ST485A Very high speed low power RS-485/RS-422 transceiver General features ■ Low supply current: 5mA max ■ High data rate > 30Mbps ■ Designed for RS 485 interface applications ■ -7 to 12 common mode input voltage range ■ Driver maintains high impedance in 3-state or with the power off ■ 70mV typical input hysteresis ■ Operate from single 5 supply ■ ±4kV ESD protection ■ Current limiting and thermal shutdown for driver overload protection ■ Latch-up free up to 500mA DIP-8 SO-8 Driver is short-circuit current limited and is protected against excessive power dissipation by thermal shutdown circuitry that place 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 circuit. Description The ST485A is a low power, high speed transceiver for RS-485 and RS-422 communications. The device contains one driver and one receiver in half duplex configuration. The ST485A draws 3mA (typ.) of supply current when unloaded or fully loaded with disabled drivers. It operates from a single 5V supply. The ST485A is designed for bi-directional data communications or multipoint bus transmission lines. Order code Part number Temperature range Package Comments ST485ACN 0 to 70 °C DIP-8 50parts per tube / 40tube per box ST485ABN -40 to 85 °C DIP-8 50parts per tube / 40tube per box ST485ACDR 0 to 70 °C SO-8 (Tape & reel) 2500 parts per reel ST485ABDR -40 to 85 °C SO-8 (Tape & reel) 2500 parts per ree March 2006 Rev 2 1/19 www.st.com 19 Contents ST485A Contents 1 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1 Logic input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.4 Driver switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.5 Receiver switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5 Test circuit and typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2/19 ST485A 1 Pin configuration Pin configuration Figure 1. 1.1 Pin configuration Pin description Table 1. Pin description Pin n° Symbol 1 RO Receiver output. If A>B by 200mV, RO will be high; if A<B by 200mV, RO will be low 2 RE 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. 3 DE Driver output enable. The driver outputs are enabled by bringing DE high. They are high impedance when DE is low. If RE is high DE is low, the device will enter a lowpower shutdown mode. If the driver outputs are enabled, the part functions as line driver, while they are high impedance, it functions as line receivers if RE is low. 4 DI Driver input. A low on DI forces output A low and output B high. Similarly, a high on DI forces output A high and output B low 5 GND 6 A Non-inverting receiver input and non-inverting driver output 7 B Inverting receiver input and inverting driver output 8 VCC Name and function Ground Supply voltage: VCC= 4.75V to 5.25V 3/19 Truth tables ST485A 2 Truth tables Table 2. Truth table (driver) Inputs Outputs Mode RE DE DI B A A X H H L H Normal X H L H L Normal L L X Z Z Normal Note: X = Don’t care; Z = High impedance Table 3. Truth table (receiver) Inputs Outputs Mode Note: 4/19 RE DE A-B L L ≥ -0.2V H Normal L L ≤ -0.2V L Normal L L H Normal INPUTS OPEN X = Don’t care; Z = High impedance RO ST485A Maximum ratings 3 Maximum ratings Table 4. Absolute maximum ratings Symbol VCC Parameter Supply voltage Value Unit 7 V VI Control input voltage (RE, DE) -0.3 to 7 V VDI Driver input voltage (DI) -0.3 to 7 V VDO Driver output voltage (A, B) -7.5 to 12.5 V VRI Receiver input voltage (A, B) -7.5 to 12.5 V VRO Receiver output voltage (RO) -0.3 to (VCC + 0.3) V Note: Absolute maximum ratings are those values beyond which damage to the device may occur. Functional operation under these condition is not implied. 5/19 Electrical characteristics ST485A 4 Electrical characteristics Table 5. (V CC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA = 25°C, VCC = 5V) (Note: 1) DC Electrical characteristics Symbol Parameter ISUPPLY VCC Power supply current Test conditions No load, VRE=0V or V CC Min Typ Max Unit VDE = VCC 2.3 5 mA VDE = 0V 2.6 5 mA CI/O Input/output capacitance 10 pF CAB Driver output capacity 10 pF 4.1 Logic input Table 6. (V CC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA = 25°C, VCC = 5V) (Note: 1) Logic input electrical characteristics Symbol Parameter Test conditions VIL Input logic threshold low DE, DI, RE VIH Input logic threshold high DE, DI, RE IIN1 Logic input current DE, DI, RE IIN2 Input current (A, B) VDE=0V, VCC = 0 or 5.25V Min Typ Max Unit 0.8 V 2 V ± 2.0 µA VIN=12V 1 mA VIN=-7V -0.8 mA 4.2 Transmitter Table 7. (V CC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA = 25°C, VCC = 5V) (Note: 1) Transmitter electrical characteristics Symbol Parameter Test conditions VOD1 Differential driver output (No load) VOD2 Differential driver output (with load) RL= 54Ω (RS-422) VCM= -7V to 12V ∆VOD Change in magnitude of driver differential output voltage for complementary output states (Note: 1) RL= 27Ω or 50Ω Driver common mode output voltage RL= 27Ω or 50Ω ∆VOC Change in magnitude of driver common mode output voltage (Note: 1) RL= 54Ω or 100Ω IOSD