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LTC1482 Low Power RS485 Transceiver with Carrier Detect and Receiver Fail-Safe DESCRIPTIO
The LTC(R)1482 is a low power RS485 compatible transceiver that offers an active low carrier detect output. The open-drain carrier detect pin allows several transceivers to share the same carrier detect line and can be used to detect the insertion or removal of a driven RS485/RS422 cable. Enhanced ESD protection allows the LTC1482 to withstand 15kV (human body model), IEC-1000-4-2 level 4 (8kV) contact and level 3 (8kV) air discharge ESD without latchup or damage. The LTC1482 receiver stays alive at all times except in shutdown. The supply current is a maximum of 700A and 900A when the driver is disabled and enabled respectively. In shutdown, the quiescent current of the LTC1482 drops to a maximum of 20A. When the driver is disabled or the LTC1482 is in shutdown, the driver outputs are three-stated and remain in a high impedance state over the RS485 common mode range. 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 LTC1482 is fully specified over the commercial and industrial temperature ranges and is available in 8-lead MSOP, PDIP and SO packages.
FEATURES
s
s s
s s s s s s
s s s s
No Damage or Latchup to 15kV (Human Body Model), IEC1000-4-2 Level 4 (8kV) Contact and Level 3 (8kV) Air Discharge Active Low Carrier Detect Output Guaranteed High Receiver Output State for Floating, Shorted or Terminated Inputs with No Signal Present Drives Low Cost Residential Telephone Wires Low Power: ICC = 700A Max with Driver Disabled ICC = 900A Max in Driver Mode Without Load 20A Max Quiescent Current in Shutdown Mode Single 5V Supply - 7V to 12V Common Mode Range Permits 7V Ground Difference Between Devices on the Data Line Maximum Data Rate of 4Mbps Power Up/Down Glitch-Free Driver Outputs Up to 32 Transceivers on the Bus Available in 8-Lead MSOP, PDIP and SO Packages
APPLICATIO S
s s s
Battery-Powered RS485/RS422 Applications Low Power RS485/RS422 Transceiver Level Translator
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
LTC1482 RO1 CD1 DE1 D DI1/SHDN1 GND1 R B1 A1 VCC1
Carrier Detect Output (2000 Foot STP Cable) RS485 Interface
DE1
LTC1482 VCC2 B2 120 120 GND2
1482 TA01
RO2 R CD2 DE2 D DI2/SHDN2
CD2 A2 B2
A2
DE1 DE2 = 0 1k PULL-UP AT CD
U
U
U
Dl1 = VCC Dl2 = VCC
1482 TA01a
1
LTC1482
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (VCC)............................................... 6.5V Control Input Voltages ................. - 0.3V to (VCC + 0.3V) Carrier Detect Voltage ................................. - 0.3V to 8V Driver Input Voltage ..................... - 0.3V to (VCC + 0.3V) Driver Output Voltages ................................. - 7V to 10V Receiver Input Voltages (Driver Disabled) .. -12V to 14V Receiver Output Voltage ............... - 0.3V to (VCC + 0.3V)
PACKAGE/ORDER INFORMATION
ORDER PART NUMBER
TOP VIEW RO CD DE DI/SHDN 1 2 3 4 8 7 6 5 VCC B A GND
LTC1482CMS8
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125C, JA = 200C/ W
MS8 PART MARKING LTCB
Consult factory for Military grade parts.
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V 5% (Notes 2 and 3) unless otherwise noted.
SYMBOL VOD1 VOD2 PARAMETER Differential Driver Output Voltage (Unloaded) Differential Driver Output Voltage (with Load) CONDITIONS IOUT = 0 R = 50 (RS422) R = 27 (RS485) Figure 1 R = 22, Figure 1 VTST = - 7V to 12V, Figure 2 R = 22, 27 or R = 50, Figure 1 VTST = - 7V to 12V, Figure 2 R = 22, 27 or R = 50, Figure 1 R = 22, 27 or R = 50, Figure 1 DE, DI/SHDN DE, DI/SHDN DE, DI/SHDN DE = 0, VCC = 0 or 5V, VIN = 12V DE = 0, VCC = 0 or 5V, VIN = -7V - 7V VCM 12V, DE = 0
q q q q q q q q q q q q q q
ELECTRICAL CHARACTERISTICS
VOD3 VOD VOC |VOC| VIH VIL IIN1 IIN2 VTHRO
Differential Driver Output Voltage (with Common Mode) 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 Input Low Voltage Input Current Input Current (A, B) with Driver Disabled Differential Input Threshold Voltage for Receiver
2
U
U
W
WW U
W
Junction Temperature .......................................... 125C Operating Temperature Range LTC1482C ........................................ 0C TA 70C LTC1482I ...................................... - 40C TA 85C Storage Temperature Range .................. - 65C to 150C Lead Temperature (Soldering, 10 sec)................... 300C
TOP VIEW RO 1 CD 2 DE 3 DI/SHDN 4 N8 PACKAGE 8-LEAD PDIP 8 7 6 5 VCC B A GND
ORDER PART NUMBER LTC1482CN8 LTC1482CS8 LTC1482IN8 LTC1482IS8 S8 PART MARKING 1482 1482I
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 125C, JA = 130C/ W (N8) TJMAX = 125C, JA = 135C/ W (S8)
MIN 2 1.5 1.5 1.5
TYP
MAX VCC 5 5 5 0.2 3 0.2
UNITS V V V V V V V V V
2 0.8 2 1.0 - 0.8 - 0.20 - 0.015
V A mA mA V
LTC1482
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V 5% (Notes 2 and 3) unless otherwise noted.
