SP3232B datasheet(11/18 Pages) SIPEX

11 / 18 page

Rev. 6/30/03

SP3222B/3232B True +3.0 to +5.5V RS-232 Transceivers

This voltage is regulated to +5.5V. At this

voltage, the internal oscillator is disabled. Si-

multaneous with the transfer of the voltage to

4, the positive side of capacitor C1 is switched

to V

CC and the negative side is connected to

GND, allowing the charge pump cycle to begin

again. The charge pump cycle will continue as

long as the operational conditions for the inter-

nal oscillator are present.

Since both V+ and V– are separately generated

from V

CC; in a no–load condition V

+ and V– will

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 250kHz. The external capacitors can

be as low as 0.1

µF with a 16V breakdown

voltage rating.

ESD Tolerance

The SP3222B/3232B series incorporates

ruggedized ESD cells on all driver output and

receiver input pins. The ESD structure is

improved over our previous family for more

rugged applications and environments sensitive

to electrostatic discharges and associated

transients.

The Human Body Model has been the generally

accepted ESD testing method for semiconduc-

tors. This method is also specified in MIL-STD-

883, Method 3015.7 for ESD testing. The premise

of this ESD test is to simulate the human body’s

potential to store electrostatic energy and

discharge it to an integrated circuit.

The simulation is performed by using a test

model as shown in Figure 18. This method

will test the IC’s capability to withstand an

ESD transient during normal handling such as

in manufacturing areas where the ICs tend to

be handled frequently.

For the Human Body Model, the current

limiting resistor (R

S) and the source capacitor

S) are 1.5kΩ and 100pF, respectively.

Figure 13. Charge Pump — Phase 1

Figure 14. Charge Pump — Phase 2

VCC = +5V

–5V

+5V

VSS Storage Capacitor

VDD Storage Capacitor

–

VCC = +5V

–10V

VSS Storage Capacitor

VDD Storage Capacitor

–

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