LTC1387IG [Linear]
Single 5V RS232/RS485 Multiprotocol Transceiver; 单5V RS232 / RS485多协议收发器
| 型号： | LTC1387IG |
| 厂家： | 
Linear |
| 描述： | Single 5V RS232/RS485 Multiprotocol Transceiver |
| 文件： | 总12页 (文件大小：171K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC1387
Sing le 5V RS232/ RS485
Multip ro to c o l Tra nsc e ive r
U
DESCRIPTIO
EATURE
S
F
The LTC®1387 is a low power reconfigurable CMOS bidi-
rectional transceiver. It can be configured as an RS485
differential port or as two RS232 single-ended ports. An
onboard charge pump uses four 0.1µF capacitors to
generate boosted positive and negative supplies, allowing
the RS232 drivers to meet ±5V output swing require-
ments with only a single 5V supply. A shutdown mode
reduces the ICC supply current to 5µA.
■
■
■
Two RS232 Transceivers or One RS485 Transceiver
Operates from a Single 5V Supply
Guaranteed Receiver Output with Inputs
Floating or Shorted to Ground
Logic Selectable Fast/Slow RS485 Driver Slew Rate
Low Supply Current: 7mA Typical
5µA Supply Current in Shutdown
Self-Testing Capability in Loopback Mode
Separate Driver and Receiver Enable Controls
Driver Maintains High Impedance in Three-State,
Shutdown or with Power Off
■
■
■
■
■
■
The RS232 transceivers are in full compliance with RS232
specification. The RS485 transceiver is in full compliance
with RS485 and RS422 specifications. The RS485 re-
ceiver assumes a known output state when the inputs are
floating or shorted to ground. All interface drivers feature
short-circuit and thermal shutdown protection. An enable
pin allows RS485 driver outputs to be forced into high
impedancewhichis maintainedevenwhentheoutputs are
forced beyond supply rails or the power is off. A loop back
modeallows thedriveroutputs tobeconnectedbacktothe
receiver inputs for diagnostic self-test.
■
Receiver Inputs Can Withstand ±25V
U
APPLICATIONS
■
Point-of-Sale Terminals
Software Selectable Multiprotocol Interface Ports
Low Power RS485/RS422/RS232/EIA562 Interface
Cable Repeaters
■
■
■
■
Level Translators
The LTC1387 is available in 20-pin plastic SSOP and SW
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
O
TYPICAL APPLICATI
19
20
1
2
2
1
20
19
3
3
LTC1387
LTC1387
18
V
5V
CC2
18
V
CC1
5V
4
4
5
17
15
17
RS485 INTERFACE
5
RECOUT
DR IN
RECOUT
120Ω
120Ω
4000-FT 24-GAUGE TWISTED PAIR
6
7
6
7
15
14
DR IN
SLEW
14
9
SLEW
8
9
12
11
8
DR ENABLE
5V
5V
DR ENABLE
5V
5V
5V
13
12
11
13
5V
10
10
ALL CAPACITORS: 0.1µF MONOLITHIC CERAMIC TYPE
LTC1387 • TA01
1
LTC 1387
W W W
U
/O
ABSOLUTE AXI U RATI GS
PACKAGE RDER I FOR ATIO
(Note 1)
ORDER PART
Supply Voltage (V ) ............................................. 6.5V
Input Voltage
TOP VIEW
CC
NUMBER
+
+
C1
C1
V
1
2
3
4
5
6
7
8
9
20 C2
19 C2
–
–
Drivers ................................... –0.3V to (V + 0.3V)
CC
Receivers ............................................. –25V to 25V
485/232, ON, DXEN
18
17
16
15
V
CC
LTC1387CG
LTC1387CSW
LTC1387IG
DD
A
R
A
B
Y
R
RXEN, SLEW ........................... –0.3V to (V + 0.3V)
B
CC
D
Y
LTC1387ISW
Output Voltage
Z
14 D /SLEW
Z
Drivers ................................................. –18V to 18V
485/232
DXEN
13 ON
Receivers ............................... –0.3V to (V + 0.3V)
CC
12 RXEN
Short-Circuit Duration
GND 10
11
V
EE
Output ........................................................ Indefinite
V , V , C1+, C1–, C2+, C2–.......................... 30 sec
G PACKAGE
SW PACKAGE
DD EE
20-LEAD PLASTIC SSOP
20-LEAD PLASTIC SO
Operating Temperature Range
LTC1387C .............................................. 0°C to 70°C
LTC1387I ........................................... –40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................ 300°C
T
JMAX = 125°C, θJA = 120°C/W (G)
TJMAX = 125°C, θJA = 75°C/W (SW)
Consult factory for Military grade parts.
