STR485LVQT

STR485 Datasheet 3.3 V RS485 compatible with 1.8 V I/Os and selectable speed 20 Mbps or 250 kbps Features DFN10 3 x 3 • • • • • • • • • • • • Half-duplex RS485 transceiver 1.65 V to 3.6 V supply for data and enable signals 3 V to 3.6 V supply for bus supply High speed: up to 20 Mbps data rate Low speed selected by SLR pin : 250 kbps Up to 256 transceivers on the bus Fail safe receiver (bus open, idle and shorted) Thermal shutdown protection Low quiescent current in shutdown mode Extended temperature range : -40 °C to +105 °C Available in industry standard DFN10 Bus-pin protection more than: – ±4 kV HBM protection – ±8 kV IEC61000-4-2 contact discharge – ±16 kV IEC61000-4-2 air discharge – Compliant IEC61000-4-4 fast transient burst Class B Description Product status link STR485 The STR485 is a low power differential line transceiver for data transmission standard RS485 applications in half-duplex mode. Data and enable signals are compatible with 1.8 V or 3.3 V supplies. Two speeds are selectable through SLR pin: fast data rate up to 20 Mbps or slow data rate for extended cable running to 250 kbps. Excessive power dissipation caused by bus contention or faults is prevented by thermal shutdown circuit that 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, shorted or idle. DS12713 - Rev 5 - July 2020 For further information contact your local STMicroelectronics sales office. www.st.com STR485 Pin connections 1 Pin connections Figure 1. Pin connections VL VCC R B DE A RE SLR D GND Table 1. Pin description DS12713 - Rev 5 Name Pin I/O Description VL 1 Logic supply 1.65 V to 3.6 V supply for logic I/O signals R 2 Digital output Receiver data output DE 3 Digital input nRE 4 Digital input D 5 Digital input GND 6 Ground SLR 7 Digital input A 8 Bus I/O Digital bus I/O, A B 9 Bus I/O Digital bus I/O, B VCC 10 Bus supply 3 V to 3.6 V supply for A and B bus lines Driver enable input: serial resistors of 150 ohms followed by 2.5 Mohms/GND Receiver enable input: serial resistors of 150 ohms followed by 2.5 Mohms/VCC Transmission data input Slew rate select: low = 20 Mbps, high = 250 kbps. Default to 20 Mbps if SLR is left floating page 2/26 STR485 Pin connections Figure 2. Typical application schematic 1.8 V VL SLR 3.3 V 3.3 V VCC A VCC SLR RT 120 Ω D B DE VL A RT 120 Ω D 1.8 V DE B R R RE RE GND GND Figure 3. Example of implementation in a PCB Adding an ESDA14V2BP6 or ETP01-2821 STMicroelectronics protection device can help the product to sustain an EFT perturbation level up to 4 kV. DS12713 - Rev 5 page 3/26 STR485 Truth tables 2 Truth tables The STR485 is a half-duplex differential driver/receiver compliant to the RS485 communication standard (ISO-IEC 8482). This product is perfectly adapted for low voltage application running with a low power supplies VL, generally set to 1.8 V and VCC set to 3.3 V. These voltages confer a low power consumption to the product. SLR is the data rate selection, this pin could be let floating but it is not recommended; in that case the high speed rate is automatically selected. The SLR pin must be connected to the ground to provide a high speed communication up to 20 Mbps. When this pin is connected to VL power supply, the data rate is limited to 250 kbps more adapted for very long distance data transmission. Figure 4. Block diagram The product is perfectly adapted to run with 256 devices on the same bus thanks to the internal output resistance that is over 96 kΩ up to 105 °C; this resistance follows the RS485 condition that requests a minimum of 12 kΩ for 32 unit loads (UL). The STR485 has internal protection against ESD that protect each device driver output and receiver input. The limits have been tested up ±4 kV electrostatic discharge (HBM) and ± 8 kV contact