LINER LTC1690CN8 Differential driver and receiver pair with fail-safe receiver output Datasheet

LTC1690
Differential Driver and
Receiver Pair with Fail-Safe
Receiver Output
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DESCRIPTIO
FEATURES
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No Damage or Latchup to ±15kV ESD (Human Body
Model), IEC1000-4-2 Level 4 (±8kV) Contact and
Level 3 (± 8kV) Air Discharge
Guaranteed High Receiver Output State for
Floating, Shorted or Terminated Inputs with No
Signal Present
Drives Low Cost Residential Telephone Wires
ICC = 600µA Max with No Load
Single 5V Supply
–7V to 12V Common Mode Range Permits ±7V
Ground Difference Between Devices on the Data Line
Power-Up/Down Glitch-Free Driver Outputs Permit
Live Insertion or Removal of Transceiver
Driver Maintains High Impedance with the Power Off
Up to 32 Transceivers on the Bus
Pin Compatible with the SN75179 and LTC490
Available in SO, MSOP and PDIP Packages
The LTC®1690 is a low power receiver/driver pair that is
compatible with the requirements of RS485 and RS422.
The receiver offers a fail-safe feature that guarantees a
high receiver output state when the inputs are left open,
shorted together or terminated with no signal present. No
external components are required to ensure the high
receiver output state.
Separate driver output and receiver input pins allow full
duplex operation. Excessive power dissipation caused by
bus contention or faults is prevented by a thermal shutdown circuit which forces the driver outputs into a high
impedance state.
The LTC1690 is fully specified over the commercial and
industrial temperature ranges. The LTC1690 is available in
8-Pin SO, MSOP and PDIP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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APPLICATIO S
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Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
Line Repeater
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TYPICAL APPLICATIO
Driving a 1000 Foot STP Cable
LTC1690
LTC1690
5
D1
3
DRIVER
Y1
120Ω
A2
8
120Ω
6
7
Z1
B2
B1
Z2
D1
2
RECEIVER
R2
B2
A2
7
R1
2
RECEIVER
120Ω
6
120Ω
8
5
A1
R2
3
DRIVER
Y2
D2
1690 TA01a
1690 TA01
1
LTC1690
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (VCC) .............................................. 6.5V
Driver Input Voltage ..................... –0.3V to (VCC + 0.3V)
Driver Output Voltages ................................. –7V to 10V
Receiver Input Voltages ......................................... ±14V
Receiver Output Voltage .............. –0.3V to (VCC + 0.3V)
Junction Temperature ........................................... 125°C
Operating Temperature Range
LTC1690C ........................................ 0°C ≤ TA ≤ 70°C
LTC1690I ..................................... – 40°C ≤ TA ≤ 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
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PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
TOP VIEW
VCC
R
D
GND
1
2
3
4
8
7
6
5
VCC 1
LTC1690CMS8
A
B
Z
Y
R
R 2
D 3
GND 4