Driver short circuit output current VO= -7V to 12V VOC 6/19 Min 1.5 Typ Max Unit 5 V 2.7 5 V 0 0.2 V 3 V 0.2 V ± 250 mA 1 0 ST485A Electrical characteristics 4.3 Receiver Table 8. (V CC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA = 25°C, VCC = 5V) (Note: 1) Receiver electrical characteristics Symbol Parameter Test conditions Min VTH Receiver Differential Threshold Voltage VCM = -7V to 12V ∆VTH Receiver Input Hysteresis VCM = 0V VOH Receiver Output High Voltage IOUT = -4mA, VID = 200mV VOL Receiver Output Low Voltage IOUT = 4mA, V ID = -200mV IOZR 3-State (High Impedance) Output Current at Receiver VO = 0.4V to 2.4V RRIN Receiver Input Resistance VCM = -7V to 12V 12 IOSR Receiver Short-Circuit Current VO = 0V to VCC 7 Typ -0.2 3.5 Max Unit 0.2 V 70 mV 4.7 V 0.2 0.4 V ±1 µA 24 KΩ 95 4.4 Driver switching Table 9. (V CC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA = 25°C, VCC = 5V) (See Note: 1, 3) Driver switching characteristics Symbol Parameter Test conditions Min Typ 30 50 Max mA Unit DR Maximum data rate Jitter < 5% tPLH tPHL Propagation delay input to output RL= 54Ω, CL1=C L2=50pF, (Figure 1) 18 30 ns Differential output delay skew RL= 54Ω, CL1=C L2=50pF, (Figure 1) 0.5 2 ns tTLH tTHL Rise or fall differential time RL= 54Ω, CL1=C L2=50pF, (Figure 1) 8 12 ns tPZL Output enable time CL= 50pF, S1 Closed 30 ns tPZH Output enable time CL= 50pF, S2 Closed 30 ns tPHZ Output disable time CL= 15pF, S2 Closed 30 ns tPLZ Output disable time CL= 15pF, S1 Closed 30 ns 2 ns 6 ns tSKEW tSK(EN) Synchronous driver operation a-b at enable tSK(DS) Synchronous driver operation A-B at disable 4 Mbps 7/19 Electrical characteristics ST485A 4.5 Receiver switching Table 10. (V CC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA = 25°C, VCC = 5V) (See Note: 1, 3) Driver switching characteristics Symbol Parameter tPLH tPHL Typ Max Unit CL = 15pF 18 30 ns |tPLH - tPHL| Propagation delay skew CL = 15pF 0.5 2 ns Propagation Delay tRPDS Test conditions Min tPZL Output enable time CRL = 15pF, S1 Closed 7 12 ns tPZH Output enable time CRL = 15pF, S2 Closed 7 12 ns tPHZ Output disable time CRL = 15pF, S2 Closed 7 12 ns tPLZ Output disable time CRL = 15pF, S1 Closed 7 12 ns Note: 8/19 1 All currents into device pins are positive; all currents out of device pins are negative; all voltages are referenced to device ground unless specified. 2 Applies to peak current. See typical Operating Characteristics. 3 tr=tf ≤ 6ms. ST485A 5 Test circuit and typical characteristics Test circuit and typical characteristics Figure 2. Driver DC test load Figure 3. Receiver timing test load Figure 4. Driver/receiver timing test circuit 9/19 Test circuit and typical characteristics 10/19 Figure 5. Driver Timing Test Load Figure 6. Driver timing test load Figure 7. Driver enable and disable time ST485A ST485A Test circuit and typical characteristics Figure 8. Receiver propagation delay Figure 9. Receiver enable and disable time 11/19 Test circuit and typical characteristics ST485A Figure 10. Receiver output current vs. output voltage (output low) Figure 11. Figure 12. Driver Diff. Output Voltage vs Common Mode Voltage (Diff. Output Low) Figure 13. Driver Diff. Output Voltage vs Common Mode Voltage (Diff. Output Low) 12/19 Receiver output current vs. output voltage (output high) ST485A Test circuit and typical characteristics Figure 14. Driver Short Circuit Current vs Line Figure 15. Driver Short Circuit Current vs. Voltage (Output High) Line Voltage (Output Low) Figure 16. Receiver Input Current vs Input Voltage 13/19 Package mechanical data 6 ST485A Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com 14/19 ST485A Package mechanical data Plastic DIP-8 MECHANICAL DATA mm. inch DIM. MIN. A TYP MAX. MIN. 3.3 TYP. MAX. 0.130 a1 0.7 B 1.39 1.65 0.055 0.065 B1 0.91 1.04 0.036 0.041 b b1 0.028 0.5 0.38 0.020 0.5 D 0.015 0.020 9.8 0.386 E 8.8 0.346 e 2.54 0.100 e3 7.62 0.300 e4 7.62 0.300 F 7.1 0.280 I 4.8 0.189 L Z 3.3 0.44 0.130 1.6 0.017 0.063 P001F 15/19 Package mechanical data ST485A SO-8 MECHANICAL DATA DIM. mm. MIN. TYP inch MAX. MIN. TYP. MAX. A 1.35 1.75 0.053 0.069 A1 0.10 0.25 0.04 0.010 A2 1.10 1.65 0.043 0.065 B 0.33 0.51 0.013 0.020 C 0.19 0.25 0.007 0.010 D 4.80 5.00 0.189 0.197 E 3.80 4.00 0.150 0.157 e 1.27 0.050 H 5.80 6.20 0.228 0.244 h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.016 0.050 k ddd 8˚ (max.) 0.1 0.04 0016023/C 16/19 ST485A Package mechanical data Tape & Reel SO-8 MECHANICAL DATA mm. inch DIM. MIN. A TYP MAX. MIN. 330 MAX. 12.992 C 12.8 D 20.2 0.795 N 60 2.362 T 13.2 TYP. 0.504 22.4 0.519 0.882 Ao 8.1 8.5 0.319 0.335 Bo 5.5 5.9 0.216 0.232 Ko 2.1 2.3 0.082 0.090 Po 3.9 4.1 0.153 0.161 P 7.9 8.1 0.311 0.319 17/19 Revision history ST485A 7 Revision history Table 11. Revision history Date Revision 28-Mar-2006 2 18/19 Changes Order codes has been updated and new template. ST485A Please Read Carefully: Information in this document is provided solely in connection with ST products. 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