DC ELECTRICAL CHARACTERISTICS
TA = 25°C, VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3), unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
RS485 Driver (485/232 = High, ON = DXEN = High)
V
Differential Driver Output Voltage (Unloaded)
Differential Driver Output Voltage (With Load)
I = 0
●
6
V
OD1
O
V
OD2
Figure 1, R = 50Ω (RS422)
Figure 1, R = 27Ω (RS485)
●
●
2.0
1.5
6
6
V
V
∆V
OD
Change in Magnitude of Driver Differential
Figure 1, R = 27Ω or R = 50Ω
●
0.2
V
Output Voltage for Complementary Output States
V
Driver Common Mode Output Voltage
Figure 1, R = 27Ω or R = 50Ω
Figure 1, R = 27Ω or R = 50Ω
●
●
3
V
V
OC
∆ V
Change in Magnitude of Driver Common Mode
Output Voltage for Complementary Output States
0.2
OC
I
Driver Short-Circuit Current
V = –7V, 12V; V = High
●
●
35
10
250
250
mA
mA
OSD
O
O
V = –7V, 12V; V = Low (Note 4)
O
O
I
Three-State Output Current (Y, Z)
–7V ≤ V ≤ 12V
±5
500
µA
OZD
O
RS232 Driver (485/232 = Low, ON = DXEN = High)
V
O
Output Voltage Swing
Figure 4, R = 3k, Positive
●
●
5
–5
6.5
–6.5
V
V
L
Figure 4, R = 3k, Negative
L
I
Output Short-Circuit Current
V = 0V
O
●
±17
±60
mA
OSD
Driver Inputs and Control Inputs
V
Input High Voltage
Input Low Voltage
Input Current
D , D , DXEN, RXEN, ON, 485/232, SLEW
●
●
2
V
V
Y
Z
IH
V
IL
D , D , DXEN, RXEN, ON, 485/232, SLEW
0.8
Y
Z
I
IN
D , D , DXEN, RXEN, ON, 485/232
●
●
±0.1
5
±10
15
µA
µA
Y
Z
SLEW (Note 5)
2
LTC1387
DC ELECTRICAL CHARACTERISTICS
TA = 25°C, VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3), unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
0.20
1
UNITS
RS485 Receiver (485/232 = High, ON = RXEN = High)
V
Differential Input Threshold Voltage
Input Hysteresis
–7V ≤ V ≤ 12V
●
–0.20
V
TH
CM
∆V
V
CM
= 0V
40
24
mV
TH
I
IN
Input Current (A, B)
V
V
IN
= 12V
= –7V
●
●
mA
mA
IN
–0.8
12
R
IN
Input Resistance
–7V ≤ V ≤ 12V
●
kΩ
IN
RS232 Receiver (485/232 = Low, ON = RXEN = High)
V
Receiver Input Voltage Threshold
Input Low Threshold
Input High Threshold
●
●
0.8
V
V
TH
2.4
7
∆V
Receiver Input Hysteresis
Receiver Input Resistance
0.6
5
V
TH
R
IN
V
IN
= ±10V
3
3.5
7
kΩ
Receiver Output (ON = RXEN = High)
V
OH
Receiver Output High Voltage
Receiver Output Low Voltage
Short-Circuit Current
I = –3mA, V = 0V, 485/232 = Low
●
●
●
●
4.6
0.2
V
V
O
IN
V
OL
I = 3mA, V = 3V, 485/232 = Low
0.4
85
O
IN
I
0V ≤ V ≤ V
mA
µA
OSR
O
CC
I
Three-State Output Current
RXEN = 0V
±0.1
±10
OZR
Power Supply Generator
V
V
Output Voltage
Output Voltage
EE
No Load, ON = DXEN = RXEN = High
8
7
V
V
DD
DD
I
DD
= –5mA, ON = DXEN = RXEN = High
V
EE
V
No Load, ON = DXEN = RXEN = High
= 5mA, ON = DXEN = RXEN = High
–7.7
–7.0
V
V
I
EE
Power Supply
I
CC
V
CC
Supply Current
No Load, ON = DXEN = RXEN = High
Shutdown, ON = DXEN = RXEN = 0V
●
●
7
5
25
100
mA
µA
AC ELECTRICAL CHARACTERISTICS
TA = 25°C, VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3), unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
RS232 Mode (ON = DXEN = RXEN = High, 485/232 = Low)
