Datasheet LTC4151 (Analog Devices) - 10
| Fabricante | Analog Devices |
| Descripción | High Voltage I2C Current and Voltage Monitor |
| Páginas / Página | 18 / 10 — applicaTions inForMaTion Using Opto-Isolators with LTC4151-1 and … |
| Formato / tamaño de archivo | PDF / 446 Kb |
| Idioma del documento | Inglés |
applicaTions inForMaTion Using Opto-Isolators with LTC4151-1 and LTC4151-2. Start and Stop Conditions. Stuck-Bus Reset
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LTC4151
applicaTions inForMaTion Using Opto-Isolators with LTC4151-1 and LTC4151-2 Start and Stop Conditions
The LTC4151-1/LTC4151-2 split the SDA line into SDAI When the I2C bus is idle, both SCL and SDA must remain (input) and SDAO (LTC4151-1 inverted output) or SDAO in the high state. A bus master signals the beginning of a (LTC4151-2 output) for convenience of opto-coupling transmission with a Start condition by transitioning SDA with a host controller that sits at a different ground level. from high to low while SCL stays high. When the master When using opto-isolators with the LTC4151-1, connect has finished communicating with the slave, it issues a Stop the SDAI to the output of the incoming opto-coupler and condition by transitioning SDA from low to high while SCL connect the SDAO to the anode of the outgoing opto- stays high. The bus is then free for another transmission. coupler (see Figure 9). With the outgoing opto-coupler clamping SDAO and internal 6V (5.5V minimum) clamps
Stuck-Bus Reset
on SDAI and SCL, the pull-up resistors on these three pins The LTC4151 I2C interface features a stuck-bus reset can be directly connected to VIN. In this way (with SDAO timer. The low conditions of the SCL and the SDA/SDAI rather than conventional SDAO), the need for a separate pins are OR’ed to start the timer. The timer is reset when low voltage supply for pull-ups is eliminated. both SCL and SDA/SDAI are pulled high. If the SCL pin or the SDA/SDAI pin is held low for over 33ms, the stuck-bus Figure 11 shows the LTC4151-2 with high speed opto- timer will expire and the internal I2C state machine will be couplers for faster bus speeds. The LTC4151-2 has a non- reset to allow normal communication after the stuck-bus inverter SDAO output. Powered from VIN, the high voltage condition is cleared. The stuck-bus timer can be disabled LT3010-5 low dropout regulator provides the supply for the by clearing control register bit G2. opto-couplers as well as the bus lines pull-up. If the SDAI and SDAO on the master controller are not tied together, the ACK bit of the SDAO must be returned back to SDAI. RS 3.3V 0.02Ω VIN 48V R1 R2 R3 R4 R5 R6 R7 20k 20k 5.1k MOCD207M 0.51k 0.51k 10k 10k SENSE+ SENSE– 8 1 SCL VIN 7 2 V SCL DD LTC4151-1 SDAI 6 3 ADR1 SDA0 µ-CONTROLLER 5 4 ADR0 ADIN VADIN MOCD207M 1 8 SDA GND GND 4151 F09 2 7 3 6 4 5
Figure 9. Opto-Isolation of the I2C Interface Between LTC4151-1 and a Microcontroller (1.5kHz Data Rate of I2C is Limited by Slew Rate of Opto-Isolators)
4151ff 10 For more information www.linear.com/LTC4151 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Application Package Description Revision History Typical Application Related Parts
applicaTions inForMaTion Using Opto-Isolators with LTC4151-1 and LTC4151-2 Start and Stop Conditions
The LTC4151-1/LTC4151-2 split the SDA line into SDAI When the I2C bus is idle, both SCL and SDA must remain (input) and SDAO (LTC4151-1 inverted output) or SDAO in the high state. A bus master signals the beginning of a (LTC4151-2 output) for convenience of opto-coupling transmission with a Start condition by transitioning SDA with a host controller that sits at a different ground level. from high to low while SCL stays high. When the master When using opto-isolators with the LTC4151-1, connect has finished communicating with the slave, it issues a Stop the SDAI to the output of the incoming opto-coupler and condition by transitioning SDA from low to high while SCL connect the SDAO to the anode of the outgoing opto- stays high. The bus is then free for another transmission. coupler (see Figure 9). With the outgoing opto-coupler clamping SDAO and internal 6V (5.5V minimum) clamps
Stuck-Bus Reset
on SDAI and SCL, the pull-up resistors on these three pins The LTC4151 I2C interface features a stuck-bus reset can be directly connected to VIN. In this way (with SDAO timer. The low conditions of the SCL and the SDA/SDAI rather than conventional SDAO), the need for a separate pins are OR’ed to start the timer. The timer is reset when low voltage supply for pull-ups is eliminated. both SCL and SDA/SDAI are pulled high. If the SCL pin or the SDA/SDAI pin is held low for over 33ms, the stuck-bus Figure 11 shows the LTC4151-2 with high speed opto- timer will expire and the internal I2C state machine will be couplers for faster bus speeds. The LTC4151-2 has a non- reset to allow normal communication after the stuck-bus inverter SDAO output. Powered from VIN, the high voltage condition is cleared. The stuck-bus timer can be disabled LT3010-5 low dropout regulator provides the supply for the by clearing control register bit G2. opto-couplers as well as the bus lines pull-up. If the SDAI and SDAO on the master controller are not tied together, the ACK bit of the SDAO must be returned back to SDAI. RS 3.3V 0.02Ω VIN 48V R1 R2 R3 R4 R5 R6 R7 20k 20k 5.1k MOCD207M 0.51k 0.51k 10k 10k SENSE+ SENSE– 8 1 SCL VIN 7 2 V SCL DD LTC4151-1 SDAI 6 3 ADR1 SDA0 µ-CONTROLLER 5 4 ADR0 ADIN VADIN MOCD207M 1 8 SDA GND GND 4151 F09 2 7 3 6 4 5
Figure 9. Opto-Isolation of the I2C Interface Between LTC4151-1 and a Microcontroller (1.5kHz Data Rate of I2C is Limited by Slew Rate of Opto-Isolators)
4151ff 10 For more information www.linear.com/LTC4151 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Application Package Description Revision History Typical Application Related Parts