 | Author | Message | | | eric | | Posted: Fri Sep 01, 2006 6:11 pm Post subject: Pull-up accelerator | | | | Site Admin Joined: 01 Jan 1970 Posts: 311 | K.S.M. Walraven
Systems like the SMBus or I2C™ use a standard resistor to pull up
the signal levels to the positive supply rail (normally 5 V). The bus
goes low because an appliance connected to it pulls the signal to
zero via its open-collector output. The well-known problem is this
output can draw a much higher current than the pull-up resistor
can compensate. This results in a steep trailing edge, but a much
more gradually rising leading edge, whose transition in addition is
not linear but exponential. This adversely affects the duty factor
of the signals and also reduces the speed of the bus.
Linear Technology have available an IC (Type LTC1694) to
replace the traditional pull-up resistor which can produce a current
that is dependent on the changes in level taking place on the
bus. When that level rises, the IC gives 2.2 mA, but when it falls,
the current is only 275 μA.
Since the IC contains two circuits for replacing both pull-up
resistors, it is possible to detect when
 | | |
| Back to top | |
|
|
All times are GMT
Audio power, headphone and pre Amplifier, Digital audio circuits, Loudspeakers projects
PLC articles, examples, hardware, hints and tips, software
SitemapPowered by phpBB // Template by Mike Lothar | 
