ST491A Low power high speed RS-485/RS-422 transceiver Features ■ Low supply current: 5mA max ■ Designed for RS485 interface applications ■ -7V to 12V common mode input voltage range ■ 70mV typical input hysteresis ■ Designed for 25Mbps operation ■ Operate from a single 5V supply ■ ±4kV ESD protection ■ Current limiting and thermal shutdown for driver overload protection DIP-14 Description The ST491A is a low power transceiver for RS485 and RS-422 communications. The device contains one driver and one receiver in full duplex configuration. The ST491A draws 5mA (typ.) of supply current when unloaded and operates from a single 5V supply. 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. Order code Part number Temperature range Package Packaging ST491ACN 0 to 70 °C DIP-14 25parts per tube / 40tube per box May 2007 Rev 6 1/17 www.st.com 17 Contents ST491A Contents 1 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Test circuit and typical characteristics 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2/17 ......................... 9 ST491A Pin configuration 1 Pin configuration Figure 1. Pin connections Table 1. Pin description Pin n° Symbol Name and function 1 NC Not connected 2 RO Receiver output. 3 RE Receiver output enable 4 DE Driver output enable 5 DI Inverting driver input 6 GND Ground 7 GND Ground 8 NC 9 Y Non-inverting driver output 10 Z Inverting driver output 11 A Inverting receiver input 12 B Non-inverting receiver input 13 VCC Supply voltage 14 VCC Supply voltage Not connected 3/17 Truth tables ST491A 2 Truth tables Table 2. Truth table (driver) Inputs Outputs DI DE Y Z L H L H H H H L X L Z Z Note: X = Don’t care; Z = High impedance Table 3. Truth table (receiver) Inputs Note: 4/17 Outputs A-B RE RO ≥ -0.2V L H between -0.2V to 0.2V L ? ≤-0.2V L L OPEN L H X H Z ?=Irrelevant; X = Don’t care; Z = High impedance ST491A Maximum ratings 3 Maximum ratings Table 4. Absolute maximum ratings Symbol Parameter VCC Supply voltage VDI Driver input voltage Value Unit 7 V -0.5 to 7 V VY, VZ Driver output voltage -7.5 to 12.5 V VA, VB Receiver input voltage -7.5 to 12.5 V -0.3 to (VCC + 0.3) V 3.5 KV VRO Receiver output voltage ESD Human body model Note: Absolute maximum ratings are those values beyond which damage to the device may occur. Functional operation under these condition is not implied. 5/17 Electrical characteristics ST491A 4 Electrical characteristics Table 5. Electrical characteristics (VCC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA=25°C) Symbol ISUPPLY Parameter Min. No load supply current Typ. Max. Unit 2 5 mA CIN Input capacitance 1.8 pF CYZ Driver output capacitance 1.2 pF Output capacitance 2.3 pF COUT Table 6. Transmitter electrical characteristics (VCC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA=25°C) Symbol Parameter VOD1 Differential drive output (no load) VOD2 Differential drive output (with load) RL= 54Ω (RS-422) (Figure 1.) 1.5 2.6 VOD3 Differential drive output (with load) RL= 100Ω (RS-422) (Figure 1.) 2 3 ΔVOD Change in magnitude of driver differential output voltage for complementary output states RL= 54Ω or 100Ω (Figure 1.) VOC Driver common mode output voltage RL= 54Ω (Figure 1.) ΔVOC Change in magnitude of driver common mode output voltage RL= 54Ω (Figure 1.) IOFF Power off output current VCC = 0V, VO=-7V to 12V IOSD Driver short circuit output current VO=-7V to 12V 6/17 VIL Input logic threshold low VIH Input logic threshold high Test conditions Min. Typ. 0 1 0 ± 35 2 Max. Unit VCC V 5 V V 0.2 V 3 V 0.2 V ± 100 μA ± 250 mA 0.8 V V ST491A Table 7. Symbol IIN Electrical characteristics Receiver electrical characteristics (VCC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA=25°C) Parameter