STEVAL-ISA051V1 STMicroelectronics, STEVAL-ISA051V1 Datasheet - Page 29

• Manufacturer Part Number: STEVAL-ISA051V1
• Description: BOARD EVAL PM6670S DDR2/3
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of STEVAL-ISA051V1

• Design Resources: STEVAL-ISA051V1 Gerber Files STEVAL-ISA051V1 Schematic STEVAL-ISA051V1 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 ~ 28V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6670
• Input Voltage: 4.5 V to 28 V
• Output Voltage: 1.8 V, 1.5 V
• Product: Power Management Modules
• Silicon Manufacturer: ST Micro
• Silicon Core Number: PM6670S
• 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: PM6670S
• Other names: 497-8411

PM6670S
No-audible pulse-skip mode
Some audio-noise sensitive applications cannot accept the switching frequency to enter the
audible range as is possible in pulse-skip mode with very light loads. For this reason, the
PM6670S implements an additional feature to maintain a minimum switching frequency of
33 kHz despite a slight efficiency loss. At very light load conditions, if any switching cycle
has taken place within 30 μs (typ.) since the last one (because the output voltage is still
higher than the reference), a no-audible pulse-skip cycle begins. The low-side MOSFET is
turned on and the output is driven to fall until the reference has been crossed. Then, the
high-side switch is turned on for a T
rectifier is enabled until the inductor current reaches the zero-crossing threshold (see
Figure 34
Figure 34.
For frequencies higher than 33 kHz (due to heavier loads) the device works in the same way
as in pulse-skip mode. It is important to notice that in both pulse-skip and no-audible pulse-
skip modes the switching frequency changes not only with the load but also with the input
voltage.
Inductor
current
).
VDDQ
Output
V
reg
Inductor current and output voltage at light load with non-audible pulse-skip
T
ON
T
OFF
Doc ID 14432 Rev 4
T
MAX
T
IDLE
ON
period and, once it has expired, the synchronous
Device description
t
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