SP3238EEA-L/TR [EXAR]
Intelligent 3.0V to 5.5V RS-232 Transceiver;
| 型号： | SP3238EEA-L/TR |
| 厂家： | 
EXAR CORPORATION |
| 描述： | Intelligent 3.0V to 5.5V RS-232 Transceiver 驱动 光电二极管 接口集成电路 驱动器 |
| 文件： | 总21页 (文件大小：854K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SP3238E
Intelligent +3.0V to +5.5V RS-232 Transceiver
FEATURES
1
2
3
4
5
6
7
28
27
26
25
24
23
C2+
GND
C2-
V-
C1+
V+
■ Meets true EIA/TIA-232-F Standards
from a +3.0V to +5.5V power supply
■ Interoperable with EIA/TIA-232 and
adheres to EIA/TIA-562 down to a +2.7V
power source
VCC
C1-
T IN
1
T OUT
1
■ AUTO ON-LINE® circuitry automatically
wakes up from a 1µA shutdown
■ Minimum 250Kbps data rate under load
■ Regulated Charge Pump Yields Stable
RS-232 Outputs Regardless of VCC
Variations
SP3238E
T
IN
T OUT
2
2
22
T
OUT
T
IN
3
3
R IN
8
9
21 R OUT
1
1
R
IN
20
19
18
17
R
OUT
2
2
10
T OUT
T IN
4
4
R
IN 11
R
T
OUT
IN
3
3
■ Enhanced ESD Specifications:
+15kV Human Body Model
T
OUT
12
5
5
ONLINE 13
16 R OUT
1
+15kV IEC61000-4-2 Air Discharge
+8kV IEC61000-4-2 Contact Discharge
SHUTDOWN 14
15
STATUS
Now Available in Lead Free Packaging
DESCRIPTION
The SP3238E device is an RS-232 transceiver solution intended for portable or hand-held applications
such as notebook and palmtop computers.The SP3238E uses an internal high-efficiency, charge-pump
power supply that requires only 0.1µF capacitors in 3.3V operation. This charge pump and Exar's driver
architecture allow the SP3238E device to deliver compliant RS-232 performance from a single power
supply ranging from +3.0V to +5.5V. The SP3238E is a 5-driver / 3-receiver device that is ideal for laptop
/ notebook computer and PDA applications. The SP3238E includes one complementary receiver that
remains alert to monitor an external device's Ring Indicate signal while the device is shutdown.
The AUTO ON-LINE® feature allows the device to automatically "wake-up" during a shutdown state
when an RS-232 cable is connected and a connected peripheral is turned on. Otherwise, the device
automatically shuts itself down drawing less than 1µA.
SELECTION TABLE
Device
Power
RS-232
RS-232
External
Auto
TTL 3-State
# of
Supplies
Drivers Receivers Components On-Line
Pins
Circuitry
SP3220E
SP3223E
SP3243E
SP3238E
+3.0V to +5.5V
+3.0V to +5.5V
+3.0V to +5.5V
+3.0V to +5.5V
1
2
3
5
1
2
5
3
4 Capacitors
4 Capacitors
4 Capacitors
4 Capacitors
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
16
20
28
28
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
1
ABSOLUTE MAXIMUM RATINGS
Power Dissipation per package
These are stress ratings only and functional operation
of the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may
affect reliability and cause permanent damage to the
device.
28-pin SSOP (derate 11.2mW/oC above +70oC)..........900mW
28-pin TSSOP (derate 13.2mW/oC above +70oC)......1100mW
V
.......................................................-0.3V to +6.0V
V+CC(NOTE 1).......................................-0.3V to +7.0V
V- (NOTE 1)........................................+0.3V to -7.0V
V+ + |V-| (NOTE 1)...........................................+13V
ICC (DC VCC or GND current).........................+100mA
Input Voltages
TxIN, ONLINE, SHUTDOWN, ....-0.3V to Vcc + 0.3V
RxIN...................................................................+25V
Output Voltages
TxOUT.............................................................+13.2V
RxOUT, STATUS.......................-0.3V to (VCC +0.3V)
Short-Circuit Duration
TxOUT....................................................Continuous
Storage Temperature......................-65°C to +150°C
NOTE 1: V+ and V- can have maximum magnitudes of 7V, but their absolute difference cannot exceed 13V.
