General description  

     The AT9517 is a CMOS integrated circuit that provides level shifting between low voltage (down to 0.9 V) and higher voltage (2.7 V to 5.5 V) I²C-bus or SMBus applications. While retaining all the operating modes and features of the I²C-bus system during the level shifts, it also permits extension of the I2C-bus by providing bidirectional buffering for both the data (SDA) and the clock (SCL) lines, thus enabling two buses of 400 pF. Using the AT9517 enables the system designer to isolate two halves of a bus for both voltage and capacitance. The SDA and SCL pins are overvoltage tolerant and are high-impedance when the AT9517 is unpowered.

     The 2.7 V to 5.5 V bus port B drivers behave much like the drivers on the PCA9515A device, while the adjustable voltage bus port A drivers drive more current and eliminate the static offset voltage. This results in a LOW on the port B translating into a nearly 0 V LOW on the port A which accommodates smaller voltage swings of lower voltage logic.

     The static offset design of the port B AT9517 I/O drivers prevent them from being connected to another device that has rise time accelerator. Port A of two or more AT9517s can be connected together, however, to allow a star topography with port A on the common bus, and port A can be connected directly to any other buffer with static or dynamic offset voltage. Multiple AT9517s can be connected in series, port A to port B, with no build-up in offset voltage with only time of flight delays to consider.

     The AT9517 drivers are not enabled unless V_CC(A) is above 0.8 V and V_CC(B) is above2.5V. The EN pin can also be used to turn the drivers on and off under system control. Caution should be observed to only change the state of the enable pin when the bus is idle.

     The output pull-down on the port B internal buffer LOW is set for approximately 0.5V, while the input threshold of the internal buffer is set about 70 mV lower (0.43 V). When the port B I/O is driven LOW internally, the LOW is not recognized as a LOW by the input.

    This prevents a lock-up condition from occurring. The output pull-down on port A drives a hard LOW and the input level is set at 0.3V_CC(A) to accommodate the need for a lower LOW level in systems where the low voltage side supply voltage is as low as 0.9V.

Features and benefits

    2 channel, bidirectional buffer isolates capacitance and allows 400 pF on either side of the device

    Voltage level translation from 0.9V to 5.5V and from 2.7V to 5.5V

    Footprint and functional replacement for AT9515/15A

    I²C-bus and SMBus compatible

    Active HIGH repeater enable input

    Open-drain input/outputs

    Lock-up free operation

    Supports arbitration and clock stretching across the repeater

    Accommodates Standard-mode and Fast-mode I²C-bus devices and multiple masters

    Powered-off high-impedance I²C-bus pins

    Port A operating supply voltage range of 0.9V to 5.5V

    Port B operating supply voltage range of 2.7V to 5.5V

    5V tolerant I²C-bus and enable pins

    0 Hz to 400 kHz clock frequency (the maximum system operating frequency may be less than 400 kHz because of the delays added by the repeater)

    ESD protection exceeds 5500 V HBM per JESD22-A114 and 1000 V CDM per JESD22-C101

    Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

    Packages offered: SO8, TSSOP8 and HWSON8

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