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Final Electrical Specifications
LTC1690 Differential Driver and Receiver Pair with Fail-Safe Receiver Output
September 1998
FEATURES
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DESCRIPTION
The LTC(R)1690 is a low power receiver/driver pair that is compatible with the requirements of EIA485 and EIA422. 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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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 = 600A 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
APPLICATIONS
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Battery-Powered EIA485/EIA422 Applications Low Power EIA485/EIA422 Transceiver Level Translator Line Repeater
TYPICAL APPLICATIO
3
LTC1690 5 D DRIVER 120 6 120 7 8
LTC1690
RECEIVER
7 R 2 RECEIVER 120 8 120
6 5 DRIVER 3 D
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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1690 TA01
1
LTC1690
ABSOLUTE MAXIMUM RATINGS
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 ........................................... 125C
PACKAGE/ORDER INFORMATION
ORDER PART NUMBER
TOP VIEW VCC R D GND 1 2 3 4 8 7 6 5 A B Z Y
LTC1690CMS8
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125C, JA = 200C/W
MS8 PART MARKING LTDA
Consult factory for Military Grade Parts
DC ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER VOD1 VOD2 VOD3 VOD VOC |VOC| VIH VIL IIN1 IIN2 VTH VTH Differential Driver Output Voltage (Unloaded) Differential Driver Output Voltage (with Load) 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) Differential Input Threshold Voltage for Receiver Receiver Input Hysteresis
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(Note 1)
Operating Temperature Range LTC1690C......................................... 0C TA 70C LTC1690I ..................................... - 40C TA 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
TOP VIEW VCC 1 R2 D3 GND 4 S8 PACKAGE 8-LEAD PLASTIC SO D 5 R 8 7 6 A B Z Y
ORDER PART NUMBER LTC1690CN8 LTC1690IN8 LTC1690CS8 LTC1690IS8 S8 PART MARKING 1690 1690I
N8 PACKAGE 8-LEAD PLASTIC DIP
TJMAX = 125C, JA = 130C/W (N) TJMAX = 125C, JA = 135C/W (S)
VCC = 5V 5% (Notes 2 and 3)
MIN
q q q
CONDITIONS IO = 0 R = 50; (EIA422) R = 22 or 27; (EIA485), Figure 1 VTST = -7V to 12V, Figure 2 R = 22, 27 or 50, Figure 1 VTST = -7V to 12V, Figure 2 R = 22, 27 or 50, Figure 1 R = 22, 27 or 50, Figure 1 Driver Input (D) Driver Input (D) Driver Input (D) VCC = 0V or 5.25V, VIN = 12V VCC = 0V or 5.25V, VIN = -7V -7V VCM 12V VCM = 0V
q q q q q q q q q
TYP
MAX VCC
UNITS V V V V V V V V
2 1.5 1.5
5 5 0.2 3 0.2
2 0.8 2 1 -0.8 - 0.20 30 - 0.01
V A mA mA V mV
LTC1690
DC ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER VOH VOL RIN ICC IOSD1 IOSD2 IOZ IOSR tPLH tPHL tSKEW tr, tf tPLH tPHL tSKD fMAX Receiver Output High Voltage Receiver Output Low Voltage Receiver Input Resistance Supply Current Driver Short-Circuit Current, VOUT = HIGH Driver Short-Circuit Current, VOUT = LOW Driver Three-State Current (Y, Z), VCC = 0V Receiver Short-Circuit Current Driver Input to Output, Figure 3, Figure 4 Driver Input to Output, Figure 3, Figure 4 Driver Output to Output, Figure 3, Figure 4 Driver Rise or Fall Time, Figure 3, Figure 4 Receiver Input to Output, Figure 3, Figure 5 Receiver Input to Output, Figure 3, Figure 5 |tPLH - tPHL|, Differential Receiver Skew, Figure 3, Figure 5 Maximum Data Rate, Figure 3, Figure 5
VCC = 5V 5% (Notes 2 and 3)
CONDITIONS IO = - 4mA, VID = 200mV IO = 4mA, VID = - 200mV -7V VCM 12V No Load -7V VO 10V -7V VO 10V -7V VO 10V 0V VO VCC RDIFF = 54, CL1 = CL2 = 100pF RDIFF = 54, CL1 = CL2 = 100pF RDIFF = 54, CL1 = CL2 = 100pF RDIFF = 54, CL1 = CL2 = 100pF RDIFF = 54, CL1 = CL2 = 100pF RDIFF = 54, CL1 = CL2 = 100pF RDIFF = 54, CL1 = CL2 = 100pF RDIFF = 54, CL1 = CL2 = 100pF
q q q q q q q q q q q q q
MIN 3.5
TYP
MAX 0.4
UNITS V V k A mA mA A mA ns ns ns ns ns ns ns Mbps
12 35 35
22 260 600 250 250 5 200 85 25 25 2 13 90 90 5 60 60 15 40 160 160
7 10 10 2 30 30 5
The q denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired.
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 = 25C.
PIN FUNCTIONS
VCC (Pin 1): Positive Supply. 4.75V < VCC < 5.25V. R (Pin 2): Receiver Output. R is high if (A - B) - 10mV and low if (A - B) - 200mV. 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. GND (Pin 4): Ground. Y (Pin 5): Driver Output. Z (Pin 6): Driver Output. B (Pin 7): Receiver Input. A (Pin 8): Receiver Input.
