參數(shù)資料
型號: SP3239EEA-L
廠商: Exar Corporation
文件頁數(shù): 15/16頁
文件大小: 0K
描述: IC TXRX RS232 INTELLIGENT 28SSOP
標(biāo)準(zhǔn)包裝: 46
類型: 收發(fā)器
驅(qū)動器/接收器數(shù): 5/3
規(guī)程: RS232
電源電壓: 3 V ~ 5.5 V
安裝類型: 表面貼裝
封裝/外殼: 28-SSOP(0.209",5.30mm 寬)
供應(yīng)商設(shè)備封裝: 28-SSOP
包裝: 管件
8
Exar Corporation 48720 Kato Road, Fremont CA, 94538 510-668-7017 www.exar.com
SP3239E_100_020111
The SP3239E includes an additional non-in-
verting receiver with an output R
1OUT. R1OUT
is an extra output that remains active and
monitors activity while the other receiver
outputs are forced into high impedance.
This allows a Ring Indicator (RI) signal from a
peripheral to be monitored without forward
biasing the TTL/CMOS inputs of the other
devices connected to the receiver outputs.
Since receiver input is usually from a transmis-
sion 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, an internal 5k pulldown resistor
to ground will commit the output of the receiver
to a HIGH state.
Charge Pump
The charge pump is an Exar–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. This is important to maintain compli-
Table 2. SHUTDOWN Logic
Figure 7. Loopback Test Circuit for RS-232 Driver
Data Transmission Rates
ant RS-232 levels regardless of power supply
fluctuations.
The charge pump operates in a discontinuous
mode using an internal oscillator. If the output
voltages are less than a magnitude of 5.5V, the
charge pump is enabled. If the output voltages
exceed a magnitude of 5.5V, the charge pump
is disabled. This oscillator controls the four
phases of the voltage shifting. A description of
each phase follows.
Figure 9. Loopback Test results at 250Kbps
(All Drivers Fully Loaded)
Figure 8. Loopback Test results at 120kbps
(All Drivers Fully Loaded)
SP3239E
TxIN
TxOUT
C1+
C1-
C2+
C2-
V+
V-
VCC
0.1F
+
C2
C5
C1
+
C3
C4
+
LOGIC
INPUTS
VCC
5k
RxIN
RxOUT
LOGIC
OUTPUTS
SHUTDOWN
GND
VCC
1000pF
0.1F
Device: SP3239E
SHUTDOWN
TxOUT
RxOUT
R
1OUT
0
High-Z
Active
1
Active
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