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LT1785/LT1785A LT1791/LT1791A 60V Fault Protected RS485/RS422 Transceivers
FEATURES
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DESCRIPTIO
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Protected from Overvoltage Line Faults to 60V Pin Compatible with LTC485 and LTC491 High Input Impedance Supports Up to 128 Nodes No Damage or Latchup to ESD IEC-1000-4-2 Level 4: 15kV Air Discharge IEC-1000-4-2 Level 2: 4kV Contact Discharge Controlled Slew Rates for EMI Emissions Control Guaranteed High Receiver Output State for Floating, Shorted or Inactive Inputs Outputs Assume a High Impedance When Off or Powered Down Drives Low Cost, Low Impedance Cables Short-Circuit Protection on All Outputs Thermal Shutdown Protection
The LT(R)1785/LT1791 are half-duplex and full-duplex differential bus transceivers for RS485 and RS422 applications which feature on-chip protection from overvoltage faults on the data transmission lines. Receiver input and driver output pins can withstand voltage faults up to 60V with respect to ground with no damage to the device. Faults may occur while the transceiver is active, shut down or powered off. Data rates to 250kbaud on networks of up to 128 nodes are supported. Controlled slew rates on the driver outputs control EMI emissions and improve data transmission integrity on improperly terminated lines. Drivers are specified to operate with inexpensive cables as low as 72 characteristic impedance. The LT1785A/LT1791A devices have "fail-safe" receiver inputs to guarantee a receiver output high for shorted, open or inactive data lines. On-chip ESD protection eliminates need for external protection devices. The LT1785/LT1785A are available in 8-lead DIP and SO packages and the LT1791/LT1791A in 14-lead DIP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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Industrial Control Data Networks CAN Bus Applications HVAC Controls
TYPICAL APPLICATIO
RO1 RE1 DE1 DI1 RX LT1785
Normal Operation Waveforms at 250kBaud
VCC1
RTERM RO
TX GND1 Y-Z VCC2
RO2 RE2 DE2 DI2
RX LT1785 RTERM DI
TX GND2
1785/91 TA01
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1785/91 TA02
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LT1785/LT1785A LT1791/LT1791A ABSOLUTE AXI U RATI GS
Supply Voltage (VCC) .............................................. 18V Receiver Enable Input Voltage .................... - 0.3V to 6V Driver Enable Input Voltage ........................ - 0.3V to 6V Driver Input Voltage .................................. - 0.3V to 18V Receiver Input Voltage ............................... - 60V to 60V Driver Output Voltage ............................... - 60V to 60V Receiver Output Voltage ................ - 0.3V to (VCC + 6V)
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW RO 1 RE 2 DE 3 DI 4 N8 PACKAGE 8-LEAD PDIP D R 8 7 6 5 VCC B A GND
LT1785CN8 LT1785CS8 LT1785IN8 LT1785IS8 LT1785ACN8 LT1785ACS8
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 150C, JA = 130C/ W (N8) TJMAX = 150C, JA = 150C/ W (S8)
S8 PART MARKING 1785 1785I 1785A
TJMAX = 150C, JA = 130C/ W (N) TJMAX = 150C, JA = 150C/ W (S)
Consult factory for Military grade parts.
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(Note 1)
Operating Temperature Range LT1785C/LT1791C/ LT1785AC/LT1791AC ............................. 0C to 70C LT1785I/LT1791I ............................... - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER
TOP VIEW NC 1 RO 2 RE 3 DE 4 DI 5 GND 6 GND 7 N PACKAGE 14-LEAD PDIP D R 14 VCC 13 NC 12 A 11 B 10 Z 9 8 Y NC
LT1791CN LT1791CS LT1791IN LT1791IS LT1791ACN LT1791ACS
S PACKAGE 14-LEAD PLASTIC SO
LT1785/LT1785A LT1791/LT1791A
DC ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C, VCC = 5V.
