C167CS Datasheet, PDF (132/517 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller

C167CS
Derivatives
Parallel Ports
Driver Characteristic
This defines either the general driving capability of the respective driver, or if the driver
strength is reduced after the target output level has been reached or not. Reducing the
driver strength increases the output’s internal resistance which attenuates noise that is
imported/exported via the output line. For driving LEDs or power transistors, however, a
stable high output current may still be required.
The controllable output drivers of the C167CS pins feature two differently sized
transistors (strong and weak) for each direction (push and pull). The time of activating/
deactivating these transistors determines the output characteristics of the respective
port driver.
Three modes can be selected to adapt the driver characteristics to the application’s
requirements:
In High Current Mode both transistors are activated all the time. In this case the driver
provides maximum output current even after the target signal level is reached.
In Low Noise Mode both transistors are activated at the beginning of a signal transition.
When the target signal level is reached the driver strength is reduced by switching off the
strong transistor. The weak transistor will keep the specified output level while the
susceptibility for noise is reduced.
In Low Current Mode only the weak transistor is activated while the strong transistor
remains off. This results in smooth transitions with low current peaks (and reduced
susceptibility for noise) on the cost of increased transition times, i.e. slower edges,
depending on the capacitive load.
User’s Manual
7-5
V2.0, 2000-07