LTC1480IS8#TRPBF

LTC1480 3.3V Ultralow Power RS485 Transceiver U FEATURES DESCRIPTIO ■ The LTC®1480 is an ultralow power differential line transceiver which provides full RS485 compatibility while operating from a single 3.3V supply. It is designed for data transmission standard RS485 applications with extended common mode range (12V to –7V). It also meets the requirements of RS422 and features high speed operation up to 2.5Mb/s. The CMOS design offers significant power savings without sacrificing ruggedness against overload or ESD damage. Typical quiescent current is only 300µA while operating and 1µA in shutdown. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ True RS485 from a Single 3.3V Supply Low Power: ICC = 500µA Max with Driver Disabled ICC = 600µA Max with Driver Enabled, No Load 1µA Quiescent in Shutdown Mode –7V to 12V Common Mode Range Permits ±7V Ground Difference Between Devices on the Data Line Thermal Shutdown Protection Power Up/Down Glitch-Free Driver Outputs Permit Live Insertion or Removal of Transceiver Driver Maintains High Impedance in Three-State or with the Power Off Up to 32 Transceivers on the Bus 50ns Typical Driver Propagation Delays with 10ns Skew Pin Compatible with the LTC485 Available in 8-Lead DIP and SO Packages The driver and receiver feature three-state outputs, with the driver outputs maintaining high impedance over the entire 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 receiver has a fail-safe feature which guarantees a high output state when the inputs are left open. U APPLICATIO S ■ ■ ■ The LTC1480 is fully specified over the commercial and extended industrial temperature range. The LTC1480 is available in 8-pin SO and DIP packages. Battery-Powered RS485/RS422 Applications Low Power RS485/RS422 Transceiver Level Translator , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. U TYPICAL APPLICATIO Driver Differential Output Voltage vs Output Current 3.3V RS485 Network 3.3V 3.5 3.3V LTC1480 VCC = 3.3V TA = 25°C LTC1480 3.0 SHIELD 120Ω RE 120Ω A D RO R B B RE DE DI SHIELD R A 3.3V B R D A DE DI OUTPUT VOLTAGE (V) RO 2.5 2.0 1.5 1.0 0.5 LTC1480 D 0 0 1480 TA01 RO RE DE DI 10 20 30 40 50 60 70 OUTPUT CURRENT (mA) 80 90 1480 TA02 1480fa 1 LTC1480 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) ................................................ 7V Control Input Voltage ..................... – 0.3V to VCC + 0.3V Driver Input Voltage ....................... – 0.3V to VCC + 0.3V Driver Output Voltage ........................................... ±14V Receiver Input Voltage .......................................... ±14V Receiver Output Voltage ................ – 0.3V to VCC + 0.3V Operating Temperature Range LTC1480C ....................................... 0°C ≤ TA ≤ 70°C LTC1480I .................................... – 40°C ≤ TA ≤ 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C TOP VIEW RO 1 R RE 2 DE 3 D DI 4 N8 PACKAGE 8-LEAD PDIP 8 VCC 7 B 6 A 5 GND S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 125°C, θJA = 130°C/ W (N8) TJMAX = 125°C, θJA = 150°C/ W (S8) ORDER PART NUMBER S8 PART MARKING LTC1480CN8 LTC1480IN8 LTC1480CS8 LTC1480IS8 1480 1480I Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range. VCC = 3.3V (Notes 2, 3). SYMBOL PARAMETER CONDITIONS MIN VOD1 Differential Driver Output Voltage (Unloaded) IO = 0V ● VOD2 Differential Driver Output Voltage (with Load) R = 27Ω (RS485) (Figure 1) R = 50Ω (RS422) ● ● ∆VOD Change in Magnitude of