SP3238EEA datasheet(9/20 Pages) SIPEX

9 / 20 page

SP3238EDS/04

SP3238E +3.0V to +5.5V RS-232 Transceivers

The SP3238E drivers can maintain high data

rates up to 250kbps fully loaded. Figure 7 shows

a loopback test circuit used to test the RS-232

Drivers. Figure 8 shows the test results of the

loopback circuit with all three drivers active at

120kbps with typical RS-232 loadsinparallelwith

1000pF capacitors. Figure 9 shows the test results

where one driver was active at 250kbps and all

three drivers loaded with an RS-232 receiver in

parallel with a 1000pF capacitor. A solid RS-232

data transmission rate of 120kbps provides

compatibility with many designs in personal

computer peripherals and LAN applications.

Receivers

The receivers convert

±5.0V EIA/TIA-232

levels to TTL or CMOS logic output levels. All

receivers have an inverting output that can be

disabled by using the EN pin.

Receivers are active when the Auto-Online

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.

The truth table logic of the driver and receiver

outputs can be found in Table 2.

Figure 7. Loopback Test Circuit for RS-232 Driver Data

Transmission Rates

The SP3238E includes an additional non-

inverting receiver with an output R

1OUT. R1OUT

is an extra output that remains active and monitors

activity while the other receiver outputs are

forced into high impedance. This allows Ring

Indicator (RI) from a peripheral to be monitored

without forward biasing the TTL/CMOS inputs

of the other devices connected to the receiver

outputs.

Figure 8. Loopback Test Circuit Result at 120kbps

(All Drivers Fully Loaded)

Figure 9. Loopback Test Circuit result at 235kbps

(All Drivers Fully Loaded)

TBD

SP3238E

TxIN

TxOUT

C1+

C1-

C2+

C2-

V+

V-

VCC

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

LOGIC

INPUTS

VCC

Ω

RxIN

RxOUT

LOGIC

OUTPUTS

SHUTDOWN

GND

VCC

ONLINE

1000pF

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