ELECTRICAL CHARACTERISTICS
VCC = +3.0V to +5.5V, C1 - C4 = 0.1µF (tested at 3.3V +/-5%), C1 - C4 = 0.22µF (tested at 3.3V +/-10%),
C1 = 0.047µF and C2 - C4 = 0.33µF (tested at 5.0V +/-10%), TAMB = TMIN to TMAX, unless otherwise noted. Typical
values are at TA = 25oC
PARAMETER
MIN.
TYP.
MAX. UNITS CONDITIONS
DC CHARACTERISTICS
Supply Current, AUTO ON-
LINE®
1.0
10
µA
All RxIN open, ONLINE = GND,
SHUTDOWN = VCC, TxIN = GND or
VCC
Supply Current, Shutdown
1.0
0.3
10
µA
SHUTDOWN = GND, TxIN = Vcc or
GND
Supply Current
AUTO ON-LINE® Disabled
1.0
mA
ONLINE = SHUTDOWN = Vcc,
no load, TxIN = GND or VCC
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold
LOW
VCC = +3.3V or +5.0V, TxIN
ONLINE, SHUTDOWN
0.8
V
V
HIGH
2.4
Input Leakage Current
+0.01
+0.05
+1.0
µA
TxIN, ONLINE, SHUTDOWN,
TAMB = +25oC
Output Leakage Current
Output Voltage LOW
Output Voltage HIGH
DRIVER OUTPUTS
Output Voltage Swing
+10
µA
V
Receivers disabled
IOUT = 1.6mA
0.4
VCC -0.6 VCC -0.1
V
IOUT = -1.0mA
+5.0
+5.4
V
All driver outputs loaded with 3KΩ to
GND
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
2
ELECTRICAL CHARACTERISTICS
VCC = +3.0V to +5.5V, C1 - C4 = 0.1µF (tested at 3.3V +/-5%), C1 - C4 = 0.22µF (tested at 3.3V +/-10%),
C1 = 0.047µF and C2 - C4 = 0.33µF (tested at 5.0V +/-10%), TAMB = TMIN to TMAX, unless otherwise noted. Typical
values are at TA = 25oC
PARAMETER
MIN.
TYP. MAX. UNITS CONDITIONS
DRIVER OUTPUTS (continued)
Output Resistance
300
Ω
VCC = V+ = V- = 0V, VOUT=+2V
Output Short-Circuit Current
RECEIVER INPUTS
Input Voltage Range
Input Threshold LOW
Input Threshold LOW
Input Threshold HIGH
Input Threshold HIGH
Input Hysteresis
+35
+60
mA
VOUT = 0V
-25
0.6
0.8
25
V
V
1.2
1.5
1.5
1.8
0.5
5
Vcc = 3.3V
Vcc = 5.0V
Vcc = 3.3V
Vcc = 5.0V
V
2.4
2.4
V
V
V
Input Resistance
3
7
kΩ
AUTO ON-LINE® CIRCUITRY CHARACTERISTICS (ONLINE = GND, SHUTDOWN = VCC)
STATUS Output Voltage LOW
STATUS Output Voltage HIGH
0.4
V
V
IOUT = 1.6mA
IOUT = -1.0mA
VCC -0.6
Receiver Threshold to Drivers
200
0.5
20
µs
µs
µs
Figure 10
Figure 10
Figure 10
Enabled (tONLINE
)
Receiver Positive or Negative
Threshold to STATUS HIGH (tSTSH
)
Receiver Positive or Negative
Threshold to STATUS LOW (tSTSL
TIMING CHARACTERISTICS
Maximum Data Rate
)
250
kbps
RL = 3KΩ, CL = 1000pF, one
driver switching
Receiver Propagation Delay
tPHL
tPLH
0.15
0.15
µs
Receiver input to Receiver out-
put, CL = 150pF
Receiver Output Enable Time
Receiver Output Disable Time
Driver Skew
200
200
100
50
ns
ns
Normal operation
Normal operation
ns
| tPHL - tPLH |, TAMB = 25°C
Receiver Skew
ns
| tPHL - tPLH
|
Transition-Region Slew Rate
30
V/µs
Vcc = 3.3V, RL = 3kΩ, TAMB =
25°C, measurements taken from
-3.0V to +3.0V or +3.0V to -3.0V
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
3
TYPICAL PERFORMANCE CHARACTERISTICS
Unless otherwise noted, the following performance characteristics apply for VCC = +3.3V, 250kbps data rate, all
drivers loaded with 3kΩ, 0.1µF charge pump capacitors, and TAMB = +25°C.