SYMBOL VTHCD VTH VOH VOL IOZR RIN ICC ISHDN IOSD1 IOSD2 IOS IPULL-UP PARAMETER Differential Input Threshold Voltage for CD = 1 Receiver Input Hysteresis CD Output High Voltage RO Output High Voltage RO and CD Output Low Voltage Three-State (High Impedance) Receiver Output Current in Shutdown Receiver Input Resistance Supply Current Supply Current in Shutdown Mode Driver Short-Circuit Current, VOUT = High (Note 4) Driver Short-Circuit Current, VOUT = Low (Note 4) RO and CD Short-Circuit Current CD Pull-Up Current CONDITIONS - 7V VCM 12V, DE = 0 VCM = 0V, DE = 0 IOUT = - 10A, (VA - VB) = 0V IOUT = - 4mA, (VA - VB) = 200mV IOUT = 4mA, (VA - VB) = - 200mV VCC = Max, 0.4V VOUT 2.4V DI/SHDN = 0, DE = 0 -7V VCM 12V No Load, Driver Enabled (DE = VCC) No Load, Driver Disabled (DE = 0) DE = 0, DI = 0 - 7V VOUT 10V - 7V VOUT 10V 0V VOUT VCC CD = 0V
q q q q q q q q q q q
ELECTRICAL CHARACTERISTICS
MIN - 0.20
TYP 30
MAX 0.20
UNITS V mV V V
3.4 3.5 0.4 1 12 22 580 430 10 35 35 7 15 30 900 700 20 250 250 85 60
V A k A A A mA mA mA A
SWITCHING CHARACTERISTICS
SYMBOL tPLH tPHL tSKEW tr, tf tZH tZL tLZ tHZ tZH(SHDN) tZL(SHDN) tHZ(SHDN) tLZ(SHDN) fMAX tPLH tPHL tSKD tCDH tCDL PARAMETER Driver Input to Output Driver Input to Output Driver Output to Output Driver Rise or Fall Time Driver Enable to Output High Driver Enable to Output Low Driver Disable Time from Low Driver Disable Time from High Driver Enable from Shutdown to Output High (Note 5) Driver Enable from Shutdown to Output Low Driver Disable on Shutdown from Output High Driver Disable on Shutdown from Output Low Maximum Data Rate (Note 6) Receiver Input to Output (Note 7) Receiver Input to Output |tPLH - tPHL| Differential Receiver Skew Receiver Input to CD Output High (Note 7) Receiver Input to CD Output Low (Note 7)
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V 5% (Notes 2 and 3) unless otherwise noted.
CONDITIONS RDIFF = 54, CL1 = CL2 = 100pF (Figures 4, 6)
q q q q
U
MIN 10 10 3
TYP 28 30 2 15 40 40 40 40 40 40 40 40
MAX 60 60 10 40 70 100 70 70 100 100 100 100 200 200
UNITS ns ns ns ns ns ns ns ns ns ns ns ns Mbps ns ns ns
CL = 100pF (Figures 5, 7) S2 Closed CL = 100pF (Figures 5, 7) S1 Closed CL = 15pF (Figures 5, 7) S1 Closed CL = 15pF (Figures 5, 7) S2 Closed CL = 100pF (Figures 5, 7) S2 Closed CL = 100pF (Figures 5, 7) S1 Closed CL = 15pF (Figures 5, 7) S2 Closed CL = 15pF (Figures 5, 7) S1 Closed RDIFF = 54, CL1 = CL2 = 100pF, (Figures 4, 8) RDIFF = 54, CL1 = CL2 = 100pF, (Figures 4, 8) RDIFF = 54, CL1 = CL2 = 100pF, (Figures 4, 8) RDIFF = 54, CL1 = CL2 = 100pF, (Figures 4, 10) DI/SHDN = VCC RDIFF = 54, CL1 = CL2 = 100pF, (Figures 4, 10) DI/SHDN = VCC
q q q q q q q q q q q
4 30 30
5 138 122 16
q q
2900 150
5000 300
ns ns
3
LTC1482
SWITCHING CHARACTERISTICS
SYMBOL PARAMETER tCDH(SHDN) Receiver Input to CD Output High at Shutdown tCDL(SHDN) Receiver Input to CD Output Low from Shutdown tZH(SHDN) Receiver Enable from Shutdown to Output High
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V 5% (Notes 2 and 3) unless otherwise noted.
