參數(shù)資料
型號(hào): TC232MJE
廠商: Microchip Technology Inc.
英文描述: LED AMBER FACE UP 1206
中文描述: 雙路RS - 232發(fā)送器/接收和電源
文件頁數(shù): 3/3頁
文件大小: 51K
代理商: TC232MJE
6-5
TELCOM SEMICONDUCTOR, INC.
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6
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DETAILED DESCRIPTION
The TC232 contains a +5V to
±
10V dual charge pump
voltage converter, a dual transmitter and a dual receiver.
+5V to
±
10V Dual Charge Pump
Voltage Converter
The TC232 power supply consists of two charge pumps.
One uses external capacitor C1 to double the +5V input to
+10V, with output impedance of about 200
. The other
uses C2 to invert +10V to – 10V, with overall output
impedance of 450
(including effects of +5V to +10V
doubler impedance).
The clock in the doubler circuit will start at
4.2V in the
typical part, but external loads may make this point rise to as
high as 4.5V with a load of 2 k
on each of the two output
voltages.
Because of this, use of the doubler and inverter to run
additional external circuits should be limited. The maximum
current should be no more than 2.5 mA from the +10V and
- 10V. in order to guarantee start-up of the doubler clock.
The test circuit employs 22
μ
F capacitors for C1 to C4,
but the value is not critical. These capacitors usually are low-
cost aluminum or tantalum electrolytic capacitors.
Increasing C1 and C2 to 47
μ
F lowers the output
impedance of the +10V doubler and the - 10V inverter by
the change in the ESR of the capacitors.
Increasing C3 and C4 lowers ripple on the
±
10V out-
puts and 16 kHz ripple on the RS-232 outputs. Where size
is critical, the value of C1 to C4 can be lowered to 1
μ
F. The
use of a low ESR capacitor will help lower the output ripple
and keep the output impedance of the
±
10V as low as
possible.
Dual Transmitter
TC232 transmitters are CMOS inverters driven by
±
10V
internally-generated voltages. The input is TTL/CMOS com-
patible, with a logic threshold of about 26% of V
CC
(1.3V for
5V V
CC
). The input of an unused transmitter can be left
unconnected, since an internal 400 k
pull-up resistor
connected between the transmitter input and V
CC
pulls the
input HIGH and forces the unused transmitter output to the
LOW state.
With V
CC
at 5V, the outputs will go from (V+ – 0.6V) to
V
with no load and will swing
±
9V when loaded with 3 k
.
The minimum output voltage swing, with V
CC
at 4.5V and at
maximum ambient temperature, is
±
5V. This conforms to
RS-232 specifications for "worst-case" conditions.
EIA/TIA RS-232E specs limit the slew rate at output
to less than 30V/
μ
s.
The powered-down output impedance (V
CC
= 0V) is
a minimum of 300
with
±
2V applied to outputs.
V
+
, V
Output Voltages vs Load Current
TEST CIRCUIT
TC232
1
2
3
4
16
15
14
13
5
6
7
12
11
8
10
9
C1
22 μF
22 μF
+
+
C2
22 μF
22 μF
+
+
RS-232
INPUT
±30V
RS-232
OUTPUT
+4.5V TO +5.5V
INPUT
3 k
RS-232
OUTPUT
RS-232
INPUT ±30V
TTL/CMOS OUTPUT
TTL/CMOS INPUT
TTL/CMOS
INPUT
TTL/CMOS OUTPUT
3 k
V+
V–
T2OUT
R2IN
VCC
GND
T1OUT
T1IN
R1OUT
T2IN
R2OUT
IN
R1
C+
1
C–
1
C+
2
C–
2
C3
C4
10
9
8
7
6
5
4
3
0
1
2
3
4
5
6
7
8
9
10
O
(CC
(CC
(CC
(CC
CONDITIONS:
A) A
°
C
B) TRANSMITTER OUTPUTS
OPEN CIRCUIT
| ILOAD
+
V
V
V
+
V
The outputs are protected and can be short-circuited to
ground indefinitely.
Dual Receiver
TC232 receivers meet RS-232 input specifications.
Input impedance is between 3 k
and 7 k
. Switching
thresholds are within the
±
3V limits, and the receivers
withstand up to
±
30V inputs. RS-232 and TTL/CMOS input
compatible, the receivers have 0.8V V
IL
and 2.4V V
IH
with
0.5V hysteresis to reject noise.
The TTL/CMOS compatible receiver output is LOW
when an RS-232 input is greater than 2.4V. It is HIGH
when an input is floating or between +0.8V and – 30V.
TC232
DUAL RS-232 TRANSMITTER/
RECEIVER AND POWER SUPPLY
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