SP3223EB datasheet(10/23 Pages) SIPEX

10 / 23 page

Date:

10/06/06

SP3223 +3.0V to +5.5V RS-232 Transceivers

6 Sipex Corporation

Receivers

The receivers convert

±5.0V EIA/TIA-232

levels to TTL or CMOS logic output levels.

Receivers have an inverting output that can be

disabled by using the EN pin.

Receivers are active when the AUTO ON-LINE®

circuitry is enabled or when in shutdown.

During the shutdown, the receivers will continue

to be active. If there is no activity present at the

receivers for a period longer than 100

µs or when

SHUTDOWN is enabled, the device goes into a

standby mode where the circuit draws 1

µA.

Driving EN to a logic HIGH forces the outputs of

the receivers into high-impedance. The truth

table logic of the SP3223 driver and receiver

outputs can be found in Table 2.

Since receiver input is usually from a transmis-

sion line where long cable lengths and system

interference can degrade the signal, the inputs

have a typical hysteresis margin of 300mV. This

ensures that the receiver is virtually immune to

noisy transmission lines. Should an input be left

unconnected, an internal 5K

Ω pulldown resistor

to ground will commit the output of the receiver

to a HIGH state.

Table 2. SHUTDOWN and EN Truth Tables

Note: In AUTO ON-LINE® Mode where ONLINE =

GND and SHUTDOWN = V

CC, the device will shut down

if there is no activity present at the Receiver inputs.

Figure 14. Loopback Test Circuit for RS-232 Driver

Data Transmission Rates

Charge Pump

The charge pump is a Sipex–patented design

(U.S. 5,306,954) and uses a unique approach

compared to older less–efficient designs. The

charge pump still requires four external

capacitors, but uses a four–phase voltage

shifting technique to attain symmetrical 5.5V

power supplies.

The internal power supply

Figure 15. Loopback Test Circuit result at 235Kbps

(All Drivers Fully Loaded)

T1 IN

T1 OUT

R1 OUT

SP3223

GND

1IN

XIN

C1+

C1-

C2+

C2-

V+

V-

VCC

0.1µF

TTL/CMOS

INPUTS

+3V to +5V

SHUTDOWN

5KΩ

1OUT

5KΩ

XIN

XOUT

TTL/CMOS

OUTPUTS

ONLINE

1IN

XOUT

1OUT

STATUS

VCC

To µP Supervisor

Circuit

1000pF

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