SR
Slew Rate
Figure 4, R = 3k, C = 15pF
●
●
30
V/µs
V/µs
L
L
Figure 4, R = 3k, C = 1000pF
4
L
L
t
t
t
t
t
Transition Time
Figure 4, R = 3k, C = 2500pF
●
●
●
●
●
0.22
1.9
0.6
0.6
0.3
0.4
3.1
4
µs
µs
µs
µs
µs
T
L
L
Driver Input to Output
Driver Input to Output
Receiver Input to Output
Receiver Input to Output
Figures 4, 10, R = 3k, C = 15pF
L L
PLH
PHL
PLH
PHL
Figures 4, 10, R = 3k, C = 15pF
4
L
L
Figures 5, 11
Figures 5, 11
6
6
RS485 Mode (Fast Slew Rate, ON = DXEN = High, 485/232 = High, SLEW = High)
t
t
t
Driver Input to Output
Driver Input to Output
Driver Output to Output
Driver Rise or Fall Time
Figures 2, 7, R = 54Ω, C = 100pF
●
●
●
●
15
15
40
40
5
70
70
15
40
ns
ns
ns
ns
PLH
PHL
L
L
Figures 2, 7, R = 54Ω, C = 100pF
L
L
Figures 2, 7, R = 54Ω, C = 100pF
SKEW
L
L
t , t
Figures 2, 7, R = 54Ω, C = 100pF
3
15
r
f
L
L
3
LTC 1387
AC ELECTRICAL CHARACTERISTICS
TA = 25°C, VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3), unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
RS485 Mode (Fast Slew Rate, ON = DXEN = High, 485/232 = High, SLEW = High)
t
t
t
t
Driver Enable to Output Low
Driver Enable to Output High
Driver Disable from Low
Driver Disable from High
Figures 3, 8, C = 100pF, S1 Closed
●
●
●
●
50
50
50
60
90
90
90
90
ns
ns
ns
ns
ZL
ZH
LZ
HZ
L
Figures 3, 8, C = 100pF, S2 Closed
L
Figures 3, 8, C = 15pF, S1 Closed
L
Figures 3, 8, C = 15pF, S2 Closed
L
RS485 Mode (Slow Slew Rate, ON = DXEN = High, 485/232 = High, SLEW = Low)
t
t
t
Driver Input to Output
Figures 2, 7, R = 54Ω, C = 100pF
●
●
●
●
●
●
●
●
100
100
700
700
200
300
600
600
100
100
1500
1500
750
ns
ns
ns
ns
ns
ns
ns
ns
PLH
L
L
Driver Input to Output
Figures 2, 7, R = 54Ω, C = 100pF
L L
PHL
Driver Output to Output
Driver Rise or Fall Time
Driver Enable to Output Low
Driver Enable to Output High
Driver Disable from Low
Driver Disable from High
Figures 2, 7, R = 54Ω, C = 100pF
L L
SKEW
t , t
Figures 2, 7, R = 54Ω, C = 100pF
150
1500
1500
1500
200
r
f
L
L
t
t
t
t
Figures 3, 8, C = 100pF, S1 Closed
L
ZL
ZH
LZ
HZ
Figures 3, 8, C = 100pF, S2 Closed
L
Figures 3, 8, C = 15pF, S1 Closed
L
Figures 3, 8, C = 15pF, S2 Closed
200
L
RS485 Mode (ON = RXEN = High, 485/232 = High)
t
t
t
Receiver Input to Output
Receiver Input to Output
Differential Receiver Skew,
Figures 2, 9, R = 54Ω, C = 100pF
●
●
20
20
70
70
10
140
140
ns
ns
ns
PLH
L
L
Figures 2, 9, R = 54Ω, C = 100pF
PHL
L
L
t
– t
PLH PHL
Figures 2, 9, R = 54Ω, C = 100pF
L L
SKEW
Receiver Output Enable/Disable (ON = High)
t
t
t
t
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable from Low
Receiver Disable from High
Figures 6, 12, C = 15pF, S1 Closed
●
●
●
●
40
40
40
40
90
90
90
90
ns
ns
ns
ns
ZL
ZH
LZ
HZ
L
Figures 6, 12, C = 15pF, S2 Closed
L
Figures 6, 12, C = 15pF, S1 Closed
L
Figures 6, 12, C = 15pF, S2 Closed
L
The
●
denotes specifications which apply over the full operating
Note 3: All typicals are given at V = 5V, C1 = C2 = C3 = C4 = 0.1µF
CC
temperature range.
and T = 25°C.