discharge and ± 16 kV air discharge shocks without latch-up. Another external protections can be used to increase the communication robustness against different perturbation that can be seen on the application. The power supplies must be well-decoupled by a minimal capacitor of 0.1 µF as closed as possible to the device power supply input. Moreover, the capacitor should be higher on the application with a minimum of 1 µF around the device. The device operating range is set from VL = 1.65 V to 3.6 V and for Vcc = 3.0 V to 3.6 V. In any case VCC must be higher or equal than VL. The applications should respect this voltage constraints to let the application communication device run to the best conditions. DS12713 - Rev 5 page 4/26 STR485 Truth tables Figure 5. Example of typical application VCC VL SLR SLR A DE VCC RT 120Ω RT 120Ω D VL A D B DE B R R B RE GND A B SLR SLR VL VL VCC GND D DE R A RE GND VCC GND D RE DE R RE Table 2. Driver truth table INPUT D ENABLE DE OUTPUT A OUTPUT B Function H H H L Actively drive bus high L H L H Actively drive bus low X L Z Z Driver disabled X Open Z Z Driver disabled by default Open H H L Actively drive bus high by default Table 3. Receiver truth table Differential input VID = VA -VB ENABLE RE OUTPUT R Function VID > VIT+ L H Receive valid bus high VIT- < VID < VIT+ L ? Indeterminate bus state VID < VIT- L L Receive valid bus low X H Z Receiver disabled X OPEN Z Receiver disabled by default Open-circuit bus L H Fail safe high output Short-circuit bus L H Fail safe high output Idle (terminated) bus L H Fail safe high output Table 4. Speed selection, SLR pin configuration DS12713 - Rev 5 SLR Data rate Typical tr / tf VL 250 kbps 200 ns GND or OPEN 20 Mbps 7 ns page 5/26 STR485 Absolute maximum ratings and operating conditions 3 Absolute maximum ratings and operating conditions Table 5. Absolute maximum ratings Symbol VL VCC Parameter Min. Max. Unit Control supply voltage -0.5 4 V Bus supply voltage -0.5 4.8 V Voltage range at A or B inputs -13 13 V Input voltage range at any logic pin -0.3 VL+0.3 V Receiver output current -12 12 mA 170 °C 150 °C IEC 61000-4-2 ESD (air-gap discharge), bus terminals and GND ± 16 kV IEC 61000-4-2 ESD (contact discharge), bus terminals and GN ±8 kV IEC 61000-4-4 EFT (fast transient or burst) bus terminals and GND ±2 kV JEDEC standard 22, test method A114, HBM, all terminals ±4 kV ± 1.5 kV TJ Junction temperature Tstg Storage temperature ESD -65 JEDEC standard 22, test method C101, (charged device model), all pins Note: All voltage values, except the differential voltage, are with respect to network ground terminal. Table 6. Operating conditions Symbol VL VCC Parameter Control supply voltage Min. Typ. 1.65 Max. Unit 3.6 Bus supply voltage 3 VI Input level at any bus terminal (separately or common mode) -7 12 VIH High level input voltage (driver, driver enabled, receiver enable inputs, and slew rate select) 0.7×VL VL VIL Low level input voltage (driver, driver enable, receiver enable inputs, and slew rate select) 0 0.3×VL VID Differential input voltage -12 12 Output current / driver -80 80 Output current / receiver -2 2 RL Differential load resistance 54 CL Differential load capacitance IO DR TA 3.3 3.6 V mA 60 Ω 50 pF Signaling rate / SLR = ‘0’ 20 Mbps Signaling rate / SLR = ‘1’ 250 kbps 105 °C Operating free-air temperature -40 Operation is specified for internal (junction temperature) up to 150 °C. Self-heating due to internal power dissipation should be considered for each application. Maximum junction temperature is internally limited by the thermal shut-down circuit which disables the driver outputs when the junction temperature reaches 165 °C. DS12713 - Rev 5 page 6/26 STR485 Absolute maximum ratings and operating conditions Table 