PCA9510A, PCA9511A, PCA9512A/B, PCA9513A, and PCA9514A highlight
PCA9510A, PCA9511A, PCA9513A, and PCA9514A Hot Swappable Bus Buffers
The PCA9510A, PCA9511A, PCA9513A, and PCA9514A are all hot swappable I2C and SMBus buffers that allow I/O card insertion into a live backplane without corrupting the clock or data buses. Control circuitry prevents the backplane I2C bus from being connected to the card I2C bus until a stop command or bus idle occurs on the backplane. When the connection is made, the bus buffers provide bi-directional buffering, keeping the backplane and card capacitances isolated.
These products incorporate:
Rise time accelerator circuitry allows the use of weaker DC pull-up currents while still meeting rise time requirements. The PCA9513A and PCA9514A rise time accelerator threshold has been moved from 0.6V to 0.8V to provide better noise margin. The rise time accelerator has been permanently disconnected on the PCA9510A.
During insertion, the PCA9511A SDA and SCL lines are precharged to 1V to minimize the current required to charge the parasitic capacitance of the chip and prevent glitching the I2C bus. The PCA9513A and PCA9514A do not have this feature since the precharge is detrimental in some applications and the new resistive tip pins are more effective than precharge in some live insertion applications. The PCA9510A only has precharge on the bus side and not the card side.
The PCA9513A supplies a 92μA current source to the backplane SCLIN and SDAIN pins in lieu of using pull-up resistors for PICMG backplane applications. Including the current source into the device reduces parts count and provides for a consistent RC time constant as cards are removed and inserted into the backplane. As more cards are added (increasing the bus capacitance), the effective pull-up resistance decreases (more current sources in parallel) and maintains the RC value constant.
PCA9512A/B Hot Swappable Bus Buffer
The PCA9512A and PCA9512B are a hot swappable I2C and SMBus buffers that allows I/O card insertion into a live backplane without corrupting the data and clock buses. The PCA9512A/B is similar to the PCA9511A, but without the digital ENABLE input pin (pin #1) and the open-drain READY output pin (pin #5). The PCA9512A/B replaces the ENABLE pin with a dedicated supply voltage pin, VCC2, for the card side, providing level shifting between 3.3V and 5V systems with optimal noise margin. Both the backplane and card may be powered with supply voltages ranging from 2.7V to 5.5V, with no constraints on which supply voltage is higher. The READY pin is replaced with a digital CMOS input pin, ACC, which enables or disables the rise-time accelerator currents for lightly loaded circuits.
A versus Non-A Versions
The "A" (or "B") versions of the PCA9510, PCA9511, PCA9512, PCA9513, and PCA9514 have higher series resistance outputs than the original non-A versions. The benefit of the increased series resistance is improved signal integrity. As such, the original, non-A versions have been discontinued. The PCA9511A is specifically designed as an alternate source for the Linear Technology LTC4300A-1, and the PCA9512A is an alternate source for the LTC4300A-2.
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