Driver Differential Output Voltage for Complementary Output States R = 27Ω or R = 50Ω (Figure 1) VOC Driver Common Mode Output Voltage ∆⏐VOC⏐ TYP MAX UNITS 3.3 V 3.3 V V ● 0.2 V R = 27Ω or R = 50Ω (Figure 1) ● 2 V Change in Magnitude of Driver Common Mode Output Voltage for Complementary Output States R = 27Ω or R = 50Ω (Figure 1) ● 0.2 V VIH Input HIGH Voltage DE, DI, RE ● VIL Input LOW Voltage DE, DI, RE ● 0.8 IIN1 Input Current DE, DI, RE ● ±2 µA IIN2 Input Current (A, B) DE = 0, VCC = 0V or 3.6V, VIN = 12V DE = 0, VCC = 0V or 3.6V, VIN = – 7V ● ● 1.0 – 0.8 mA mA VTH Differential Input Threshold Voltage for Receiver – 7V ≤ VCM ≤ 12V ● – 0.2 0.2 V ∆VTH Receiver Input Hysteresis VCM = 0V VOH Receiver Output HIGH Voltage IO = – 4mA, VID = 200mV ● 2 VOL Receiver Output LOW Voltage IO = 4mA, VID = – 200mV ● 0.4 V IOZR Three-State (High Impedance) Output Current at Receiver VCC = Max, 0.4V ≤ VO ≤ 2.4V ● ±1 µA RIN Receiver Input Resistance – 7V ≤ VCM ≤ 12V ● ICC Supply Current No Load, Output Enabled No Load, Output Disabled ● ● ISHDN Supply Current in Shutdown Mode DE = 0, RE = VCC 1.5 2.0 2 V 70 V mV V 12 kΩ 400 300 600 500 µA µA 1 10 µA 1480fa 2 LTC1480 U SWITCHI G CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range. VCC = 3.3V (Notes 2, 3). SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IOSD1 Driver Short-Circuit Current, VOUT = HIGH – 7V ≤ VO ≤ 12V ● IOSD2 Driver Short-Circuit Current, VOUT = LOW – 7V ≤ VO ≤ 12V ● 35 250 mA 35 250 mA IOSR Receiver Short-Circuit Current 0V ≤ VO ≤ VCC ● 7 tPLH Driver Input to Output RDIFF = 54Ω, CL1 = CL2 = 100pF, (Figures 3, 5) ● 25 50 85 mA 80 ns tPHL Driver Input to Output ● 25 50 80 ns tSKEW Driver Output to Output ● 10 20 ns t R , tF Driver Rise or Fall Time ● 5 15 40 ns tZH Driver Enable to Output HIGH tZL tLZ tHZ tPLH tPHL Receiver Input to Output tSKD ⏐tPLH – tPHL⏐ Differential Receiver Skew tZL Receiver Enable to Output LOW CRL = 15pF (Figures 2, 8), S1 Closed ● 50 80 ns tZH Receiver Enable to Output HIGH CRL = 15pF (Figures 2, 8), S2 Closed ● 50 80 ns tLZ Receiver Disable from LOW CRL = 15pF (Figures 2, 8), S1 Closed ● 50 80 ns tHZ Receiver Disable from HIGH CRL = 15pF (Figures 2, 8), S2 Closed ● 50 80 fMAX Maximum Data Rate tSHDN Time to Shutdown tZH(SHDN) Driver Enable from Shutdown to Output HIGH tZL(SHDN) tZH(SHDN) tZL(SHDN) CL = 100pF (Figures 4, 6), S2 Closed ● 70 120 ns Driver Enable to Output LOW CL = 100pF (Figures 4, 6), S1 Closed ● 70 120 ns Driver Disable Time from LOW CL = 15pF (Figures 4, 6), S1 Closed ● 70 120 ns Driver Disable Time from HIGH CL = 15pF (Figures 4, 6), S2 Closed ● 70 120 ns Receiver Input to Output RDIFF = 54Ω, CL1 = CL2 = 100pF, (Figures 3, 7) ● 30 140 200 ns ● 30 140 200 ns 13 ns ns ● 2.5 DE = 0, RE = ● 50 200 600 ns CL = 100pF (Figures 4, 6), S2 Closed ● 70 120 ns Driver Enable from Shutdown to Output LOW CL = 100pF (Figures 4, 6), S1 Closed ● 70 120 ns Receiver Enable from Shutdown to Output HIGH CL = 15pF (Figures 2, 8), S2 Closed ● 4500 ns Receiver Enable from Shutdown to Output LOW CL = 15pF (Figures 2, 8), S1 Closed ● 4500 ns Note 2: All currents into device pins are positive; all currents out ot device pins are negative. All voltages are referenced to device ground unless otherwise specified. Note 3: All typicals are given for VCC = 3.3V and TA = 25°C. Mbits/s Note 1: Absolute maximum ratings are those beyond which the safety of the device cannot be guaranteed. U W TYPICAL PERFOR A CE CHARACTERISTICS 150 425 350 325 