25
20
6
15
POS. SR
4
NEG SR
10
2
VOH
0
5
VOL
0
1000
2000
3000
4000
5000
-2
-4
-6
0
0
1000
2000
3000
4000
5000
pF
pF
Figure 2. Slew Rate VS. Load Capacitance
Figure 1. Transmitter Output Voltage VS. Load
Capacitance
60
50
40
250Kbps
30
20
10
0
120Kbps
20Kbps
0
1000
2000
3000
4000
5000
pF
Figure 3. Supply Current VS. Load Capacitance
when Transmitting Data
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
4
NAME
C2+
FUNCTION
PIN NUMBER
Positive terminal of the symmetrical charge-pump capacitor C2.
Ground.
1
2
GND
C2-
Negative terminal of the symmetrical charge-pump capacitor C2.
Regulated -5.5V output generated by the charge pump.
RS-232 Driver Output.
3
V-
4
T1OUT
T2OUT
T3OUT
R1IN
5
RS-232 Driver Output.
6
RS-232 Driver Output.
7
RS-232 receiver input.
8
R2IN
RS-232 receiver input.
9
T4OUT
R3IN
RS-232 Driver Output.
10
11
12
13
RS-232 receiver input.
T5OUT
ONLINE
RS-232 Driver Output.
Apply logic HIGH to override AUTO ON-LINE® circuitry keeping drivers
active (SHUTDOWN must also be logic HIGH, refer to Table 2).
SHUTDOWN Apply logic LOW to shut down drivers and charge pump.
14
15
This overrides all AUTO ON-LINE® circuitry and ONLINE (Refer to table 2).
STATUS
TTL/CMOS Output indicating if a RS-232 signal is present on any receiver
input.
R1OUT
T5IN
Non-Inverting receiver - 1 output, active in shutdown.
TTL/CMOS driver input.
16
17
18
19
20
21
22
23
24
25
26
27
28
R3OUT
T4IN
TTL/CMOS receiver output.
TTL/CMOS driver input.
R2OUT
R1OUT
T3IN
TTL/CMOS receiver output.
TTL/CMOS receiver output.
TTL/CMOS driver input.
T2IN
TTL/CMOS driver input.
T1IN
TTL/CMOS driver input.
C1-
Negative terminal of the symmetrical charge-pump capacitor C1.
+3.0V to +5.5V supply voltage.
Vcc
V+
Regulated +5.5V output generated by the charge pump.
Positive terminal of the symmetrical charge-pump capacitor C1.
C1+
Table 1. Device Pin Description
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
5
1
2
3
4
5
6
7
28
27
26
25
24
C2+
GND
C2-
V-
C1+
V+
VCC
C1-
T IN
1
T OUT
1
SP3238E
23 T IN
T OUT
2
2
22
T OUT
3
T IN
3
R IN
1
R IN
2
8
9
21 R OUT
1
20
19
18
17
R OUT
2
T IN
4
10
T OUT
4
R IN 11
R OUT
3
3
T OUT
T IN
12
5
5
ONLINE 13
16 R OUT
1
SHUTDOWN 14
15
STATUS
Figure 4. SP3238E Pinout Configuration
V
CC
+
+
26
0.1µF
0.1µF
C5
C1
VCC
28
27
4
C1+
V+
V-
+
+
C3
C4
0.1µF
0.1µF
25
1
C1-
SP3238E
C2+
+
C2
0.1µF
3
C2-
T1IN
T2IN
T3IN
T4IN
T5IN
T1OUT
T2OUT
T3OUT
T4OUT
T5OUT
5
24
23
22
19
17
6
7
RS-232
TTL/CMOS
INPUTS
OUTPUTS
10
12
R1OUT
R1OUT
16
21
R1IN
R2IN
R3IN
8
5kΩ
TTL/CMOS
OUTPUTS
R2OUT
R3OUT
9
20
18
RS-232
INPUTS
5kΩ
5kΩ
11
VCC
14
13
SHUTDOWN
ONLINE
To µP Supervisor
Circuit
15
STATUS
GND
2
Figure 5. SP3238E Typical Operating Circuit
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
6
DESCRIPTION
In many portable or hand-held applications, an
RS-232cablecanbedisconnectedoraconnected
peripheral can be turned off. Under these condi-
tions,theinternalchargepumpandthedriverswill
be shut down. Otherwise, the system automati-
cally comes online. This feature allows design
engineers to address power saving concerns
without major design changes.