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 200°C/W
ORDER PART
NUMBER
TOP VIEW
MS8 PART MARKING
8
A
7
B
6
Z
5
Y
D
S8 PACKAGE
8-LEAD PLASTIC SO
LTC1690CN8
LTC1690IN8
LTC1690CS8
LTC1690IS8
N8 PACKAGE
8-LEAD PLASTIC DIP
S8 PART MARKING
TJMAX = 125°C, θJA = 130°C/W (N)
TJMAX = 125°C, θJA = 135°C/W (S)
LTDA
1690
1690I
Consult factory for Military Grade Parts
DC ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5% (Notes 2, 3)
SYMBOL PARAMETER
CONDITIONS
MIN
VOD1
Differential Driver Output Voltage (Unloaded)
IO = 0
●
VOD2
Differential Driver Output Voltage (with Load)
R = 50Ω; (RS422)
R = 22Ω or 27Ω; (RS485), Figure 1
●
●
TYP
MAX
UNITS
VCC
V
2
1.5
5
V
V
1.5
5
V
VOD3
Differential Driver Output Voltage (with Common Mode)
VTST = –7V to 12V, Figure 2
∆VOD
Change in Magnitude of Driver Differential Output
Voltage for Complementary Output States
R = 22Ω, 27Ω or 50Ω, Figure 1
VTST = –7V to 12V, Figure 2
●
0.2
V
VOC
Driver Common Mode Output Voltage
R = 22Ω, 27Ω or 50Ω, Figure 1
●
3
V
∆|VOC|
Change in Magnitude of Driver Common Mode
Output Voltage for Complementary Output States
R = 22Ω, 27Ω or 50Ω, Figure 1
●
0.2
V
VIH
Input High Voltage
Driver Input (D)
●
VIL
Input Low Voltage
Driver Input (D)
●
0.8
V
IIN1
Input Current
Driver Input (D)
●
±2
µA
IIN2
Input Current (A, B)
VCC = 0V or 5.25V, VIN = 12V
VCC = 0V or 5.25V, VIN = –7V
●
●
1
–0.8
mA
mA
VTH
Differential Input Threshold Voltage for Receiver
–7V ≤ VCM ≤ 12V
●
– 0.01
V
∆VTH
Receiver Input Hysteresis
VCM = 0V
2
2
V
– 0.20
±30
mV
LTC1690
DC ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V ±5% (Notes 2, 3)
SYMBOL PARAMETER
CONDITIONS
VOH
Receiver Output High Voltage
IO = – 4mA, VID = 200mV
●
VOL
Receiver Output Low Voltage
IO = 4mA, VID = – 200mV
●
RIN
Receiver Input Resistance
–7V ≤ VCM ≤ 12V
●
ICC
Supply Current
No Load
●
IOSD1
Driver Short-Circuit Current, VOUT = HIGH
–7V ≤ VO ≤ 10V
IOSD2
Driver Short-Circuit Current, VOUT = LOW
–7V ≤ VO ≤ 10V
IOZ
Driver Three-State Current (Y, Z)
–7V ≤ VO ≤ 10V, VCC = 0V
●
IOSR
Receiver Short-Circuit Current
0V ≤ VO ≤ VCC
●
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tPLH
Driver Input to Output, Figure 3, Figure 4
RDIFF = 54Ω, CL1 = CL2 = 100pF
●
tPHL
Driver Input to Output, Figure 3, Figure 4
RDIFF = 54Ω, CL1 = CL2 = 100pF
●
tSKEW
Driver Output to Output, Figure 3, Figure 4
RDIFF = 54Ω, CL1 = CL2 = 100pF
●
tr, tf
Driver Rise or Fall Time, Figure 3, Figure 4
RDIFF = 54Ω, CL1 = CL2 = 100pF
●
2
tPLH
Receiver Input to Output, Figure 3, Figure 5
RDIFF = 54Ω, CL1 = CL2 = 100pF
●
tPHL
Receiver Input to Output, Figure 3, Figure 5
RDIFF = 54Ω, CL1 = CL2 = 100pF
●
tSKD
|tPLH – tPHL|, Differential Receiver Skew, Figure 3, Figure 5
RDIFF = 54Ω, CL1 = CL2 = 100pF
fMAX
Maximum Data Rate, Figure 3, Figure 5
RDIFF = 54Ω, CL1 = CL2 = 100pF
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
MIN
TYP
MAX
3.5
V
0.4
12
22
V
kΩ
600
µA
35
250
mA
35
250
mA
5
200
µA
85
mA
10
22.5
60
ns
10
25
60
ns
2.5
15
ns
13
40
ns
30
94
160
ns
30
89
160
ns
260
5
●
UNITS
ns
5
Mbps
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 3: All typicals are given for VCC = 5V and TA = 25°C.
