ST3485E

ST3485EBDR UMW | Alldatasheet

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3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver Features:  3.3V power supply, half-duplex;  1/8 unit load allows up to 256 devices on the bus;  Driver output short-circuit protection function;  Over temperature protection function;  Low power shutdown function;  Receiver open circuit protection function;  Strong anti-noise ability;  Integrated transient voltage resistance function;  Transmission rate up to 12Mbps in an electrical noise environment;Description The ST3485E is a 3.3V powered, half-duplex, low-power RS-485 transceiver that fully meets the requirements of the TIA/EIA-485 standard. The ST3485E includes a driver and a receiver, both of which can be independently enabled and disabled. When both are disabled, both the driver and the receiver output a high impedance state. The ST3485E has a 1/8 load that allows 256 ST3485E transceivers to be connected to the same communication bus. Error-free data transfer of up to 12Mbps is possible. The ST3485E operates from a voltage range of 3.0 to 3.6V and features fail-safe, over temperature protection, current limit protection, over-voltage protection, and other functions. Pin configuration RO VCC RE B DE A DI GNDFi gure 1 ST3485E pin configuration UMW R www.umw-ic.com 1 友台半导体有限公司

Parameter Symbol Value Unit Supply voltage VCC +7 V Voltage of control port /RE, DE, DI -0.3~+7 V Bus side input voltage A, B -7~13 V Receiver output voltage RO -0.3~+7 V Operating temperature range -40~85 °C Storage temperature range -60~150 °C Welding temperature 300 °C Continuous power dissipation SOP8 400 mW MSOP8/8μMAX/VSSOP8MAX/VSSOP8 830 mW DIP8 700 mW The maximum limit parameter value means that exceeding these values may cause irreversible damage to the device. Under these conditions, it is not conducive to the normal operation of the device. Continuous operation of the device under the maximum allowable rating may affect the reliability of the device. The reference point of all voltages is ground. Pin functions Pin number Pin name Pin function 1 RO Receiver output When /RE is low level: if A-B ≧ 200mV, RO = high; if A-B ≦ -200mV, RO = low 2 /RE Receiver output enable control When /RE is low level, receiver output is enabled, and RO output is available. When /RE is high level, receiver output is disabled, and RO is in high impedance state. When /RE is high level and DE is low level, the device enters low power consumption mode. 3 DE Driver output enable control When DE is high level, driver output is available; when DE is low level, the output is in high impedance state. When /RE is high level and DE is low level, the device enters low power consumption mode. 4 DI Driver input When DE is high level, the DI low level forces the non-inverting driver output A low and inverting driver output B high; The DI high level forces the non-inverting driver output A high and inverting driver output B low.

5 GND Ground

6 A Non-inverting receiver input and non-inverting driver output

7 B Inverting receiver input and inverting driver output

8 VCC Power supply

ww.umw-ic.com 2 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

threshold voltage VIT+ -7V V≦ CM 12V≦ +200 mV Negative-going input threshold voltage VIT- -7V V≦ CM 12V≦ -200 mV Hysteresis voltage Vhys -7V V≦ CM 12V≦ 10 30 mV High level output voltage VOH IOUT = −2.5mA, VID = +200 mV VCC-1.5 V Low level output voltage VOL IOUT = +2.5mA, VID = -200 mV 0.4 V Tristate leakage current IOZR 0.4V < VO < 2.4V ±1 μMAX/VSSOP8A Receiver input resistance RIN -7V V≦ CM 12V≦ 96 kΩ Receiver short-circuit current IOSR 0V ≤ VO ≤ VCC ±8 ±60 mA (unless otherwise stated VCC=3.3V±10%, Temp=TMIN~TMAX, typical value is VCC=+3.3V, Temp＝25°C) Supply current Driver switching characteristics Parameter Symbol Test conditions Min Typ Max Unit Driver differential output delay tDD RDIFF = 60 Ω, CL1=CL2=100pF (see Figure 3 and Figure 4) 10 35 ns Driver differential output transition time tTD 12 25 ns Driver propagation delay, low-to-high tPLH RDIFF = 27 Ω, (see Figure 3 and Figure 4) 8 35 ns Driver propagation delay, high-to-low tPHL 8 35 ns Parameter Symbol Test conditions Min Typ Max Unit Supply current ICC1 /RE = 0V, DE = 0V 520 800 μMAX/VSSOP8A ICC2 /RE = VCC, DE = VCC 540 700 μMAX/VSSOP8Aw ww.umw-ic.com 4 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

