Dallas Semiconductor DS232A, DS232AS-T-R, DS232AS-N-T-R, DS232AS-N, DS232AS Datasheet
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FEATURES
Compatible with LT1181A and MAX232A
High data rate - 250 kbits/sec under load
16-pin DIP or SOIC package
20-pin TSSOP package for height restricted
applications
Operate from single +5V power
Meets all EIA-232E and V0.28 specifications
Uses small capacitors: 0.1 µF
Optional industrial temperature range
available (-40°C to +85°C)
ORDERING INFORMATION
DS232A 16-pin DIP
DS232A-N 16-pin DIP (Industrial)
DS232AR 16-pin SOIC (150-Mil)
DS232AR-N 16-pin SOIC (150-Mil) (Industrial)
DS232AS 16-pin SOIC (300-Mil)
DS232AS-N 16-pin SOIC (300-Mil) (Industrial)
DS232AE 20-pin TSSOP
DS232AE-N 20-pin TSSOP (Industrial)
PIN ASSIGNMENT
PIN DESCRIPTION
VCC - +5-Volt Supply
GND - Ground
V+ - Positive Supply Output
V- - Negative Supply Output
T1
IN
, T2
IN
- RS-232 Driver Inputs
T1
OUT
, T2
OUT
- RS-232 Driver Outputs
R1IN, R2
IN
- Receiver Inputs
R1
OUT
, R2
OUT
- Receiver Outputs
C1+, C1- - Capacitor 1 Connections
C2+, C2- - Capacitor 2 Connections
DESCRIPTION
The DS232A is a dual RS-232 driver/receiver pair that generates RS-232 voltage levels from a single +5volt power supply. Additional ±12-volt supplies are not needed since the DS232A uses on-board charge
pumps to convert the +5-volt supply to ±10 volts. The DS232A is fully compliant with EIA RS-232E and
V0.28/V0.24 standards. The DS232A contains two drivers and two receivers. Driver slew rates and d ata
rates are guaranteed up to 250k bits/sec. The DS232A operates with only 0.1 µF charge pump capacitors.
OPERATION
The diagram in Figure 1 shows the main elements of the DS232A. The following paragraphs describe the
function of each pin.
DS232
A
Dual RS-232 Transmitter/Receive
r
www.dalsemi.com
16-Pin DIP AND SOIC
15
C1-
C2-
T2
OUT
R2
IN
V
CC
R1
IN
R1
OUT
T1
IN
T2
IN
R2
OUT
1
2
3
4
5
6
7
8
16
14
13
12
11
10
9
V+
C2+
V-
C1+
GND
T1
OUT
20-Pin TSSOP
19
C1-
NC
V-
NC
T2
OUT
R2
IN
NC
T1
OUT
R1
IN
R1
OUT
NC
T1
IN
T2
IN
R2
OUT
1
2
3
4
5
6
7
8
9
10
20
18
17
16
15
14
13
12
11
V+
C2+
C2-
C1+
V
CC
GND
DS232A
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FUNCTIONAL DIAGRAM OF DS232A Figure 1
NOTE: C5 is a recommended decoupling capacitor which is the same value as C1, C2, C3, and C4.
( ) Are for TSSOP package only.
PIN DESCRIPTIONS
VCC, GND: DC power is provided to the device on these pins. VCC is the +5-volt input.
V+: Positive supply output (RS-232). V+ requires an ex ternal storage char ge capacitor o f at least 0.1 µF.
A larger capacitor (up to 10 µF) can be used to reduce supply ripple.
V-: Negative supply output (RS-232). V- requires an external storage capacitor of at least 0.1 µF. A
larger capacitor (up to 10 µF) can be used to reduce supply ripple.
T1IN, T2
IN
: Standard TTL/CMOS inputs for the RS-232 drivers. The inputs of unused drivers can b e left
unconnected since each input has a 400 kΩ pullup resistor.
T1
OUT
, T2
OUT
: Driver outputs at RS-232 levels. Driver output swing meets RS-232 levels for loads up to
3 kΩ. These driver outputs provide current necessary to meet RS-232 levels for loads up to 2500 pF.
DS232A
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R1
IN
, R2
IN
: Receiver inputs. These inputs accept RS-232 level signals (±25 volts) into a protected 5 kΩ
terminating resistor. Each receiver provides 0.5V hysteresis (typical) for noise immunity.
R1
OUT
, R2
OUT
: Receiver outputs at TTL/CMOS levels.
C1+, C1-, C2+, C2-: Charge pump capacitor inputs. These pins require two external capacitors (0.1 µF
minimum, 10 µF maximum and should be the same size as C3 and C4). Capacitor 1 is connected between
C1+ and C1-. Capacitor 2 is connected between C2+ and C2-. Capacitor C1 can be omitted if +12 volts is
connected directly to V+. Likewise, C2 can be omitted if -12V is connected directly to V-.
DUAL CHARGE PUMP CONVERTERS
The DS232A has a two-stage on-board charge pump circuit that is used to generate ±10 volts from a
single +5-volt supply. In the first stage, capacitor C1 doubles the +5V supply to +10 volts which is then
stored on capacitor C3. The second stage uses capacitor C2 to invert the +10V potential to -10V. This
charge is then stored on capacitor C4. The ±10-volt supplies allow the DS232A to provide the necessary
output levels for RS-232 communication. The DS232A will operate with charge pump capacitors as low
as 0.1 µF. Larger capacitors (up to 10 µF) can be used to reduce supply ripple.
RS-232 DRIVERS
The two RS-232 drivers are powered by the internal ±10-volt supplies generated b y the on-board charge
pump. The driver inputs are both TTL and CMOS compatible. Each input has an internal 400 kΩ=pullup
resistor so that unused transmitter inputs can be left unconnected. The open circuit output voltage swing
is from (V+ - 0.6) to V- volts. Worst case conditions for EIA-232E/V.28 of ±5-volt driving a 3 kΩ=load
and 2500 pF are met at maximum operating temperature and VCC equal to 4.5 volts. Typical voltage
swings of ±8 volts occur when loaded with a nominal 5 kΩ=RS -232 receiver. As required by EIA-232E
and V.28 specifications, the slew rate at the output is limited to less than 30 volts/µs. Typical slew rates
are 20 volts/µs unloaded and 12 volts/µs with 3 kΩ=and 2500 pF load. These slew rates allow for bit rates
of over 250k bits/s. Driver outputs maintain high impedance when power is off.
RS-232 RECEIVERS
The two receivers conform fully to the RS-232E specifications. The input impedance is typically 5
kΩ=and can withstand up to ±25 volts with or without VCC applied. The input switching thresholds are
within the ±3-volt limit of RS-232E specification with an input threshold low of 0.8 volts and an input
threshold high of 2.4 volts. The receivers have 0.5 volts of hysteresis (typical) to improve noise rejection.
The TTL/CMOS compatible outputs of the receivers will be low whenever the RS-232 input is greater
than 2.4 volts. The receiver output will be high when the input is floating or driven between +0.8 volts
and -25 volts.
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