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TYPICAL PERFOR A CE CHARACTERISTICS
VCM = 12V
VCC = 5V
–40
–60
VCM = 0V
–80
–100
VCM = –7V
–120
–140
–160
–180
–200
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G01
Receiver Hysteresis vs
Temperature
0
–20
100
VCC = 5V
90
–40
RECEIVER HYSTERESIS (mV)
0
–20
Receiver Input Threshold Voltage
(Output Low) vs Temperature
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
Receiver Input Threshold Voltage
(Output High) vs Temperature
–60
–80
VCM = 12V
–100
VCM = 0V
–120
–140
–160
VCM = –7V
–180
–200
–55 –35 –15
VCC = 5V
80
70
60
VCM = 12V
VCM = 0V
50
40
30
VCM = –7V
20
10
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G02
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G03
3
LTC1690
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TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Offset Voltage vs
Temperature
Receiver Input Threshold Voltage
vs Supply Voltage
VCC = 5V
–40
VCM = 0V
–60
VCM = –7V
–80
–100
–120
–140
VCM = 12V
–160
–180
–200
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
–40
–25
TA = 25°C
–60
OUTPUT HIGH
–80
–100
OUTPUT LOW
–120
–140
–160
4.5
25
20
15
10
5
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
–55 –35 –15
2
tPHL
80
60
–55 –35 –15
8
7
6
5
3
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G10
0.5
0.4
0.3
0.2
0.1
5 25 45 65 85 105 125
TEMPERATURE (°C)
Receiver Propagation Delay vs
Supply Voltage
110
VCC = 5V
4
70
I = 8mA
VCC = 4.75V
1690 G09
2
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G11
RECEIVER PROPAGATION DELAY (ns)
RECEIVER SKEW (ns)
RECEIVER PROPAGATION DELAY (ns)
9
110
90
0.6
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
10
VCC = 5V
4
Receiver Output Low Voltage vs
Temperature
Receiver Skew tPLH – tPHL vs
Temperature
120
2
1690 G06
1690 G08
Receiver Propagation Delay vs
Temperature
tPLH
4.5
4
3
2.5
3.5
RECEIVER OUTPUT HIGH VOLTAGE (V)
0.7
I = 8mA
VCC = 4.75V
1690 G07
100
–5
5
RECEIVER OUTPUT LOW VOLTAGE (V)
RECEIVER OUTPUT HIGH VOLTAGE (V)
RECEIVER OUTPUT CURRENT (mA)
30
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
RECEIVER OUTPUT LOW VOLTAGE (V)
–10
5.5
4.8
0
–15
Receiver Output High Voltage vs
Temperature
40
35
–20
1690 G05
Receiver Output Low Voltage vs
Output Current
TA = 25°C
VCC = 4.75V
TA = 25°C
VCC = 4.75V
0
4.75
5
5.25
SUPPLY VOLTAGE (V)
1690 G04
0
RECEIVER OUTPUT CURRENT (mA)
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
RECEIVER INPUT OFFSET VOLTAGE (mV)
0
–20
Receiver Output High Voltage vs
Output Current
100
90
tPLH
tPHL
80
70
60
50
4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4 5.5
SUPPLY VOLTAGE (V)
1690 G12
LTC1690
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TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Short-Circuit Current vs
Temperature
1.75
320
300
OUTPUT LOW
40
30
OUTPUT HIGH
20
280
VCC = 5.25V
260
240
220
VCC = 4.75V
200
180
VCC = 5V
160
10
140
0
–55 –35 –15
120
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G13
2.7
VCC = 5.25V
VCC = 5V
2.3
2.1
1.9
VCC = 4.5V
1.7
VCC = 4.75V
1.5
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
2.9
2.7
RL = 54Ω
VCC = 5.25V
VCC = 5V
2.5
2.3
2.1
VCC = 4.5V
1.9
