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STC3485E
General Description
3.3V-Powered, 15kV ESD-Protected, and Slew-Rate-Limited True RS-485 Transceivers
The STC3485E is +15 KV ESD protected, slew-rate limited, ultra lower differential line transceivers which provide full RS485 compatibility while operating from single 3.3V supply. Each part contains one driver and one receiver, which is designed for data transmission with extended common mode range (-7V to 12V). The STC3485E features slew-rate limited driver that minimizes EMI and reduces reflections caused by improperly terminated cables, allowing error-free data transmission at data rate up to 500kbps. All devices feature enhanced electrostatic discharge (ESD) protection. All transmitter outputs and receiver inputs are protected to 15kV using IEC 1000-4-2 Air-Gap Discharge and 15kV using the Human Body Model. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if both inputs are open, shorted or idle. Both parts have power up/down glitch free driver outputs permit live insertion or removal of transceiver from/to data bus. The CMOS design offers significant power savings without sacrificing ruggedness against overload or ESD damage. Typical quiescent current is only 500 while operating and 1 in shutdown. A A The STC3485E are fully specified over the commercial an extended industrial temperature range and are available in 8-pin and DIP packages.
Applications
Telecommunications Low-Power RS-485 Transceivers Integrated Services Digital Networks Transceivers for EMI-Sensitive Applications Packet Switching
Features
ESD Protection for RS-485 I/O Pins 15kV-- Human Body Model 15kV-- IEC 1000-4-2, Air-Gap Discharge Operate from a Single 3.3V supply Interoperable with +5V Logic Slew-Rate Limited for Errorless Data Transmission 1 Low-Current Shutdown Mode A - to +12V Common-Mode Input Voltage Range 7V Allows up to 256 Transceivers on the Bus Thermal Shutdown Current-Limiting for Driver Overload Protection
Ordering Information
PART STC3485EESA STC3485EEPA TEMP. RANGE -40 to +85 C C -40 to +85 C C PIN-PACKAGE 8 SO 8 Plastic DIP
Selector Guide
PART NUMBER STC3485E GUARANTEED DATA RATE (Mbps) 0.5 SUPPLY VOLTAGE (V) 3.0 to 3.6 SLEW-RATE LIMITED Yes DRIVER/ RECEIVER ENABLE Yes SHUTDOWN CURRENT (A) 1 15kV ESD PROTECTION Yes PIN COUNT 8
Absolute Maximum Ratings
Supply Voltage (VCC) ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 5V Control Input Voltage (/RE, DE) ... ... ... ... ... ... ... ... ... ... ... -0.3V to 5V Driver Input Voltage (DI) ... ... ... ... ... ... ... ... ... ... ... ... ... ... -0.3V to 5V Driver Output Voltage (A, B) ... ... ... ... ... ... ... ... ... ... ... ... -7V to 12V Receiver Input Voltage (A, B) ... ... ... ... ... ... ... ... ... ... ... ... -7V to 12V Receiver Output Voltage (RO) ... ... ... ... ... ... ... -0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70 C) 8-Pin Plastic DIP (derate 9.09mW/ above +70 ... ... ... ... 727mW C C) 8-Pin SO (derate 5.88mW/ above +70 ... ... ... ... ... ... ... ... 471mW C ) Operating Temperature Ranges STC3485EE_ _ ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... -40 to +85 C C Storage Temperature Range... ... ... ... ... ... ... ... ... ... -65 to +160 C C Lead Temperature (soldering, 10sec) ... ... ... ... ... ... ... ... ... ... +300 C