The SP3238E device meets the EIA/TIA-232
and ITU-T V.28/V.24 communication protocols
and can be implemented in battery-powered,
portable, or hand-held applications such as
notebook or palmtop computers. The SP3238E
devices feature Exar's proprietary and patented
(U.S.-- 5,306,954) on-board charge pump cir-
cuitrythatgenerates±5.5VRS-232voltagelevels
from a single +3.0V to +5.5V power supply. The
SP3238E devices can guarantee a data rate of
250kbps fully loaded.
THEORY OF OPERATION
The SP3238E device is made up of four basic
circuit blocks:
1. Drivers
2. Receivers
The SP3238E is a 5-driver/3-receiver device,
ideal for portable or hand-held applications.
The SP3238E includes one complementary
always-active receiver that can monitor an
external device (such as a modem) in shutdown.
This aids in protecting the UART or serial
controller IC by preventing forward biasing
of the protection diodes where VCC may be
disconnected.
3. The Exar proprietary charge pump, and
4. AUTO ON-LINE® circuitry.
Drivers
The drivers are inverting level transmitters that
convert TTL or CMOS logic levels to 5.0V EIA/
TIA-232 levels with an inverted sense relative
to the input logic levels. Typically, the RS-232
output voltage swing is +5.4V with no load and
+5Vminimumfullyloaded. Thedriveroutputsare
protected against infinite short-circuits to ground
without degradation in reliability. These drivers
comply with the EIA-TIA-232-F and all previous
RS-232 versions.
The SP3238E device is an ideal choice for power
sensitivedesigns.The SP3238Edevicefeatures
AUTO ON-LINE® circuitry which reduces the
power supply drain to a 1µA supply current.
Thedriverscanguaranteeadatarateof250kbps
fully loaded with 3kΩ in parallel with 1000pF,
ensuring compatibility with PC-to-PC communi-
cation software. All unused drivers inputs should
be connected to GND or VCC.
V
CC
+
+
26
C5
C1
0.1µF
V
CC
28
27
4
C1+
V+
V-
+
+
0.1µF
C3
C4
0.1µF
0.1µF
25
1
C1-
C2+
SP3238E
+
0.1µF
C2
3
24
23
22
19
C2-
T1IN
T1OUT
T2OUT
T3OUT
T4OUT
T5OUT
5
RxD
CTS
DSR
The slew rate of the driver output is internally
limited to a maximum of 30V/µs in order to meet
theEIAstandards(EIARS-232D2.1.7,Paragraph
5). The transition of the loaded output from HIGH
toLOWalsomeetsthemonotonicityrequirements
of the standard.
T2IN
T3IN
T4IN
T5IN
6
7
RS-232
OUTPUTS
10
12
DCD
RI
UART
or
17
Serial µC
R1OUT
16
21
R1IN
R2IN
R3IN
R
1OUT
TxD
RTS
DTR
8
5kΩ
5kΩ
5kΩ
R2OUT
R3OUT
20
18
9
RS-232
INPUTS
11
Figure 7 shows a loopback test circuit used to
test the RS-232 drivers. Figure 8 shows the test
results of the loopback circuit with all five drivers
active at 120kbps with typical RS-232 loads in
parallel with 1000pF capacitors. Figure 9 shows
the test results where one driver was active
at 250kbps and all five drivers loaded with an
RS-232 receiver in parallel with a 1000pF ca-
pacitor. A solid RS-232 data transmission rate
of 120kbps provides compatibility with many
designs in personal computer peripherals and
LAN applications.
