STEVAL-ISA051V2 STMicroelectronics, STEVAL-ISA051V2 Datasheet - Page 22

• Manufacturer Part Number: STEVAL-ISA051V2
• Description: BOARD EVAL PM6670AS DDR2/3
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA051V2

• Design Resources: STEVAL-ISA051V2 Gerber Files STEVAL-ISA051V2 Schematic STEVAL-ISA051V2 Bill of Material
• Main Purpose: Special Purpose DC/DC, DDR Memory Supply
• Outputs And Type: 4, Non-Isolated
• Voltage - Output: 1.5V, 1.8V
• Voltage - Input: 4.5 ~ 36V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6670A
• Input Voltage: 4.5 V to 36 V
• Output Voltage: 1.8 V, 1.5 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: PM6670AS
• Kit Application Type: Power Management
• Application Sub Type: DDR2/3 Memory Power Supply Controller
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• For Use With/related Products: PM6670AS
• Other names: 497-8412

Device description
7.1.1
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Figure 27. Switching frequency selection and VOSC pin
The suggested voltage range for VOSC pin is 0.3V to 2V, for better switching frequency
programmability.
Constant-on-time architecture
Figure 28
The switching regulator of the PM6670AS 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.
shows the simplified block diagram of the constant-on-time controller.
Doc ID 14436 Rev 2
R2
R1
VIN
VOSC
PM6670AS
PM6670
PM6670AS