SP334DS/10

Programmable RS-232/RS-485 Transceiver

SP334

Programmable RS-232/RS-485 Transceiver

+5V Only Operation

Software Programmable RS-232 or RS-
485 Selection

Three RS-232 Drivers and Five Receivers
in RS-232 Mode

Two RS-485 Full-Duplex Transceivers in
RS-485 Mode

Full Differential Driver Tri-State (Hi-Z)
Control

Receiver Output Tri-State Control

DESCRIPTION...

The SP334 is a programmable RS-232 and/or RS-485 transceiver IC. The SP334 contains three
drivers and five receivers when selected in RS-232 mode; and two drivers and two receivers when
selected in RS-485 mode.

The RS-232 transceivers can typically operate at 230kbps while adhering to the RS-232
specifications. The RS-485 transceivers can operate up to 10Mbps while adhering to the RS-485
specifications. The RS-485 drivers can be disabled (High-Z output) by the TXEN enable pin. The
RS-232 and RS-485 receiver outputs can be disabled by the RXEN enable pin.

TI3

TXEN(n/c)

TX4(n/c)

TX3

VCC

TX1
TX2

GND

C1+

V+

C2+
C1
C2

TI2
TI1
RXEN
RS232/RS485
RI5
RX5
RX4
RX3
RX2
RX1
RI4
RI3
RI2
RI1

28
27
26
25
24
23
22
21
20
19
18
17
16
15

1
2
3
4
5
6
7
8
9

10
11
12
13
14

SP334

(in RS-232 mode)

SP334DS/10

Programmable RS-232/RS-485 Transceiver

ABSOLUTE MAXIMUM RATINGS

These are stress ratings only and functional operation
of the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may
affect reliability.

...........................................................................+7V

Storage Temperature..........................-65°C to +150°C
Power Dissipation

28-pin Plastic DIP...........................1000mW
28-pin Plastic SOIC.......................1000mW

Package Derating:
28-pin Plastic DIP

....................................................40

C/W

28-pin Plastic SOIC

....................................................40

C/W

SPECIFICATIONS

Typically 25

C @ Vcc = +5V unless otherwise noted.

MIN.

TYP.

MAX.

UNITS

CONDITIONS

LOGIC INPUTS
V

0.8

Volts

2.0

Volts

LOGIC OUTPUTS
V

0.4

Volts

OUT

= -3.2mA

2.4

Volts

OUT

= 1.0mA

Output Tri-state Leakage

0.4V

OUT

+2.4V

RS-232 DRIVER
DC Characteristics

HIGH Level Output

+5.0

+15

Volts

=3k

, V

=0.8V

LOW Level Output

15.0

5.0

Volts

=3k

, V

=2.0V

Open Circuit Voltage

+15

Volts

Short Circuit Current

100

OUT

= 0V

Power Off Impedance

300

= 0V, V

out

2.0V

AC Characteristics

Slew Rate

=3k

, C

= 50pF

= +5.0V, T

@ +25

Transition Time

1.56

=3k

, C

=2500pF ;

between

3V, T

@ +25

Maximum Data Rate

120

235

kbps

=3k

, C

=2500pF

Propagation Delay
t

PHL

Measured from 1.5V of V

PLH

to 50% of V

OUT

;

=3k

RS-232 RECEIVER
DC Characteristics

HIGH Threshold

1.7

3.0

Volts

LOW Threshold

0.8

1.2

Volts

Receiver Open Circuit Bias

+2.0

Volts

Input Impedance

= +15V to 15V

AC Characteristics

Maximum Data Rate

120

235

kbps

Propagation Delay
t

PHL

0.25

Measured from 50% of V

PLH

0.25

to 1.5V of V

OUT

RS-485 DRIVER
DC Characteristics

Open Circuit Voltage

6.0

Volts

Differential Output

1.5

5.0

Volts

=54

, C

=50pF

SP334DS/10

Programmable RS-232/RS-485 Transceiver

SPECIFICATIONS

Typically 25

C @ Vcc = +5V unless otherwise noted.

MIN.

TYP.

MAX.