Stresses beyond those listed under " Absolute Maximum Ratings"may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC Electrical Characteristics
(VCC = 3.3V 0.3V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25 C)
PARAMETER Differential Driver Output Change in Magnitude of Driver Differential Output Voltage for Complementary Output States (Note 1) Driver Common-Mode Output Voltage Change in Magnitude of Common-Mode Output Voltage (Note 1) Input High Voltage Input Low Voltage Logic Input Current Input Current (A, B) Receiver Differential Threshold Voltage Receiver Input Hysteresis Receiver Output High Voltage Receiver Output Low Voltage Three-State (High Impedance) Output Current at Receiver Receiver Input Resistance VIH VIL IIN1 IIN2 VTH ?VTH VOH VOL IOZR RIN DE = 0V, VCC = 0V or 3.6V DE, DI, /RE DE, DI, /RE DE, DI, /RE VIN = 12V VIN = -7V -0.2 20 VCC - 0.4 0.4 A 1 96 2.0 0.8 A 2 1.0 -0.8 -0.05 V V A mA V mV V V A kO ?VOC RL = 54Oor 100O, Figure 2 0.2 V VOC RL = 54O?r 100O, Figure 2 o 2 V ?VOD RL = 54O?r 100O, Figure 2 o 0.2 V SYMBOL VOD CONDITIONS RL = 54O ? (RS-485), Figure 2 RL = 60O ? (RS-485), VCC = 3.3V, Figure3 MIN 1.2 1.2 TYP MAX UNITS V
-7VU VCMU 12V VCM = 0V IOUT = -1.5mA, VID = 200mV, Figure 4 IOUT = 2.5mA, VID = 200mV, Figure 4 VCC = 3.6V, 0VU VOUTUVCC -7VU VCMU12V No load, DI = 0V or VCC DE = VCC, /RE = 0V or VCC DE = 0V, /RE = 0V VOUT = -7V VOUT = 12V 0VU VROUVCC
Supply Voltage Range
Supply Current Supply Current in Shutdown Mode Driver Short-Circuit Output Current Receiver Short-Circuit Output Current
VCC
ICC ISHDN IOSD IOSR
3.0
0.6 0.5 1.0
3.6
1.2 1.0 -250 250
V
mA A mA mA
DE = 0V, /RE = VCC, DI = VCC or 0V
A 8
A 60
ESD Protection for A, B
Human Body Model IEC 1000-4-2 Air Discharge
15 15
kV
Receiver Switching Characteristics
(VCC = 3.3V, TA = +25 C)
PARAMETER
SYMBOL tDD tTD tPLH tPHL tPDS tPZL tPZH tPHZ tPLZ tPSL tPSH
CONDITIONS RL = 60O, Figure 5 RL = 60O, Figure 5 RL = 27O, Figure 6 RL = 27O, Figure 6 RL = 27O, Figure 6 RL = 110O, Figure 8 RL = 110O, Figure 7 RL = 110O, Figure 7 RL = 110O, Figure 8 RL = 110O, Figure 8 RL = 110O, Figure 7
MIN 0.5 600 400 700 700
TYP MAX 900 740 930 930 1400 1200 1500 1500
UNITS Mbps ns ns ns ns ns
Maximum Data Rate
Driver Differential Output Delay Driver Differential Output Transition Time Driver Propagation Delay, Low-to-High Level Driver Propagation Delay, High-to-Low Level |tPLH - tPHL| Driver Propagation Delay Skew (Note 2)
A 50
900 600 50 50 1.9 2.2 1300 800 80 80 2.7 3.0
DRIVER-OUTPUT ENABLE/DISABLE TIMES