CONDITIONS RDIFF = 54, CL1 = CL2 = 100pF, (Figures 4, 11) DI/SHDN = DE RDIFF = 54, CL1 = CL2 = 100pF, (Figures 4, 11) DI/SHDN = DE CL = 15pF (Figures 3, 9) S2 Closed, A = 750mV, B = - 750mV, DE = 0, DI/SHDN = CL = 15pF (Figures 3, 9) S1 Closed, A = - 750mV, B = 750mV, DE = 0, DI/SHDN = CL = 15pF (Figures 3, 9) S2 Closed, A = 750mV, B = - 750mV, DE = 0, DI/SHDN = CL = 15pF (Figures 3, 9) S1 Closed, A = - 750mV, B = 750mV, DE = 0, DI/SHDN =
q q q
tZL(SHDN)
Receiver Enable from Shutdown to Output Low
tHZ(SHDN)
Receiver Disable from High on Shutdown
tLZ(SHDN)
Receiver Disable from Low on Shutdown
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: All typicals are given for VCC = 5V and TA = 25C. Note 3: 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
Receiver Output Voltage vs Input Voltage
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
6 TA = 25C RECEIVER OUTPUT VOLTAGE (V) 5 4 3 2 1 0 -0.2 0 -0.02 -0.04 -0.06 -0.08 -0.1 -0.12 -0.14 -0.16 -0.18 -0.20 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G02
VCM = 12V
VCC = 5V VTHRO(HIGH)
RECEIVER INPUT THRESHOLD VOLTAGE (mV)
VTHRO(LOW) -0.16
VTHRO(HIGH) 0
1482 G01
-0.12 -0.08 -0.04 INPUT VOLTAGE (V)
4
UW
U
MIN
TYP 2600 2600 30
MAX 5000 5000 600
UNITS ns ns ns
q
2600
5000
ns
q
200
600
ns
q
200
600
ns
Note 4: For higher ambient temperatures, the part may enter thermal shutdown during short-circuit conditions. Note 5: Both driver input and driver enable pins are pulled high simultaneously. Note 6: Guaranteed by design. Note 7: Measured with an external LTC1485 driver.
Receiver Input Threshold Voltage (Output High) vs Temperature
0 -0.02 -0.04 -0.06 -0.08 -0.1 -0.12 -0.14 -0.16 -0.18
Receiver Input Threshold Voltage (Output Low) vs Temperature
VCC = 5V VTHRO(LOW)
VCM = 12V
VCM = 0V VCM = -7V
VCM = 0V VCM = -7V 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G03
-0.20 -55 -35 -15
LTC1482 TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Input Offset Voltage vs Temperature
0
RECEIVER INPUT OFFSET VOLTAGE (mV)
-20 -40
VCC = 5V
90 80 HYSTERESIS (mV) 70 60 50 40 30 20 10 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G04
VCC = 5V
RECEIVER INPUT THRESHOLD VOLTAGE (V)
-60 -80 -100 -120 -140 -160 -180 -200 -55 -35 -15 VCM = 0V VCM = -7V VCM = 12V
Carrier Detect Output Voltage vs Receiver Input Voltage
CARRIER DETECT THRESHOLD VOLTAGE (V)
CARRIER DETECT THRESHOLD VOLTAGE (V)
5.0 CARRIER DETECT OUTPUT VOLTAGE (V) 4.5 4.0 3.5 NEGATIVE, VTHCD(HIGH) 3.0 2.5 NEGATIVE VTHCD(LOW) 2.0 1.5 1.0 0.5 0 -0.25 -0.15 -0.05 0.05 0.15 RECEIVER INPUT VOLTAGE (V) 0.25
1482 G07
POSITIVE, VTHCD(HIGH)
POSITIVE VTHCD(LOW)
Receiver Output High Voltage vs Temperature
RECEIVER OUTPUT HIGH VOLTAGE (V) 4.4 4.3 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G10
VCC = 4.75V IOUT = -8mA
CARRIER DETECT OUTPUT HIGH VOLTAGE (V)
4.5
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -35 -30 -25 -20 -15 -10 OUTPUT CURRENT (A) -5 0
OUTPUT CURRENT (mA)
UW
Receiver Hysteresis vs Temperature
100 0 -0.02 -0.04 -0.06 -0.08 -0.10 -0.12 -0.14 -0.16 -0.18 -0.20
Receiver Input Threshold Voltage vs Supply Voltage
TA = 25C
VTHRO(HIGH)
VCM = -7V TO 12V
VTHRO(LOW)
0 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G05
4.5
4.75 5 5.25 SUPPLY VOLTAGE (V)
5.5
1482 G06
Carrier Detect Threshold Voltage (Output High) vs Temperature
0.25 0.20 0.15 0.10 0.05 0 -0.05 -0.10 -0.15 -0.20 VCC = 5V 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G08
Carrier Detect Threshold Voltage (Output Low) vs Temperature
0.25 0.20 0.15 0.10 0.05 0 -0.05 -0.10 -0.15 -0.20 VCC = 5V VCM = 0V VCM = -7V NEGATIVE VTHCD(LOW) VCM = 12V VCM = 0V POSITIVE VTHCD(LOW) VCM = 12V VCM = -7V
POSITIVE VTHCD(HIGH)
VCM = 12V VCM = -7V
NEGATIVE VTHCD(HIGH)
VCM = 0V VCM = 12V VCM = 0V VCM = -7V
-0.25 -55 -35 -15
-0.25 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G09
Carrier Detect Output High Voltage vs Output Current
