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SP3238EEA-L
Specification
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Datasheet SP3238EEA-L Specification

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Page 1
SP3238E
T4IN
1
2
3
4
25
26
27
28
5
6
7
24
23
22
SHUTDOWN
C2-
V-
R1IN
R2IN
IN
ONLINE
C2+
C1-
GND
V
CC
V+
T1IN
8
9
10
11
18
19
20
21
12
13
14
17
16
15
T OUT
T2OUT
T3OUT
T3IN
T2IN
T5IN
R3OUT
R2OUT
R1OUT
R1OUT
SP3238E
C1+
T4OUT
T5OUT
STATUS
1
3
R
Intelligent +3.0V to +5.5V RS-232 Transceiver
FEATURES
■ 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
■ 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
■ Enhanced ESD Specications:
+15kV Human Body Model +15kV IEC61000-4-2 Air Discharge +8kV IEC61000-4-2 Contact Discharge
Now Available in Lead Free Packaging
The SP3238E device is an RS-232 transceiver solution intended for portable or hand-held applications
DESCRIPTION
such as notebook and palmtop computers. The SP3238E uses an internal high-efciency, 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.
Device Power
SP3220E +3.0V to +5.5V 1 1 4 Capacitors No Yes 16
SP3223E +3.0V to +5.5V 2 2 4 Capacitors Yes Yes 20
SP3243E +3.0V to +5.5V 3 5 4 Capacitors Yes Yes 28
SP3238E +3.0V to +5.5V 5 3 4 Capacitors Yes Yes 28
Supplies
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3238E_100_020111
RS-232
Drivers
RS-232
Receivers
External
Components
1
Auto
On-Line
Circuitry
SELECTION TABLE
TTL 3-State # of
Pins
Page 2
ABSOLUTE MAXIMUM RATINGS
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 specications
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.
VCC.......................................................-0.3V to +6.0V
V+ (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.
Power Dissipation per package
28-pin SSOP (derate 11.2mW/oC above +70oC)..........900mW
28-pin TSSOP (derate 13.2mW/oC above +70oC)......1100mW
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%), T
values are at TA = 25oC
AMB
= T
MIN
to T
, unless otherwise noted. Typical
MAX
PARAMETER MIN. TYP. MAX. UNITS CONDITIONS
DC CHARACTERISTICS
Supply Current, AUTO ON­LINE®
1.0 10 µA All RxIN open, ONLINE = GND, SHUTDOWN = VCC, TxIN = GND or V
CC
Supply Current, Shutdown 1.0 10 µA SHUTDOWN = GND, TxIN = Vcc or
GND
Supply Current AUTO ON-LINE® Disabled
0.3 1.0 mA ONLINE = SHUTDOWN = Vcc, no load, TxIN = GND or V
CC
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold LOW HIGH 2.4
0.8 V
VCC = +3.3V or +5.0V, TxIN
ONLINE, SHUTDOWN
V
Input Leakage Current +0.01 +1.0 µA TxIN, ONLINE, SHUTDOWN,
T
= +25oC
AMB
Output Leakage Current +0.05 +10 µA Receivers disabled
Output Voltage LOW 0.4 V I
Output Voltage HIGH VCC -0.6 VCC -0.1 V I
= 1.6mA
OUT
= -1.0mA
OUT
DRIVER OUTPUTS
Output Voltage Swing +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
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Page 3
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%), T
values are at TA = 25oC
ELECTRICAL CHARACTERISTICS
= T
to T
AMB
MIN
, unless otherwise noted. Typical
MAX
PARAMETER MIN. TYP. MAX. UNITS CONDITIONS
DRIVER OUTPUTS (continued)
Output Resistance 300 Ω VCC = V+ = V- = 0V, V
Output Short-Circuit Current +35 +60 mA V
OUT
= 0V
OUT
=+2V
RECEIVER INPUTS
Input Voltage Range -25 25 V
Input Threshold LOW 0.6 1.2 V Vcc = 3.3V
Input Threshold LOW 0.8 1.5 V Vcc = 5.0V
Input Threshold HIGH 1.5 2.4 V Vcc = 3.3V
Input Threshold HIGH 1.8 2.4 V Vcc = 5.0V
Input Hysteresis 0.5 V
Input Resistance 3 5 7 kΩ
AUTO ON-LINE® CIRCUITRY CHARACTERISTICS (ONLINE = GND, SHUTDOWN = VCC)
STATUS Output Voltage LOW 0.4 V I
STATUS Output Voltage HIGH V
Receiver Threshold to Drivers Enabled (t
ONLINE
