SI53119-A03A Datasheet, PDF (16/34 Pages) Silicon Laboratories – PLL or bypass mode

Si53119-A03A
2.6. Miscellaneous Requirements
Data Transfer Rate: 100 kbps (standard mode) is the base functionality required. Fast mode (400 kbps)
functionality is optional.
Logic Levels: SMBus logic levels are based on a percentage of V_DD for the controller and other devices on the
bus. Assume all devices are based on a 3.3 V supply.
Clock Stretching: The clock buffer must not hold/stretch the SCL or SDA lines low for more than 10 ms. Clock
stretching is discouraged and should only be used as a last resort. Stretching the clock/data lines for longer than
this time puts the device in an error/time-out mode and may not be supported in all platforms. It is assumed that all
data transfers can be completed as specified without the use of clock/data stretching.
General Call: It is assumed that the clock buffer will not have to respond to the “general call.”
Electrical Characteristics: All electrical characteristics must meet the standard mode specifications found in
Section 3 of the SMBus 2.0 specification.
Pull-Up Resistors: Any internal resistor pull-ups on the SDATA and SCLK inputs must be stated in the individual
data sheet. The use of internal pull-ups on these pins of below 100 K is discouraged. Assume that the board
designer will use a single external pull-up resistor for each line and that these values are in the 5–6 k range.
Assume one SMBus device per DIMM (serial presence detect), one SMBus controller, one clock buffer, one clock
driver plus one/two more SMBus devices on the platform for capacitive loading purposes.
Input Glitch Filters: Only fast mode SMBus devices require input glitch filters to suppress bus noise. The clock
buffer is specified as a standard mode device and is not required to support this feature. However, it is considered
a good design practice to include the filters.
PWRDN: If a clock buffer is placed in PWRDN mode, the SDATA and SCLK inputs must be Tri-stated and the
device must retain all programming information. IDD current due to the SMBus circuitry must be characterized and
in the data sheet.
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Rev. 1.0