V
CC
14
13
SHUTDOWN
ONLINE
15
STATUS
GND
2
µP
Supervisor
IC
V
IN
RESET
Figure 6. Interface Circuitry Controlled by
Microprocessor Supervisory Circuit
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
7
VCC
Receivers
+
+
The receivers convert +5.0V EIA/TIA-232
levels to TTL or CMOS logic output levels. Re-
ceivers are High-Z when the AUTO ON-LINE®
circuitry is enabled or when in shutdown.
0.1µF
0.1µF
C5
C1
V
CC
C1+
V+
V-
+
+
C3
C4
0.1µF
0.1µF
C1-
C2+
SP3238E
+
C2
0.1µF
The SP3238E includes an additional non-in-
verting receiver with an output R1OUT. 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.
C2-
TxOUT
RxIN
TxIN
LOGIC
INPUTS
1000pF
RxOUT
LOGIC
OUTPUTS
5kΩ
VCC
ONLINE
SHUTDOWN
GND
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 5kΩ pulldown resistor
to ground will commit the output of the receiver
to a HIGH state.
Figure 7. Loopback Test Circuit for RS-232 Driver
Data Transmission Rates
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 (VCC) over the +3.0V to +5.5V
range. This is important to maintain compli-
ant RS-232 levels regardless of power supply
fluctuations.
Figure 8. Loopback Test results at 120kbps
(All Drivers Fully Loaded)
Figure 9. Loopback Test results at 250Kbps
(All Drivers Fully Loaded)
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
8
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.
Phase 4
— VDD transfer — The fourth phase of the clock
connects the negative terminal of C2 to GND,
and transfers this positive generated voltage
across C2 to C4, the VDD storage capacitor. This
voltage is regulated to +5.5V. At this voltage,
the internal oscillator is disabled. Simultane-
ous with the transfer of the voltage to C4, the
positive side of capacitor C1 is switched to VCC
and the negative side is connected to GND, al-
lowing the charge pump cycle to begin again.
The charge pump cycle will continue as long
as the operational conditions for the internal
oscillator are present.
Phase 1
— VSS charge storage — During this phase of the
clock cycle, the positive side of capacitors C1 and
C2 areinitiallychargedtoVCC. Cl+ isthenswitched
toGNDandthechargeinC1– istransferredtoC2–.
SinceC2+ isconnectedtoVCC,thevoltagepotential
across capacitor C2 is now 2 times VCC.
Since both V+ and V– are separately generated
from VCC, in a no–load condition V+ and V– will
besymmetrical. Olderchargepumpapproaches
that generate V– from V+ will show a decrease in
the magnitude of V– compared to V+ due to the
inherent inefficiencies in the design.
Phase 2
— VSS transfer — Phase two of the clock
connects the negative terminal of C2 to the VSS
storage capacitor and the positive terminal of
C2 to GND. This transfers a negative gener-
ated voltage to C3. This generated voltage is
regulated to a minimum voltage of -5.5V.
SimultaneouswiththetransferofthevoltagetoC3,
thepositivesideofcapacitorC1 isswitchedtoVCC
and the negative side is connected to GND.
Phase 3
The clock rate for the charge pump typically
operates at 500kHz. The external capacitors
can be as low as 0.1µF with a 16V breakdown
voltage rating.
— VDD charge storage — The third phase of the
clock is identical to the first phase — the charge
transferred in C1 produces –VCC in the negative
terminal of C1, which is applied to the negative
side of capacitor C2. Since C2+ is at VCC, the volt-
age potential across C2 is 2 times VCC.
