STEVAL-ISA052V1 STMicroelectronics, STEVAL-ISA052V1 Datasheet - Page 22

• Manufacturer Part Number: STEVAL-ISA052V1
• Description: KIT EVAL PM6675S HE CTLR 2A REG
• Manufacturer: STMicroelectronics

Specifications of STEVAL-ISA052V1

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 1.5V, 0.6 ~ 3.3V
• Current - Output: 10A, 2A
• Voltage - Input: 4.5 ~ 28 V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6675
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-8426

Device description
7.1.1
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Figure 33. Switching frequency selection and VOSC pin
The voltage seen at this pin must be greater than 0.8 V and lower than 2 V in order to
ensure the system linearity.
Constant-On-Time architecture
Figure 34
The switching regulator of the PM6675S controls a one-shot generator that turns on the
high-side MOSFET when the following conditions are simultaneously satisfied: the PWM
comparator is high (i.e. output voltage is lower than Vr = 0.6 V), the synchronous rectifier
current is below the current limit threshold and the minimum off-time has expired.
A minimum Off-Time contraint (300ns 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 = 0.6 V), the low-side MOSFET is turned off according to the anti-cross conduction logic
once again, and a new cycle begins.
shows the simplified block diagram of the Constant-On-Time controller.
R1
R1
R2
R2
VIN
VIN
VOSC
VOSC
PM6675
PM6675
PM6675S
PM6675S