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| 型号： | SP332ET-L/TR |
| 厂商： | Exar Corporation |
| 文件页数： | 8/11页 |
| 文件大小： | 0K |
| 描述： | IC TXRX RS232/485 SRL 28WSOIC |
| 标准包装： | 1,500 |
| 类型： | 收发器 |
| 驱动器/接收器数： | 4/4 |
| 规程： | RS232，RS485 |
| 电源电压： | 5V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 28-SOIC W |
| 包装： | 带卷 (TR) |
6
Exar Corporation 48720 Kato Road, Fremont CA, 94538 50-668-707 www.exar.com
SP332_00_0260
The
SP332 is single chip device that can be
configured via software for either RS-232,
RS-485 or both interface modes at any
time. The
SP332 is made up of three basic
circuit elements, single-ended drivers and
receivers, differential drivers and receivers
and charge pump.
DIFFERENTIAL DRIVER/RECEIVER...
RS-485, RS-422 Drivers...
The differential drivers and receivers comply
with the RS-485 and RS-422 standards.The
driver circuits are able to drive a minimum
of 1.5V when terminated with a 54 resistor
across the two outputs. The typical propa-
gation delay from driver input to output is
60ns. The driver outputs are current limited
to less than 250mA, and can tolerate shorts
to ground, or to any voltage within a +10V
to -7V range with no damage.
RS-485, RS-422 Receivers...
The differential receivers of the
SP332 com-
ply with the RS-485 and RS-422 standards,
The input to the receiver is equipped with a
common mode range of +12V to -7V. The
input threshold over this range is a minimum
of +/-200mV. The differential receivers can
receive data up to 10Mbps. The typical
propagation delay from the receiver input
to output is 90ns.
SINGLE ENDED DRIVER / RECEIVER...
RS-232 (V.28) Drivers...
The single-ended drivers and receivers
comply with the RS-232 and V.28 standards.
The drivers are inverting transmitters which
accepteitherTTLorCMOSinputsandoutput
the RS-232 signals with an inverted sense
relative to the input logic levels. Typically,
the RS-232 driver output voltage swing is
+/-9V with no load and is guaranteed to be
greater than +/-5V under full load. The driv-
ers rely on the V+ and V- voltages generated
by the on-chip charge pump to maintain
proper RS-232 output levels. With worst
case load conditions of 3k and 2500pF, the
four RS-232 drivers can still maintain +/-5V
output levels. The drivers can operate up to
120kbps; the propagation delay from input
to output is typically 2s.
RS-232 (V.28) Receivers...
The RS-232 receivers convert RS-232
input signals to inverted TTL signals. Each
of the four receivers features 500mV of
hysteresis margin to minimize the affects
of noisy transmission lines. The inputs
also have a 5k resistor to ground, in
an open circuit situation the input of the
receiver will be forced low, committing
the output to a logic high state. The input
resistance will maintain 3k to 7k over
a +/-15V range. The maximum operating
voltage range for the receiver is +/-30V,
under these conditions the input current to
the receiver must be limited to less than
100mA. Due to the on-chip ESD protec-
tion circuitry, the receiver inputs will be
clamped to +/-5V levels. The RS-232
receivers can operate up to 120kbps.
Charge–Pump
Thechargepumpisa
Exar–patenteddesign
(U.S.5,306,954)andusesauniqueapproach
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 7(a) shows the
waveformfoundonthepositivesideofcapci-
tor C2, and Figure 7(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
— V
SS charge storage —During this phase of
theclockcycle,thepositivesideofcapacitors
C
and C2 are initially charged to +5V. Cl
+
is
then switched to ground and charge on C
–
is
transferred to C
2
–
. Since C
2
+
is connected to
+5V, the voltage potential across capacitor
C
2 is now 0V.
Phase 2
— V
SS transfer — Phase two of the clock con-
nects the negative terminal of C
2 to the VSS
storage capacitor and the positive terminal
of C
2 to ground, and transfers the generated
–l0V to C
3. Simultaneously, the positive side
of capacitor C
is switched to +5V and the
negative side is connected to ground.
THEORY OF OPERATION
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| SP332K | 制造商:Cornell Dubilier Electronics 功能描述: 制造商:Mallory Sonalert Products Inc 功能描述: |
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