power in battery-pow-

ered systems. To activate the shutdown mode,

which stops the operation of the charge pump, a

logic “0” is applied to the appropriate control line.

For the SP310E, this control line is ON/OFF (pin

18). Activating the shutdown mode also puts the

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