7. Thermal information DS12713 - Rev 5 Symbol Parameter Min. Typ. Rth-ja Thermal resistance, junction-to-ambient 40 Rth-jc Thermal resistance, junction-to-case 5.2 Max. Unit °C/W page 7/26 STR485 Electrical characteristics 4 Electrical characteristics Table 8. Receiver: over recommended operating conditions (unless otherwise specified. Please, see "Operating conditions" table) Symbol Parameter Test conditions Min. Typ. Max. Unit Receiver/DC VIT+ Positive-going receiver differential input voltage threshold (1) -60 -20 VIT- Negative-going receiver differential input voltage threshold -200 -130 (1) 40 70 VL = 1.65 V, IOH = - 2 mA 1.25 1.45 VL = 3 V, IOH = - 2 mA 2.75 2.9 VHYS Receiver differential input voltage threshold hysteresis (VIT+ - VIT- )(1) VOH Receiver high-level output voltage VOL Receiver low-level output voltage COD Differential output capacitance IOZ Receiver output highimpedance current Rin Receiver input impedance VL = 1.65 V, IOL = 2 mA 0.2 0.45 VL = 3 V, IOL = 2 mA 0.1 0.25 15 VO = 0 V or VL, nRE at VL -7 V ≤ Vincm ≤ +12 V -40 °C ≤ Temp ≤ 105 °C -1 II 1 µA kΩ 85(2) VI = 12 V, -40 °C ≤ Temp ≤ 105 ° VI = -7 V, -40 °C ≤ Temp ≤ 105 ° V pF 96 (2) 1V65 < VL < 3.3 V, VCC = 3.3 V Receiver input current (disabled driver) mV 125(2) µA -100(2) Receiver / switching characteristics, SLR = ‘X’ tr, tf Receiver output rise/fall time tPHL, tPLH Receiver propagation delay time tSK(P) Receiver pulse skew, | tPHL – tPLH| tPLZ, tPHZ Receiver disable time tPLZ, tPZH, tPZL, tPZH Receiver enable time CL=15 pF 15 5 15 25 60 15 12 20 Driver enabled CL=15 pF with 1 kΩ 15 80 Driver disabled CL=15 pF with 1 kΩ 2 8 ns µs 1. Under any specific conditions, VIT+, is specified to be at least VHYS higher than VIT2. Guaranteed by design simulation in temperature. DS12713 - Rev 5 page 8/26 STR485 Electrical characteristics Table 9. Driver: over recommended operating conditions (unless otherwise specified. Please, see "Operating conditions" table) Symbol Parameter Test conditions Min. Typ. Max. Unit 2 µA DC driver/ DC II |VOD| Driver input, driver enable, and receiver enable input current Driver differential output voltage magnitude Δ|VOD| Change in magnitude of driver differential output voltage V°C(SS) Steady-state commonmode output voltage ΔV°C Change in differential driver output commonmode voltage V°C(PP) Peak-to-peak driver common-mode output voltage -2 RL = 60 Ω, 375 Ω on each output to –7 V to 12 1.5 2 RL = 54 Ω (RS-485) 1.5 2 RL = 100 Ω (RS-422) TJ ≥ 0 °C, VCC ≥ 3.2 2 RL = 54 Ω, CL = 50 pF Center of two 27-Ω load resistors V -50 0 50 mV 1 VCC/2 3 V -50 0 50 mV 500 Driver/switching characteristics, SLR='1', 250 kbps, bit time ≥ 4 µs tr, tf Driver differential output rise/fall time tPHL, tPLH Driver propagation delay time tSK(P) Driver pulse skew, |tPHL – tPLH| tPLZ, tPHZ tPLZ, tPZH 0.05 0.2 1 0.4 1 1.5 RL=54 Ω, CL=50 pF 0.3 Driver disable time Driver enable time 0.017 0.035 Receiver enabled CL=50 pF with 110 kΩ 0.7 1.2 Receiver disabled CL=50 pF with 110 kΩ 1.64 2.4 µs µs Driver/switching characteristics, SLR= '0', 20 Mbps, bit time ≥ 50 ns DS12713 - Rev 5 tr, tf Driver differential output rise/fall time tPHL, tPLH Driver propagation delay tSK(P) Driver pulse skew, |tPHL – tPLH| tPLZ, tPHZ Driver disable time tPZL, tPZH Driver enable time RL=54 Ω, CL=50 pF 4 7 15 6 12 25 4 17 40 Receiver enabled 9 18 Receiver disabled 1 2.4 ns µs page 9/26 STR485 Electrical characteristics Table 10. Supply current and protections: over recommended operating conditions (unless otherwise specified. Please, see "Operating conditions" table) Symbol Parameter Test conditions Min. Typ. Max. Unit Supply current Driver and receiver enabled 625 DE = VL, RE = GND, no load, Tamb µA Driver and receiver enabled 900 (1) DE = VL, RE = GND, no load, T