)
Receiver Positive or Negative
Threshold to STATUS HIGH (t
STSH
)
Receiver Positive or Negative
Threshold to STATUS LOW (t
STSL
)
-0.6 V I
CC
200 µs Figure 10
0.5 µs Figure 10
20 µs Figure 10
= 1.6mA
OUT
= -1.0mA
OUT
TIMING CHARACTERISTICS
Maximum Data Rate 250 kbps RL = 3KΩ, CL = 1000pF, one
driver switching
Receiver Propagation Delay
t t
PHL
PLH
0.15
0.15
µs Receiver input to Receiver out-
put, CL = 150pF
Receiver Output Enable Time 200 ns Normal operation
Receiver Output Disable Time 200 ns Normal operation
Driver Skew 100 ns | t
Receiver Skew 50 ns | t
Transition-Region Slew Rate 30 V/µs Vcc = 3.3V, RL = 3kΩ, T
- t
|, T
PHL
PLH
- t
PHL
PLH
25°C, measurements taken from
= 25°C
AMB
|
AMB
-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
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-6
-4
-2
0
2
4
6
0 100 0 200 0 300 0 400 0 500 0
pF
V ol t
V OH
V OL
TYPICAL PERFORMANCE CHARACTERISTICS
0
5
10
15
20
25
0 1 000 2 000 300 0 4 000 500 0
pF
V /uS
P OS . S R
NE G SR
0
10
20
30
40
50
60
0 1 0 00 20 0 0 30 00 4 00 0 50 00
pF
m A
25 0K b ps
12 0K b ps
20 K bp s
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 T
= +25°C.
AMB
Figure 1. Transmitter Output Voltage VS. Load
Capacitance
Figure 3. Supply Current VS. Load Capacitance when Transmitting Data
Figure 2. Slew Rate VS. Load Capacitance
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3238E_100_020111
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NAME FUNCTION PIN NUMBER
C2+ Positive terminal of the symmetrical charge-pump capacitor C2. 1
GND Ground. 2
C2- Negative terminal of the symmetrical charge-pump capacitor C2. 3
V- Regulated -5.5V output generated by the charge pump. 4
T1OUT RS-232 Driver Output. 5
T2OUT RS-232 Driver Output. 6
T3OUT RS-232 Driver Output. 7
R1IN RS-232 receiver input. 8
R2IN RS-232 receiver input. 9
T4OUT RS-232 Driver Output. 10
R3IN RS-232 receiver input. 11
T5OUT RS-232 Driver Output. 12
ONLINE 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.
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 Non-Inverting receiver - 1 output, active in shutdown. 16
T5IN TTL/CMOS driver input. 17
R3OUT TTL/CMOS receiver output. 18
T4IN TTL/CMOS driver input. 19
R2OUT TTL/CMOS receiver output. 20
R1OUT TTL/CMOS receiver output. 21
T3IN TTL/CMOS driver input. 22
T2IN TTL/CMOS driver input. 23
T1IN TTL/CMOS driver input. 24
C1- Negative terminal of the symmetrical charge-pump capacitor C1. 25
Vcc +3.0V to +5.5V supply voltage. 26
V+ Regulated +5.5V output generated by the charge pump. 27
C1+ Positive terminal of the symmetrical charge-pump capacitor C1. 28
13
14
15
Table 1. Device Pin Description
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3238E_100_020111
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SP3238E
28
25
3
1
27
4
26
GND
C1+
C1-
C2+
C2-
V+
V-
V
CC
0.1µF
+
C2
C5
C1
+
+
C3
C4
+
+
To µP Supervisor
Circuit
13
14
15
V
CC
V
CC
2
ONLINE
SHUTDOWN
STATUS
5kΩ
16
21
20
18
8
9
11
RS-232 INPUTS
TTL/CMOS
OUTPUTS
R1OUT
R1IN
R1OUT
R2IN
R3IN
R2OUT
R3OUT
24
23
22
5
6
7
RS-232 OUTPUTS
TTL/CMOS
INPUTS
T1IN
T2OUT
T2IN
T3IN
T3OUT
T1OUT
19
17
10
12
T4OUT
T4IN
T5IN
T5OUT
0.1µF
0.1µF
0.1µF
0.1µF
5kΩ
5kΩ
T4IN
1
2
3
4
25
26
27
28
5
6
7
24
23
22
SHUTDOWN
C2-
V-
R1IN
R2IN
IN
ONLINE
C2+
C1-
GND
V
CC
V+
T1IN
8
9
10
11
18
19
20
21
12
13
14
17
16
15
T OUT
T2OUT
T3OUT
T3IN
T2IN
T5IN
R3OUT
R2OUT
R1OUT
R1OUT
SP3238E
C1+
T4OUT
T5OUT
STATUS
1
3
R
Figure 4. SP3238E Pinout Conguration
Figure 5. SP3238E Typical Operating Circuit
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3238E_100_020111
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DESCRIPTION
SP3238E
28
25
3
1
27
4
26
GND
C1+
C1-