UNITS

CONDITIONS

RS-485 DRIVER

Balance

0.2

Volts

| - |V

Common-Mode Output

3.0

Volts

Output Current

28.0

=54

Short Circuit Current

250

Terminated in 7V to +10V

AC Characteristics
Maximum Data Rate

Mbps

=54

Output Transition Time

Rise/fall time, 10%90%

Propagation Delay

See Figures 3A & 5

PHL

120

DIFF

=54

, C

=100pF

PLH

120

DIFF

=54

, C

=100pF

Driver Output Skew

per figure 5, t

SKEW

= |t

DPLH

- t

DPHL

RS-485 RECEIVER
DC Characteristics
Inputs

Common Mode Range

7.0

+12.0

Volts

Receiver Sensitivity

0.2

Volts

+12V

Input Impedance

+12V

AC Characteristics
Maximum Data Rate

Mbps

Propagation Delay

See Figures 3A & 7

PHL

130

200

DIFF

=54

, C

=100pF

PLH

130

200

DIFF

=54

, C

=100pF

Differential Receiver Skew

SKEW

= | t

PLH

PHL

|; R

DIFF

=54

=100pF, see Figure 8

ENABLE TIMING
RS-485 Driver
Enable Time

See Figures 4 & 6

Enable to Low

100

150

=15pF, S

Closed

Enable to High

100

150

=15pF, S

Closed

Disable Time

See Figures 4 & 6

Disable From Low

100

120

=15pF, S

Closed

Disable From High

100

120

=15pF, S

Closed

RS-485 Receiver
Enable Time

See Figures 2 & 8

Enable to Low

100

150

=15pF, S

Closed

Enable to High

100

150

=15pF, S

Closed

Disable Time

See Figures 2 & 8

Disable From Low

100

120

=15pF, S

Closed

Disable From High

100

120

=15pF, S

Closed

POWER REQUIREMENTS
Supply Voltage V

+4.75

+5.25

Volts

Supply Current I

No Load (T

Disabled)

TXEN = 0V

No Load (RS-232 Mode)

RS232/RS485 = 0V

No Load (RS-485 Mode)

RS232/RS485 = +5V

ENVIRONMENTAL
Operating Temperature

Commercial (..C..)

+70

Industrial (..E..)

+85

Storage Temperature

+150

SP334DS/10

Programmable RS-232/RS-485 Transceiver

Figure 6. Driver Enable and Disable Times

Figure 7. Receiver Propagation Delays

RECEIVER OUT

1.5V

PHL

f = 1MHz; t

10ns; t

10ns

OUTPUT

0D2

A B

PLH

INPUT

Figure 5. Driver Propagation Delays

SWITCHING WAVEFORMS

+3V

A, B

1.5V

f = 1MHz; t

10ns; t

10ns

A, B

2.3V

0.5V

Output normally LOW

Output normally HIGH

+3V

DRIVER INPUT

DRIVER

OUTPUT

DIFFERENTIAL

OUTPUT

1.5V

PLH

1MHz; t

10ns; t

10ns

1/2V

PHL

SKEW

= |t

DPLH

- t

DPHL

DPLH

DPHL

SP334DS/10

Programmable RS-232/RS-485 Transceiver

Figure 12. Typical Operating Circuit

Figure 11. SP334 Pinout

+5V

GND

TTL/CMOS

0.1

VCC

V+

TTL/CMOS

TX1

TX2

TX3

RI1

TI1

TI2

TI3

RX1

RX5

RX4

RX3

RX2

RI5

RI4

RI3

RI2

0.1

C1+

C1-

C2+

C2-

RS232/RS485

400K

Vcc

400K

Vcc

400K

Vcc

RS-232

TTL/CMOS

RS-232

SP334

RS-232

RXEN

TTL/CMOS

N/C

TTL/CMOS

0.1

C1+

C1-

C2+

C2-

TXEN

+5V

VCC

GND

RS-485

TTL/CMOS

0.1

V+

+5V

RS-485

RI2

RI1

TX3

TX4

TX1

TX2

TI1

TI3

RX1

TTL/CMOS

RI4

RI3

RX3

15K

400K

Vcc

400K

Vcc

RXEN

RS-485

SP334

RS232/RS485

15K

TTL/CMOS

TI3

TXEN(n/c)

