Datasheet
SRK2000 main characteristics AN3303
12/27 Doc ID 18164 Rev 2
time check is re-enabled. The number of ignored resonant converter switching cycles is 128
after entering sleep mode and 256 after exiting sleep mode.
Figure 11 shows some examples of operation mode transition.
Figure 11. Operation mode transitions
1.5 Enable pin
Pin EN can be used to remotely enable or disable power MOSFET driving. A voltage above
1.8 V enables the IC outputs which are otherwise inhibited.
By connecting the EN pin to Vcc through a resistor divider, the minimum Vcc voltage, at
which the IC starts driving power MOSFETs, can be precisely set. If the SR power
MOSFETs are logic level, the IC can start driving as soon as Vcc reaches the turn-on
threshold (4.5 V), but if the SR power MOSFETs are standard level, it is better to keep the IC
inhibited until the Vcc achieves the voltage necessary to properly drive the power MOSFETs
(i.e. 10 V).
The EN pin has an additional function which allows setting the SR power MOSFETs turn-off
threshold. It is set before the IC starts operating, when Vcc ramps up from 0 V to 4.5 V
(VccOn). During this time window, if the voltage on pin EN is below 0.36 V (typ.), the turn-off
threshold is set to -25 mV, if it is above VEN-Th, the threshold is set to -12.5 mV. This
function gives the possibility to change the turn-off threshold according to the SR power
MOSFET R
DS(on)
and to the converter operation. Details of divider resistor calculation can
be found in the SRK2000 datasheet.
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