C2+
C2-
V+
V-
V
CC
0.1µF
+
C2
C5
C1
+
+
C3
C4
+
+
13
14
15
V
CC
2
ONLINE
SHUTDOWN
STATUS
µP
Supervisor
IC
V
CC
V
IN
RESET
5kΩ
5kΩ
5kΩ
24
23
22
16
21
20
18
5
6
7
8
9
11
RS-232 OUTPUTS
RS-232 INPUTS
T1IN
R1OUT
R1IN
T2OUT
R1OUT
T2IN
T3IN
T3OUT
T1OUT
R2IN
R3IN
R2OUT
R3OUT
UART
or
Serial µC
TxD
RTS
DTR
RxD
CTS
DSR
DCD
RI
19
17
10
12
T4OUT
T4IN
T5IN
T5OUT
0.1µF
0.1µF
0.1µF
0.1µF
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 cir­cuitry that generates ±5.5V RS-232 voltage levels from a single +3.0V to +5.5V power supply. The
SP3238E devices can guarantee a data rate of
250kbps fully loaded.
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.
The SP3238E device is an ideal choice for power sensitive designs. The SP3238E device features
AUTO ON-LINE® circuitry which reduces the
power supply drain to a 1µA supply current.
In many portable or hand-held applications, an
RS-232 cable can be disconnected or a connected peripheral can be turned off. Under these condi­tions, the internal charge pump and the drivers will
be shut down. Otherwise, the system automati­cally comes online. This feature allows design
engineers to address power saving concerns without major design changes.
THEORY OF OPERATION
The SP3238E device is made up of four basic
circuit blocks:
1. Drivers
2. Receivers
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 +5V minimum fully loaded. The driver outputs are protected against innite short-circuits to ground without degradation in reliability. These drivers comply with the EIA-TIA-232-F and all previous
RS-232 versions.
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
The drivers can guarantee a data rate of 250kbps
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.
The slew rate of the driver output is internally limited to a maximum of 30V/µs in order to meet the EIA standards (EIA RS-232D 2.1.7, Paragraph
5). The transition of the loaded output from HIGH to LOW also meets the monotonicity requirements
of the standard.
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 ve 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 ve drivers loaded with an RS-232 receiver in parallel with a 1000pF ca­pacitor. A solid RS-232 data transmission rate
of 120kbps provides compatibility with many
designs in personal computer peripherals and LAN applications.
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SP3238E
TxIN
TxOUT
C1+
C1-
C2+
C2-
V+
V-
V
CC
0.1µF
+
C2
C5
C1
+
+
C3
C4
+
+
LOGIC
INPUTS
V
CC
5kΩ
RxIN
RxOUT
LOGIC
OUTPUTS
SHUTDOWN
GND
V
CC
ONLINE
1000pF
0.1µF
0.1µF
0.1µF
0.1µF
Figure 7. Loopback Test Circuit for RS-232 Driver Data Transmission Rates
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
Receivers
The receivers convert +5.0V EIA/TIA-232 levels to TTL or CMOS logic output levels. Re­ceivers are High-Z when the AUTO ON-LINE® circuitry is enabled or when in shutdown.
The SP3238E includes an additional non-in­verting 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.
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, an internal 5kΩ 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 (VCC) over the +3.0V to +5.5V
range. This is important to maintain compli-
ant RS-232 levels regardless of power supply uctuations.
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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 1
— VSS charge storage — During this phase of the clock cycle, the positive side of capacitors C1 and
C2 are initially charged to VCC. C
to GND and the charge in C
Since C
+
is connected to VCC, the voltage potential
2
+
is then switched
l
–
is transferred to C
1
–
2
across capacitor C2 is now 2 times VCC.