TX4(n/c)

TX3

VCC

TX1
TX2

GND

C1+

V+

C2+
C1
C2

TI2
TI1
RXEN
RS232/RS485
RI5
RX5
RX4
RX3
RX2
RX1
RI4
RI3
RI2
RI1

28
27
26
25
24
23
22
21
20
19
18
17
16
15

1
2
3
4
5
6
7
8
9

10
11
12
13
14

SP334

(in RS-232 mode)

SP334DS/10

Programmable RS-232/RS-485 Transceiver

THEORY OF OPERATION

The SP334 is made up of four separate circuit
blocks -- the charge pump, drivers, receivers,
and decoder. Each of these circuit blocks is
described in more detail below.

ChargePump

The charge pump is a Sipexpatented design
(U.S. 5,306,954) and uses a unique approach
compared to older lessefficient designs. The
charge pump still requires four external
capacitors, but uses a fourphase voltage
shifting technique to attain symmetrical 10V
power supplies. Figure 17(a) shows the
waveform found on the positive side of capcitor
C2, and figure 17(b) shows the negative side of
capcitor C2. There is a freerunning oscillator
that controls the four phases of the voltage
shifting. A description of each phase follows.

Phase 1

-- V

charge storage --During this phase of

the clock cycle, the positive side of capacitors
C

and C

are initially charged to +5V. C

then switched to ground and charge on C

transferred to C

. Since C

is connected to

+5V, the voltage potential across capacitor C

is now 10V.

Phase 2

-- V

transfer -- Phase two of the clock

connects the negative terminal of C

to the V

storage capacitor and the positive terminal of C

to ground, and transfers the generated l0V to
C

. Simultaneously, the positive side of capaci-

tor C

is switched to +5V and the negative side

is connected to ground.

Phase 3

-- V

charge storage -- The third phase of the

clock is identical to the first phase -- the charge
transferred in C

produces 5V in the negative

terminal of C

, which is applied to the negative

side of capacitor C

. Since C

is at +5V, the

voltage potential across C

is l0V.

Phase 4

-- V

transfer -- The fourth phase of the

clock connects the negative terminal of C

ground and transfers the generated l0V across
C

to C

, the V

storage capacitor. Again,

simultaneously with this, the positive side of

Figure 13. Charge Pump Phase 1.

Figure 14a. Charge Pump Phase 2.

capacitor C

is switched to +5V and the negative

side is connected to ground, and the cycle begins
again.

Since both V+ and V

are separately generated

from V

in a noload 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 15kHz. The external capacitors
must be a minimum of 0.1

F with a 16V

breakdown rating.

External Power Supplies

For applications that do not require +5V only,
external supplies can be applied at the V+ and
V

pins. The value of the external supply volt-

ages must be no greater than

l0V. The current

drain for the

10V supplies is used for RS232.

For the RS-232 driver the current requirement
will be 3.5mA per driver. The external power
supplies should provide a power supply se-
quence of :+l0V, then +5V, followed by l0V.

Drivers

The SP334 has three independent RS-232 single-
ended drivers and two differential RS-485
drivers. Control for the mode selection is done
by the RS-232/RS-485 select pin. The drivers
are pre-arranged such that for each mode of

= +5V

+5V

Storage Capacitor

= +5V

10V

Storage Capacitor

SP334DS/10

Programmable RS-232/RS-485 Transceiver

Figure 15. Charge Pump Phase 3.

Figure 16. Charge Pump Phase 4.

operation the relative position and functionality
of the drivers are set up to accommodate the
selected interface mode. As the mode of the
drivers is changed, the electrical characteristics
will change to support the requirements of clock,
data, and control line signal levels. Unused
driver inputs can be left floating; however, to
ensure a desired state with no input signal,
pullup resistors to +5V or pulldown resistors
to ground are suggested. Since the driver inputs
are both TTL or CMOS compatible, any value
resistor less than 100k

will suffice.

When in RS-232 mode, the single-ended RS-
232 drivers produce compliant RS-232E and
ITU V.28 signals. Each of the three drivers
output single-ended bipolar signals in excess of

= +5V

+5V

Storage Capacitor

= +5V

+10V

Storage Capacitor

Figure 17. Charge Pump Waveforms

5V with a full load of 3k

and 2500pF applied

as specified. These drivers can also operate at
least 120kbps.