5.0 4.5 4.0 30 25 20 15 10 5 0 VCC = 4.75V TA = 25C 40 35
Receiver and Carrier Detect Output Low Voltage vs Output Current
TA = 25C VCC = 4.75
0
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 OUTPUT LOW VOLTAGE (V)
2
1482 G11
1482 G12
5
LTC1482 TYPICAL PERFOR A CE CHARACTERISTICS
Receiver Output High Voltage vs Temperature
CARRIER DETECT OUTPUT HIGH VOLTAGE (V)
4.8 4.6 4.4 OUTPUT VOLTAGE (V) 4.2 4.0 3.8 3.6 3.4 3.2 3.0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G13
RECEIVER AND CARRIER DETECT OUTPUT LOW VOLTAGE
VCC = 4.75V I = 8mA
Receiver Propagation Delay vs Temperature
200 RECEIVER PROPAGATION DELAY (ns) 180 160 140 120 100 80 60 40 20 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G16
25 RECEIVER SKEW (ns) tPLH tPHL 20 |tPLH - tPHL| 15 10 5 0 -55 -35 -15
RECEIVER PROPAGATION DELAY (ns)
VCC = 5V
Receiver Short-Circuit Current vs Temperature
RECEIVER SHORT-CIRCUIT CURRENT (mA) 100 90 80 SUPPLY CURRENT (A) 70 60 50 40 30 20 10 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G19
900 800 OUTPUT LOW SHORT TO VCC 700 600 500 400 300 200 100
LOGIC INPUT THRESHOLD VOLTAGE (V)
VCC = 5.25V
OUTPUT HIGH SHORT TO GROUND
6
UW
Carrier Detect Output High Voltage vs Temperature
4.00 3.95 3.90 3.85 3.80 3.75 3.70 3.65 3.60 3.55 3.50 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G14
Receiver and Carrier Detect Output Low Voltage vs Temperature
0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G15
VCC = 4.75V IOUT = 10A
VCC = 4.75V IOUT = 8mA
VOH
Receiver Skew vs Temperature
30 VCC = 5V 150
Receiver Propagation Delay vs Supply Voltage
TA = 25C 140 tPLH
130 tPHL 120
110
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G17
100
4.5
4.75 5 5.25 SUPPLY VOLTAGE (V)
5.5
1482 G18
Supply Current vs Temperature
1000 VCC = 5V THERMAL SHUTDOWN WITH DRIVER ENABLED 2.00 1.95 1.90 1.85 1.80 1.75 1.70 1.65 1.60 1.55
Logic Input Threshold vs Temperature
DRIVER ENABLED NO LOAD
VCC = 5.25V
VCC = 5V
DRIVER DISABLED
VCC = 4.75V
0 -55 -30 -5
20 45 70 95 120 145 170 TEMPERATURE (C)
1482 G20
1.50 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G21
LTC1482 TYPICAL PERFOR A CE CHARACTERISTICS
Driver Differential Output Voltage vs Temperature
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V) DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V) 3.0 RL = 44 2.5 2.0 1.5 1.0 0.5 VOD, VCC = 4.5V TO 5.25V 0 -0.5 -55 -35 -15 3.0 2.5 2.0 1.5 1.0 0.5 VOD, VCC = 4.5V TO 5.25V 0 -0.5 -55 -35 -15 VCC = 5.25V VCC = 5V VCC = 4.75V VCC = 4.5V
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
VCC = 5.25V
VCC = 5V VCC = 4.75V VCC = 4.5V
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G22
Driver Common Mode Output Voltage vs Temperature
3.0 DRIVER COMMON MODE VOLTAGE (V) 2.5 2.0 1.5 1.0 0.5 VOC, VCC = 4.5V TO 5.25V 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G25
RL = 44 DRIVER COMMON MODE VOLTAGE (V)
2.5 2.0 1.5 1.0 0.5 VOC, VCC = 4.5V TO 5.25V 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G26
DRIVER COMMON MODE VOLTAGE (V)
VCC = 5.25V
VCC = 5V VCC = 4.75V VCC = 4.5V
Driver Differential Output Voltage vs Temperature
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V) SEE FIGURE 2 3.0 2.5 2.0 1.5 1.0 0.5 0 -0.5 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G28
VCM = -7V VOD3 DI/SD HIGH
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
3.5
VCC = 5.25V
VCC = 5V VCC = 4.75V VCC = 4.5V
VOD3 FOR VCC = 4.5V TO 5.25V
UW
Driver Differential Output Voltage vs Temperature
RL = 54 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0
Driver Differential Output Voltage vs Temperature
RL = 100
VCC = 5.25V
VCC = 5V VCC = 4.75V VCC = 4.5V
VOD, VCC = 4.5V TO 5.25V
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G23
-0.5 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G24
Driver Common Mode Output Voltage vs Temperature
3.0 RL = 54 3.0 2.5 2.0 1.5 1.0 0.5