SYMBOL VOD1 VOD2 PARAMETER Differential Driver Output Voltage (Unloaded) Differential Driver Output Voltage (With Load) CONDITIONS IO = 0 R = 50 (RS422), Figure 1 R = 27 (RS485), Figure 1 R = 18 R = 27 or R = 50, Figure 1 R = 27 or R = 50, Figure 1 R = 27 or R = 50, Figure 1 DI, DE, RE DI, DE, RE DI, DE, RE VIN = 12V VIN = - 7V - 60V VIN 60V LT1785/LT1791: - 7V VCM 12V LT1785A/LT1791A: - 7V VCM 12V - 7V < VCM < 12V IO = - 400A, VID = 200mV IO = 1.6mA, VID = - 200mV RE > 2V or Power Off - 7V VCM 12V - 60V VCM 60V - 7V VCM 12V VOUT = HIGH, Force VO = - 7V VOUT = LOW, Force VO = 12V VO = 60V VO = - 60V 0V VO VCC -7V VO 12V - 60V VO 60V No Load, RE = 0V, DE = 5V No Load, RE = 5V, DE = 5V No Load, RE = 0V, DE = 0V No Load, RE = 5V, DE = 0V
q q q q q q q q q q q q q q q q q q q q
MIN 2.0 1.5 1.2
TYP 4.1 2.70 2.45 2.2
MAX 5
UNITS V V V V
VOD VOC VOC VIH VIL IIN1 IIN2
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); (LT1791 or LT1785 with DE = 0V) Differential Input Threshold Voltage for Receiver Receiver Input Hysteresis Receiver Output High Voltage Receiver Output Low Voltage Three-State (High Impedance) Output Current at Receiver 0V < VOUT < 6V
0.2 2 2.5 3 0.2 2 0.8 5 - 0.15 -6 - 0.2 - 0.2 20 3.5 -1 85 50 35 35 -6 30 - 0.2 -6 5.5 5.5 4.5 0.2 0.3 6 9 9 8 0.3 125 125 90 0.25 250 250 6 4 0.3 0.5 1 0.15 - 0.08 0.3 6 0.2 0
V V V V V A mA mA mA V V mV V V A k k k mA mA mA mA mA mA mA mA mA mA mA
VTH VTH VOH VOL
RIN
Receiver Input Resistance (LT1791) LT1785 RS485 Unit Load
ISC
Driver Short-Circuit Current Driver Output Fault Current Receiver Short-Circuit Current Driver Three-State Output Current
q q q q q q q q q q q
ICC
Supply Current
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LT1785/LT1785A LT1791/LT1791A
SWITCHI G CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C, VCC = 5V.
SYMBOL tPLH tPHL tSKEW tr, tf tZH tZL tLZ tHZ tPLH tPHL tSKD tZL tZH tLZ tHZ fMAX tSHDN tZH(SHDN) tZL(SHDN) tZH(SHDN) tZL(SHDN) 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 Receiver Input to Output Receiver Input to Output Differential Receiver Skew Receiver Enable to Output Low Receiver Enable to Output High Receiver Disable from Low Receiver Disable from High Maximum Data Rate Time to Shut Down Driver Enable from Shutdown to Output High Driver Enable from Shutdown to Output Low Receiver Enable from Shutdown to Output High Receiver Enable from Shutdown to Output Low Figures 2, 6, 8 Figures 2, 6; RE = 5V Figures 2, 6; RE = 5V Figures 2, 8; DE = 0V Figures 2, 8; DE = 0V Figures 2, 8 Figures 2, 8 Figures 2, 8 Figures 2, 8
q q q q q
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Differential Output Voltage vs Load Resistance
4 TA = 25C
OUTPUT VOLTAGE (V)
3
DIFFERENTIAL VOLTAGE (V)
2
1.5 1.0 0.5
DELAY (ns)
1
0 10 100 LOAD RESISTANCE () 1k
1785/91 G01
4
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CONDITIONS Figures 3, 5 Figures 3, 5 Figures 3, 5 Figures 3, 5 Figures 4, 6 Figures 4, 6 Figures 4, 6 Figures 4, 6 Figures 3, 7 Figures 3, 7
q q q q q q q q q
MIN
TYP 700 700 100
MAX 2000 2000 2000 3000 3000 5000 5000 900 900 1000 1000 1000 1000
UNITS ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns kbps s s s s s
200
800 500 800 200 800 400 400 200 300 300 400 400
250 3 12 12 4 4
Driver Differential Output Voltage vs Temperature
3.0 2.5 2.0 600 1000
Receiver Propagation Delay vs Temperature
800
tPHL
400
tPLH
200
R = 27 0 -40 -20
40 20 0 60 TEMPERATURE (C)
80
100
0 -40
-20
40 0 60 20 TEMPERATURE (C)
80
100
1785/91 G03
1785/91 G03
LT1785/LT1785A LT1791/LT1791A TYPICAL PERFORMANCE CHARACTERISTICS
Driver Propagation Delay vs Temperature
1000 900
PROPAGATION DELAY (ns)
800 700 600 500 400 300 200 100 0 -40 -20 40 0 60 20 TEMPERATURE (C) 80 100 LH
HL
LT1785 Input Characteristics Pins A or B; DE = RE = 0V
7 6 5
ICC (mA)
1mA/DIV
4 3 2
DELAY (ns)
- 60V VA, VB
PIN FUNCTIONS
