BL15721A Meter-Bus Transceiver Features Meter-Bus Transceiver (for Slave) Meets Standard EN-1434-3 Adjustable Constant-Current Sink via Resister Receiver Logic With Dynamic Level Recognition Module Supply Voltage Switch 3.3V Constant Voltage Source Remote Powering Polarity Independent Power Fail Function Up to 9600 Baud in Half Duplex for UART Protocol Slave Power Support – Supply From Meter-Bus via Output VDD – Supply From Meter-Bus via Output VDD or From Backup Battery – Supply From Battery – Meter-Bus Active for Data Transmission Only SOP16 package General Description BL15721A is a single chip transceiver developed for Meter-Bus standard (EN1434-3) applications. The BL15721A interface circuit adjusts the different potentials between a slave system and the Meter-Bus master. The connection to the bus is polarity independent and supports full galvanic slave isolation with optocouplers. The receiver has dynamic level recognition, and the transmitter has a programmable current sink. The circuit is supplied by the master via the bus. Therefore, this circuit offers no additional load for the slave battery. The BL15721A integrates a power-fail function. And a 3.3V voltage regulator, with power reserve for a delayed switch off at bus fault, is integrated. Order Information Part Number Package BL15721A SOP16 Packing Tape & Reel Tube http://www.belling.com.cn - Page 1 of 11 - Ver1.0 BL15721A Pin Diagram Block Diagram Pin Description Pin # Name Description 1 BUSL2 Meter-Bus 2 VB Differential bus voltage after rectifier 3 STC Support capacitor 4 RIDD Current adjustment input 5 RF Power fail output 6 SC Sampling capacitor 7 TXI Data output inverted 8 TX Data output 9 BAT Logic level adjust 10 VS Switch for bus or battery supply output 11 VDD Voltage regulator output 12 RX Data input 13 RXI Data input inverted 14 RIS Adjust input for modulation current 15 GND Ground 16 BUSKL1 Meter-Bus http://www.belling.com.cn - Page 2 of 11 - Ver1.0 BL15721A Data Transmission， ，Master to Slave The mark level on the bus lines VBUS = MARK is defined by the difference of BUSL1 and BUSL2 at the slave. It is dependent on the distance of Master to Slave, which affects the voltage drop on the wire. To make the receiver independent, a dynamic reference level on the SC pin is used for the voltage comparator TC3 (see Figure 1). Figure 1. Data Transmission, Master to Slave A capacitor CSC at pin SC is charged by a current ISCcharge and is discharged with a current ISCdischarge where: There must be sufficient time to recharge the capacitor CSC. The input level detector TC3 detects voltage modulations from the master, and switches the inverted output TXI and the non-inverted output TX. Data Transmission, Slave to Master The device uses current modulation to transmit information from the slave to the master while the bus voltage remains constant. The current source CS3 modulates the bus current and the master detects the modulation. The constant current source CS3 is controlled by the inverted input RXI or the non-inverted input RX. The current source CS3 can be programmed by an external resistor RRIS. The modulation supply current IMS flows in addition to the current source CS3 during the modulation time. Because the BL15721A is configured for half-duplex only, the current modulation from RX or RXI is repeated concurrently as ECHO on the outputs TX and TXI. If the slave, as well as the master, is trying to send information via the lines, the added signals