VCC = 4.75V
1.7
1.5
–55 –35 –15
VCC = 5V
VCC = 4.75V
VCC = 4.5V
1.0
0.5
RL = 44Ω
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G19
DRIVER COMMON MODE OUTPUT VOLTAGE (V)
DRIVER COMMON MODE OUTPUT VOLTAGE (V)
2.5
0
–55 –35 –15
1.55
VCC = 4.75V
5 25 45 65 85 105 125
TEMPERATURE (°C)
Driver Differential Output Voltage
vs Temperature
3.4
RL = 100Ω
3.2
VCC = 5.25V
3.0
VCC = 5V
2.8
VCC = 4.75V
2.6
VCC = 4.5V
2.4
2.2
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G18
Driver Common Mode Output
Voltage vs Temperature
3.0
1.5
1.60
1690 G17
Driver Common Mode Output
Voltage vs Temperature
2.0
VCC = 5V
1690 G15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G16
VCC = 5.25V
1.65
Driver Differential Output Voltage
vs Temperature
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
RL = 44Ω
VCC = 5.25V
1690 G14
Driver Differential Output Voltage
vs Temperature
2.9
1.70
1.50
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
50
Driver Common Mode Output
Voltage vs Temperature
3.0
2.5
VCC = 5.25V
2.0
VCC = 5V
VCC = 4.75V
VCC = 4.5V
1.5
1.0
0.5
RL = 54Ω
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G20
DRIVER COMMON MODE OUTPUT VOLTAGE (V)
60
LOGIC INPUT THRESHOLD VOLTAGE (V)
340
VCC = 5.25V
SUPPLY CURRENT (µA)
SHORT-CIRCUIT CURRENT (mA)
70
2.5
Logic Input Threshold Voltage vs
Temperature
Supply Current vs Temperature
3.0
2.5
VCC = 5.25V
2.0
VCC = 5V
VCC = 4.75V
VCC = 4.5V
1.5
1.0
0.5
RL = 100Ω
0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G21
5
LTC1690
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TYPICAL PERFOR A CE CHARACTERISTICS
Driver Differential Output Voltage
vs Output Current
Driver Output High Voltage vs
Output Current
100
–100
100
TA = 25°C
VCC = 5V
TA = 25°C
90
80
60
50
40
30
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
70
–60
–40
20
60
50
40
30
10
0
0
0
1
2
3
4
5
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
0
0
0
1
2
3
4
DRIVER OUTPUT HIGH VOLTAGE (V)
Driver Propagation Delay vs
Temperature
Driver Propagation Delay vs
Supply Voltage
30
4.0
3.5
DRIVER SKEW (ns)
tPHL
20
DRIVER PROPAGATION DELAY (ns)
VCC = 5V
VCC = 5V
tPLH
15
10
3.0
2.5
2.0
1.5
5
0
–55 –35 –15
1.0
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
200
OUTPUT HIGH
SHORT TO –7V
OUTPUT LOW
SHORT TO 10V
50
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G29
RECEIVER INPUT RESISTANCE (kΩ)
DRIVER SHORT-CIRCUIT CURRENT (mA)
10
5
0
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5
SUPPLY VOLTAGE (V)
1690 G27
25
VCC = 5.25V
0
–55 –35 –15
15
Receiver Input Resistance vs
Temperature
250
100
tPLH
20
5 25 45 65 85 105 125
TEMPERATURE (°C)
Driver Short-Circuit Current vs
Temperature
150
tPHL
25
1690 G26
1690 G25
3
1690 G24
Driver Skew vs Temperature
30
25
0.5
1
1.5
2
2.5
DRIVER OUTPUT LOW VOLTAGE (V)
1690 G23
1690 G22
DRIVER PROPAGATION DELAY (ns)
70
20
–20
10
6
TA = 25°C
VCC = 5V
90
–80
80
OUTPUT CURRENT (mA)
Driver Output Low Voltage vs
Output Current
VCC = 5V
24
23
VCM = 12V
22
VCM = –7V
21
20
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
1690 G30
LTC1690
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PIN FUNCTIONS
VCC (Pin 1): Positive Supply. 4.75V < VCC < 5.25V.
