Sony Ericsson GR64 - Manual (Page 36)

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5.3.1.2 I2C Level Shifter Interface
Because of the nature of the I 2 C interface signals, SDA (data) & SCL (clock), they
utilize a different type of level-shifting technology to that of the ‘common’ IO. The
I
2 C level shifter IC uses an open drain construction with no direction pin, ideally
suited to bi-directional low voltage (such as the GR64 1.8 V processor) I 2 C port
translation to the normal 3.3 V or 5.0 V I 2 C-bus signal levels. Unlike the common
level shifters, the I 2 C level shifters have a very low (6.5ohm RDS
ON
) resistance
between input and output pins.
The I 2 C level shifters use VREF as the host-side voltage reference and the internal
1.8V digital IO core as the module-side reference.