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| 型号： | SP3220EEA |
| 英文描述： | LOCATOR TO USE WITH AMT23004DA |
| 中文描述： | 3.0V至5.5V的RS - 232驱动器/接收器 |
| 文件页数： | 10/18页 |
| 文件大小： | 114K |
| 代理商： | SP3220EEA |
11/07/02 SP3220E True +3.0 to +5.0V RS-232 Transceivers
Copyright 2002 Sipex Corporation
10
Table 2. Truth Table Logic for Shutdown and
Enable Control
N
D
H
S
N
E
T
U
O
x
T
T
U
O
x
R
0
0
e
T
e
v
A
0
1
e
T
e
T
1
0
e
v
A
e
v
A
1
1
e
v
A
e
T
Receivers
The receiver converts EIA/TIA-232 levels to
TTL or CMOS logic output levels. The receiver
has an inverting high-impedance output. This
receiver output (RxOUT) is at high-impedance
when the enable control EN = HIGH. In the
shutdown mode, the receiver can be active or
inactive. EN has no effect on TxOUT. The truth
table logic of the
SP3220E
driver and receiver
outputs can be found in
Table 2
.
Since receiver input is usually from a transmission
line where long cable lengths and system
interference can degrade the signal, the inputs
have a typical hysteresis margin of 300mV.
This ensures that the receiver is virtually
immune to noisy transmission lines. Should an
input be left unconnected, a 5k
pulldown
resistor to ground will commit the output of the
receiver to a HIGH state.
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 5.5V power
supplies. The internal power supply consists of
a regulated dual charge pump that provides
output voltages 5.5V regardless of the input
voltage (V
CC
) over the +3.0V to +5.5V range.
In most circumstances, decoupling the power
supply can be achieved adequately using a 0.1
μ
F
bypass capacitor at C5 (refer to
Figures 5
).
In applications that are sensitive to power-
supply noise, decouple V
to ground with a
capacitor of the same value as charge-pump
capacitor C1. Physically connect bypass
capacitors as close to the IC as possible.
The charge pumps operate in a discontinuous
mode using an internal oscillator. If the output
voltages are less than a magnitude of 5.5V, the
charge pumps are enabled. If the output voltage
exceed a magnitude of 5.5V, the charge pumps
are disabled. This oscillator 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 V
. C
switched to GND and the charge in C
transferred to C
the voltage potential across capacitor C
2
is now
2 times V
CC
.
+
is then
–
is
–
. Since C
+
is connected to V
,
Phase 2
— V
transfer — Phase two of the clock
connects the negative terminal of C
to the V
SS
storage capacitor and the positive terminal of C
2
to GND. This transfers a negative generated
voltage to C
. This generated voltage is
regulated to a minimum voltage of -5.5V.
Simultaneous with the transfer of the voltage to
C
, the positive side of capacitor C
is switched
to V
CC
and the negative side is connected to GND.
Phase 3
— V
charge storage — The third phase of the
clock is identical to the first phase — the charge
transferred in C
produces –V
in the negative
terminal of C
, which is applied to the negative
side of capacitor C
. Since C
voltage potential across C
2
is 2 times V
CC
.
+
is at V
CC
, the
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PDF描述 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP3220EEA/TR | 制造商:Exar Corporation 功能描述: |
| SP3220EEA-L | 功能描述:RS-232接口集成电路 RS232 1drvr/1rcvr temp -40C to 85C RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| SP3220EEA-L/TR | 功能描述:RS-232接口集成电路 3V-5.5V RS-232 1-DRV/1-RCV LOW PWR RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| SP3220EEA-LTR | 制造商:EXAR 制造商全称:EXAR 功能描述:3.0V to 5.5V RS-232 Driver/Receiver Pair |
| SP3220EET | 制造商:SIPEX 制造商全称:Sipex Corporation 功能描述:+3.0V to +5.5V RS-232 Driver/Receiver Pair |
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