A
Note 1: Absolute Maximum Ratings are those values beyond which the life
Note 4: Short-circuit current for RS485 driver output low state folds back
of the device may be impaired.
above V . Peak current occurs around V = 3V.
CC O
Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to device ground unless
otherwise specified.
Note 5: SLEW includes an internal pull-up in RS485 mode.
U
U
U
PIN FUNCTIONS
C1+ (Pin 1): Commutating Capacitor C1 Positive Terminal.
Requires an external 0.1µF capacitor between Pins 1 and 2.
B (Pin 5): Receiver Input B. Inverting input of RS232
receiver B in RS232 mode; noninverting RS485 receiver
input in RS485 mode.
C1– (Pin 2): Commutating Capacitor C1 Negative Terminal.
Y(Pin6):DriverOutputY.InvertingRS232driverYoutput
in RS232 mode; inverting RS485 driver output in RS485
mode.
VDD (Pin 3): Charge Pump Positive Supply Output.
Requires an external 0.1µF capacitor to ground.
A (Pin 4): Receiver Input A. Inverting input of RS232
receiver A in RS232 mode; inverting RS485 receiver input
in RS485 mode.
Z (Pin 7):Driver Output Z. Inverting RS232 driver Z output
in RS232 mode; noninverting RS485 driver output in
RS485 mode.
4
LTC1387
U
U
U
PI FU CTIO S
485/232 (Pin 8): Interface Mode Select Input. A low logic
input enables two RS232 drivers and two RS232 receiv-
ers. A high input enables the RS485 driver and the RS485
receiver.
be configured for one-, two- or three-wire control: one-
wire mode – all three inputs connected together; two-wire
mode–inputs ONandRXENconnectedtoonewire, DXEN
a separate wire; three-wire mode – separate wires to each
input. See the Function Tables.
DXEN (Pin 9): Driver Enable Input. A high logic input
enables the drivers and a low logic input disables the
drivers. When disabled, all driver outputs are in high
impedance
DZ/SLEW (Pin 14): Driver Z or Slew Input. In RS232
mode, this pin is the driver Z input. In RS485 mode, this
pin controls the slew rate of the RS485 driver. With the
SLEW pin high, the RS485 driver runs at maximum (fast)
slew rate and can transmit signals up to 5MBd. With the
SLEW pin low, the RS485 driver runs with reduced (slow)
slewratetocontrolreflections withimproperlyterminated
cables. In slow mode, the RS485 driver can support data
rates up to 150kBd. This SLEW pin has internal 5µA pull-
up during RS485 mode.
GND (Pin 10): Ground.
V
EE
(Pin 11): Charge Pump Negative Supply Output.
Requires an external 0.1µF capacitor to ground.
RXEN (Pin 12): Receiver Enable Input. A high logic input
enables the receivers and a low logic input disables the
receivers. When disabled, all receiver outputs are in high
impedance.
DY (Pin 15): Driver Y Input. Input Y in RS232 mode; the
ON(Pin13):AhighlogiclevelatONinputkeeps thecharge
pump active regardless of the state of the DXEN and RXEN
inputs. When the charge pump is active, the drivers and
receivers can be enabled or disabled without waiting for
chargepumpstabilizationtime(typically100µs with0.1µF
capacitors). A low logic state at the ON, DXEN and RXEN
inputs will put the transceiver and charge pump in shut-
down mode and reduces ICC to 5µA. Whenever the trans-
ceiver is activated from shutdown, the charge pump
should be allowed to stabilize before data transmission.
When DXEN and RXEN are high and ON is low, the charge
pump, drivers and receivers are all active and the driver
outputs are internally looped back to the inputs of the
receiver.Thethreecontrolinputs ON,DXENandRXENcan
differential driver input in RS485 mode.
RB (Pin 16): Receiver B Output. Output B in RS232 mode;
output is high impedance in RS485 mode.
RA (Pin 17): Receiver A Output. Output A in RS232 mode;
the differential receiver output in RS485 mode.
