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LNBP21D2 Datasheet(PDF) 5 Page - STMicroelectronics |
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LNBP21D2 Datasheet(HTML) 5 Page - STMicroelectronics |
5 / 24 page LNBP21 5/24 Figure 3: Typical Application Circuit (*) Set to GND if not used (**) filter to be used according to EUTELSAT recommendation to implement the DiSEqCTM 2.x, not needed if bidirectional DiSEqCTM 2.x is not implemented (see DiSEqC implementation note) (***) IC2 is a ST Fettky, STS4DNFS30L, that includes both the schottky diode and the N-Channel MosFet, needed for the DC/DC converter, in a So-8 package. It can be replaced by a schottky diode (STPS2L3A or similar) and a N-Channel MosFet (STN4NF03L or similar) I2C BUS INTERFACE Data transmission from main µP to the LNBP21 and viceversa takes place through the 2 wires I2C bus interface, consisting of the two lines SDA and SCL (pull-up resistors to positive supply voltage must be externally connected). DATA VALIDITY As shown in fig. 3, the data on the SDA line must be stable during the high period of the clock. The HIGH and LOW state of the data line can only change when the clock signal on the SCL line is LOW. START AND STOP CONDITIONS As shown in fig. 4 a start condition is a HIGH to LOW transition of the SDA line while SCL is HIGH. The stop condition is a LOW to HIGH transition of the SDA line while SCL is HIGH. A STOP conditions must be sent before each START condition. BYTE FORMAT Every byte transferred to the SDA line must contain 8 bits. Each byte must be followed by an ac-knowledge bit. The MSB is transferred first. ACKNOWLEDGE The master (µP) puts a resistive HIGH level on the SDA line during the acknowledge clock pulse (see fig. 4). The peripheral (LNBP21) that acknowledges has to pull-down (LOW) the SDA line during the acknowledge clock pulse, so that the SDA line is stable LOW during this clock pulse. The peripheral which has been addressed has to generate an acknowledge after the reception of each byte, other-wise the SDA line remains at the HIGH level during the ninth clock pulse time. In this case the master transmitter can generate the STOP information in order to abort the transfer. The LNBP21 won't generate the acknowledge if the VCC supply is below the Undervoltage Lockout threshold (6.7V typ.). TRANSMISSION WITHOUT ACKNOWLEDGE Avoiding to detect the acknowledge of the LNBP21, the µP can use a simpler transmission: simply it waits one clock without checking the slave acknowledging, and sends the new data. This approach of course is less protected from misworking and decreases the noise immunity. 270µH 15 ohm see Note 2 Vup Gate Vin 12V L1=22µH Sense C2 220µF Vcc LT1 Master STB Vo LT2 DETIN (Note 1) C8 10nF to LNB SDA SCL DSQOUT DSQIN(Note 1) ADDRESS Byp C5 470nF GND 0<Vaddr<V Byp EXTM C6 10nF 270µH 15 ohm see Note 2 Vup Gate Vin 12V L1=22µH Sense C2 220µF Vcc LT1 Master STB Vo LT2 DETIN (Note 1) C8 10nF to LNB SDA SCL DSQOUT DSQIN(Note 1) ADDRESS Byp C5 470nF GND 0<Vaddr<V Byp EXTM C6 10nF Rsc 0.1 Ω Ω Ω Ω C3 470nF Ceramic D1 1N4001 C1 220µF C4 470nF Ceramic D2 BAT43 C7 10nF STS4DNFS30L Rsc 0.1 Ω Ω Ω Ω C3 470nF Ceramic D1 1N4001 C1 220µF C4 470nF Ceramic D2 BAT43 C7 10nF STS4DNFS30L IC2 (Note 3) IC1 (Note 4) LNBP21 Rsc 0.1 Ω Ω Ω Ω C3 470nF Ceramic D1 1N4001 C1 220µF C4 470nF Ceramic D2 BAT43 C7 10nF STS4DNFS30L Rsc 0.1 Ω Ω Ω Ω C3 470nF Ceramic D1 1N4001 C1 220µF C4 470nF Ceramic D2 BAT43 C7 10nF STS4DNFS30L IC2 (Note 3) IC1 (Note 4) LNBP21 |
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Similar Description - LNBP21D2 |
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