STLUX385ATR datasheet(10/99 Pages) STMICROELECTRONICS

10 / 99 page

System architecture

STLUX385A

10/98

DocID024387 Rev 2

System architecture

The STLUX385A generates and controls PWM signals by means of a state machine, called

SMED (state machine event driven). The following picture gives an overview of the internal

architecture.

Figure 1. STLUX385A internal design

The core of the device is the SMED unit: a hardware state machine driven by system

events. The SMED includes 4 states (S0, S1, S2 and S3) available during running

operations. A special HOLD state is provided as well. The SMED allows the user to

configure, for every state, which system events trigger a transaction to a new state. During a

transaction from one state to the other, the PWM output signal level can be updated.

Once a SMED is configured and running, it becomes an autonomous unit, so no interaction

is required since the SNMED automatically reacts to system events.

Thanks to the SMED's 96 MHz operating frequency and their automatic dithering function,

the PWM maximum resolution is 1.3 ns.

The STLUX385A has 6 SMEDs available. Multiple SMEDs can operate independently from

each other or they can be grouped together to form a more powerful state machine.

The STLUX385A also integrates a low-power STM8 microcontroller which is used to

configure and monitor the SMED activity and to supply external communication such as

DALI. The STM8 controller has full access to all the STLUX385A sub-systems, including the

SMEDs. The STLUX385A also features a sequential ADC, which can be configured to

continuously sample up to 8 channels.

The following section illustrates the overall system block and shows how SMEDs have been

implemented in the STLUX385A architecture.

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