Y (Pin 5): Driver Output.
R (Pin 2): Receiver Output. R is high if (A – B) ≥ – 10mV
and low if (A – B) ≤ – 200mV.
Z (Pin 6): Driver Output.
D (Pin 3): Driver Input. If D is high, Y is taken high and Z
is taken low. If D is low, Y is taken low and Z is taken high.
A (Pin 8): Receiver Input.
B (Pin 7): Receiver Input.
GND (Pin 4): Ground.
TEST CIRCUITS
+
Y
375Ω
Y
Y
R
D
60Ω
VOD3
VOC
Z
A
RDIFF
VOD2
R
CL1
Z
VTST
–7V TO 12V
R
+
CL2
+
B
15pF
375Ω
Z
1690 F01
1690 F02
1690 F03
Figure 1. Driver
DC Test Load #1
Figure 3. Driver/Receiver
Timing Test Load
Figure 2. Driver
DC Test Load #2
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SWITCHI G TI E WAVEFOR S
3V
f = 1MHz, t r ≤ 10ns, t f ≤ 10ns
1.5V
D
0V
VO
–VO
1.5V
tPLH
90%
50%
10%
tPHL
VO = V(A) – V(B)
tr
Z
VOD2
A–B
–VOD2
0V
50%
10%
tf
t SKEW
0V
tPLH
5V
90%
R
VOL
1.5V
1/2 VO
OUTPUT
NOTE: tSKD = |tPHL – tPLH|
VO
Y
f = 1MHz, t r ≤ 10ns, t f ≤ 10ns
INPUT
tPHL
1.5V
1690 F05
Figure 5. Receiver Propagation Delays
t SKEW
1690 F04
Figure 4. Driver Propagation Delays
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FUNCTION TABLES
Driver
Receiver
D
Z
Y
A–B
R
1
0
1
≥ – 0.01V
1
0
1
0
≤ – 0.20V
0
Inputs Open
1
Inputs Shorted
1
Note: Table valid with or without termination resistors.
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LTC1690
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APPLICATIONS INFORMATION
A typical application is shown in Figure 6. Two twisted pair
wires connect two driver/receiver pairs for full duplex data
transmission. Note that the driver and receiver outputs are
always enabled. If the outputs must be disabled, use the
LTC491. There are no restrictions on where the chips are
connected, and it isn’t necessary to have the chips connected to the ends of the wire. However, the wires must be
terminated at the ends with a resistor equal to their
characteristic impedance, typically 120Ω. Because only
one driver can be connected on the bus, the cable need
only be terminated at the receiving end. The optional
shields around the twisted pair are connected to GND at
one end and help reduce unwanted noise.
logic 1 state when the receiver inputs are left floating or
shorted together. This is achieved without external components by designing the trip-point of the LTC1690 to be
within – 200mV to –10mV. If the receiver output must be
a logic 0 instead of a logic 1, external components are
required.
The LTC1690 can be used as a line repeater as shown in
Figure 7. If the cable is longer that 4000 feet, the LTC1690
is inserted in the middle of the cable with the receiver
output connected back to the driver input.
The driver outputs generate fast rise and fall times. If the
LTC1690 receiver inputs are not terminated and floating,
switching noise from the LTC1690 driver can couple into
the receiver inputs and cause the receiver output to glitch.
This can be prevented by ensuring that the receiver inputs
are terminated with a 100Ω or 120Ω resistor, depending
on the type of cable used. A cable capacitance that is
greater than 10pF (≈1ft of cable) also prevents glitches if
no termination is present. The receiver inputs should not
be driven typically above 8MHz to prevent glitches.
Receiver Fail-Safe
Some encoding schemes require that the output of the
receiver maintains a known state (usually a logic 1) when
data transmission ends and all drivers on the line are
forced into three-state. The receiver of the LTC1690 has a
fail-safe feature which guarantees the output to be in a
The LTC1690 fail-safe receiver is designed to reject fast
–7V to 12V common mode steps at its inputs. The slew
rate that the receiver will reject is typically 400V/µs, but
–7V to 12V steps in 10ns can be tolerated if the frequency
of the common mode step is moderate (<600kHz).
