PM6680ATR datasheet(23/48 Pages) STMICROELECTRONICS

Part #	PM6680ATR

Description	Dual synchronous step-down controller with adjustable output voltages plus LDO

PDF	48 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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23 / 48 page

PM6680A

Device description

23/48

7.5

No-audible skip mode

If SKIP pin is tied to VREF, a no-audible skip mode with a minimum switching frequency of

33 kHz is enabled. At light load condition, If there is not a new switching cycle within a 30

µs

(typ.) period, a no-audible skip mode cycle begins.

Figure 32.

No audible skip mode

The low side switch is turned on until the output voltage crosses about Vreg + 1 %. Then the

high side MOSFET is turned on for a fixed on time period. Afterwards the low side switch is

enabled until the inductor current reaches the zero-crossing threshold. This keeps the

switching frequency higher than 33 kHz. As a consequence of the control, the regulated

voltage can be slightly higher than Vreg (up to 1 % ).

If, due to the load, the frequency is higher than 33 kHz, the device works like in skip mode.

No-audible skip mode reduces audio frequency noise that may occur in pulse skip mode at

very light loads, keeping the efficiency higher than in PWM mode.

PM6680ATR Datasheet(PDF) 23 Page - STMicroelectronics