Phase 2
— VSS transfer — Phase two of the clock
connects the negative terminal of C2 to the V
SS
storage capacitor and the positive terminal of C2 to GND. This transfers a negative gener­ated voltage to C3. This generated voltage is regulated to a minimum voltage of -5.5V. Simultaneous with the transfer of the voltage to C3, the positive side of capacitor C1 is switched to VCC
and the negative side is connected to GND.
Phase 3
— VDD charge storage — The third phase of the clock is identical to the rst 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 C
+
is at VCC, the volt-
2
age potential across C2 is 2 times VCC.
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. Simultane­ous 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, al­lowing 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.
Since both V+ and V– are separately generated from VCC, in a no–load condition V+ and V– will be symmetrical. Older charge pump approaches that generate V– from V+ will show a decrease in the magnitude of V– compared to V+ due to the inherent inefciencies in the design.
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.
Figure 10. Charge Pump Waveform
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VCC = +5V
VSS Storage Capacitor
VDD Storage Capacito
r
C
1
C
2
C
3
C
4
+
+
+ +
–
–
––
-5.5V
VCC = +5V
–5V –5V
+5V
VSS Storage Capacitor
VDD Storage Capacitor
C
1
C
2
C
3
C
4
+
+
+ +
–
–
––
Figure 11. Charge Pump — Phase 1
VCC = +5V
–5V –5V
+5V
VSS Storage Capacitor
VDD Storage Capacitor
C
1
C
2
C
3
C
4
+
+
+ +
–
–
––
VCC = +5V
VSS Storage Capacitor
VDD Storage Capacito
r
C
1
C
2
C
3
C
4
+
+
+ +
–
–
––
+5.5V
Figure 12. Charge Pump — Phase 2
Figure 13. Charge Pump — Phase 3
Figure 14. Charge Pump — Phase 4
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6. DCE Ready
7. Request to Send
8. Clear to Send
9. Ring Indicator
DB-9 Connector Pins:
1. Received Line Signal Detector
2. Received Data
3. Transmitted Data
4. Data Terminal Ready
5. Signal Ground (Common)
6 7 8 9
1 2 3 4 5
DB-9
Connector
26
V
CC
0.1µF
C5
+
V
CC
GND
2
To µPSupervisor
Circuit
8
9
11
5kΩ
5kΩ
5kΩ
16
21
20
18
5
6
7
R1OUT
R1IN
R1OUT
R2IN
R3IN
R2OUT
R3OUT
10
12
24
23
22
T1IN
T2OUT
T2IN
T3IN
T3OUT
T1OUT
19
17
T4OUT
T4IN
T5IN
T5OUT
SP3238E
28
25
3
1
27
4
C3
C4
+
+
C1+
C1-
C2+
C2-
V+
V-
+
C2
C1
+
13
14
15
V
CC
ONLINE
SHUTDOWN
STATUS
0.1µF
0.1µF
0.1µF
0.1µF
Figure 15. Circuit for the connectivity of the SP3238E with a DB-9 connector
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3238E_100_020111
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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 SP3238E device incorporates an AUTO ON-LINE® circuit that automatically enables itself
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 AUTO ON-LINE® circuit has two stages:
1) Inactive Detection
2) Accumulated Delay
The rst 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 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 STATUS pin outputs a logic LOW signal if
the device is shutdown. This pin goes to a logic
HIGH when the external transmitters are enabled
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 Indica­tor signal. Tying ONLINE and SHUTDOWN together will bypass the AUTO ON-LINE® cir­cuitry so this connection acts like a shutdown
input pin
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 around 20µs. When the SP3238E drivers or inter­nal 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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Figure 16. AUTO ON-LINE® Timing Waveforms
RECEIVER
RS-232 INPUT
VOLTAGES
STATUS
+5V
0V
-5V
t
STSL
t
STSH
t
ONLINE
V
CC
0V
DRIVER
RS-232 OUTPUT
VOLTAGES
0V
+2.7V
-2.7V
S H U
T
D O W N
RS-232
Receiver Block
RXINACT
Inactive Detection Block
RXIN
RXOUT
R1INACT
R2INACT
R3INACT
R4INACT
R5INACT
Delay Stage
Delay Stage
Delay Stage
Delay Stage
Delay Stage
SHUTDOWN
STATUS
Figure 17. Stage I of AUTO ON-LINE® Circuitry
Figure 18. Stage II of AUTO ON-LINE® Circuitry