Figure 10. Charge Pump Waveform
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
9
V
= +5V
CC
C
+5V
4
+
–
+
V
V
Storage Capacitor
Storage Capacitor
DD
+
–
+
–
C
C
2
1
–
SS
C
–5V
–5V
3
Figure 11. Charge Pump — Phase 1
V
CC
= +5V
C
4
+
–
V
V
Storage Capacitor
DD
+
–
+
C
1
C
2
–
+
–
Storage Capacitor
SS
C
3
-5.5V
Figure 12. Charge Pump — Phase 2
V
= +5V
CC
C
+5V
4
+
–
V
V
Storage Capacitor
Storage Capacitor
DD
+
–
+
–
C
C
2
1
+
–
SS
C
–5V
–5V
3
Figure 13. Charge Pump — Phase 3
V
CC
= +5V
+5.5V
+
C
4
+
–
+
V
Storage Capacitor
DD
+
–
C
1
C
2
–
–
V
SS
Storage Capacitor
C
3
Figure 14. Charge Pump — Phase 4
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
SP3238E_100_020111
10
VCC
+
26
0.1µF
C5
28
C1+
+
C1
0.1µF
27
4
25
1
C1-
V+
V-
+
+
C3
C4
0.1µF
0.1µF
SP3238E
C2+
+
C2
0.1µF
3
16
21
C2-
R1OUT
R1IN
R2IN
R3IN
R1OUT
R2OUT
R3OUT
8
5kΩ
5kΩ
5kΩ
9
20
18
11
T1OUT
T2OUT
T3OUT
T4OUT
T5OUT
T1IN
T2IN
T3IN
T4IN
T5IN
5
24
23
6
22
19
17
7
10
12
DB-9
Connector
VCC
14
13
SHUTDOWN
ONLINE
1
2
3
4
5
6
µP
To
Supervisor
Circuit
15
STATUS
7
8
9
2
DB-9 Connector Pins:
1. Received Line Signal Detector 6. DCE Ready
2. Received Data
7. Request to Send
8. Clear to Send
9. Ring Indicator
3. Transmitted Data
4. Data Terminal Ready
5. Signal Ground (Common)
Figure 15. Circuit for the connectivity of the SP3238E with a DB-9 connector
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SP3238E_100_020111
11
AUTO ONLINE CIRCUITRY
The SP3238E device has a patent pending
AUTO ON-LINE® circuitry on board that saves
power in applications such as laptop computers,
palmtop (PDA) computers and other portable
systems.
the RS-232 cable is disconnected or the RS-232
drivers of the connected peripheral are turned
off.
The AUTO ON-LINE® mode can be disabled by
the SHUTDOWN pin. If this pin is a logic LOW,
the AUTO ON-LINE® function will not operate
regardless of the logic state of the ONLINE pin.
Table 3 summarizes the logic of the AUTO ON-
LINE® operating modes.
The SP3238E device incorporates an AUTO
ON-LINE® circuitthatautomaticallyenablesitself
when the external transmitters are enabled and
the cable is connected. Conversely, the AUTO
ON-LINE® circuit also disables most of the inter-
nal circuitry when the device is not being used
and goes into a standby mode where the device
typically draws 1µA. This function is externally
controlled by the ONLINE pin. When this pin is
tied to a logic LOW, the AUTO ON-LINE® func-
tion is active. Once active, the device is enabled
until there is no activity on the receiver inputs.
The receiver input typically sees at least +3V,
which are generated from the transmitters at
the other end of the cable with a +5V minimum.
When the external transmitters are disabled or
the cable is disconnected, the receiver inputs will
be pulled down by their internal 5kΩ resistors to
ground. When this occurs over a period of time,
the internal transmitters will be disabled and the
device goes into a shutdown or standby mode.
When ONLINE is HIGH, the AUTO ON-LINE®
mode is disabled.
The STATUS pin outputs a logic LOW signal if
the device is shutdown. This pin goes to a logic
HIGHwhentheexternaltransmittersareenabled
and the cable is connected.
When the SP3238E device is shutdown, the
charge pumps are turned off. V+ charge pump
output decays to VCC, the V- output decays to
GND. The decay time will depend on the size
of capacitors used for the charge pump. Once
in shutdown, the time required to exit the shut
down state and have valid V+ and V- levels is
typically 200ms.
For easy programming, the STATUS can
be used to indicate DTR or a Ring Indica-
tor signal. Tying ONLINE and SHUTDOWN
together will bypass the AUTO ON-LINE® cir-
cuitry so this connection acts like a shutdown
input pin
The AUTO ON-LINE® circuit has two stages:
1) Inactive Detection
2) Accumulated Delay
The first stage, shown in Figure 17, detects an
inactive input. A logic HIGH is asserted on
RXINACT if the cable is disconnected or the
external transmitters are disabled. Otherwise,
RXINACT will be at a logic LOW. This circuit is
duplicated for each of the other receivers.