V
CC
(Pin 18): Positive Supply. 4.75V ≤ V ≤ 5.25V.
CC
Requires an external 0.1µF bypass capacitor to ground.
C2– (Pin 19): Commutating Capacitor C2 Negative Termi-
nal. Requires an external 0.1µF capacitor between Pins 19
and 20.
C2+ (Pin 20): Commutating Capacitor C2 Positive
Terminal.
5
LTC 1387
U
U
FU CTIO TABLES
Select Modes
SELECT INPUTS
RECEIVER
DRIVER
CHARGE PUMP LOOPBACK
COMMENTS
ON RXEN DXEN 485/232 RXA RXB DXY DXZ
1
1
1
1
0
0
1
1
0
1
0
1
0
0
0
0
Z
Z
Z
Z
Z
Z
ON
ON
ON
ON
OFF
OFF
OFF
OFF
RS232 Mode, DX and RX Off
RS232 Mode, DXY and DXZ On, RX Off
RS232 Mode, DX Off, RXA and RXB On
ON ON
ON ON
ON ON
Z
Z
ON ON
RS232 Mode, DXY and DXZ On,
RXA and RXB On
0
0
0
1
1
0
0
0
Z
Z
Z
ON
ON
Z
Z
ON
ON
OFF
OFF
RS232 Mode, DXY On, DXZ Off, RX Off
ON
RS232 Mode, DXY On,
DXZ Off, RXA Off, RXB On
0
1
1
0
ON ON
ON ON
ON
ON
RS232 Loopback Mode, DXY and DXZ On,
RXA and RXB On
0
1
0
0
0
1
1
1
0
0
1
0
1
1
X
1
1
1
1
1
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
Z
OFF
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
ON
Shutdown, RS485 R
IN
RS485 Mode, DX and RX Off
RS485 Mode, DX On, RX Off
X
X
1
Z
ON ON
ON
ON
ON
Z
Z
RS485 Mode, DX Off, RX On
ON ON
ON ON
RS485 Mode, DX On, RX On
0
RS485 Loopback Mode, DX On, RX On
RS485 Driver Slew Rate
INPUTS
RS232 Driver Mode
INPUTS
OUTPUTS
OUTPUTS
DXEN
485/232
SLEW
SLEW RATE
SELECTED 485/232
D
0
CONDITIONS
No Fault
Y, Z
1
1
0
1
1
1
0
Slow
Fast
Z
YES
YES
YES
NO
0
0
0
0
1
1
1
No Fault
0
X
X
X
Thermal Fault
X
Z
Z
RS485 Driver Mode
INPUTS
OUTPUTS
RS232 Receiver Mode
DXEN
485/232
D
0
CONDITIONS
No Fault
Z
0
Y
1
INPUTS
485/232
OUTPUTS
R , R
A B
1
1
1
0
1
1
1
1
SELECTED
YES
A, B
1
No Fault
1
0
0
0
0
0
0
1
X
X
Thermal Fault
X
Z
Z
Z
Z
YES
1
Inputs Open
X
0
1
Z
YES
NO
RS485 Receiver Mode
INPUTS
485/232
OUTPUTS
RXEN
B – A
< –0.2V
> 0.2V
R
A
R
B
1
1
1
1
1
1
0
1
1
Z
Z
Z
Inputs Open
or Shorted to Ground
0
1
X
Z
Z
6
LTC1387
W
BLOCK DIAGRAM
RS232 MODE
RS485 MODE
WITHOUT LOOPBACK
RS232 MODE
WITH LOOPBACK
RS485 MODE
WITH LOOPBACK
WITHOUT LOOPBACK
1
20
1
20
1
20
1
20
C1
C2 C1
C2 C1
C2 C1
C2
2
3
19
18
2
3
19
18
2
3
19
18
2
3
19
18
V
V
V
DD
V
V
DD
V
V
V
CC
DD
CC
CC
CC
DD
17
17
4
17
R
A
R
A
A
R
A
4
5
17
16
A
B
R
A
16
15
16
15
5
6
16
15
R
B
R
B
B
Y
Z
R
B
R
B
D
Y
D
Y
6
7
6
7
6
15
Y
Z
Y
Z
Y
Z
D
Y
D
Y
7
8
14
13
7
8
14
13
14
13
14
13
SLEW
ON
D
Z
D
Z
SLEW
ON
8
8
485/232
485/232*
485/232
485/232*
ON
ON
12
11
12
11
12
11
9
9
9
12
11
9
DXEN
GND
DXEN
GND
DXEN*
GND
RXEN
RXEN
RXEN*
DXEN*
GND
RXEN*
10
10
10
10
V
EE
V
EE
V
EE