Driver-Receiver Crosstalk
5V
5V
1
LTC1690
SHIELD
5
D
3
DRIVER
1
LTC1690
8
120Ω
7
6
2
RECEIVER
R
0.01µF
0.01µF
SHIELD
7
R
2
RECEIVER
6
120Ω
8
5
3
DRIVER
4
4
1690 F06
Figure 6. Typical Application
8
D
LTC1690
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APPLICATIONS INFORMATION
Fault Protection
When shorted to –7V or 10V at room temperature, the
short-circuit current in the driver outputs is limited by
internal resistance or protection circuitry to 250mA maximum. Over the industrial temperature range, the absolute
maximum positive voltage at any driver output should be
limited to 10V to avoid damage to the driver outputs. At
higher ambient temperatures, the rise in die temperature
due to the short-circuit current may trip the thermal
shutdown circuit.
The receiver inputs can withstand the entire –7V to 12V
RS485 common mode range without damage.
The LTC1690 includes a thermal shutdown circuit that
protects the part against prolonged shorts at the driver
outputs. If a driver output is shorted to another output or
to VCC, the current will be limited to a maximum of 250mA.
If the die temperature rises above 150°C, the thermal
shutdown circuit three-states the driver outputs to open
the current path. When the die cools down to about 130°C,
the driver outputs are taken out of three-state. If the short
persists, the part will heat again and the cycle will repeat.
This thermal oscillation occurs at about 10Hz and protects
the part from excessive power dissipation. The average
fault current drops as the driver cycles between active and
three-state. When the short is removed, the part will return
to normal operation.
If the outputs of two or more LTC1690 drivers are shorted
directly, the driver outputs cannot supply enough current
to activate the thermal shutdown. Thus, the thermal shutdown circuit will not prevent contention faults when two
drivers are active on the bus at the same time.
LTC1690
5
D
3
DRIVER
DATA
OUT
6
8
R
2
RECEIVER
120Ω
7
DATA
IN
1690 F07
Figure 7. Line Repeater
9
LTC1690
U
W
U
U
APPLICATIONS INFORMATION
Cables and Data Rate
ESD PROTECTION
The transmission line of choice for RS485 applications is
a twisted pair. There are coaxial cables (twinaxial) made
for this purpose that contain straight pairs, but these are
less flexible, more bulky and more costly than twisted
pairs. Many cable manufacturers offer a broad range of
120Ω cables designed for RS485 applications.
The ESD performance of the LTC1690 driver outputs (Z, Y)
and the receiver inputs (A, B) is as follows:
Losses in a transmission line are a complex combination
of DC conductor loss, AC losses (skin effect), leakage and
AC losses in the dielectric. In good polyethylene cables
such as Belden 9841, the conductor losses and dielectric
losses are of the same order of magnitude, leading to
relatively low overall loss (Figure 8).
c) Meets IEC1000-4-2 Level 3 (±8kV) air discharge specifications.
When using low loss cable, Figure 9 can be used as a
guideline for choosing the maximum length for a given
data rate. With lower quality PVC cables, the dielectric loss
factor can be 1000 times worse. PVC twisted pairs have
terrible losses at high data rates (>100kbits/s), reducing
the maximum cable length. At low data rates, they are
acceptable and are more economical. The LTC1690 is
tested and guaranteed to drive CAT 5 cable and terminations as well as common low cost residential telephone
wire.
a) Meets ±15kV Human Body Model (100pF, 1.5kΩ).
b) Meets IEC1000-4-2 Level 4 (±8kV) contact mode specifications.
This level of ESD performance means that external voltage
suppressors are not required in many applications, when
compared with parts that are only protected to ±2kV. The
LTC1690 driver input (D) and receiver output are protected to ±2kV per the Human Body Model.
