描述 Description

The P82B715 is a bipolar IC intended for application in IC-bus and derivative bus systems. While retaining all the operating modes and features of the IC-bus it permits extension of the practical separation distance between components on the I2C-bus by buffering both the data (SDA) and the clock (SCL) lines.
The IC-bus capacitance limit of 400 pF restricts practical communication distances to a few meters. Using one P82B715 at each end of a long cable (connecting Lx/Ly to Lx/Ly) reduces that cables loading on the linked IC-buses by a factor of 10 and allows the total system capacitance load (all devices, cable, connectors, and traces or wires connected to the IC-bus) to be around 3000 pF while the loading on each IC-bus on the Sx/Sy sides remains below 400 pF. Longer cables or low-cost, general-purpose wiring may be used to link IC-bus based modules without degrading noise margins. Multiple P82B715s can be connected together, linking their Lx/Ly ports, in a star or multi-point architecture as long as the total capacitance of the system is less than about 3000 pF and each bus at an Sx/Sy connection is well below 400 pF. This configuration, with the master and/or slave devices attached to the Sx/Sy port of each P82B715, has full multi-master communication capability. The P82B715 alone does not support voltage level translation, but it can be simply implemented using low cost transistors when required. There is no restriction on interconnecting the Sx/Sy I/Os, and, because the device output levels are always held within 100 mV of input drive levels, P82B715 is compatible with bus buffers that use voltage level offsets, e.g., PCA9511A, PCA9517, Sx/Sy side of P82B96.
The lower VOL level and ability to operate with any master, slave or bus buffer is the primary advantage of the using the P82B715 for long distance buses at the disadvantage of not isolating bus capacitance like the P82B96 or PCA9600 are able to do. The primary disadvantage of the P82B96 and PCA9600 is that the static level offset needed to isolate bus capacitance does not allow these devices to operate with other bus buffers with special offset levels or with master/slaves that require a VIL lower than 0.8 V with noise margin. A proven quick design-in point-to-point/multi-point circuit is included in Section 8.2 to allow rapid use of the P82B715 along with comparison waveforms so that the designer can clearly see the trade-offs between the P82B715 and the P82B96/PCA9600 and choose the type of device that is best for their application.

特性 Features

Dual, bidirectional, unity voltage gain buffer with no external directional control required
Compatible with I2C-bus and its derivatives SMBus, PMBus, DDC, etc.
Logic signal levels may include (but not exceed) both supply and ground
Logic signal input voltage levels are output without change and are independent of VCC
x10 impedance transformation, but does not change logic voltage levels
Supply voltage range 3 V to 12 V
Clock speeds to at least 100 kHz and 400 kHz when other system delays permit
ESD protection exceeds 2500 V HBM per Mil. Std 883C-3015.7 and 400 V MM per JESD22-A115 (I/Os have diodes to VCC and GND)
Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

應(yīng)用 Application

Increase the total connected capacitance of an I2C-bus system to around 3000 pF
Drive IC-bus signals over long cables to approximately 50 meters or 3000 pF
Drives x10 lower impedance bus wiring for improved noise immunity
Multi-drop distribution of IC-bus signals using low cost twisted-pair cables
AdvancedTCA radial IPMB architecture
Driving 30 mA Fm+ devices from standard 3 mA parts