V
EE
*485/232, DXEN, RXEN = V
CC
LTC1387 • BD
TEST CIRCUITS
V
CC
Y
R
S1
SLEW
C
L
Y
Z
A
B
R
500Ω
D
V
OD
R
L
DR OUT
C
L
15pF
V
OC
C
L
S2
R
Z
485 = 3V, DXEN = 3V, RXEN = 3V
LTC1387 • F02
LTC1387 • F01
LTC1387 • F03
Figure 1. RS485 Driver
Test Load
Figure 2. RS485 Driver/Receiver
Timing Test Circuit
Figure 3. RS485 Driver Output
Enable/Disable Timing Test Load
V
CC
S1
1k
RECEIVER
OUT
Y, Z
D
Y, Z A, B
R
D
R
L
C
L
C
L
S2
15pF
LTC1387 • F05
232 = 0V, DXEN = 3V
232 = 0V, DXEN = 3V, RXEN = 3V
LTC1387 • F06
LTC1387 • F04
Figure 4. RS232 Driver
Timing Test Circuit
Figure 5. RS232 Receiver
Timing Test Circuit
Figure 6. Receiver Output
Enable/Disable Timing Test Load
7
LTC 1387
U
W
SWITCHI G WAVEFOR S
f = 1MHz: t ≤ 10ns: t ≤ 10ns (FAST SLEW RATE MODE)
r
f
f = 100kHz: t ≤ 10ns: t ≤ 10ns (SLOW SLEW RATE MODE)
r
f
3V
0V
1.5V
1.5V
D
t
t
PHL
PLH
V
O
90%
90%
V
DIFF
= V(A) – V(B)
Z – Y
50%
50%
10%
10%
–V
O
1/2 V
O
t
t
f
r
Y
Z
V
O
t
t
SKEW
LTC1387 • F07
SKEW
Figure 7. RS485 Driver Propagation Delays
f = 1MHz: t ≤ 10ns: t ≤ 10ns (FAST SLEW RATE MODE)
r
f
f = 100kHz: t ≤ 10ns: t ≤ 10ns (SLOW SLEW RATE MODE)
r
f
3V
1.5V
1.5V
DXEN
Y, Z
0V
5V
t
t
LZ
ZL
2.3V
2.3V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
0.5V
0.5V
V
OL
t
t
ZH
HZ
V
OH
0V
Z, Y
LTC1387 • F08
Figure 8. RS485 Driver Enable and Disable Times
V
OD2
f = 1MHz: t ≤ 10ns: t ≤ 10ns
r
f
INPUT
0V
B – A
–V
0V
OD2
t
t
PHL
PLH
OUTPUT
V
OH
R
1.5V
1.5V
V
OL
LTC1387 • F09
Figure 9. RS485 Receiver Propagation Delays
3V
1.5V
1.5V
D
0V
t
t
PLH
PHL
V
O
LTC1387 • F10
Y, Z
–V
0V
0V
O
Figure 10. RS232 Driver Propagation Delays
8
LTC1387
U
W
SWITCHI G WAVEFOR S
V
IH
1.7V
1.3V
A, B
V
IL
t
t
PLH
PHL
V
OH
LTC1387 • F11
2.4V
R
0.8V
V
OL
Figure 11. RS232 Receiver Propagation Delays
3V
f = 1MHz: t ≤ 10ns: t ≤ 10ns
r
f
1.5V
1.5V
RXEN
R
0V
5V
t
t
LZ
ZL
1.5V
1.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
0.5V
0.5V
V
OL
t
t
ZH
HZ
V
OH
0V
R
LTC1387 • F12
Figure 12. Receiver Enable and Disable Times
O U
S
W
U
PPLICATI
A
I FOR ATIO
Basic Theory of Operating
Both the interface drivers and the receivers feature three-
state outputs. Driver outputs are forced into high
impedance when the driver is disabled, in the shutdown
mode or with the power off. The driver outputs can be
forced beyond power supply levels without damage up to
±18V. The receiver inputs can withstand ±25V without
damage. The receiver input resistance is typically 24k in
RS485 mode, shutdown mode or power off but drops to
5k in RS232 mode.