TEST CIRCUITS
Y R VOD2 R Z
1690 F01
VOC
Figure 1. Driver DC Test Load #1
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375 Y
D Y RDIFF Z
CL1
A R
VOD3
60 375
VTST -7V TO 12V
1690 F02
+
CL2
B
+
15pF
Z
1690 F03
Figure 2. Driver DC Test Load #2
Figure 3. Driver/Receiver Timing Test Load
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LTC1690
SWITCHI G TI E WAVEFOR S
3V D 0V VO -VO Z VO Y t SKEW 1/2 VO t SKEW
1690 F04
1.5V
f = 1MHz, t r 10ns, t f 10ns tPLH 90% tr 90%
1.5V tPHL
50% 10%
VO = V(A) - V(B)
tf
Figure 4. Driver Propagation Delays
FUNCTION TABLES
Driver
D 1 0 Z 0 1 Y 1 0
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 120. 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. 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. 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 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 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/s, but -7V to 12V steps in 10ns can be tolerated if the frequency of the common mode step is moderate (<600kHz).
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VOD2 A-B -VOD2 5V R VOL
0V
f = 1MHz, t r 10ns, t f 10ns INPUT tPHL 1.5V OUTPUT
0V tPLH 1.5V
1690 F05
50% 10%
NOTE: tSKD = |tPHL - tPLH|
Figure 5. Receiver Propagation Delays
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Receiver
A-B - 0.01V - 0.20V Inputs Open Inputs Shorted R 1 0 1 1
Note: Table valid with or without termination resistors.
LTC1690
APPLICATIONS INFORMATION
5V 1 LTC1690 5 D 3 DRIVER 6 SHIELD 120 7 8 RECEIVER 2 R LTC1690 1 5V
0.01F 7 R 2 RECEIVER 120 8 5 SHIELD 6 DRIVER 3 D
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1690 F06
Figure 6. Typical Application
Driver-Receiver Crosstalk 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 100 or 120 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. 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 maxiLTC1690 5 D 3 DRIVER 6
R
2
RECEIVER
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0.01F
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mum. 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 EIA485 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 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
DATA OUT
8 120 7 DATA IN
1690 F07
Figure 7. Line Repeater
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LTC1690
APPLICATIONS INFORMATION
LOSS PER 100 FT (dB)
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. Cables and Data Rate The transmission line of choice for EIA485 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 120 cables designed for EIA485 applications. 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). 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. ESD PROTECTION The ESD performance of the LTC1690 driver outputs (Z, Y) and the receiver inputs (A, B) is as follows: a) Meets 15kV Human Body Model (100pF, 1.5k). b) Meets IEC1000-4-2 Level 4 (8kV) contact mode specifications.
CABLE LENGTH (FT)
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1.0
0.1 0.1 1.0 10 100
1690 F08
FREQUENCY (MHz)
Figure 8. Attenuation vs Frequency for Belden 9841
10k
1k
100
10 10k
100k
1M
2.5M
10M
1690 F09
DATA RATE (bps)
Figure 9. EIA485 Cable Length Specification. Applies for 24 Gauge, Polyethylene Dielectric Twisted Pair
c) Meets IEC1000-4-2 Level 3 (8kV) air discharge 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 typically 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.
LTC1690
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) TYP 0.192 0.004 (4.88 0.10) 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)
0.065 (1.651) TYP 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 0.003 (0.457 0.076)
(
+0.035 0.325 -0.015 8.255 +0.889 -0.381
)
0.100 0.010 (2.540 0.254)
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
0.016 - 0.050 0.406 - 1.270
*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
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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) 1197
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
0.045 - 0.065 (1.143 - 1.651)
0.130 0.005 (3.302 0.127)
0.255 0.015* (6.477 0.381)
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2
3
4
N8 1197
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 - 0.197* (4.801 - 5.004) 0.053 - 0.069 (1.346 - 1.752) 0.004 - 0.010 (0.101 - 0.254) 8 7 6 5
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) TYP
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
SO8 0996
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LTC1690
TYPICAL APPLICATIONS
Receiver with Low Failsafe Output EIA232 Receiver
1.2k
EIA232 IN
120
RECEIVER
1.2k
1690 TA02 1690 TA03
RELATED PARTS
PART NUMBER LTC485 LTC490 LTC1481 LTC1483 LTC1485 LTC1487 LTC1480 LTC1482 LTC1484 LTC1685 LTC1686/LTC1687 DESCRIPTION 5V Low Power RS485 Interface Transceiver 5V Differential Driver and Receiver Pair 5V Ultralow Power RS485 Transceiver with Shutdown 5V Ultralow Power RS485 Low EMI Transceiver with Shutdown 5V Differential Bus Transceiver 5V Ultralow Power RS485 with Low EMI, Shutdown and High Input Impedance 3.3V Ultralow Power RS485 Transceiver with Shutdown 5V Low Power RS485 Transceiver with Carrier Detect Output 5V Low Power RS485 Transceiver with Receiver Open Circuit Fail-Safe 52Mbps, RS485 Fail-Safe Transceiver 52Mbps, RS485 Fail-Safe Driver/Receiver COMMENTS Low Power Low Power Lowest Power Low EMI, Lowest Power High Speed Highest Input Impedance, Low EMI, Lowest Power Lower Supply Voltage Low Power, High Output State when Inputs are Open, Shorted or Terminated. Carrier Detect Output. Low Power, High Output State when Inputs are Open, Shorted or Terminated Pin Compatible with LTC485 Pin Compatible with LTC490/LTC491
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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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2.7k
RX
2.7k
RECEIVER
RX
1690i LT/TP 0998 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1998

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