The second stage of the AUTO ON-LINE®
circuitry, shown in Figure 18, processes all the
receiver's RXINACT signals with an accumulated
delay that disables the device to a 1µA supply
current. The STATUS pin goes to a logic LOW
when the cable is disconnected, the external
transmitters are disabled, or the SHUTDOWN
pin is invoked. The typical accumulated delay is
around20µs.WhentheSP3238Edriversorinter-
nal charge pump are disabled, the supply current
is reduced to 1µA. This can commonly occur in
handheld or portable applications where
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SP3238E_100_020111
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S
H
U
T
+2.7V
0V
RECEIVER
RS-232 INPUT
VOLTAGES
D
O
W
N
-2.7V
VCC
STATUS
0V
t
STSL
tSTSH
t
ONLINE
+5V
DRIVER
RS-232 OUTPUT
VOLTAGES
0V
-5V
Figure 16. AUTO ON-LINE® Timing Waveforms
R INACT
X
Inactive Detection Block
RS-232
Receiver Block
R OUT
X
R IN
X
Figure 17. Stage I of AUTO ON-LINE® Circuitry
Delay
Stage
Delay
Stage
Delay
Stage
Delay
Stage
Delay
Stage
STATUS
R1INACT
R4INACT
R5INACT
R2INACT
R3INACT
SHUTDOWN
Figure 18. Stage II of AUTO ON-LINE® Circuitry
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SP3238E_100_020111
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SHUTDOWN ONLINE
RS-232 SIGNAL AT
RECEIVER INPUT
STATUS
OUTPUT
TRANSCEIVER
STATUS
TXOUT RXOUT R1OUT
INPUT
INPUT
Normal
HIGH
-
YES
NO
HIGH
LOW
LOW
Active
Active
Active
Active
Active
Active
Active
Operation
Normal
Operation
HIGH
HIGH
HIGH
LOW
Shutdown
(Auto-Online)
NO (>100µs)
High-Z Active
LOW
LOW
-
-
YES
NO
HIGH
LOW
High-Z High-Z
High-Z High-Z
Active
Active
Shutdown
Shutdown
Table 2. AUTO ON-LINE® Logic
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SP3238E_100_020111
14
most of the ESD current when the ESD source
is applied to the connector pins. The test circuit
for IEC61000-4-2 is shown on Figure 20. There
are two methods within IEC61000-4-2, the Air
Discharge method and the Contact Discharge
method.
ESD TOLERANCE
The SP3238E device incorporates ruggedized
ESD cells on all driver output and receiver input
pins. The ESD structure is improved over our
previous family for more rugged applications
and environments sensitive to electro-static dis-
chargesandassociatedtransients.Theimproved
ESD tolerance is at least +15kV without damage
nor latch-up.
With the Air Discharge Method, an ESD voltage
is applied to the equipment under test (EUT)
throughair. Thissimulatesanelectricallycharged
person ready to connect a cable onto the rear of
the system only to find an unpleasant zap just
before the person touches the back panel. The
high energy potential on the person discharges
through an arcing path to the rear panel of the
system before he or she even touches the sys-
tem. This energy, whether discharged directly
or through air, is predominantly a function of
the discharge current rather than the discharge
voltage. Variables with an air discharge such as
approach speed of the object carrying the ESD
potential to the system and humidity will tend to
change the discharge current. For example, the
rise time of the discharge current varies with the
approach speed.
There are different methods of ESD testing ap-
plied:
a) MIL-STD-883, Method 3015.7
b) IEC61000-4-2 Air-Discharge
c) IEC61000-4-2 Direct Contact
The Human Body Model has been the generally
accepted ESD testing method for semi-con-
ductors. This method is also specified in
MIL-STD-883, Method 3015.7 for ESD testing.
The premise of this ESD test is to simulate the
human body’s potential to store electro-static
energy and discharge it to an integrated circuit.
The simulation is performed by using a test
model as shown in Figure 19. This method
will test the IC’s capability to withstand an ESD
transient during normal handling such as in
manufacturing areas where the IC's tend to be
handled frequently.
The Contact Discharge Method applies the ESD
current directly to the EUT. This method was
devised to reduce the unpredictability of the ESD
arc. The discharge current rise time is constant
sincetheenergyisdirectlytransferredwithoutthe
air-gap arc. In situations such as hand held sys-
tems, the ESD charge can be directly discharged
to the equipment from a person already holding
the equipment. The current is transferred on to
the keypad or the serial port of the equipment
directly and then travels through the PCB and
finally to the IC.
