參數(shù)資料
型號(hào): DS232A
廠商: MAXIM INTEGRATED PRODUCTS INC
元件分類: 通用總線功能
英文描述: Dual RS232 Transmitter/Receiver(雙路RS232發(fā)送器/接收器)
中文描述: LINE TRANSCEIVER, PDIP16
封裝: 0.300 INCH, DIP-16
文件頁數(shù): 3/10頁
文件大?。?/td> 88K
代理商: DS232A
DS232A
021998 3/10
PIN DESCRIPTIONS
V
CC
, GND:
DC power is provided to the device on these
pins. V
CC
is the +5 volt input.
V+:
Positive supply output (RS–232). V+ requires an
external storage charge capacitor of at least 0.1
μ
F. A
larger capacitor (up to 10
μ
F) can be used to reduce
supply ripple.
V–:
Negative supply output (RS–232). V– requires an
external storage capacitor of at least 0.1
μ
F. A larger
capacitor (up to 10
μ
F) can be used to reduce supply rip-
ple.
T1
IN
, T2
IN
:
Standard TTL/CMOS inputs for the RS–232
drivers. The inputs of unused drivers can be left uncon-
nected since each input has a 400K
pull–up resistor.
T1
OUT
, T2
OUT
:
Driver outputs at RS–232 levels. Driver
output swing meets RS–232 levels for loads up to 3K
.
These driver outputs provide current necessary to meet
RS–232 levels for loads up to 2500 pF.
R1
IN
, R2
IN
:
Receiver inputs. These inputs accept
RS–232 level signals (
±
25 volts) into a protected 5K
terminating resistor. Each receiver provides 0.5V hys-
teresis (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
μ
F mini-
mum, 10
μ
F 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 capaci-
tor 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
μ
F. Larger capac-
itors (up to 10
μ
F) can be used to reduce supply ripple.
RS–232 DRIVERS
The two RS–232 drivers are powered by the internal
±
10 volt supplies generated by the on–board charge
pump. The driver inputs are both TTL and CMOS com-
patible. Each input has an internal 400K
pull–up resis-
tor so that unused transmitter inputs can be left uncon-
nected. 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 3K
load and 2500
pF are met at maximum operating temperature and V
CC
equal to 4.5 volts. Typical voltage swings of
±
8 volts
occur when loaded with a nominal 5K
RS–232
receiver. As required by EIA–232E and V.28 specifica-
tions, the slew rate at the output is limited to less than 30
volts/
μ
s. Typical slew rates are 20 volts/
μ
s unloaded
and 12 volts/
μ
s with 3K
and 2500 pF load. These slew
rates allow for bit rates of over 250K bits/s. Driver out-
puts maintain high impedance when power is off.
RS–232 RECEIVERS
The two receivers conform fully to the RS–232E specifi-
cations. The input impedance is typically 5K
and can
withstand up to
±
25 volts with or without V
CC
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 out-
put will be high when the input is floating or driven
between +0.8 volts and –25 volts.
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