The LTC1387 is a single 5V supply, single-port logic
reconfigurableRS485/RS232transceiverwithanonboard
charge pump. The interface port offers a flexible combina-
tion of an RS485 driver and an RS485 receiver or two
RS232 drivers and two RS232 receivers. The RS485
transceiver and the RS232 transceivers are designed to
sharethesameI/Opins.Alogicinput485/232controls the
selection between RS485 and RS232 transceiver modes.
The RS485 transceiver supports both RS485 and RS422
standards, whereas the RS232 transceivers support both
In RS485 mode, the DXEN and RXEN control the three-
state outputs of the driver and receiver respectively. The
RS232andEIA562standards. Withfouradditionalcontrol SLEW input is active during RS485 mode and the logic
inputs: ON, DXEN, RXEN and SLEW, the LTC1387 can
easily be reconfigured via software to adapt to various
communication needs including a one-signal-line RS232
I/O mode. Four examples ofinterface port connections are
shown in Figures 13 through 16.
level controls the differential driver slew rate. This pin has
an internal 5µA pull-up current source during the RS485
mode. A high logic selects fast differential driver slew rate
and a low logic selects slow slew rate. In slow slew mode,
the maximum signal bandwidth is reduced, minimizing
9
LTC 1387
PPLICATI
O U
W
U
A
S I FOR ATIO
EMI and signal reflection problems. Slow slew rate sys-
tems can often use improperly terminated or even
unterminated cables with acceptable results. The RS485
differential input receiver features an offset input thresh-
old of –80mV at 0V common mode voltage. This allows
the receiver output to have a known High output state
when the inputs are open or shorted. The receiver also
features an input hysteresis of 40mV. The charge pump
can be kept active regardless of the state of DXEN and
RXEN pins by keeping the ON pin High. This improves the
receiver response time by removing the 100µs charge
pump start-up time.
All the interface driver outputs are fault protected by a
currentlimitingandthermalshutdowncircuit.Thethermal
shutdown circuit disables both the RS232 and RS485
driver outputs when the die temperature reaches 150°C.
The thermal shutdown circuit reenables the drivers when
the die temperature cools to 135°C.
Aloopbackmodeenables internalconnections fromdriver
outputs to receiver inputs for self-test. The driver outputs
are not isolated from the external loads during loopback.
The charge pump generates boosted positive voltage VDD
and negative voltage VEE for true RS232 levels from a
single 5V VCC supply. The charge pump requires four
0.1µF capacitors.
In RS232 mode, the drivers and receivers can be selected
from the Function Tables with control inputs ON, RXEN
and DXEN. The receivers feature a typical 0.6V input
hysteresis.
LTC1387
RS232 RS485
RS485
R
A
A
A
R
A
INTERFACE
R
B
B
Y
B
R
B
D
Y
D
Y
DX/RX
D /SLEW
Z
Z
V
CC
ON
D
Z
CONTROLLER
RXEN
RXEN
DXEN
485/232
DXEN
MODE
RS232
TRANSMIT MODE
RS232
RECEIVE MODE
RS485
TRANSMIT MODE
RS485
RECEIVE MODE
SHUTDOWN
MODE
RXEN = 0
DXEN = 1
MODE = 0
RXEN = 1
RXEN = 0
RXEN = 1
RXEN = 0
DXEN = 0
DXEN = 0
DXEN = 1
DXEN = 0
MODE = 0
MODE = 1
MODE = 1
MODE = X
1387 • F13
Figure 13. Half-Duplex RS232 (1-Channel), Half-Duplex RS485
10
LTC1387
O U
W
U
PPLICATI
A
S
I FOR ATIO
LTC1387
RS232 RS485
R
A
A
A
TXD
R
A
RX
INTERFACE
RS232 RS485
RXD
R
B
B
Y
B
R
B
D
Y
CONTROLLER