Driver Common Mode Output Voltage vs Temperature
RL = 100
VCC = 5.25V
VCC = 5V VCC = 4.75V VCC = 4.5V
VCC = 5.25V
VCC = 5V VCC = 4.75V VCC = 4.5V
VOC, VCC = 4.5V TO 5.25V 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G27
Driver Differential Output Voltage vs Temperature
3.0 2.5 2.0 1.5 1.0 0.5 VOD3 FOR VCC = 4.5V TO 5.25V 0 -0.5 -55 -35 -15 VCC = 5.25V 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0
Driver Differential Output Voltage vs Output Current
VCC = 5V
VCC = 5V VCC = 4.75V VCC = 4.5V
VCM = 12V VOD3 DI/SD HIGH SEE FIGURE 2
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G29
0
10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA)
1482 G30
7
LTC1482 TYPICAL PERFOR A CE CHARACTERISTICS
Driver Output High Voltage vs Output Current
5.0 DRIVER OUTPUT HIGH VOLTAGE (V) DRIVER OUTPUT LOW VOLTAGE (V) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 OUTPUT CURRENT (mA)
1482 G31
DRIVER PROPAGATION DELAY (ns)
VCC = 4.75V
Driver Skew vs Temperature
5.0 DRIVER PROPAGATION DELAY (ns) 4.5 4.0 DRIVER SKEW (ns) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G34
35 30
tPHL tPLH
DRIVER SHORT-CIRCUIT CURRENT (mA)
PIN FUNCTIONS
RO (Pin 1): Receiver Output. If a carrier is present (CD low) and the part is not in shutdown, RO is high if the receiver input differential voltage (A - B) VTHRO(MAX) and low if (A - B) VTHRO(MIN). RO is forced to high (fail-safe state) if a carrier is not present (CD = 1). In shutdown, RO is three-stated. If the driver is enabled, RO follows the logic level at the driver input. CD (Pin 2): Open-Drain Carrier Detect Output. Provided that the part is not in shutdown, the CD output is low if VTHCD(MIN) (A - B) VTHCD(MAX) and high if VTHCD(MIN) < (A - B) < VTHCD(MAX). This is true regardless of whether the A and B pins are driven by the internal (DE = 1) or an external (DE = 0) driver. A weak internal pull-up removes the need for an external pull-up resistor if fast rise times are not important. Several LTC1482s can share the same CD line. CD = 1 forces RO to the high fail-safe state. In shutdown, CD is three-stated. This pin can be pulled above VCC but should not be taken above 8V to avoid damage. DE (Pin 3): Driver Enable Input. DE = 0 disables or threestates the driver outputs. DE = 1 enables the driver outputs with the high/low state of the outputs set by DI/SHDN. DI/SHDN (Pin 4): Driver Input and Shutdown Input. It is used together with the DE pin to put the part in shutdown
8
UW
Driver Output Low Voltage vs Output Current
3.0 VCC = 4.75V 2.5 2.0 1.5 1.0 0.5 0 40 35 30
Driver Propagation Delay vs Temperature
VCC = 5V tPLH tPHL 25 20 15 10 5 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G33
0
10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA)
1482 G32
Driver Propagation Delay vs Supply Voltage
40 TA = 25C 250
Driver Short-Circuit Current vs Temperature
VCC = 5.25V 200
25 20 15 10 5 0 4.5 4.75 5 5.25 SUPPLY VOLTAGE (V) 5.5
1482 G35
150
DRIVER OUTPUT HIGH SHORT TO -7V
100
DRIVER OUTPUT LOW SHORT TO 10V
50
0 -55 -35 -15
5 25 45 65 85 105 125 TEMPERATURE (C)
1482 G36
U
U
U
LTC1482
PIN FUNCTIONS
(DE = 0, DI/SHDN = 0) or to disable the driver while keeping the receiver alive (DE = 0, DI/SHDN = 1). When the driver is enabled (DE = 1), DI/SHDN = 0 forces the A output low and the B output high. DI/SHDN = 1 forces the A output high and the B output low. GND (Pin 5): Ground. A (Pin 6): Driver Output/Receiver Input. The input resistance is typically 22k when the driver is disabled (DE = 0). When the driver is enabled, the A output follows the logic level at the DI/SHDN pin. B (Pin 7): Driver Output/Receiver Input. The input resistance is typically 22k when the driver is disabled (DE = 0). When the driver is enabled, the B output is inverted from the logic level at the DI/SHDN pin. VCC (Pin 8): Positive Supply. 4.75V < VCC < 5.25V. A 0.1F bypass capacitor is recommended.