appear on the outputs TX and TXI, which indicates the data collision to the slave. The bus topology requires a constant current consumption by each connected slave. http://www.belling.com.cn - Page 3 of 11 - Ver1.0 BL15721A Figure 2. Data Transmission, Slave to Master To calculate the value of the programming resistor RRIS, use the formula shown in Figure 3. Figure 3. Calculate Programming Resistor RRIS Slave Supply, 3.3 V The BL15721A has an internal 3.3V voltage regulator. The output power of this voltage regulator is supplied by the storage capacitor CSTC at pin STC. The storage capacitor CSTC at pin STC is charged with constant current ISTC_use from the current source CS1. The maximum capacitor voltage is limited to REF1. The charge current ISTC has to be defined by an external resistor at pin RIDD. The adjustment resistor RRIDD can be calculated using below Equation. Where, ISTC = current from current source CS1 ISTC_use = charge current for support capacitor ICI = internal current VRIDD = voltage on pin RIDD http://www.belling.com.cn - Page 4 of 11 - Ver1.0 BL15721A RRIDD = value of adjustment resistor The voltage level of the storage capacitor CSTC is monitored with comparator TC1. Once the voltage VSTC reaches VVDD_on, the switch SVDD connects the stabilized voltage VVDD to pin VDD. VDD is turned off if the voltage VSTC drops below the VVDD_off level. Voltage variations on the capacitor CSTC create bus current changes (see Figure 4). Figure 4. Single Mode Bus Load At a bus fault the shut down time of VDD (toff) in which data storage can be performed depends on the system current IVDD and the value of capacitor CSTC. See Figure 5, which shows a correlation between the shutdown of the bus voltage VBUS and VDD_off and toff for dimensioning the capacitor. The output VS is meant for slave systems that are driven by the bus energy, as well as from a battery should the bus line voltage fail. The switching of VS is synchronized with VDD and is controlled by the comparator TC1. An external transistor at the output VS allows switching from the Meter-Bus remote supply to battery. Power On/Off Figure 5. Power On/Off Timing http://www.belling.com.cn - Page 5 of 11 - Ver1.0 BL15721A Power Fail Function Because of the rectifier bridge BR at the input, BUSL1, and BUSL2, the BL15721A is polarity independent. The pin VB to ground (GND) delivers the bus voltage VVB less the voltage drop over the rectifier BR. The voltage comparator TC2 monitors the bus voltage. If the voltage VVB > VSTC + 0.8 V, then the output PF = 1. The output level PF = 0 (power fail) provides a warning of a critical voltage drop to the microcontroller to save the data immediately. Absolute Maximum Ratings Over operating free-air temperature range(unless otherwise noted) VMB Voltage, BUSL1 to BUSL2 VI Input voltage range ±50V RX and RXI –0.3 V to 5.5 V BAT –0.3 V to 5.5 V TA Operating free-air temperature range TSTG Storage temperature range –25°C to 85°C –65°C to 150°C Recommended Operating Conditions (note1) Min Max Receiver 10.8 42 Transmitter 12 42 VB(receive mode) 9.3 BAT(note2) 2.5 3.8 RRIDD RIDD resistor 13 80 RRIS RIS resistor 100 TA Operating free-air temperature -25 VMB Bus voltage, |BUSL2-BUSL1| VI Input voltage Unit V V KΩ Ω ℃ 85 Note1: All voltage values are measured with respect to the GND terminal unless otherwise noted. Note2: VBAT(max) ≤ VSTC – 1 V Electrical Characteristics(note1) over operating free-air temperature range (unless otherwise