The IEC-61000-4-2, formerly IEC801-2, is gen-
erally used for testing ESD on equipment and
systems. For system manufacturers, they must
guarantee a certain amount of ESD protection
since the system itself is exposed to the outside
environment and human presence. The premise
with IEC61000-4-2 is that the system is required
to withstand an amount of static electricity when
ESD is applied to points and surfaces of the
equipment that are accessible to personnel dur-
ing normal usage. The transceiver IC receives
R
S
R
C
SW1
SW2
Device
C
DC Power
Source
S
Under
Test
Figure 19. ESD Test Circuit for Human Body Model
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SP3238E_100_020111
15
Contact-Discharge Model
R
R
R
V
C
S
SW1
SW2
Device
Under
Test
C
DC Power
Source
S
and
add up to 330Ω for IEC61000-4-2.
R
V
R
S
Figure 20. ESD Test Circuit for IEC61000-4-2
ThecircuitmodelsinFigures19and20represent
the typical ESD testing circuit used for all three
methods. The CS is initially charged with the DC
power supply when the first switch (SW1) is on.
Now that the capacitor is charged, the second
switch (SW2) is on while SW1 switches off. The
voltage stored in the capacitor is then applied
through RS, the current limiting resistor, onto the
device under test (DUT). In ESD tests, the SW2
switch is pulsed so that the device under test
receives a duration of voltage.
30A
15A
0A
t = 0ns
t = 30ns
For the Human Body Model, the current limiting
resistor (RS) and the source capacitor (CS) are
1.5kΩan100pF,respectively. ForIEC-61000-4-2,
thecurrentlimitingresistor(RS)andthesourceca-
pacitor (CS) are 330Ω an 150pF, respectively.
t →
Figure 21. ESD Test Waveform for IEC61000-4-2
The higher CS value and lower RS value in the
IEC61000-4-2 model are more stringent than the
Human Body Model. The larger storage capaci-
tor injects a higher voltage to the test point when
SW2 is switched on. The lower current limiting
resistor increases the current charge onto the
test point.
DEVICE PIN
TESTED
HUMAN BODY
MODEL
IEC61000-4-2
Air Discharge Direct Contact
Level
Driver Outputs
Receiver Inputs
+15kV
+15kV
+15kV
+15kV
+8kV
+8kV
4
4
Table 3. Transceiver ESD Tolerance Levels
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SP3238E_100_020111
16
PACKAGE: 28 PIN SSOP
e
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SP3238E_100_020111
17
PACKAGE: 28 PIN TSSOP
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SP3238E_100_020111
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ORDERING INFORMATION
Part Number
Temp. Range
0C to +70C
0C to +70C
0C to +70C
0C to +70C
-40C to +85C
-40C to +85C
-40C to +85C
-40C to +85C
Package
SP3238ECA-L
SP3238ECA-L/TR
SP3238ECY-L
28 Pin SSOP
28 Pin SSOP
28 Pin TSSOP
28 Pin TSSOP
28 Pin SSOP
28 Pin SSOP
28 Pin TSSOP
28 Pin TSSOP
SP3238ECY-L/TR
SP3238EEA-L
SP3238EEA-L/TR
SP3238EEY-L
SP3238EEY-L/TR
For Tape and Reel option add "/TR", Example: SP3238ECA-L/TR.
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SP3238E_100_020111
19
REVISION HISTORY
DATE
REVISION DESCRIPTION
03/04/05
02/01/11
--
Legacy Sipex Datasheet
1.0.0
Convert to Exar Format, Update ordering information and
change ESD specification to IEC61000-4-2
Notice
EXAR Corporation reserves the right to make changes to any products contained in this publication in order to improve design, performance or reli-
ability. EXAR Corporation assumes no representation that the circuits are free of patent infringement. Charts and schedules contained herein are
only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully
checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can
reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for
use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been
minimized ; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Copyright 2011 EXAR Corporation
Datasheet February 2011
For technical support please email Exar's Serial Technical Support group at : serialtechsupport@exar.com
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
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SP3238E_100_020111
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