DX
D
Y
D /SLEW
Z
Z
V
CC
RS232
MODE
RS485
TRANSMIT MODE
RS485
RECEIVE MODE
SHUTDOWN
ON
D
Z
MODE
RXEN
DXEN
485/232
RXEN
RXEN = 1
DXEN = 0
MODE = 0
RXEN = 0
DXEN = 1
MODE = 1
RXEN = 1
RXEN = 0
DXEN = 0
DXEN
MODE
DXEN = 0
MODE = 1
MODE = 0
1387 • F14
Figure 14. Full-Duplex RS232 (1-Channel), Half-Duplex RS485
LTC1387
RS232 RS485
RXD
R
A
A
A
B
R
A
RX
RS485
R
B
B
Y
R
B
INTERFACE RS232 RS485
D
Y
Y
CONTROLLER
DX
TXD
D
Y
RS485
D /SLEW
Z
Z
Z
V
CC
RS232
MODE
RS485
MODE
SHUTDOWN
ON
D
Z
MODE
RXEN
DXEN
485/232
RXEN
RXEN = 1
DXEN = 1
MODE = 0
RXEN = 1
DXEN = 1
MODE = 1
RXEN = 0
DXEN = 0
DXEN
MODE
MODE = X
1387 • F15
Figure 15. Full-Duplex RS232 (1-Channel), Full-Duplex RS485/RS422
LTC1387
RS232 RS485
R
A
A
A
RXD
R
A
RX1
RX2
RS232
CTS
RS485
R
B
B
Y
B
R
B
INTERFACE RS232 RS485
D
Y
Y
CONTROLLER
DX1
TXD
D
Y
RS232 RS485
D /SLEW
Z
RS232
MODE
RS485
MODE
SHUTDOWN
MODE
Z
Z
DX2/SLEW
ON
RTS
ON
D
Z
ON = 1
ON = 1
ON = 0
RXEN
DXEN
485/232
RXEN
RXEN = 1
DXEN = 1
MODE = 0
RXEN = 1
DXEN = 1
MODE = 1
RXEN = 0
DXEN = 0
DXEN
MODE
MODE = X
1387 • F16
Figure 16. Full-Duplex RS232 (2-Channel), Full-Duplex RS485/RS422 with SLEW Control
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofits circuits as describedhereinwillnotinfringeonexistingpatentrights.
11
LTC 1387
U
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
G Package
20-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
0.278 – 0.289*
(7.07 – 7.33)
20 19 18 17 16 15 14 13 12 11
0.205 – 0.212**
(5.20 – 5.38)
0.068 – 0.078
(1.73 – 1.99)
0.301 – 0.311
(7.65 – 7.90)
0° – 8°
0.0256
(0.65)
BSC
0.005 – 0.009
(0.13 – 0.22)
0.022 – 0.037
(0.55 – 0.95)
0.002 – 0.008
(0.05 – 0.21)
0.010 – 0.015
(0.25 – 0.38)
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
5
7
8
1
2
3
4
6
9 10
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
G20 SSOP 0595
SW Package
20-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
0.496 – 0.512*
(12.598 – 13.005)
0.291 – 0.299**
(7.391 – 7.595)
19 18
16
14 13 12 11
20
17
15
0.037 – 0.045
(0.940 – 1.143)
0.093 – 0.104
(2.362 – 2.642)
0.010 – 0.029
(0.254 – 0.737)
× 45°
0° – 8° TYP
NOTE 1
0.394 – 0.419
(10.007 – 10.643)
0.050
(1.270)
TYP
NOTE 1
0.004 – 0.012
(0.102 – 0.305)
0.009 – 0.013
(0.229 – 0.330)
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.356 – 0.482)
TYP
NOTE:
1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
2
3
5
7
8
9
10
1
4
6
S20 (WIDE) 0396
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
Single 5V Supply, Wide Common Mode Range
LTC485
LT®1137A
Low Power RS485 Interface Transceiver
Low Power RS232 Transceiver
AppleTalk® Transceiver
±15kV IEC-1000-4-2 ESD Protection, Three Drivers, Five Receivers
AppleTalk/LocalTalk® Compliant
LTC1320
LTC1321/LTC1322/LTC1335
LTC1323
RS232/EIA562/RS485 Transceivers
Single 5V AppleTalk Transceiver
Single Supply RS232/RS485 Transceiver
5V Low Power RS232 Transceiver
Configurable
AppleTalk /LocalTalk Compliant 10kV ESD
Single 5V Supply, Configurable
LTC1334
LTC1347
Three Drivers/Five Receivers, Five Receivers Alive in Shutdown
AppleTalk and LocalTalk are registered trademarks of Apple Computer Corp.
1387f LT/GP 0197 7K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1997
Linear Technology Corporation
●
1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900
12
●
●
FAX: (408) 434-0507 TELEX: 499-3977 www.linear-tech.com
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