noted) Symbol ∆VBR ∆VCS1 IBUS ∆IBUS ICC Parameter Conditions Voltage drop at rectifier BR IBUS = 3 mA Voltage drop at current source CS1 BUS current BUS current accuracy Supply current http://www.belling.com.cn RRIDD = 13 kΩ Spec Min. Max. 1.03 1.5 V 0.95 1.8 V VSTC=6.5V, RRIDD = 13 kΩ 2.84 3.3 IMC=0mA RRIDD = 30 kΩ 1.34 1.8 ∆VBUS = 10V, IMC = 0 mA, RRIDD = 13 kΩ to 30 kΩ VSTC = 6.5 V, IMC = 0 mA, VBAT = 3.8 V, RRIDD = 13 kΩ(note2) - Page 6 of 11 - Unit Typ. 480 mA 2 % 650 µA Ver1.0 BL15721A VSTC = 6.5 V, IMC = 0 mA, VBAT = ICL1 CI1 current 350 µA -0.5 0.5 µA VBUS = 0 V, VSTC = 0 V -0.5 0.5 µA 3.1 3.25 3.5 V 2 5 Ω 3.8 V, RRIDD = 13 kΩ, VBUS = 6.5 V, RX/RXI = off (note2) IBAT BAT current IBAT + IVDD BAT plus VDD current VVDD VDD voltage –IVDD = 1 mA, VSTC = 6.5 V RVDD VDD resistance –IVDD = 2 to 8 mA, VSTC = 4.5 V VSTC STC voltage VDD = on, VS = on 5.6 6.16 6.4 VDD = off, VS = off 3.4 4.0 4.3 IVDD < ISTC_use 6.5 7.18 7.7 V RRIDD=30 kΩ 0.65 1.2 RRIDD=13 kΩ 1.85 2.5 1.23 1.33 V VSTC-0.4 VSTC V 0.3 1 MΩ ISTC_use STC current VSTC = 5 V VRIDD RIDD voltage RRIDD = 30 kΩ VVS VS voltage VDD = on, IVS = –5 µA RVS VS resistance VDD = off VVB = VSTC + 1.2 V, IPF = –100 µA VBAT- mA VBAT 0.6 VVB = VSTC + VPF PF voltage VSTC=6.5V 0.5 V, IPF = 1 0 0.6 0 0.9 V µA VVB = VSTC + 0.5 V, IPF = 5 µA Note1: All voltage values are measured with respect to the GND terminal, unless otherwise noted. Note2: Inputs RX/RXI and outputs TX/TXI are open, ICC = ICI1 + ICI2 Receiver Section Electrical Characteristics(note1) over operating free-air temperature range (unless otherwise noted) Symbol Parameter Conditions VT Min Typ MARK0.82 Max Unit MARK5.7 V VVB V -40 µA VSC SC voltage ISCcharge SC charge current VSC = 24 V, VVB = 36 V -15 ISCdischarge SC discharge current VSC = VVB = 24 V 0.3 -0.033X ISCdischarge µA VOH High-level output voltage (TX, TXI) ITX/ITXI = –100 µA， VBAT0.6 VBAT V Low-level output voltage(TX, ITX/ITXI = 100 µA 0 0.47 0.6 ITX = 1.1 mA 0 1.0 1.5 VOL http://www.belling.com.cn -24.7 V - Page 7 of 11 - Ver1.0 BL15721A TXI) ITX ITXI TX, current TXI VTX = 7.5V, VVB = 12 V, VSTC = 6V, VBAT = 3.8 V 0 0.8 µA 10 Note1: All voltage values are measured with respect to the GND terminal, unless otherwise noted. Transmitter Section Electrical Characteristics(note1) Over operating free-air temperature range(unless otherwise noted) Symbol Parameter Conditions Min IMC MC voltage RRIS=100Ω VRIS RIS voltage Typ Max Unit 11.5 19.5 mA RRIS=100Ω 1.4 1.7 V RRIS=1000Ω 1.5 1.8 VIH High-level input voltage(RX,RXI) See Figure 2(note2) VBAT0.8 5.5 V VIL Low-level input voltage(RX,RXI) See Figure 2 0 0.8 V IRX RX current VRX = VBAT = 3V, VVB = VSTC = 0V -0.5 0.5 µA VRX = 0V, VBAT = 3V, VSTC = 6.5 V -10 -40 VRXI = VBAT = 3V, VVB = VSTC = 0V 10 40 VRXI = VBAT = 3 V, VSTC = 6.5 V 10 40 IRXI RXI current µA Note1: All voltage values are measured with respect to the GND terminal, unless otherwise noted. Note 2：VIH(max) = 5.5 V is valid only when VSTC > = 6.5 V. http://www.belling.com.cn - Page 8 of 11 - Ver1.0 BL15721A Application Information Figure 6. Basic Application Circuit Using Support Capacitor CSTC > 50 µF Figure 7. Basic Application Circuit for Supply From Battery http://www.belling.com.cn - Page 9 of 11 - Ver1.0 BL15721A Figure 8. Basic Applications for Different Supply Modes Figure 9. Basic Optocoupler Application http://www.belling.com.cn - Page 10 of 11 - Ver1.0 BL15721A Outline Dimension（ （SOP-16） ） http://www.belling.com.cn - Page 11 of 11 - Ver1.0