Test conditions Other input = 0V VCC = 0 or 5.25V Input current (A, B) Typ. Max. VIN=12V 0.5 1 VIN=-7V -0.35 -0.8 VTH Receiver differential threshold voltage VCM = -7V to 12V ΔVTH Receiver input hysteresis VCM = 0V VOH Receiver output high voltage IOUT = -8mA, VID = 200mV VOL Receiver output low voltage IOUT = 8mA, VID = -200mV RRIN Receiver input resistance VCM = -7V to 12V Table 8. Symbol Min. Unit mA -0.2 3.5 0.2 70 mV 4.7 V 0.3 12 V 0.5 24 V KΩ Driver switching characteristics (VCC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA=25°C) Parameter Test conditions Min. Typ. 25 50 Max. Unit DR Maximum data rate Jitter <5% tPLH tPHL Propagation delay input to output RL= 54Ω, CL1=CL2=50pF, (Figure 1.) 10 16 ns tSKEW Differential output delay skew RL= 54Ω, CL1=CL2=50pF, (Figure 1.) 1 3 ns tTLH tTHL Rise or fall differential time RL= 54Ω, CL1=CL2=50pF, (Figure 1.) 8 12 ns tPZL Output enable time CL= 50pF, S1 Closed 14 25 ns tPZH Output enable time CL= 50pF, S2 Closed 14 25 ns tPHZ Output disable time CL= 15pF, S2 Closed 10 25 ns tPLZ Output disable time CL= 15pF, S1 Closed 16 25 ns Mbps 7/17 Electrical characteristics Table 9. Symbol 8/17 ST491A Receiver switching characteristics (VCC = 4.5V to 5.5V, TA = -40 to 85°C, unless otherwise specified. Typical values are referred to TA=25°C) Parameter Test conditions Min. Typ. Max. Unit tPLH tPHL Propagation delay input to output CL = 15pF, (Figure 2., Figure 4.) 19 30 ns tSKD |tPLH - tPHL| Receiver output skew CL = 15pF, (Figure 2., Figure 4.) 1 3 ns tTLH tTHL Rise or fall time CL = 15pF, (Figure 2., Figure 4.) 6 tPZL Output enable time CRL= 15pF, S1 Closed 6 12 ns tPZH Output enable time CRL= 15pF, S2 Closed 7 12 ns tPHZ Output disable time CRL= 15pF, S2 Closed 6 12 ns tPLZ Output disable time CRL= 15pF, S1 Closed 6 12 ns ns ST491A Test circuit and typical characteristics 5 Test circuit and typical characteristics Figure 2. Driver DC test load Figure 3. Receiver timing test load 9/17 Test circuit and typical characteristics Figure 4. Driver/receiver timing test circuit Figure 5. Driver timing test load 10/17 ST491A ST491A Test circuit and typical characteristics Figure 6. Driver propagation delay Figure 7. Receiver propagation delay 11/17 Test circuit and typical characteristics Figure 8. Receiver output current vs. output low voltage (output low) ST491A Figure 9. Receiver output current vs. output high voltage (output high) Figure 10. Driver diff. output voltage vs Figure 11. Driver diff. output voltage vs common mode voltage (diff. output common mode voltage (diff. output low) high) Figure 12. Driver short circuit current vs line voltage (output high) 12/17 Figure 13. Receiver high level output voltage vs. temperature ST491A Test circuit and typical characteristics Figure 14. Receiver input current vs input voltage 13/17 Package mechanical data 6 ST491A 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 14/17 ST491A Package mechanical data Plastic DIP-14 MECHANICAL DATA mm. inch DIM. MIN. a1 0.51 B 1.39 TYP MAX. MIN. TYP. MAX. 0.020 1.65 0.055 0.065 b 0.5 0.020 b1 0.25 0.010 D 20 0.787 E 8.5 0.335 e 2.54 0.100 e3 15.24 0.600 F 7.1 0.280 I 5.1 0.201 L Z 3.3 1.27 0.130 2.54 0.050 0.100 P001A 15/17 Revision history ST491A 7 Revision history Table 10. Revision history Date Revision 10-May-2005 3 Mistake on Figure 1. 04-Jul-2005 4 Mistake on Figure 1 and Table 1 (Pin 13). 28-Apr-2006 5 Order codes has been updated and new template. 28-May-2007 6 Order codes has been updated. 16/17 Changes ST491A Please Read Carefully: Information in this document is provided solely in connection with ST products. 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