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NWODTUHS
TUPNI TUPNI
TUPNI
TUPNI TUPNI
ENILNO
TUPNI TUPNI
TUPNI
TUPNI TUPNI
TALANGIS232-SR
TUPNIREVIECER TUPNIREVIECER
TUPNIREVIECER
TUPNIREVIECER TUPNIREVIECER
SUTATS
TUPTUO TUPTUO
TUPTUO
TUPTUO TUPTUO
TXTUO RXTUO R1TUO
REVIECSNART
SUTATS SUTATS
SUTATS
SUTATS SUTATS
HGIH - SEY HGIH evitcA evitcA evitcA
lamroN
noitarepO
HGIH HGIH ON WOL evitcA evitcA evitcA
lamroN
noitarepO
HGIH WOL 001>(ON µ )s WLO High-Z Active veitcA
nwodtuhS
( enilnO-otuA )
WOL - SEY HGIH Z-hgiH Z-hgiH evitcA nwodtuhS
WOL - ON WOL Z-hgiH Z-hgiH evitcA nwodtuhS
Table 2. AUTO ON-LINE® Logic
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ESD TOLERANCE
R
C
Device Under
Test
DC Power
Source
C
S
R
S
SW1
SW2
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 dis­charges and associated transients. The improved
ESD tolerance is at least +15kV without damage
nor latch-up.
There are different methods of ESD testing ap­plied:
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 IEC-61000-4-2, formerly IEC801-2, is gen­erally 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 dur­ing normal usage. The transceiver IC receives
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.
With the Air Discharge Method, an ESD voltage is applied to the equipment under test (EUT) through air. This simulates an electrically charged person ready to connect a cable onto the rear of the system only to nd 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 sys­tem. 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.
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
since the energy is directly transferred without the air-gap arc. In situations such as hand held sys­tems, 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 nally to the IC.
Figure 19. ESD Test Circuit for Human Body Model
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Figure 20. ESD Test Circuit for IEC61000-4-2
R
S
and
R
V
add up to 330Ω for IEC61000-4-2.
R
C
Device Under
Test
DC Power
Source
C
S
R
S
SW1
SW2
R
V
Contact-Discharge Model
t = 0ns t = 30ns
0A
15A
30A
I →
t →
The circuit models in Figures 19 and 20 represent
the typical ESD testing circuit used for all three
methods. The CS is initially charged with the DC
power supply when the rst 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.
For the Human Body Model, the current limiting resistor (RS) and the source capacitor (CS) are
1.5kΩ an 100pF, respectively. For IEC-61000-4-2, the current limiting resistor (RS) and the source ca­pacitor (CS) are 330Ω an 150pF, respectively.
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.
Figure 21. ESD Test Waveform for IEC61000-4-2
DEVICE PIN HUMAN BODY IEC61000-4-2 TESTED MODEL Air Discharge Direct Contact Level
Driver Outputs +15kV +15kV +8kV 4 Receiver Inputs +15kV +15kV +8kV 4
Table 3. Transceiver ESD Tolerance Levels
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PACKAGE: 28 PIN SSOP
▲
▲
e
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PACKAGE: 28 PIN TSSOP
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ORDERING INFORMATION
Part Number Temp. Range Package
SP3238ECA-L 0C to +70C 28 Pin SSOP
SP3238ECA-L/TR 0C to +70C 28 Pin SSOP
SP3238ECY-L 0C to +70C 28 Pin TSSOP
SP3238ECY-L/TR 0C to +70C 28 Pin TSSOP
SP3238EEA-L -40C to +85C 28 Pin SSOP
SP3238EEA-L/TR -40C to +85C 28 Pin SSOP
SP3238EEY-L -40C to +85C 28 Pin TSSOP
SP3238EEY-L/TR -40C to +85C 28 Pin TSSOP
For Tape and Reel option add "/TR", Example: SP3238ECA-L/TR.
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REVISION HISTORY
DATE REVISION DESCRIPTION
03/04/05 -- Legacy Sipex Datasheet
02/01/11 1.0.0 Convert to Exar Format, Update ordering information and
change ESD specication 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 reli­ability. 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 specic 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 signicantly 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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