RO: Receiver Output. TTL level logic output. If the receiver is active (RE pin low), RO is high if receiver input A B by 200mV. If A B by 200mV, then RO will be low. RO assumes a high impedance output state when RE is high or the part is powered off. RO is protected from output shorts from ground to 6V. RE: Receiver Output Enable. TTL level logic input. A logic low on RE enables normal operation of the receiver output RO. A logic high level at RE places the receiver output pin RO into a high impedance state. If receiver enable RE and driver enable DE are both in the disable state, the circuit goes to a low power shutdown state. Placing either RE or DE into its active state brings the circuit out of shutdown. Shutdown state is not entered until a 3s delay after both RE and DE are disabled, allowing for logic skews in toggling between transmit and receive modes of operation. For CAN bus applications, RE should be tied low to prevent the circuit from entering shutdown. DE: Driver Output Enable. TTL level logic input. A logic high on DE enables normal operation of the driver outputs (Y and Z on LT1791, A and B on LT1785). A logic low level at DE places the driver output pins into a high impedance
UW
1785/91 G04
LT1791 Driver Output Leakage DE = 0V
LT1791 Receiver Input Current vs VIN
1mA/DIV
200A/DIV
- 60V VOUT
60V
1785/91 G05
- 60V VIN
60V
1785/91 G06
Supply Current vs Temperature
700
Receiver Propagation Delay vs Differential Input Voltage
600 HL VCM = -7V 500 HL VCM = 12V LH VCM = -7V LH VCM = 12V
DRIVER AND RECEIVER ON
RECEIVER ONLY
400 300 200 100
60V
1785/91 G07
1 0 -40 STANDBY -20 40 0 60 20 TEMPERATURE (C) 80 100
0 0 1 3 4 2 VIN DIFFERENTIAL (V) 5
1785/91 G09
1785/91 G08
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LT1785/LT1785A LT1791/LT1791A
PIN FUNCTIONS
state. If receiver enable RE and driver enable DE are both in the disable state, the circuit goes to a low power shutdown state. Placing either RE or DE into its active state brings the circuit out of shutdown. Shutdown state is not entered until a 3s delay after both RE and DE are disabled, allowing for logic skews in toggling between transmit and receive modes of operation. For CAN bus operation the DE pin is used for signal input to place the data bus in dominant or recessive states. DI: Driver Input. TTL level logic input. A logic high at DI causes driver output A or Y to a high state, and output B or Z to a low state. Complementary output states occur for DI low. For CAN bus applications DI should be tied low. GND: Ground. Y: Driver Output. The Y driver output is in phase with the driver input DI. In the LT1785 driver output Y is internally connected to receiver input A. The driver output assumes a high impedance state when DE is low, power is off or thermal shutdown is activated. The driver output is protected from shorts between 60V in both active and high impedance modes. For CAN applications, output Y is the CANL output node. Z: Driver Output. The Z driver output is opposite in phase to the driver input DI. In the LT1785 driver output Z is internally connected to receiver input B. The driver output assumes a high impedance state when DE is low, power is off or thermal shutdown is activated. The driver output is protected from shorts between 60V in both active and high impedance modes. For CAN applications, output Z is the CANH output node. A: Receiver Input. The A receiver input forces a high receiver output when V(A) [V(B) + 200mV]. V(A) [V(B) - 200mV] forces a receiver output low. Receiver inputs A and B are protected against voltage faults between 60V. The high input impedance allows up to 128 LT1785 or LT1791 transceivers on one RS485 data bus. The LT1785A/LT1791A have guaranteed receiver input thresholds -200mV < VTH < 0. Receiver outputs are guaranteed to be in a high state for 0V inputs. B: Receiver Input. The B receiver input forces a high receiver output when V(A) [V(B) + 200mV]. When V(A) [V(B) - 200mV], the B receiver forces a receiver output low. Receiver inputs A and B are protected against voltage faults between 60V. The high input impedance allows up to 128 LT1785 or LT1791 transceivers on one RS485 data bus. The LT1785A/LT1791A have guaranteed receiver input thresholds -200mV < VTH < 0. Receiver outputs are guaranteed to be in a high state for 0V inputs. VCC: Positive Supply Input. For RS422 or RS485 operation, 4.75V VCC 5.25V. Higher VCC input voltages increase output drive swing. VCC should be decoupled with a 0.1F low ESR capacitor directly at Pin 8 (VCC).
