LTC490
Differential Driver and
Receiver Pair
FEATURES
s
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DESCRIPTIO
s
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Low Power: I
CC
= 300µA Typical
Designed for RS485 or RS422 Applications
Single 5V Supply
– 7V to 12V Bus Common Mode Range
Permits
±7V
Ground Difference Between Devices
on the Bus
Thermal Shutdown Protection
Power-Up/-Down Glitch-Free Driver Outputs Permit
Live Insertion or Removal of Package
Driver Maintains High Impedance with the
Power Off
Combined Impedance of a Driver Output and
Receiver Allows up to 32 Transceivers on the Bus
70mV Typical Input Hysteresis
28ns Typical Driver Propagation Delays with
5ns Skew for 2.5MB Operation
Pin Compatible with the SN75179
Available in 8-Lead PDIP and SO Packages
The LTC
®
490 is a low power differential bus/line trans-
ceiver designed for multipoint data transmission standard
RS485 applications with extended common mode range
(12V to –7V). It also meets the requirements of RS422.
The CMOS design offers significant power savings over its
bipolar counterpart without sacrificing ruggedness against
overload or ESD damage.
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
receiver has a fail safe feature which guarantees a high
output state when the inputs are left open.
Both AC and DC specifications are guaranteed from 0°C to
70°C and 4.75V to 5.25V supply voltage range.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
Low Power RS485/RS422 Transceiver
Level Translator
TYPICAL APPLICATIO
LTC490
5
D
3
DRIVER
120Ω
6
4000 FT BELDEN 9841
120Ω
RECEIVER
R
8
R
2
RECEIVER
120Ω
7
4000 FT BELDEN 9841
120Ω
DRIVER
D
U
LTC490
LTC490 • TA01
U
U
490fb
1
LTC490
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
CC
1
R 2
D 3
D
Supply Voltage (V
CC
) ............................................... 12V
Driver Input Currents ........................... – 25mA to 25mA
Driver Input Voltages ...................... –0.5V to V
CC
+ 0.5V
Driver Output Voltages ..........................................
±14V
Receiver Input Voltages .........................................
±14V
Receiver Output Voltages ............... –0.5V to V
CC
+ 0.5V
Operating Temperature Range
LTC490C ................................................ 0°C to 70°C
LTC490I ............................................. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
8
R
A
B
Z
Y
ORDER PART
NUMBER
LTC490CN8
LTC490CS8
LTC490IN8
LTC490IS8
S8 PART MARKING
490
490I
7
6
5
GND 4
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 100°C/ W (N8)
T
JMAX
= 150°C,
θ
JA
= 150°C/ W (S8)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
SYMBOL
V
OD1
V
OD2
∆V
OD
V
OC
∆
V
OC
V
IH
V
IL
l
IN1
l
IN2
V
TH
∆V
TH
V
OH
V
OL
I
OZR
I
CC
R
IN
I
OSD1
I
OSD2
I
OSR
I
OZ
PARAMETER
Differential Driver Output Voltage (Unloaded)
Differential Driver Output Voltage (with Load)
Change in Magnitude of Driver Differential Output
Voltage for Complementary Output States
Driver Common Mode Output Voltage
Change in Magnitude of Driver Common Mode
Output Voltage for Complementary Output States
Input High Voltage (D)
Input Low Voltage (D)
Input Current (D)
Input Current (A, B)
Differential Input Threshold Voltage for Receiver
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
Three-State Output Current at Receiver
Supply Current
Receiver Input Resistance
Driver Short-Circuit Current, V
OUT
= High
Driver Short-Circuit Current, V
OUT
= Low
Receiver Short-Circuit Current
Driver Three-State Output Current
The
q
denotes the specificatiions which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V
±5%
CONDITIONS
I
O
= 0
R = 50Ω (RS422)
R = 27Ω (RS485) (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
q
q
q
q
q
q
q
q
q
MIN
2
1.5
TYP
MAX
5
5
0.2
3
0.2
UNITS
V
V
V
V
V
V
V
2.0
0.8
±2
1
– 0.8
– 0.2
70
3.5
0.4
±1
300
12
100
100
7
±2
250
250
85
±200
500
0.2
V
CC
= 0V or 5.25V
– 7V
≤
V
CM
≤
12V
V
CM
= 0V
V
IN
= 12V
V
IN
= – 7V
q
q
q
q
q
q
q
q
q
q
q
q
q
I
O
= –4mA, V
ID
= 0.2V
I
O
= 4mA, V
ID
= – 0.2V
V
CC
= Max 0.4V
≤
V
O
≤
2.4V
No Load; D = GND or V
CC
– 7V
≤
V
O
≤
12V
V
O
= – 7V
V
O
= 12V
0V
≤
V
O
≤
V
CC
V
O
= – 7V to 12V
2
U
V
µA
mA
mA
V
mV
V
V
µA
µA
kΩ
mA
mA
mA
µA
490fb
W
U
U
W W
W
LTC490
SWITCHI G CHARACTERISTICS
SYMBOL
t
PLH
t
PHL
t
SKEW
t
r
, t
f
t
PLH
t
PHL
t
SKD
PARAMETER
Driver Input to Output
Driver Input to Output
Driver Output to Output
Driver Rise or Fall Time
Receiver Input to Output
Receiver Input to Output
t
PLH
– t
PHL
Differential Receiver Skew
The
q
denotes the specificatiions which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V
±5%
CONDITIONS
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF (Figures 2, 3)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF (Figures 2, 3)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF (Figures 2, 3)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF (Figures 2, 3)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF (Figures 2, 4)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF (Figures 2, 4)
R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF (Figures 2, 4)
q
q
q
q
q
q
q
Note 1:
Absolute maximum ratings are those beyond which the safety of
the device cannot be guaranteed.