Driver Output Enable Time to Low Level Driver Output Enable Time to High Level Driver Output Disable Time from High Level Driver Output Disable Time from Low Level Driver Output Enable Time from Shutdown to Low Level Driver Output Enable Time from Shutdown to High Level
ns ns ns ns
s s
Receiver Switching Characteristics
(VCC = +3.3V, TA = +25 C.) PARAMETER Time to Shutdown Receiver Propagation Delay, Low-to-High Level Receiver Propagation Delay, High-to-Low Level SYMBOL tSHDN tRPLH CONDITIONS (Note 3) VID = 0 to 3.0V, CL = 15pF, Figure 9 STC3485E VID = 0 to 3.0V, CL = 15pF, Figure 9 STC3485E VID = 0 to 3.0V, CL = 15pF, Figure 9 tRPDS STC3485E tPRZL tPRZH tPRHZ tPRLZ tPRSL tPRSH CL = 15pF, Figure 10, STC3485E CL = 15pF, Figure 10, STC3485E CL = 15pF, Figure 10, STC3485E CL = 15pF, Figure 10, STC3485E CL = 15pF, Figure 12, STC3485E CL = 15pF, Figure 10, STC3485E 12 25 25 25 25 720 720 20 50 50 45 45 1400 1400 ns ns ns ns ns ns MIN 80 25 25 25 25 TYP 190 62 75 62 75 6 MAX 300 90 120 90 120 10 ns UNITS ns ns
tRPHL
ns
|tPLH - tPHL| Receiver
Propagation-Delay Skew Receiver-Output Enable Time to Low Level Receiver-Output Enable Time to High Level Receiver-Output Disable Time from High Level Receiver-Output Disable Time from Low Level Receiver-Output Enable Time from Shutdown to Low Level Receiver-Output Enable Time from Shutdown to High Level
Note 1: ? VOD and ? VOC are the changes in VOD and VOC, respectively, when the DI input changes state. Note 2: Measured on |tPLH (Y) - tPHL (Y)| and |tPLH (Z) - tPHL (Z)|. Note 3: The transceivers are put into shutdown by bringing /RE high and DE low. If the inputs are in this state for less than 80ns, the parts are guaranteed not to enter shutdown. If the inputs are in this state for at least 300ns, the parts are guaranteed to have entered shutdown. See Low-Power Shutdown Mode section.
Typical Operating Characteristics
(VCC = 3.3V, TA = +25 unless otherwise noted.) C, OUTPUT CURRENT vs. RECEIVER OUTPUT HIGH VOLTAGE OUTPUT CURRENT vs. RECEIVER OUTPUT LOW VOLTAGE RECEIVER OUTPUT HIGH VOLTAGE vs.TEMPERATURE 25 -20 3.30 -18 3.25 -16 20 -14 3.20 -12 15 -10 3.15 -8 10 3.10 -6 5 -4 3.05 -2 3.00 0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 -40 -20 0 20 40 60 80 100 TEMPERATURE ae (c) OUTPUT LOW VOLTAGE V (c) OUTPUT HIGH VOLTAGE V (c) OUTPUT CURRENT(mA) RECEIVER OUTPUT LOW VOLTAGE DRIVER OUTPUT CURRENT vs. DRIVER DIFFERENTIAL OUTPUT vs.TEMPERATURE DIFFERENTIAL OUTPUT VOLTAGE VOLTAGE vs.TEMPERATURE 100 0.8 2.6 2.5 90 0.7 80 2.4 0.6 70 2.3 0.5 2.2 60 50 2.1 0.4 40 2.0 0.3 1.9 30 0.2 1.8 20 0.1 10 1.7 0 0 1.6 -40 -20 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 TEMPERATURE ae (c) TEMPERATURE ae (c) DIFFERENTIAL OUTPUT VOLTAGE(V) OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE OUTPUT VOLTAGE (c) mA OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE DIFFERENTIAL OUTPUT VOLTAGE V (c) OUTPUT HIGHVOLTAGE V (c) OUTPUT CURRENT(mA) OUTPUT LOW VOLTAGE V (c)
OUTPUT CURRENT(mA)
175 150 125 100 75 50 25 0 0
OUTPUT CURRENT(mA)
-100 -80 -60 -40 -20 0
2
4 6 8 10 12 OUTPUT LOW VOLTAGE(V) SHUTDOWN CURRENT(nA)