|tPLH -tPHL | tPDS 1 8 ns Driver enable to output high tPZH RL = 110Ω, (see Figure 5, 6) 20 90 ns Driver enable to output low tPZL 20 90 ns Driver disable time from low tPLZ RL = 110Ω, (see Figure 5,6) 20 80 ns Driver disable time from high tPHZ 20 80 ns Driver enable from shutdown to output high tDSH RL = 110Ω, (see Figure 5,6) 500 900 ns Driver enable from shutdown to output low tDSL RL = 110Ω, (see Figure 5,6) 500 900 ns Receiver switching characteristics Parameter Symbol Test Conditions Min Typ Max Unit Receiver input to output delay (low to high) tRPLH CL=15pF See Figure 7 and Figure 8 80 150 ns Receiver input to output delay (high to low) tRPHL 80 150 ns |tRPLH − tRPHL| tRPDS 7 10 ns Receiver enable to output low tRPZL CL=15pF See Figure 7 and Figure 8 20 50 ns Receiver enable to output high tRPZH CL=15pF See Figure 7 and Figure 8 20 50 ns Receiver disable time from low tPRLZ CL=15pF See Figure 7 and Figure 8 20 45 ns Receiver disable time from high tPRHZ CL=15pF See Figure 7 and Figure 8 20 45 ns Receiver enable from shutdown to output high tRPSH CL=15pF See Figure 7 and Figure 8 200 1400 ns Receiver enable from shutdown to output low tRPSL CL=15pF See Figure 7 and Figure 8 200 1400 ns Time to shutdown tSHDN NOTE2 80 300 ns NOTE2: The device is put into shutdown by bringing RE high and DE low. If the enable inputs are in this state for less than 80ns, the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 300ns, the device is guaranteed to have entered shutdown.w ww.umw-ic.com 5 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

/RE DE DI A B X 1 1 H L X 1 0 L H 0 0 X Z Z 1 0 X Z (shutdown) X: don’t care; Z: high impedance Control Input Output /RE DE A-B RO

0 X ≥200mV H

0 X ≤-200mV L

0 X Open/short-

1 X X Z

X: don’t care; Z: high impedancew ww.umw-ic.com 6 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

Fig. 2 Driver DC test load CL includes probe and stray capacitance (same as below) Fig. 3 Driver differential output delay and transition times Fig. 4 Driver propagation times Test circuitw ww.umw-ic.com 7 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

Fig. 5 Driver enable and disable times Fig. 6 Driver enable and disable times w ww.umw-ic.com 8 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

Fig. 8 Receiver enable and disable times Fig. 7 Receiver propagation delayw ww.umw-ic.com 9 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

1 Brief desc

TheST3485E is a half-duplex high-speed transceiver for RS-485/RS-422 communication, and includes one driver and one receiver. It has fail-safe, over-voltage protection and over-current protection. The ST3485E allows error-free data transmissi- on up to 12Mbps.

2 Allowing up to 256 transceivers on the bus

The standard RS-485 receiver has an input impedance of 12kΩ (1 unit load), and the standard driver can drive up to 32 unit loads. The receiver of the ST3485E transceiver has a 1/8 unit load receiver input impedance (96kΩ), allowing up to 256 tran- sceivers to be connected in parallel on one bus. These devices can be combined arbitrarily, or combined with other RS-485 transceivers, as long as the total load does not exceed 32 units.

3 Driver output protection

Two mechanisms are used to avoid faults or bus collisions that cause excessive output current and excessive power consumption. First, over-current protection provides fast short-circuit protection over the entire common-mode voltage range (refer to the typical operating characteristics). Second, the thermal shutdown circuit forces the driver output into a high- impedance state when the die temperature exceeds 140°C.4 Typical

applications

4.1 Bus networking: The ST3485E RS485 transceiver is designed for bidirectional data communication on

multi-point bus transmission lines. Figure 9 shows a typical network application circuit. These devices can also be used as linear repeaters with cables longer than 4000 feet. In order to reduce reflections, terminal matching should be done at both ends of the transmission line with their characteristic impedance, and the length of the branch wires other than the main line should be as short as possible. Fig. 9 Bus-type RS485 half-duplex communication network General description www.umw-ic.com 10 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

4.2 Hand-in-hand networking: Also known as daisy chain topology, it is the standard and specification of RS485 bus wiring, and is the RS485 bus topology recommended by organizations such as TIA. The wiring method is that the master control device and multiple slave devices form a hand-in-hand connection, as shown in Figure 10, the hand-in- hand way is to leave no branches. This wiring method has the advantages of low signal reflection and high communication success rate. Fig. 10 Hand-in-hand type RS485 half-duplex communication network

4.3 Bus port protection : In harsh environments, RS485 communication ports are usually protected against

static electricity, lightning and surge protection, etc. and it is even necessary to prevent 380V power supply access to avoid damage of smart meters and industrial control hosts. Figure 11 shows 3 common kinds of RS485 bus port protection schemes. The first scheme is to connect the TVS device to the protection ground in parallel with the AB port, the TVS device in parrallel with the AB port, the thermistor in series with the AB port and the gas discharge tube is connected to the protection ground to form a three-level protection scheme. The second scheme is a three-level protection scheme including TVS connected to the ground in parallel with AB, the thermistor in series and the varistor in parallel with AB. The third one includes pull-down resistors connected to the power supply and ground respectively for AB, TVS between AB and the thermistor connected to A or B port. Fig. 11 Port protection scheme w ww.umw-ic.com 11 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R

ww.umw-ic.com 12 友台半导体有限公司ST3485E 3.3V power supply, up to 256 nodes, 12Mbps half-duplex, RS485/RS422 transceiver UMW R Min Max Min Max A 1.350 1.750 0.053 0.069 A1 0.100 0.250 0.004 0.010 A2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 D 4.700 5.100 0.185 0.200 E 3.800 4.000 0.150 0.157 E1 5.800 6.200 0.228 0.244 e L 0.400 1.270 0.016 0.050 θ 0 °8 °0 °8 ° Dimensions In Millimeters Dimensions In InchesSymbol 1.270(BSC) 0.050(BSC)