Test results and significant waveforms

AN3063

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Doc ID 16261 Rev 3

Figure 32.

EVL6563H on/off control by a cascaded converter controller via the

PFC_OK or RUN pin

The third communication line is the PWM_STOP (pin #11), which works in conjunction with

the RUN (pin #12). The purpose of the PWM_STOP pin is to inhibit the PWM activity of both

the PFC stage and the cascaded DC-DC converter. The pin is an open collector, normally

open, that goes low if the device is disabled by a voltage lower than 0.8 V on the RUN (pin

#12). It is important to point out that this function works correctly in systems where the PFC

stage is the master and the cascaded DC-DC converter is the slave or, in other words,

where the PFC stage starts first, powers both controllers and enables/disables the operation

of the DC-DC stage. This function is quite flexible and can be used in different ways. In

systems comprising an auxiliary converter and a main converter (e.g. a desktop PC's silver

box or hi-end flatscreen TV or monitor), where the auxiliary converter also powers the

controllers of the main converter, the RUN (pin #12) can be used to start and stop the main

converter. In the simplest case, to enable/disable the PWM controller the PWM_STOP (pin

#11) can be connected to either the output of the error amplifier or, if the chip is provided

with it, to its soft-start pin.

The EVL6563H-100W offers the possibility to test these functions by connecting it to the

cascaded converter via the series resistors R28, R29, R30. Regarding the PWM_STOP (pin

#11) pin that is an open collector type, if it needs a pull-up resistor, please connect it close to

the cascaded PWM for better noise immunity.

Figure 33.

Interface circuits that let the

L6563H switch on or off a PWM

controller, not latched

Figure 34.

Interface circuits that let the

L6563H switch on or off a PWM

controller, latched