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 OUTPUT HIGH VOLTAGE(V) SHUTDOWN CURRENT vs.TEMPERATURE 100 90 80 70 60 50 40 30 20 10 0 -40 -20 0 20 40 60 80 100 TEMPERATURE ae (c)
SUPPLY CURRENT vs.TEMPERATURE SUPPLY CURRENT(mA) 1.2 1.1 1.0 0.9 0.8 0.7 -40 -20
0 20 40 60 80 100 TEMPERATURE ae (c)
Pin Description
PIN NAME RO /RE FUNCTION Receiver Output. If A > B by -50mV, RO will be high; if A < B by 200mV, RO will be low. Receiver Output Enable. RO is enabled when RE is low; RO is high impedance when RE is high. If RE is high and DE is low, the device will enter a low-power shutdown mode. Driver Output Enable. The driver outputs are enabled by bringing DE high. They are high impedance when DE is low. If /RE is high and DE is low, the device will enter a low-power shutdown mode. If the driver outputs are enabled, the parts function as line drivers. While they are high impedance, they function as line receivers if /RE is low. Driver Input. A low on DI forces output B high and output A low. Similarly, a high on DI forces output B low and output A high. Ground Noninverting Receiver Input and Noninverting Driver Output Inverting Receiver Input and Inverting Driver Output Positive Supply: 3.0VU VCCU 3.6V
1 2
3
DE
4 5 6 7 8
DI GND A B VCC
TOP VIEW STC3485E RO1 RE2 DE3 DI 4 R 8 7 6 5 Vcc B A GND RO1 RE2 DE3 DI 4 R 8 Vcc 7B Rt 6 A 5 GND B A DE D DI
Rt
D SO/DIP
D
R RE
RO
Figure 1. STC3485E Pin Configuration and Typical Operating Circuit
375| R L 2 D V CC V DD RV L CC 2 V CC D V DD R L 375| V= CM -7V to +12V
Figure 2. Driver VOD and VOC
Figure 3. Driver VOD with Varying Common-Mode Voltage
V ID OV
R
V OL
OH ICL V (+)
IOH (-)
Figure 4. Receiver VOH and VOL
3V IN CL D GENERATOR OTE(c) 50 | N 4 V CC CL C =15pFN OTE 5 L (c) R= OUT L 60| OUT t DD 50% 10% t TD 90% t DD 90% O 2.0V 50% 10% t TD O -2.0V 1.5V 1.5V 0V
Figure 5. Driver Differential Output Delay and Transition Times
3V V CM R=27 L | S1 D GENERATOR OTE(c) 50 | N 4 V CC V =V +V O OM OHCL 1.5V 2 Z OUT OUT C=15pF L OTE(c) N 5 Y OUT t PLH V OM t PHL V OM t PHL V OH V DM V OL t PLH V OH V DM V OL Figure 6. Driver Propagation Times IN 1.5V 1.5V 0V
3V S1 0V OR 3V D C=15pF L OTE(c) N 5 GENERATOR OTE(c) 50| N 4 V = V +V O OM OHCL 1.5V 2 Figure 7. Driver Enable and Disable Times (tPZH, tPSH, tPHZ) V CC S1 0V OR 3V D C=50pF L OTE(c) N 5 GENERATOR OTE(c) 50| N 4 OUT t PZL V OM 0.25V V OL t PLZ V CC R=110 L| OUT IN 1.5V 1.5V 0V 3V Y OUT OUT R=110 L| t PZH V OM t PHZ 0.25V V OH 0V IN 1.5V 1.5V 0V
Figure 8. Driver Enable and Disable Times (tPZL, tPSL, tPLZ)
3.0V VR ID GENERATOR (c) 50 NOTE 4 | OUT C=15pF L (NOTE 5) V CC VOM= 2 IN tRPLH OUT V OM 1.5V 1.5V 0V tRPHL V CC V OM 0V
1.5V 0V
Figure 9. Receiver Propagation Delay
1.5V -1.5V
S3 VR ID
S1 1K S2 C L (NOTE 5)
V CC
GENERATOR (c) 50 NOTE 4 |
Figure 10. Receiver Enable and Disable Times Note 4: The input pulse is supplied by a generator with the following characteristics: PRR = 250kHz, 50% duty cycle, tr=6.0ns, ZO = 50O. Note 5: CL includes probe and stray capacitance.
