1
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
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–
V–
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 © Copyright 2000 Sipex Corporation
2
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.
VCC...........................................................................+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
øJA....................................................40 °C/W
28-pin Plastic SOIC
øJA....................................................40 °C/W
SPECIFICATIONS
Typically 25°C @ Vcc = +5V unless otherwise noted.
MIN. TYP. MAX. UNITS CONDITIONS
LOGIC INPUTS
VIL 0.8 Volts
VIH 2.0 Volts
LOGIC OUTPUTS
VOL 0.4 Volts IOUT= -3.2mA
VOH 2.4 Volts IOUT= 1.0mA
Output Tri-state Leakage 10 µA 0.4V ≤ VOUT ≤ +2.4V
RS-232 DRIVER
DC Characteristics
HIGH Level Output +5.0 +15 Volts RL=3kΩ, VIN=0.8V
LOW Level Output –15.0 –5.0 Volts RL=3kΩ, VIN=2.0V
Open Circuit Voltage –15 +15 Volts
Short Circuit Current ±100 mA VOUT = 0V
Power Off Impedance 300 ΩVcc = 0V, Vout = ±2.0V
AC Characteristics
Slew Rate 30 V/µsR
L
=3kΩ, CL= 50pF
VCC = +5.0V, TA @ +25°C
Transition Time 1.56 µsR
L
=3kΩ, CL=2500pF ;
between ±3V, TA @ +25°C
Maximum Data Rate 120 235 kbps RL=3kΩ, CL=2500pF
Propagation Delay
tPHL 28 µs Measured from 1.5V of VIN
tPLH 28 µs to 50% of VOUT; RL=3kΩ
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 3 5 7 kΩVIN = +15V to –15V
AC Characteristics
Maximum Data Rate 120 235 kbps
Propagation Delay
tPHL 0.25 1 µs Measured from 50% of VIN
tPLH 0.25 1 µs to 1.5V of VOUT.
RS-485 DRIVER
DC Characteristics
Open Circuit Voltage 6.0 Volts
Differential Output 1.5 5.0 Volts RL=54Ω, CL=50pF
3
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
SPECIFICATIONS
Typically 25°C @ Vcc = +5V unless otherwise noted.
MIN. TYP. MAX. UNITS CONDITIONS
RS-485 DRIVER
Balance ±0.2 Volts |VT| - |VT|
Common-Mode Output 3.0 Volts
Output Current 28.0 mA RL=54Ω
Short Circuit Current ±250 mA Terminated in –7V to +10V
AC Characteristics
Maximum Data Rate 10 Mbps RL=54Ω
Output Transition Time 30 ns Rise/fall time, 10%–90%
Propagation Delay See Figures 3A & 5
tPHL 80 120 ns RDIFF=54Ω, CL1=CL2=100pF
tPLH 80 120 ns RDIFF=54Ω, CL1=CL2=100pF
Driver Output Skew 5 20 ns per figure 5, tSKEW = |tDPLH - tDPHL|
RS-485 RECEIVER
DC Characteristics
Inputs
Common Mode Range –7.0 +12.0 Volts
Receiver Sensitivity ±0.2 Volts –7V ≤ VCM ≤ +12V
Input Impedance 12 15 kΩ–7V ≤ VCM ≤ +12V
AC Characteristics
Maximum Data Rate 10 Mbps
Propagation Delay See Figures 3A & 7
tPHL 130 200 ns RDIFF=54Ω, CL1=CL2=100pF
tPLH 130 200 ns RDIFF=54Ω, CL1=CL2=100pF
Differential Receiver Skew 10 20 ns tSKEW= | tPLH – tPHL |; RDIFF=54Ω,
CL1=CL2=100pF, see Figure 8
ENABLE TIMING
RS-485 Driver
Enable Time See Figures 4 & 6
Enable to Low 100 150 ns CL=15pF, S1 Closed
Enable to High 100 150 ns CL=15pF, S2 Closed
Disable Time See Figures 4 & 6
Disable From Low 100 120 ns CL=15pF, S1 Closed
Disable From High 100 120 ns CL=15pF, S2 Closed
RS-485 Receiver
Enable Time See Figures 2 & 8
Enable to Low 100 150 ns CL=15pF, S1 Closed
Enable to High 100 150 ns CL=15pF, S2 Closed
Disable Time See Figures 2 & 8