When programmed to RS-485 mode, the
differential RS-485 drivers produce complaint
RS-485 signals. Each RS-485 driver outputs
a unipolar signal on each output pin with a
magnitude of at least 1.5V while loaded with
a worst case of 54

between the driver's two

output pins. The signal levels and drive
capability of the RS-485 drivers allow the
drivers to also comply with RS-422 levels. The
transmission rate for the differential drivers is
10Mbps.

Receivers

The SP334 has five single-ended receivers
when programmed for RS-232 mode and two
differential receivers when programmed for
RS-485 mode.

Control for the mode selection is done by the
same select pin as the drivers. As the operating
mode of the receivers is changed, the electrical
characteristics will change to support the
requirements of the appropriate serial standard.
Unused receiver inputs can be left floating
without causing oscillation. To ensure a desired
state of the receiver output, a pullup resistor of
100k

to +5V should be connected to the

inverting input for a logic low, or the
noninverting input for a logic high. For
single-ended receivers, a pulldown resistor to
ground of 5k

is internally connected, which

will ensure a logic high output.

+10V

a) C

GND

-10V

b) C

SP334DS/10

Programmable RS-232/RS-485 Transceiver

outputs. The drivers can only be tri-stated in
RS-485 mode. The drivers are always active in
RS-232 mode.

The receiver outputs can also be tri-stated by
use of the RXEN pin. A logic LOW will enable
the receiver outputs and a logic HIGH will
tri-state the outputs. The receiver tri-state
capability is offered for both RS-232 and
RS-485 modes. The input impedance if the
receivers during tri-state is at least 12k

Applications

The SP334 allows the user flexibility in having
a RS-232 or RS-485 serial port without using
two different discrete active ICs. Figure 18
shows a connection to a standard DB-9 RS-232
connector. In RS-485 mode, the SP334 is a full
duplex transceiver, however, a half duplex
configuration can be made by connecting the
driver outputs to the receiver inputs.

+5V

GND

CTS

TxD

RTS

0.1

VCC

V+

DTR

RxD

TX1

TX2

TX3

RI1

TI1

TI2

TI3

RX1

RX5

RX4

RX3

RX2

RI5

RI4

RI3

RI2

0.1

C1+

C1-

C2+

C2-

RS232/RS485

400K

Vcc

400K

Vcc

400K

Vcc

DSR

DCD

SP334

RXEN

TxD

DTR

RTS

RxD

CTS

DSR

DCD

Figure 18. SP334 Configuration to a DB-9 Serial Port

The RS-232 receiver has a singleended input
with a threshold of 0.8V to 2.4V. The RS-232
receiver has an operating voltage range of

15V

and can receive signals up to 120kbps. RS-232
receivers are used in RS-232 mode for all signal
types include data, clock, and control lines of
the RS-232 serial port.

The differential RS-485 receiver has an input
impedance of 15k

and a differential threshold

200mV. Since the characteristics of an RS-

422 receiver are actually subsets of RS485, the
receivers for RS-422 requirements are identical
to the RS-485 receivers. All of the differential
receivers can receive data up to 10Mbps.

Enable Pins

The SP334 drivers can be enabled by use of the
TXEN pin. A logic HIGH will enable the driver
outputs and a logic LOW will tri-state the

SP334DS/10

Programmable RS-232/RS-485 Transceiver

ORDERING INFORMATION

Model

Temperature Range

Package Types

SP334CT ........................................................................... 0

C to +70

C .................................................................................. 28-pin Plastic SOIC

SP334ET ........................................................................ -40

C to +85

C .................................................................................. 28-pin Plastic SOIC

Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others.

Corporation

SIGNAL PROCESSING EXCELLENCE

Please consult the factory for pricing and availability on a Tape-On-Reel option.

Sipex Corporation

Headquarters and
Sales Office
22 Linnell Circle
Billerica, MA 01821
TEL: (978) 667-8700
FAX: (978) 670-9001
e-mail: sales@sipex.com

Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600

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