Function Tables
Devices with Receiver/Driver Enable Table 1. Transmitting
INPUTS /RE X X DE DI OUTPUTS B A
Table 2. Receiving
INPUTS /RE DE X X X 0 A, B OUTPUTS MODE RO 0 0
MODE Normal Normal Normal Shutdown
0 1
1 1 0 0
1 0
X X
0 1
High-Z High-Z
1 0
High-Z High-Z
Y ?0.05V U ?0.2V
Inputs Open X
0 1
1 0 1
High-Z
Normal Normal Normal Shutdown
Applications Information
The STC3485E is low-power transceivers for RS-485 communications. The STC3485E can transmit and receive at data rates up to 500kbps. The STC3485E is half-duplex. Driver Enable (DE) and Receiver Enable (/RE) pins are included on the STC3485E. When disabled, the driver and receiver outputs are high impedance.
Reduced EMI and Reflections
The STC3485E is slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 11 shows the output waveform of the slew-rate-limited STC3485E transmitting a 125kHz signal, as well as the Fourier analysis of that waveform. The high-frequency harmonics have much lower amplitudes, and the potential for EMI is significantly reduced.
Low-Power Shutdown Mode
A low-power shutdown mode is initiated by bringing both /RE high and DE low. The devices will not shut down unless both the driver and receiver are disabled (high impedance). In shutdown, the devices typically draw only 1 of supply current. For these A devices, the tPSH and tPSL enable times assume the part was in the low-power shutdown mode; the tPZH and tPZL enable times assume the receiver or driver was disabled, but the part was not shut down.
Figure 11. Driver Output Waveform and FFT Plot of STC3485E Transmitting a 125kHz Signal
Figure 12. STC3485E Driver Propagation Delay
Figure 13. STC3485E Receiver Propagation Delay
Figure 14. STC3485E System Differential Voltage at 125kHz Driving 4000 ft of Cable
Driver Output Protection
Excessive output current and power dissipation caused by faults or by bus contention are prevented by two mechanisms. A foldback current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range (see Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature rises excessively.
Propagation Delay
Figures 12 and 13 show the typical propagation delays. Skew time is simply the difference between the low-to-high and high-to-low propagation delay. Small driver/receiver skew times help maintain a symmetrical mark-space ratio (50% duty cycle). The receiver skew time, |tPRLH - tPRHL|, is under 10ns (20ns for the STC3485E). The driver skew times are typically under 50ns for the STC3485E.
Line Length vs. Data Rate
The RS-485 standard covers line lengths up to 4000 feet. Figure 13 shows the system differential voltage for parts driving 4000 feet of 26AWG twisted-pair wire at 125kHz into 120O loads.
15kV ESD Protection
As with all STC devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The driver outputs and receiver inputs of the STC3485E family of devices have extra protection against static electricity. STC' engineers have developed state-of-the-art structures to protect these pins against ESD of 15kV s without damage. The ESD structures withstand high. ESD in all states: normal operation, shutdown, and powered down. After an ESD event, Union' E versions keep working without s latchup or damage. ESD protection can be tested in various ways; the transmitter outputs and receiver inputs of this product family are characterized for protection to the following limits: 1) 15kV using the Human Body Model 2) 15kV using IEC 1000-4-2' Air-Gap method. s
Human Body Model
Figure 15a shows the Human Body Model and Figure 15b shows the current waveform it generates when discharged into a low impedance. This model consists of 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the test device through a 1.5kO resistor. ?
