PM6670S View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'PM6670S' PDF : 53 Pages View PDF
PM6670S
Device description
7.1.1
Constant-on-time architecture
Figure 30 shows the simplified block diagram of the constant-on-time controller.
The switching regulator of the PM6670S owns a one-shot generator that ignites the high-
side MOSFET when the following conditions are simultaneously satisfied: the PWM
comparator is high (i.e. output voltage is lower than Vr = 0.9 V), the synchronous rectifier
current is below the current limit threshold and the minimum off-time has expired.
A minimum off-time constraint (300 ns typ.) is introduced to assure the boot capacitor
charge and allow inductor valley current sensing on low-side MOSFET. A minimum on-time
is also introduced to assure the start-up switching sequence.
Once the on-time has timed out, the high side switch is turned off, while the synchronous
rectifier is ignited according to the anti-cross conduction management circuitry.
When the output voltage reaches the valley limit (determined by internal reference
Vr = 0.9 V), the low-side MOSFET is turned off according to the anti-cross conduction logic
once again, and a new cycle begins.
Figure 30. Switching section simplified block diagram
Doc ID 14432 Rev 4
23/54
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