AN4460 datasheet(20/54 Pages) STMICROELECTRONICS

20 / 54 page

SMED implementation

AN4460

20/54

DocID026129 Rev 1

4.4

SMED state time evolution

Figure 6 describes the SMED state time evolution. Only one PWM period is illustrated.

Figure 6. SMED state evolution. Timing

The colors identify the case of a correct or incorrect situation:



The black trace is the output current observed during a correct setup where the SMED

evolution is triggered by timer events only. In this case, no event_Seq or event_Jmp

are received; note that S2 may not have reached the peak level during S(2).



The blue trace represents the situation where the current reaches the limit point

(event_Seq) during S(2).



The red line shows the SMED evolution when an OCP event (event_Jmp) is detected

during S1. The SMED is programmed to generate an interrupt when an OCV condition

happens. The main program receives the interrupt and stops the SMED.

STATE

IDLE

S(0)

PWM

time

Current

S(1)

S(2)

S(0)

Fault zone

Current limit

off time

Fixed-

33% TON

132%

TON +20%

Current limit

Fault OCP

S(4)

off time

Fixed-

AM16706v1

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