TEST CIRCUITS
A R VOD R B
1785/91 F01
Figure 1. Driver DC Test Load
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RECEIVER OUTPUT
VOC
TEST POINT
S1
1k VCC
CRL
1k
S2
1785/91 F02
Figure 2. Receiver Timing Test Load
LT1785/LT1785A LT1791/LT1791A
TEST CIRCUITS
5V DE A DI B RDIFF CL2 CL1 A RO B RE 15pF
S1 OUTPUT UNDER TEST 500 S2 CL
1785/91 F04
1785/91 F03
VCC
Figure 3. Driver/Receiver Timing Test Circuit
Figure 4. Driver Timing Test Load
FU CTIO TABLES
LT1785 Transmitting
INPUTS RE 0 0 1 1 1 DE 1 1 0 1 1 DI 0 1 X 0 1 A 0 1 Hi-Z 0 1 OUTPUTS B 1 0 Hi-Z 1 0 RO 0 1 Hi-Z Hi-Z Hi-Z RE 0 0 0 0 0 0 INPUTS RE 0 0 0 1 DE 0 0 0 0 DI X X X X A-B - 200mV 200mV* Open X OUTPUT RO 0 1 1 Hi-Z 0 0 0 1 1 1 DE 0 0 0 1 1 1 1 1 1 0 1 1
LT1785 Receiving
* 0mV for LT1785A
SWITCHI G TI E WAVEFOR S
5V DI 0V t PLH B VO A VO 0V -VO 1/2 VO 10% tr tSKEW 90% VDIFF = V(A) - V(B) tf t SKEW 90% 10%
1785/91 F05
1.5V
Figure 5. Driver Propagation Delays
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LT1791
INPUTS DI X X X 0 0 0 1 1 1 X 0 1 A-B - 200mV 200mV* Open - 200mV 200mV* Open - 200mV 200mV* Open X X X Y Hi-Z Hi-Z Hi-Z 0 0 0 1 1 1 Hi-Z 0 1 OUTPUTS Z Hi-Z Hi-Z Hi-Z 1 1 1 0 0 0 Hi-Z 1 0 RO 0 1 1 0 1 1 0 1 1 Hi-Z Hi-Z Hi-Z
* 0mV for LT1791A
f = 125kHz, t r 10ns, t f 10ns t PHL
1.5V 1/2 VO
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LT1785/LT1785A LT1791/LT1791A
SWITCHI G TI E WAVEFOR S
5V DE 0V 5V A, B VOL VOH A, B 0V t ZH(SHDN), t ZH t HZ
1785/91 F06
Figure 6. Driver Enable and Disable Times
VOH RO VOL t PHL VOD2 A-B -VOD2 0V 1.5V OUTPUT f = 125kHz, t r 10ns, t f 10ns INPUT t PLH 0V
1785/91 F07
Figure 7. Receiver Propagation Delays
5V RE 0V 5V RO 1.5V f = 125kHz, tr 10ns, tf 10ns t ZL(SHDN), tZL 1.5V OUTPUT NORMALLY LOW t LZ 0.5V 1.5V
RO 0V
Figure 8. Receiver Enable and Disable Times
APPLICATIO S I FOR ATIO
Overvoltage Protection
The LT1785/LT1791 RS485/RS422 transceivers answer an applications need for overvoltage fault tolerance on data networks. Industrial installations may encounter common mode voltages between nodes far greater than the - 7V to 12V range specified for compliance to RS485 standards. CMOS RS485 transceivers can be damaged by voltages above their absolute maximum ratings of typi-
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1.5V
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f = 125kHz, t r 10ns, t f 10ns t ZL(SHDN), t ZL t LZ
1.5V
2.3V
OUTPUT NORMALLY LOW
0.5V
2.3V
OUTPUT NORMALLY HIGH
0.5V
1.5V
1.5V
OUTPUT NORMALLY HIGH t HZ
0.5V
1785/91 F08
t ZH(SHDN), tZH
cally - 8V to 12.5V. Replacement of standard RS485 transceiver components with the LT1785 or LT1791 devices eliminates field failures due to overvoltage faults or the use of costly external protection devices. The limited overvoltage tolerance of CMOS RS485 transceivers makes implementation of effective external protection networks difficult without interfering with proper data network performance within the - 7V to 12V region of RS485 operation.