When powered up, the LTC1690 does not latch up or
sustain damage when the Z, Y, A or B pins are subjected
to any of the conditions listed above. The data during the
ESD event may be corrupted, but after the event the
LTC1690 continues to operate normally.
The additional ESD protection at the LTC1690 Z, Y, A and
B pins is important in applications where these pins are
exposed to the external world via socket connections.
10k
CABLE LENGTH (FT)
LOSS PER 100 FT (dB)
10
1.0
0.1
0.1
1.0
10
100
FREQUENCY (MHz)
100
10
10k
100k
1M
2.5M
10M
DATA RATE (bps)
1690 F08
Figure 8. Attenuation vs Frequency for Belden 9841
10
1k
1690 F09
Figure 9. RS485 Cable Length Recommended. Applies
for 24 Gauge, Polyethylene Dielectric Twisted Pair
LTC1690
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.118 ± 0.004*
(3.00 ± 0.102)
0.034 ± 0.004
(0.86 ± 0.102)
8
7 6
5
0° – 6° TYP
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
BSC
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
MSOP (MS8) 1098
1
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
4
2 3
N8 Package
8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.300 – 0.325
(7.620 – 8.255)
0.009 – 0.015
(0.229 – 0.381)
(
0.045 – 0.065
(1.143 – 1.651)
+0.889
–0.381
0.130 ± 0.005
(3.302 ± 0.127)
0.065
(1.651)
TYP
+0.035
0.325 –0.015
8.255
0.400*
(10.160)
MAX
)
8
7
6
5
1
2
3
4
0.255 ± 0.015*
(6.477 ± 0.381)
0.125
(3.175) 0.020
MIN
(0.508)
MIN
0.018 ± 0.003
0.100
(2.54)
BSC
(0.457 ± 0.076)
N8 1098
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*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
8
7
6
5
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
2
3
4
SO8 1298
11
LTC1690
U
TYPICAL APPLICATIONS
Receiver with Low Fail-Safe Output
RS232 Receiver
5V
1.2k
2.7k
RS232 IN
120Ω
RECEIVER
2.7k
RX
RX
RECEIVER
1.2k
1690 TA03
1690 TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC485
5V Low Power RS485 Interface Transceiver
Low Power
LTC1480
3.3V Ultralow Power RS485 Transceiver with Shutdown
Lower Supply Voltage
LTC1481
5V Ultralow Power RS485 Transceiver with Shutdown
Lowest Power
LTC1482
5V Low Power RS485 Transceiver with Carrier Detect Output
Low Power, High Output State when Inputs are Open,
Shorted or Terminated, ±15kV ESD Protection
LTC1483
5V Ultralow Power RS485 Low EMI Transceiver with Shutdown
Low EMI, Lowest Power
LTC1484
5V Low Power RS485 Transceiver with Fail-Safe Receiver Circuit
Low Power, High Output State when Inputs are Open,
Shorted or Terminated, ±15kV ESD Protection
LTC1485
5V RS485 Transceiver
High Speed, 10Mbps
LTC1487
5V Ultralow Power RS485 with Low EMI, Shutdown and
High Input Impedance
Highest Input Impedance, Low EMI, Lowest Power
LTC490
5V Differential Driver and Receiver Pair
Low Power, Pin Compatible with LTC1690
LTC491
5V Low Power RS485 Full-Duplex Transceiver
Low Power
LTC1535
Isolated RS485 Transceiver
2500VRMS Isolation, Full Duplex
LTC1685
52Mbps, RS485 Fail-Safe Transceiver
Pin Compatible with LTC485
LTC1686/LTC1687
52Mbps, RS485 Fail-Safe Driver/Receiver
Pin Compatible with LTC490/LTC491
LT1785/LT1791
±60V Fault Protected RS485 Half-/Full-Duplex Transceiver
±15kV ESD Protection
12
Linear Technology Corporation
1690f LT/TP 0400 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1998