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.
TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output High Voltage
vs Output Current
–96
OUTPUT CURRENT (mA)
T
A
= 25°C
OUTPUT CURRENT (mA)
–72
48
OUTPUT CURRENT (mA)
– 48
–24
0
0
1
2
3
OUTPUT VOLTAGE (V)
4
LTC490 • TPC01
U W
U
MIN
10
10
5
40
40
TYP
30
30
5
5
70
70
13
MAX
50
50
25
150
150
UNITS
ns
ns
ns
ns
ns
ns
ns
Note 3:
All typicals are given for V
CC
= 5V and Temperature = 25°C.
Driver Differential Output Voltage
vs Output Current
64
T
A
= 25°C
80
Driver Output Low Voltage
vs Output Current
T
A
= 25°C
60
32
40
16
20
0
0
1
2
3
OUTPUT VOLTAGE (V)
4
LTC490 • TPC02
0
0
1
2
3
OUTPUT VOLTAGE (V)
4
LTC490 • TPC03
490fb
3
LTC490
TYPICAL PERFOR A CE CHARACTERISTICS
TTL Input Threshold
vs Temperature
1.63
5
INPUT THRESHOLD VOLTAGE (V)
SUPPLY CURRENT (µA)
1.61
TIME (ns)
1.59
1.57
1.55
–50
0
50
TEMPERATURE (°C )
Driver Differential Output Voltage
vs Temperature
2.3
R
O
= 54Ω
DIFFERENTIAL VOLTAGE (V)
2.1
OUTPUT VOLTAGE (V)
1.9
TIME (ns)
1.7
1.5
–50
0
50
TEMPERATURE (°C )
4
U W
100
LTC490 • TPC04
Driver Skew vs Temperature
350
Supply Current vs Temperature
4
340
3
330
2
320
1
–50
0
50
TEMPERATURE (°C )
100
LTC490 • TPC05
310
–50
0
50
TEMPERATURE (°C )
100
LTC490 • TPC06
Receiver
t
PLH
-t
PHL
vs Temperature
7
0.8
Receiver Output Low Voltage
vs Temperature
I = 8mA
6
0.6
5
0.4
4
0.2
100
LTC490 • TPC07
3
–50
0
50
TEMPERATURE (°C )
100
LTC490 • TPC08
0
–50
0
50
TEMPERATURE (°C )
100
LTC490 • TPC09
490fb
LTC490
PI FU CTIO S
V
CC
(Pin 1):
Positive Supply; 4.75V
≤
V
CC
≤
5.25V.
R (Pin 2):
Receiver Output. If A > B by 200mV, R will be
high. If A < B by 200mV, then R will be low.
D (Pin 3):
Driver Input. A low on D forces the driver outputs
Y low and Z high. A high on D will force Y high and Z low.
GND (Pin 4):
Ground Connection.
Y (Pin 5):
Driver Output.
Z (Pin 6):
Driver Output.
B (Pin 7):
Receiver Input.
A (Pin 8):
Receiver Input.
TEST CIRCUITS
Y
R
V
OD2
R
Z
LTC490 • F01
LTC490 • F02
Figure 1. Driver DC Test Load
SWITCHI G TI E WAVEFOR S
3V
D
0V
t
PLH
V
O
–V
O
50%
10%
t
r
Z
V
O
Y
1/2 V
O
t
SKEW
1/2 V
O
t
SKEW
LTC490 • F03
1.5V
f = 1MHz : t
r
≤
10ns : t
f
≤
10ns
80%
V
DIFF
= V(Y) – V(Z)
Figure 3. Driver Propagation Delays
V
OD2
A-B
–V
OD2
V
OH
R
V
OL
0V
t
PLH
1.5V
f = 1MHz ; t
r
≤
10ns : t
f
≤
10ns
Figure 4. Receiver Propagation Delays
490fb
W
W
U
U
U
U
Y
D
V
OC
DRIVER
Z
R
DIFF
C
L1
A
RECEIVER
R
15pF
C
L2
B
Figure 2. Driver/Receiver Timing Test Circuit
1.5V
t
PHL
90%
t
f
50%
20%
INPUT
0V
t
PHL
OUTPUT
1.5V
LTC490 • F04
5
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