LT1785/LT1785A LT1791/LT1791A
APPLICATIO S I FOR ATIO
The high overvoltage rating of the LT1785/LT1791 facilitates easy extension to almost any level. Simple discrete component networks that limit the receiver input and driver output voltages to less than 60V can be added to the device to extend protection to any desired level. Figure 11 shows a protection network against faults to the 120VAC line voltage. The LT1785/LT1791 protection is achieved by using a high voltage bipolar integrated circuit process for the transceivers. The naturally high breakdown voltages of the bipolar process provides protection in powered-off and high impedance conditions. The driver outputs use a foldback current limit design to protect against overvoltage faults while still allowing high current output drive. ESD Protection The LT1785/LT1791 I/O pins have on-chip ESD protection circuitry to eliminate field failures caused by discharges to exposed ports and cables in application environments. The LT1785 pins A and B and the LT1791 driver output pins Y and Z are protected to IEC-1000-4-2 level 2. These pins will survive multiple ESD strikes of 15kV air discharge or 4kV contact discharge. Due to their very high input impedance, the LT1791 receiver pins are protected to IEC-1000-4-2 level 2, or 15kV air and 4kV contact discharges. This level of ESD protection will guarantee immunity from field failures in all but the most severe ESD environments. The LT1791 receiver input ESD tolerance may be increased to IEC level 4 compliance by adding 2.2k resistors in series with these pins. Low Power Shutdown The LT1785/LT1791 have RE and DE logic inputs to control the receive and transmit modes of the transceivers. The RE input allows normal data reception when in the low state. The receiver output goes to a high impedance state when RE is high, allowing multiplexing the RO data
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line. The DE logic input performs a similar function on the driver outputs. A high state on DE activates the differential driver outputs, a low state places both driver outputs into high impedance. Tying the RE and DE logic inputs together may be done to allow one logic signal to toggle the transceiver from receive to transmit modes. The DE input is used as the data input in CAN bus applications. Disabling both the driver and receiver places the device into a low supply current shutdown mode. An internal time delay of 3s minimum prevents entering shutdown due to small logic skews when a toggle between receive and transmit is desired. The recovery time from shutdown mode is typically 12s. The user must be careful to allow for this wake-up delay from shutdown mode. To allow full 250kbaud data rate transmission in CAN applications, the RE pin should be tied low to prevent entering shutdown mode. Slew Limiting for EMI Emissions Control The LT1785/LT1791 feature controlled driver output slew rates to control high frequency EMI emissions from equipment and data cables. The slew limiting limits data rate operation to 250kbaud. Slew limiting also mitigates the adverse affects of imperfect transmission line termination caused by stubs or mismatched cable. In some low speed, short distance networks, cable termination may be eliminated completely with no adverse effect on data transmission. Data Network Cable Selection and Termination Long distance data networks operating at high data transmission rates should use high quality, low attenuation cable with well-matched cable terminations. Short distance networks at low data rates may use much less expensive PVC cable. These cables have characteristic impedances as low as 72. The LT1785/LT1791 output drivers are guaranteed to drive cables as low as 72.