Disable From Low 100 120 ns CL=15pF, S1 Closed
Disable From High 100 120 ns CL=15pF, S2 Closed
POWER REQUIREMENTS
Supply Voltage VCC +4.75 +5.25 Volts
Supply Current ICC
No Load (Tx Disabled) 12 20 mA TXEN = 0V
No Load (RS-232 Mode) 20 50 mA RS232/RS485 = 0V
No Load (RS-485 Mode) 15 50 mA RS232/RS485 = +5V
ENVIRONMENTAL
Operating Temperature
Commercial (..C..) 0 +70 °C
Industrial (..E..) –40 +85 °C
Storage Temperature –65 +150 °C
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
4
Figure 3a. Driver/Receiver Timing Test Circuit Figure 4. Driver Timing Test Load #2 Circuit
Figure 1. Driver DC Test Load Circuit Figure 2. Receiver Timing Test Load Circuit
C
L1
15pF
RO
A
B
A
B
DI
C
L2
R
L
A
B
R
R
V
OD
V
OC
500Ω
CL
Output
Under
Test
S1
S2
VCC
1KΩ
1KΩC
RL
Receiver
Output S
1
S
2
Test Point V
CC
TEST CIRCUITS
RECEIVER INPUT GRAPH
+1.0mA
–0.6mA
+12V+6V
–3V–7V
1 Unit Load
Maximum Input Current
versus Voltage
RS-485 RECEIVER
5
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
Figure 6. Driver Enable and Disable Times
Figure 7. Receiver Propagation Delays
V
OH
V
OL
RECEIVER OUT 1.5V 1.5V
t
PHL
f = 1MHz; t
R
≤ 10ns; t
F
≤ 10ns
OUTPUT
V
0D2
+
V
0D2
–
A – B 0V 0V
t
PLH
INPUT
Figure 5. Driver Propagation Delays
SWITCHING WAVEFORMS
+3V
0V
T
x
EN
5V
V
OL
A, B 0V
1.5V 1.5V
t
ZL
t
ZH
f = 1MHz; t
R
≤ 10ns; t
F
≤ 10ns
V
OH
A, B 2.3V
2.3V
t
LZ
t
HZ
0.5V
0.5V
Output normally LOW
Output normally HIGH
+3V
0V
DRIVER INPUT
A
B
DRIVER
OUTPUT
V
O
+
DIFFERENTIAL
OUTPUT
V
A
– V
B
0V
V
O
–
1.5V 1.5V
t
PLH
t
F
t
R
f ≥ 1MHz; t
R
≤ 10ns; t
F
≤ 10ns
V
O
1/2V
O
1/2V
O
t
PHL
t
SKEW
= |t
DPLH
- t
DPHL
|
t
DPLH
t
DPHL
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
6
Figure 8. Receiver Enable and Disable Times
+3V
0V
5V
0V
1.5V 1.5V
t
ZL
t
ZH
f = 1MHz; t
R
≤ 10ns; t
F
≤ 10ns
RECEIVER OUT 1.5V
1.5V
t
LZ
t
HZ
0.5V
0.5V
Output normally LOW
Output normally HIGH
V
IL
V
IH
RECEIVER OUT
R
X
EN
t
SKEW
= |t
PHL
- t
PLH
|
Figure 9. Typical RS-232 Driver Output Figure 10. Typical RS-485 Driver Output
TTL
Input
Driver
Output
7
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
Figure 12. Typical Operating Circuit
Figure 11. SP334 Pinout
25
12
14
+5V
GND
TTL/CMOS
TTL/CMOS
TTL/CMOS
0.1µF
0.1µF
VCC
V+
V–
TTL/CMOS
TTL/CMOS
T1
T2
T3
R1
TX1
TX2
TX3
RI1
TI1
TI2
TI3
RX1
RX5
RX4
RX3
RX2
RI5
RI4
RI3
RI2
19 15
4
5
6
7
8
10
0.1µF
0.1µF
C1+
C1-
C2+
C2-
9
11
13
23
22
21
20 16
RS232/RS485
27
28
1
400KΩ
Vcc
400KΩ
Vcc
400KΩ
Vcc
RS-232
0V
TTL/CMOS
TTL/CMOS
TTL/CMOS
17
18 RS-232
RS-232
RS-232
RS-232
24
5KΩ
5KΩ
5KΩ
5KΩ
SP334
R2
R3
5KΩ
R4
R5
RS-232
RS-232
RS-232
RXEN
TTL/CMOS
26
3N/C
N/C 2
TTL/CMOS
TTL/CMOS
TTL/CMOS
0.1µF
0.1µF
C1+
C1-
C2+
C2-
TXEN
2
+5V
VCC
5
GND
8
9
11
12
13
19
27
1
R1
RS-485
RS-485
RS-485
TTL/CMOS
0.1µF
0.1µF
V+
V–
+5V
RS-485
RS-485
RS-485
4
6
7
10
14
16
15
26
25
RI2
RI1
TX3
TX4
TX1
TX2
TI1
TI3
RX1
TTL/CMOS 21 17
18RI4
RI3
RX3
15KΩ
15KΩ
400KΩ
Vcc
400KΩ
Vcc
RXEN
RS-485
RS-485
SP334
3
RS232/RS485
15KΩ
15KΩ
R3
T1
T3
TTL/CMOS
TI3
TXEN(n/c)
TX4(n/c)
TX3
VCC
TX1
TX2
GND
C1+
V+
C2+
C1–
C2–
V–
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 © Copyright 2000 Sipex Corporation
8
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.