FU CTIO TABLES
Driver Enabled (DE = 1)
DI/SHDN 0 1 X A 0 1 B 1 0 RO 0 1 1 CD 0 0 1
A Shorted to B
Note 1: DE = 0, DI/SHDN = 0 puts the part in ICC shutdown and the supply current drawn by the VCC pin drops to 20A max. The receiver is always alive except in shutdown. Note 2: The table is valid regardless of the presence of an external termination resistor. Note 3: Although the RO and the driver outputs are three-stated, the A and B pins each present a 22k receiver input resistance to ground.
TEST CIRCUITS
375
A R VOD R B
1482 F01
Figure 1. Driver DC Test Load #1
DE A DI B RDIFF CL2 CL1 A
Figure 4. Driver/Receiver Timing Test Load
U
U
U
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Driver Disabled (DE = 0, Notes 1, 2)
DI/SHDN 0 1 1 1 1 1 A-B X (Note 3) VTHCD(MIN) < (A - B) < VTHCD(MAX) A and B are Open A and B are Shorted VTHCD(MIN) (A - B) VTHCD(MAX) and (A - B) VTHRO(MIN) VTHCD(MIN) (A - B) VTHCD(MAX) and (A - B) VTHRO(MAX) RO Z 1 1 1 0 1 CD 1 (Internal Pull-Up) 1 1 1 0 0
X = Don't Care Z = High Impedance
A
RECEIVER OUTPUT
VOD3
VOC
TEST POINT
S1
1k VCC
60 375
VTST -7V TO 12V
1482 F02
CL
1k
S2
1482 F03
B
Figure 2. Driver DC Test Load #2
VCC 1k CD RO B 15pF
Figure 3. Receiver Timing Test Load
S1 OUTPUT UNDER TEST 500 CL S2
1482 F05
VCC
1482 F04
Figure 5. Driver Timing Test Load
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LTC1482
SWITCHI G TI E WAVEFOR S
3V DI/SHDN 0V VO -VO B VO A 1/2 VO NOTE: DE = 1 tSKEW t SKEW
1482 F06
1.5V t PLH t DSKEW 10% tr 90% 50%
Figure 6. Driver Propagation Delays
3V DE 0V 5V A, B VOL VOH A, B 0V t ZH(SHDN), t ZH 2.3V t ZL(SHDN), t ZL 2.3V 1.5V
NOTE: DI = 0 FOR tZL(SHDN), tLZ(SHDN); DI = DE FOR tZH(SHDN), tHZ(SHDN); DI = DE FOR tZL, tLZ; DI = VCC FOR tZH, tHZ
Figure 7. Driver Enable and Disable Timing
VOD2 A-B - VOD2 5V RO VOL
0V t PHL 1.5V NOTE: tSKD = |tPHL - tPLH|, DE = VCC
Figure 8. Receiver Propagation Delays
3V DI 1.5V t ZL(SHDN) 1.5V 0V 5V RO 0V t ZH(SHDN) 1.5V
5V RO
NOTE: DE = 0, RO IS THREE-STATED IN SHUTDOWN, 1k PULL-UP FOR NORMALLY LOW OUTPUT, 1k PULL-DOWN FOR NORMALLY HIGH OUTPUT
Figure 9. Receiver Enable and Shutdown Timing
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f = 1MHz, tr 10ns, tf 10ns t PHL VO = V(A) - V(B)
1.5V
50% tf
90% 10%
f = 1MHz, tr 10ns, tf 10ns t LZ, t LZ(SHDN) OUTPUT NORMALLY LOW 500 PULL-UP TO VCC
1.5V
0.5V 0.5V t HZ, t HZ(SHDN)
1482 F07
OUTPUT NORMALLY HIGH, 500 PULL-DOWN TO GND
INPUT f = 1MHz, tr 10ns, tf 10ns OUTPUT t PLH
0V
1.5V
1482 F08
f = 1MHz, tr 10ns, tf 10ns t LZ(SHDN) OUTPUT
1.5V
0.5V 0.5V t HZ(SHDN)
1482 F09
OUTPUT
LTC1482
SWITCHI G TI E WAVEFOR S
VOD2 A-B - VOD2 VOH CD VOL NOTE: 1k PULL-UP AT CD 1.5V 1.5V
1482 F10
0V t CDL
Figure 10. Carrier Detect Timing
5V DI 0V t CDH(SHDN) VOH CD VOL VOD2 A-B - VOD2 5V RO 0V NOTE: 1k PULL-UP AT CD
1482 F11
1.5V
Figure 11. Shutdown Carrier Detect Timing
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INPUT t CDH
1.5V t CDL(SHDN) 1.5V 1.5V
THREE-STATE
11
LTC1482
APPLICATIONS INFORMATION
Carrier Detect Operation The carrier detect or CD pin is an open-drain output with a weak internal pull-up (30A typical). This allows several LTC1482s to share the same carrier detect line. The internal pull-up has a series diode, permitting users to tie the CD output to a voltage higher than VCC (8V max). When driving low, the CD output can sink up to 4mA while maintaining the output below a TTL VOL of 0.4V. An external pull-up resistor is recommended if fast rise times are important. The LTC1482 defines the presence of a