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LT1785/LT1785A LT1791/LT1791A
APPLICATIO S I FOR ATIO
A 12 RO RE DE DI 2 3 4 5 LT1791 Z 10 TX RX B 11
120 11 B
Y9
Figure 9. Full-Duplex RS422
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.400* (10.160) MAX 8 7 6 5
0.300 - 0.325 (7.620 - 8.255)
0.045 - 0.065 (1.143 - 1.651)
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)
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP 0.053 - 0.069 (1.346 - 1.752) 0.189 - 0.197* (4.801 - 5.004) 0.004 - 0.010 (0.101 - 0.254) 8 7 6 5
0.016 - 0.050 0.406 - 1.270
0.014 - 0.019 (0.355 - 0.483)
*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 1 2 3 4
SO8 0996
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12 A TX 5 4 LT1791 10 Z 120 9Y RX 2 3 DI DE RE RO
1785/91 F09
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0.130 0.005 (3.302 0.127)
0.255 0.015* (6.477 0.381)
1
2
3
4
N8 1197
0.050 (1.270) TYP
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
LT1785/LT1785A LT1791/LT1791A
PACKAGE DESCRIPTION
0.300 - 0.325 (7.620 - 8.255)
0.009 - 0.015 (0.229 - 0.381) 0.005 (0.125) MIN 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) +0.035 0.325 -0.015 +0.889 8.255 -0.381
(
)
S Package 14-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.337 - 0.344* (8.560 - 8.738) 14 13 12 11 10 9 8
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
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 circuits as described herein will not infringe on existing patent rights.
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Dimensions in inches (millimeters) unless otherwise noted. N Package 14-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.770* (19.558) MAX 14 13 12 11 10 9 8
0.255 0.015* (6.477 0.381)
1 0.130 0.005 (3.302 0.127) 0.020 (0.508) MIN
2
3
4
5
6
7
0.045 - 0.065 (1.143 - 1.651)
0.065 (1.651) TYP 0.125 (3.175) MIN 0.018 0.003 (0.457 0.076)
N14 1197
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
5
6
7
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) TYP
S14 0695
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LT1785/LT1785A LT1791/LT1791A
TYPICAL APPLICATIONS
RO RE DE DI 1 2 3 4 LT1785 A6 6 A LT1785 7 B 6 A LT1785 7 B 6A LT1785 RX B7 RT 120 RT 120 7B RX 1 2 3 4 RO RE DE DI
1785/91 F10
TX
RO RE DE DI
1 2 3 4
RX LT1785
TX
Figure 11. RS485 Network with 120V AC Line Fault Protection
RELATED PARTS
PART NUMBER LTC485 LTC491 LTC1483 LTC1485 LTC1487 LTC1520 LTC1535 LTC1685 LTC1687 DESCRIPTION Low Power RS485 Interface Transceiver Differential Driver and Receiver Pair Ultralow Power RS485 Low EMI Transceiver Differential Bus Transceiver Ultralow Power RS485 with Low EMI, Shutdown and High Input Impedance 50Mbps Precision Quad Line Receiver Isolated RS485 Full-Duplex Transceiver 52Mbps RS485 Half-Duplex Transceiver 52Mbps RS485 Full-Duplex Transceiver COMMENTS ICC = 300A (Typ) ICC = 300A Controlled Driver Slew Rate 10Mbaud Operation Up to 256 Transceivers on the Bus Channel-to-Channel Skew 400ps (Typ) 2500VRMS Isolation in Surface Mount Package Propagation Delay Skew 500ps (Typ) Propagation Delay Skew 500ps (Typ)
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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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TX
4 DI DE
3
2 RE
1 RO
4 DI
3 DE
2 RE
1 RO
Figure 10. Half-Duplex RS485 Network Operation
8 B7
VCC
RAYCHEM POLYSWITCH TR600-150 x2 47 RT,120
A6 5 0.1F 47 300V CARBON COMPOSITE 5W 1.5KE36CA
1785/91 F11
178591f LT/TP 0300 4K * PRINTED IN THE USA
(c) LINEAR TECHNOLOGY CORPORATION 1998

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