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 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 free–running oscillator
that controls the four phases of the voltage
shifting. A description of each phase follows.
Phase 1
— VSS charge storage —During this phase of
the clock cycle, the positive side of capacitors
C1 and C2 are initially charged to +5V. Cl+ is
then switched to ground and charge on C1– is
transferred to C2–. Since C2+ is connected to
+5V, the voltage potential across capacitor C2
is now 10V.
Phase 2
— VSS transfer — Phase two of the clock
connects the negative terminal of C2 to the VSS
storage capacitor and the positive terminal of C2
to ground, and transfers the generated –l0V to
C3. Simultaneously, the positive side of capaci-
tor C 1 is switched to +5V and the negative side
is connected to ground.
Phase 3
— VDD charge storage — The third phase of the
clock is identical to the first phase — the charge
transferred in C1 produces –5V in the negative
terminal of C1, which is applied to the negative
side of capacitor C2. Since C2+ is at +5V, the
voltage potential across C2 is l0V.
Phase 4
— VDD transfer — The fourth phase of the
clock connects the negative terminal of C2 to
ground and transfers the generated l0V across
C2 to C4, the VDD storage capacitor. Again,
simultaneously with this, the positive side of
Figure 13. Charge Pump Phase 1.
Figure 14a. Charge Pump Phase 2.
capacitor C1 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 VCC 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 15kHz. The external capacitors
must be a minimum of 0.1µF 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
V
CC
= +5V
–5V –5V
+5V
V
SS
Storage Capacitor
V
DD
Storage Capacitor
C
1
C
2
C
3
C
4
+
+
++
–
–
––
V
CC
= +5V
–10V
V
SS
Storage Capacitor
V
DD
Storage Capacitor
C
1
C
2
C
3
C
4
+
+
++
–
–
––
9
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
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,
pull–up resistors to +5V or pull–down resistors
to ground are suggested. Since the driver inputs
are both TTL or CMOS compatible, any value
resistor less than 100kΩ 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
V
CC
= +5V
–5V
+5V
–5V
V
SS
Storage Capacitor
V
DD
Storage Capacitor
C
1
C
2
C
3
C
4
+
+
++
–
–
––
V
CC
= +5V
+10V
V
SS
Storage Capacitor
V
DD
Storage Capacitor
C
1
C
2
C
3
C
4
+
+
++
–
–
––
Figure 17. Charge Pump Waveforms
±5V with a full load of 3kΩ 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 54Ω 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 pull–up resistor of
100kΩ to +5V should be connected to the
inverting input for a logic low, or the
non–inverting input for a logic high. For
single-ended receivers, a pull–down resistor to
ground of 5kΩ is internally connected, which
will ensure a logic high output.
+10V
a) C2+
GND
GND
-10V
b) C2-
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
10
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 12kΩ.
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.
25
12
14
+5V
GND
CTS
TxD
RTS
0.1µF
0.1µF
VCC
V+
V–
DTR
RxD
T1
T2
T3
R1
TX1
TX2
TX3
RI1
TI1
TI2
TI3
RX1
RX5
RX4
RX3
RX2
RI5
RI4
RI3
RI2
19 15
4
5
6
7
8
10
0.1µF
0.1µF
C1+
C1-
C2+
C2-
9
11
13
23
22
21
20 16
RS232/RS485
27
28
1
400KΩ
Vcc
400KΩ
Vcc
400KΩ
Vcc
0V
DSR
DCD
RI
17
18
24
5KΩ
5KΩ
5KΩ
5KΩ
SP334
R2
R3
5KΩ
R4
R5
RXEN
26
1
9
5
6
TxD
DTR
RTS
RxD
CTS
DSR
DCD
RI
SG
Figure 18. SP334 Configuration to a DB-9 Serial Port
The RS-232 receiver has a single–ended 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 15kΩ and a differential threshold
of ±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
11
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
D
EH
PACKAGE: 28-PIN PLASTIC
SMALL OUTLINE (SOIC)
DIMENSIONS (Inches)
Minimum/Maximum
(mm)
A
A1
Ø
L
Be
A
A1
B
D
E
e
H
L
Ø
28–PIN
0.093/0.104
(2.352/2.649)
0.004/0.012
(0.102/0.300)
0.013/0.020
(0.330/0.508)
0.698/0.706
(17.73/17.93)
0.291/0.299
(7.402/7.600)
0.050 BSC
(1.270 BSC)
0.394/0.419
(10.00/10.64)
0.016/0.050
(0.406/1.270)
0°/8°
(0°/8°)
SP334DS/10 Programmable RS-232/RS-485 Transceiver © Copyright 2000 Sipex Corporation
12
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