carrier as VTHCD(MIN) (A - B) VTHCD(MAX). CD pulls low when a carrier is present. When the carrier is absent, the weak internal pull-up pulls CD high. For slow moving input signals (below about 32kHz for signals conforming to RS485 specifications), the CD output will go high when the (A - B) signal is within the VTHCD(MIN) to VTHCD(MAX) range. For faster input signals, the CD output does not glitch high when the (A - B) signal is traversing the transition region. This is achieved through internal delays in the CD signal path. It takes tCDH ( 5s) for CD to go high after the carrier signal is removed. There are no additional built-in delays for CD going low so that tCDL is only 300ns max. When the LTC1482 is not in shutdown mode, CD = 1 always forces the receiver output (RO) high. If the driver is enabled (DE = 1), CD = 0 as long as VTHCD min (A - B) VTHCD max. Shorting the A and B pins together or excessive loading between these pins will cause this condition to be violated and the CD pin will pull high. If the driver is disabled, CD is guaranteed to go high when: a) A is shorted to B, b) A and B are open (with or without termination) or c) VTHCD min A - B VTHCD max The last condition occurs if the external driver is loaded excessively. In shutdown mode, RO is three-stated and CD is taken high by the weak internal pull-up. On exiting shutdown, it takes longer (tCDL(SHDN) = 5s max) for CD to pull low when a carrier is present. When VCC is applied, some time is needed for CD and RO to become valid. The time needed depends on the capacitance at the CD pin, the VCC rise time and the loads connected to the A and B pins. For a load capacitance of 15pF and a 1s VCC rise time, a wait time of 10s is recommended. Receiver Output and Fail-Safe If CD is low, the receiver output, RO, responds to the input differential voltage and is guaranteed (by testing) to go high if (A - B) VTHRO(MAX) and low if (A - B) VTHCD(MIN). Some data encoding schemes require that the output of the receiver maintain a known state (usually logic 1) when data transmission ends and all drivers on the line are forced into three-state. The carrier detect mechanism ensures that RO will be high regardless of whether the line is open, floating or shorted together, or whether the line is terminated or not. This removes external components required with earlier RS485 devices for the case where the required known state is a logic 1. External components are needed if the required state is a logic 0. Fail-safe operates over the - 7V to 12V common mode range and fast common mode steps do not affect the receiver output. Note that the CD output only goes high after all the drivers are three-stated due to built-in delays (tCDH) in the CD signal path (see Carrier Detect Operation). During the time interval (see Figure 11) beginning at driver three-state and ending at CD going high, the receiver output stays at the last state just prior to the driver three-stating. ICC Shutdown Mode The supply current of the LTC1482 is reduced to 20A max by taking both the DE and DI/SHDN pins low. In shutdown, all internal circuits are powered down and the driver and receiver outputs are three-stated. The CD output is taken high by the weak internal pull-up. Logic within the LTC1482 prevents slow DE and DI/SHDN transitions from generating internal shutdown pulses by rejecting "shutdown pulses" of less than 50ns (typ) in duration. Without this logic, the driver outputs will glitch when three-stated momentarily.
