PM6675AS STMicroelectronics, PM6675AS Datasheet - Page 25

• Manufacturer Part Number: PM6675AS
• Description: IC CTLR STP DWN HE LDO VFQFPN24
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of PM6675AS

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.5V, 0.6 ~ 3.3 V
• Current - Output: ±1A, ±2A
• Frequency - Switching: 33kHz
• Voltage - Input: 4.5 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-VFQFN, 24-VFQFPN
• Power - Output: 2.3W
• For Use With: 497-8426 - KIT EVAL PM6675S HE CTLR 2A REG497-8413 - BOARD EVAL BASED ON PM6675A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PM6675AS
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
PM6675AS implements an additional feature to maintain a minimum switching frequency of
33 kHz despite of 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 of 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 Ton period and, once it has expired, the synchronous
rectifier is enabled until the inductor current reaches the zero-crossing threshold
(see
Figure 28.
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
Output
voltage
V
Figure 28
reg
Inductor current and output voltage at light load with non-audible pulse-skip
T
).
ON
T
OFF
T
MAX
T
IDLE
Device description
t
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