IEC 1000-4-2
The IEC 1000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The STC3485E family devices help you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without the need for additional ESD-protection components. The major difference between tests done using the Human Body Model and IEC 1000-4-2 is higher peak current in IEC 1000-4-2, because series resistance is lower in the IEC 1000-4-2 model. Hence, the ESD withstand voltage measured to IEC 1000-4-2 is generally lower than that measured using the Human Body Model. Figure 16a shows the IEC 1000-4-2 model, and Figure 16b shows the current waveform for the 8kV IEC 1000-4-2, Level 4 ESD contact-discharge test. The air-gap test involves approaching the device with a charged probe.
Machine Model
The Machine Model for ESD tests all pins using a 200pF storage capacitor and zero discharge resistance. Its objective is to emulate the stress caused when I/O pins are contacted by handling equipment during test and assembly. Of course, all pins require this protection, not just RS-485 inputs and outputs.
Typical Applications
The STC3485E transceivers are designed for bidirectional data communications on multipoint bus transmission lines. Figures 1 shows typical network applications circuits. To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible. The slew-rate-limited STC3485E is more tolerant of imperfect termination.
R C 1M
R D 1500 |
CHARGE-CURRENT DISCHARGE LIMIT RESISTOR RESISTANCE HIGHVOLTAGE DC SOURCE C S 100pF STORAGE CAPACITOR DEVICE UNDER TEST
Figure 15a. Human Body ESD Test Model
Figure 15b. Human Body Current Waveform
R C R D 50M to 100M 330 | CHARGE-CURRENT DISCHARGE LIMIT RESISTOR RESISTANCE HIGHVOLTAGE DC SOURCE C S 150pF STORAGE CAPACITOR DEVICE UNDER TEST
Figure 16a. IEC 1000-4-2 ESD Test Model
Figure 16b. IEC 1000-4-2 ESD Generator Current Waveform
Package Information ES M E D I M MIIN C HA XMIIL L I M X T E R S NM NMA A 0 . 0 5 30 . 0 6 91 . 3 5 1 . 7 5 A 1 0 . 0 0 40 . 0 1 00 . 1 0 0 . 2 5 0a - 8a B 0 . 0 1 40 . 0 1 90 . 3 5 0 . 4 9 C 0 . 0 0 70 . 0 1 00 . 1 9 0 . 2 5 E 0 . 1 5 00 . 1 5 73 . 8 0 4 . 0 0 e 0.050 1.27 H 0 . 2 2 80 . 2 4 45 . 8 0 6 . 2 0 L 0 . 0 1 60 . 0 5 00 . 4 0 1 . 2 7
D A1 A e B 0.101mm 0.004in. C
L
M DIM PINS INCHES ILLIMETERS MINMAX MINMAX SO 0.197 4.80 5.00 SMALL OUTLINE D 8 0.189 D 14 0.337 0.344 8.55 8.75 PACKAGE D 16 0.386 0.394 9.8010.00 0 .150in. (c) 21-0041A
E
H
D A A2 L A1 e D1 B1 B A3
E E1
0a a - 15 eA eB C
Plastic DIP PLASTIC DUAL-IN-LINE PACKAGE (0.300in.)
INCHES ILLIMETERS M DIM MIN MAXMINMAX A - 0.200 - 5.08 A1 0.015 - 0.38 A2 0.125 0.1753.18 4.45 A3 0.055 0.0801.40 2.03 B 0.016 0.0220.41 0.56 B1 0.045 0.0651.14 1.65 C 0.008 0.0120.20 0.30 D1 0.005 0.0800.13 2.03 E 0.300 0.3257.62 8.26 E1 0.240 0.3106.10 7.87 e 0.100 - 2.54 eA 0.300 - 7.62 eB - 0.400 - 10.16 L 0.115 0.1502.92 3.81 INCHES MILLIMETERS DIM PIN MINMAX MINMAX D8 0.348 0.390 8.849.91 D 14 0.735 0.765 8.67 9.43 11 D 16 0.745 0.765 8.92 9.43 11 D 18 0.885 0.915 22.48 3.24 2 D 20 1.015 1.045 25.78 6.54 2 D 24 1.14 1.265 28.96 2.13 3

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