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LTC1482
APPLICATIONS INFORMATION
The supply current does not drop below 20A immediately. DE and DI/SHDN must be low for a least 600ns simultaneously for ICC to drop to half its operating value (driver outputs unloaded) and for tCDH(SHDN) before dropping to the 20A level. Taking either DE or DI/SHDN high will wake the LTC1482 within 5s. In some applications, the A and B lines are pulled to VCC or GND through external resistors to force the line to a high or low state when all connected drivers are disabled. In shutdown, the supply current will be higher than 10A due to the additional current drawn through the external pullup and the 22k input resistance of the LTC1482. ESD Protection The ESD performance of the LTC1482 A and B pins is characterized to meet 15kV using the Human Body Model (100pF, 1.5k), IEC-1000-4-2 Level 4 (8kV) contact mode and IEC-1000-4-2 Level 3 (8kV) air discharge mode. This means that external voltage suppressors are not required in many applications, when compared with parts that are only protected to 2kV. Pins other than the A and B pins are protected to 3kV typical per the Human Body Model. When powered up, the LTC1482 does not latch up or sustain damage when the A and B pins are tested using any of the three conditions listed. The data during the ESD event may be corrupted, but after the event the LTC1482 continues to operate normally. The additional ESD protection at the A and B pins is important in applications where these pins are exposed to the external world via connections to sockets. Fault Protection When shorted to - 7V or 10V at room temperature, the short-circuit current in the driver pins is limited by internal protection circuitry to 250mA. Over the industrial temperature range, the absolute maximum positive voltage at any driver pin should be limited to 10V to avoid damage to the part. At higher ambient temperatures, the rise in die temperature, due to the short-circuit current, may trip the thermal shutdown circuit. This circuit 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 250mA. If the die temperature rises above 150C, the thermal shutdown circuit three-states the driver outputs to open the current path. When the die cools down to about 130C, 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. When the driver is disabled, the receiver inputs can withstand the entire - 7V to 12V RS485 common mode range without damage.
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LTC1482
PACKAGE DESCRIPTION
0.007 (0.18) 0.021 0.006 (0.53 0.015)
0 - 6 TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC 0.193 0.006 (4.90 0.15) 0.118 0.004** (3.00 0.102)
* 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
0.300 - 0.325 (7.620 - 8.255)
0.009 - 0.015 (0.229 - 0.381)
(
+0.035 0.325 -0.015 8.255 +0.889 -0.381
)
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
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Dimensions in inches (millimeters), unless otherwise noted.
MS8 Package 8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 0.004* (3.00 0.102)
0.040 0.006 (1.02 0.15)
0.034 0.004 (0.86 0.102)
8
76
5
0.006 0.004 (0.15 0.102)
MSOP (MS8) 1098
1
23
4
N8 Package 8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.400* (10.160) MAX 8 7 6 5
0.255 0.015* (6.477 0.381)
1
2
3
4 0.130 0.005 (3.302 0.127)
0.045 - 0.065 (1.143 - 1.651)
0.065 (1.651) TYP 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 0.003 (0.457 0.076)
N8 1098
0.100 (2.54) BSC
LTC1482
PACKAGE DESCRIPTION
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
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
0.016 - 0.050 (0.406 - 1.270)
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.
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Dimensions in inches (millimeters), unless otherwise noted.
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 - 0.197* (4.801 - 5.004) 8 7 6 5
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.050 (1.270) BSC
SO8 1298
15
LTC1482
TYPICAL APPLICATIO
RELATED PARTS
PART NUMBER LTC485 LTC1480 LTC1481 LTC1483 LTC1484 LTC1485 LTC1487 LTC1535 LTC1685 LTC1690 LT1785 DESCRIPTION 5V Low Power RS485 Interface Transceiver 3.3V Ultralow Power RS485 Transceiver with Shutdown 5V Ultralow Power RS485 Transceiver with Shutdown 5V Ultralow Power RS485 Low EMI Transceiver with Shutdown 5V Low Power RS485 Transceiver with Fail-Safe Receiver Output 5V RS485 Transceiver 5V Ultralow Power RS485 with Low EMI, Shutdown and High Input Impedance Isolated RS485 Transceiver 52Mbps RS485 Transceiver 5V Differential Driver and Receiver Pair with Fail-Safe Receiver Output 60V Fault Protected RS485 Transceiver COMMENTS Low Power Lower Supply Voltage Lowest Power Low EMI/Lowest Power Low Power, High Output State When Inputs are Open, Shorted or Terminated High Speed, 10Mbps, 15kV ESD Protection Highest Input Impedance, Low EMI, Lowest Power 2500VRMS Isolation Propagation Delay Skew 500ps (Typ) Low Power, 15kV ESD Protection 15kV ESD Protection, Industry Standard Pinout
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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Fail-Safe "0" Application (Idle State = Logic "0")
5V RO CD DE DI I2 I1 RO CD DE DI/ SHDN
1482 TA02
LTC1482 R VCC B A D GND "A" "B"
1482f LT/TP 0400 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1998

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