300 DRIVER DISABLED 275 250 2.2 VCC = 3.3V TA = 25°C 100 50 0 – 50 0 25 50 75 100 125 150 175 TEMPERATURE (°C) 1480 G01 2.0 1.9 RL = 54Ω 1.8 1.7 –100 1.6 –150 1.5 –40 –20 VCC = 3.3V 200 –50 –25 RL = 100Ω 2.1 DIFFERENTIAL VOLTAGE (V) THERMAL SHUTDOWN WITH DRIVER ENABLED 375 OUTPUT CURRENT (mA) SUPPLY CURRENT (µA) 400 225 Driver Differential Output Voltage vs Temperature Driver Output Low/High Voltage vs Output Current Supply Current vs Temperature VCC = 3.3V 0 0.5 1.0 1.5 2.0 2.5 OUTPUT VOLTAGE (V) 3.0 3.5 1480 G02 40 20 60 0 TEMPERATURE (°C) 80 100 1480 G03 1480fa 3 LTC1480 U W TYPICAL PERFORMANCE CHARACTERISTICS Receiver Output Low Voltage vs Output Current Driver Skew vs Temperature 25 7.0 – 16 VCC = 3.3V TA = 25°C VCC = 3.3V 6.5 – 14 5.0 4.5 4.0 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) 5.5 15 10 5 3.5 – 12 – 10 –8 –6 –4 –2 3.0 – 40 – 20 0 0 40 60 20 TEMPERATURE (°C) 80 100 0 3.30 3.05 2.80 2.55 2.30 2.05 1.80 1.55 1.30 OUTPUT VOLTAGE (V) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 OUTPUT VOLTAGE (V) 1480 G05 1480 G04 Receiver ⏐tPLH – tPHL⏐ vs Temperature 1480 G06 Receiver Output Low Voltage vs Temperature 12 Receiver Output High Voltage vs Temperature 3.0 0.6 10 OUTPUT VOLTAGE (V) 0.5 8 6 4 2.8 0.4 0.3 0.2 40 20 60 0 TEMPERATURE (°C) 80 100 0 –40 –20 2.6 2.4 2.2 0.1 2 0 –40 –20 VCC = 3.3V IO = 8mA VCC = 3.3V IO = 8mA OUTPUT VOLTAGE (V) VCC = 3.3V TIME (ns) VCC = 3.3V TA = 25°C 20 6.0 TIME (ns) Receiver Output High Voltage vs Output Current 40 20 60 0 TEMPERATURE (°C) 1480 G07 80 100 2.0 – 40 – 20 40 20 0 60 TEMPERATURE (°C) 1480 G08 80 100 1480 G09 U U U PI FU CTIO S RO (Pin 1): Receiver Output. If the receiver output is enabled (RE LOW) and A > B by 200mV, then RO will be HIGH. If A < B by 200mV, then RO will be LOW. RE (Pin 2): Receiver Output Enable. A LOW enables the receiver output, RO. A HIGH input forces the receiver output into a high impedance state. DE (Pin 3): Driver Outputs Enable. A HIGH on DE enables the driver output. A, B and the chip will function as a line driver. A low input will force the driver outputs into a high impedance state and the chip will function as a line receiver. If RE is high and DE is LOW, the part will enter a low power (1µA) shutdown state. If RE is low and DE is high, the driver outputs will be fed back to the receiver and the receive output will correspond to the driver input. DI (Pin 4): Driver Input. If the driver outputs are enabled (DE HIGH) then a low on DI forces the outputs A LOW and B HIGH. A HIGH on DI with the driver outputs enabled will force A HIGH and B LOW. GND (Pin 5): Ground. A (Pin 6): Driver Output/Receiver Input. B (Pin 7): Driver Output/Receiver Input. VCC (Pin 8): Positive Supply. 3.0V < VCC < 3.6V. 1480fa 4 LTC1480 U U FU CTIO TABLES LTC1480 Receiving LTC1480 Transmitting INPUTS INPUTS OUTPUTS RE DE DI B A RE DE X 1 1 0 1 0 OUTPUTS A–B RO 0 ≥ 0.2V 1 0 ≤ – 0.2V 0 X 1 0 1 0 0 0 0 X Z Z 0 0 Inputs Open 1 1 0 X Z* Z* 1 0 X Z* *Shutdown mode *Shutdown mode TEST CIRCUITS A S1 TEST POINT RECEIVER OUTPUT R VCC VOD VOC R 1k 1k CRL S2 B 1480 F02 1480 F01 Figure 1. Driver DC Test Load Figure 2. Receiver Timing Test Load 3V DE A DI LTC1480 DRIVER CL1 RDIFF B CL2 A S1 LTC1480 B RECEIVER RE VCC RO 15pF 500Ω OUTPUT UNDER TEST S2 CL 1480 F03 1480 F04 Figure 4. Driver Timing Test Load Figure 3. Driver/Receiver Timing Test Circuit U W W SWITCHI G TI E WAVEFOR S 3V f = 1MHz, tr ≤ 10ns, tf ≤ 10ns 1.5V DI 1.5V 0V t PLH 1/2 VO t PHL B VO A VO 0V –VO tSKEW 1/2 VO 90% 10% tr t SKEW 90% 10% VDIFF = V(A) – V(B) tf 1480 F05 Figure 5. Driver Propagation Delays 1480fa 5 LTC1480 U W W SWITCHI G TI E WAVEFOR S 3V f = 1MHz, tr ≤ 10ns, tf ≤ 10ns 1.5V DE 1.5V 0V t LZ t ZL(SHDN), t ZL 3.3V A, B VOL 2.3V OUTPUT NORMALLY LOW 0.5V 2.3V OUTPUT NORMALLY HIGH 0.5V VOH A, B 0V t HZ t ZH(SHDN), t ZH 1480 F06 Figure 6. Driver Enable and Disable Times VOH 1.5V RO VOL 1.5V OUTPUT f = 1MHz, tr ≤ 10ns, tf ≤ 10ns t PHL VOD2 A–B –VOD2 0V t PLH 0V INPUT 1480 F07 Figure 7. Receiver Propagation Delays 3V 1.5V RE t ZL(SHDN), tZL 3.3V RO VOL t LZ 1.5V OUTPUT NORMALLY LOW 0.5V 1.5V OUTPUT NORMALLY HIGH 0.5V VOH RO 1.5V f = 1MHz, tr ≤ 10ns, tf ≤ 10ns 0V 0V t HZ t ZH(SHDN), tZH 1480 F08 Figure 8. Receiver Enable and Disable Times U W U U APPLICATIO S I FOR ATIO VCC CMOS Output Driver The LTC1480 transceiver provides full RS485 compatibility while operating from a single 3.3V supply. The RS485 specification requires that a transceiver withstand common mode voltages of up to 12V or –7V at the RS485 line connections. Additionally, the transceiver must be immune to both ESD and latch-up. This rules out traditional CMOS drivers, which include parasitic diodes from their driver outputs to each supply rail (Figure 9). The LTC1480 uses a proprietary process enhancement which adds a pair of Schottky diodes to the output stage (Figure 10), preventing VCC SD3 P1 P1 D1 D1 OUTPUT LOGIC N1 D2 1480 F09 Figure 9. Conventional CMOS Output Stage OUTPUT LOGIC SD4 N1 D2 1480 F10 Figure 10. LTC1480 Output Stage 1480fa 6 LTC1480 U W U U APPLICATIO S I FOR ATIO current from flowing when the common mode voltage exceeds the supply rails. Latch-up at the output drivers is virtually eliminated and the driver is prevented from loading the line under RS485 specified fault conditions. When two or more drivers are connected to the same transmission line, a potential condition exists whereby more than two drivers are simultaneously active. If one or more drivers is sourcing current while another driver is sinking current, excessive power dissipation may occur within either the sourcing or sinking element. This condition is defined as driver contention, since multiple drivers are competing for one transmission line. The LTC1480 provides a current limiting scheme to prevent driver contention failure. When driver contention occurs, the current drawn is limited to about 70mA preventing excessive power dissipation within the drivers. The LTC1480 has a thermal shutdown feature which protects the part from excessive power dissipation. Under extreme fault conditions, up to 250mA can flow through the part causing rapid internal temperature rise. The thermal shutdown circuit will disable the driver outputs when the internal temperature reaches 150°C and turns them back on when the temperature cools to 130°C. This cycle will repeat as necessary until the fault condition is removed. Receiver Inputs The LTC1480 features an input common mode range covering the entire RS485 specified range of –7V to 12V. Differential signals of greater than ±200mV within the specified input common mode range will be converted to a TTL compatible signal at the receiver output. A small amount of input hysteresis is included to minimize the effects of noise on the line signals. If the receiver inputs are floating (unterminated) an internal pull-up of 10µA at the A input will force the receiver output to a known high state. Low Power Operation The LTC1480 draws very little supply current whenever the driver outputs are disabled. In shutdown mode the quiescent current is typically less than 1µA. With the receiver active and the driver outputs disabled, the LTC1480 will typically draw 300µA quiescent current. With the driver outputs enabled but unterminated, quiescent current will rise as one of the two outputs sources current into the internal receiver input resistance. With the minimum receiver input resistance of 12k and the maximum output swing of 3.3V, the quiescent current will rise by a maximum of 275µA. Typical quiescent current rise with the driver enabled is about 100µA. The quiescent current rises significantly if the driver is enabled when it is externally terminated. With 1/2 termination load (120Ω between the driver outputs) the quiescent current will jump to at least 13mA as the drivers force a minimum of 1.5V across the termination resistance. With a fully terminated 60Ω line attached, the current will rise to greater than 25mA with the driver enabled, completely overshadowing the extra 100µA drawn by internal receiver inputs. Shutdown Mode Both the receiver output (RO) and the driver outputs (A, B) can be placed in three-state mode by bringing RE HIGH and DE LOW respectively. In addition, the LTC1480 will enter shutdown mode when RE is HIGH and DE is LOW. In shutdown the LTC1480 typically draws only 1µA of supply current. In order to guarantee that the part goes into shutdown, RE must be high and DE must be LOW for at least 600ns simultaneously. If this time duration is less than 50ns the part will not enter shutdown mode. Propagation Delay Many digital encoding schemes are dependent upon the difference in the propagation delay times of the driver and receiver. Figure 11 shows the test circuit for the LTC1480 propagation delay. The receiver delay times are: ⏐tPLH – tPHL⏐ = 13ns Typ, VCC = 3.3V The driver’s skew times are: tSKEW = 10ns Typ, VCC = 3.3V 20ns Max, VCC = 3.3V, TA = – 40°C to 85°C 1480fa 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. 7 LTC1480 U U W U APPLICATIO S I FOR ATIO 100pF BR TTL IN t r, t f < 6ns D RECEIVER OUT R R 100Ω 1480 F11 100pF Figure 11. Receiver Propagation Delay Test Circuit U PACKAGE DESCRIPTIO N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 8.255 +0.889 –0.381 NOTE: 1. DIMENSIONS ARE .130 ± .005 (3.302 ± 0.127) .045 – .065 (1.143 – 1.651) .300 – .325 (7.620 – 8.255) .065 (1.651) TYP ) .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 .100 (2.54) BSC .400* (10.160) MAX 8 7 6 1 2 3 5 .255 ± .015* (6.477 ± 0.381) (0.457 ± 0.076) 4 N8 1002 INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .045 ±.005 .050 BSC .245 MIN 8 .160 ±.005 .189 – .197 (4.801 – 5.004) NOTE 3 7 6 .053 – .069 (1.346 – 1.752) 5 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .004 – .010 (0.101 – 0.254) .050 (1.270) BSC .014 – .019 (0.355 – 0.483) TYP .010 – .020 × 45° (0.254 – 0.508) .030 ±.005 TYP 1 2 3 4 .008 – .010 (0.203 – 0.254) RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 0°– 8° TYP .016 – .050 (0.406 – 1.270) SO8 0303 RELATED PARTS PART NUMBER LTC485 LTC1481 LTC1483 LTC1485 LTC1487 DESCRIPTION 5V Low Power RS485 Interface Transceiver 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 COMMENTS Low Power Lowest Power Low EMI/Lowest Power High Speed, 10Mbps High Input Impedance/Low EMI/Lowest Power 1480fa 8 Linear Technology Corporation LT/LT 0605 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1995