A6986F datasheet(32/72 Pages) STMICROELECTRONICS

Numer części	A6986F

Szczegółowy opis	38 V 1.5 A synchronous step-down switching regulator

PDF	72 Pages

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Producent	STMICROELECTRONICS [STMicroelectronics]

Strona internetowa	http://www.st.com

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Functional description

A6986F

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sense threshold. The low-side operation is able to prevent the high-side turn on, so the

device can skip pulses decreasing the swathing frequency.

Figure 23. Valley current sense operation in overcurrent condition

Figure 23 shows the switching frequency reduction during the valley current sense

operation in case of extremely low duty cycle (VIN 38 V, fSW = 500 kHz short-circuit

condition).

In a worst case scenario (like Figure 23) of the overcurrent protection the switch current is

limited to:

Equation 15

where IVALLEY_TH is the current threshold of the valley sensing circuitry (see Table 5:

Electrical characteristics on page 8) and TMASK_HS is the masking time of the high-side

switch 100 nsec. typ.).

In most of the overcurrent conditions the conduction time of the high-side switch is higher

than the masking time and so the peak current protection limits the switch current.

Equation 16

IMAX = IPEAK_TH

IMAX

IVALLEYTH

VIN VOUT

–

------------------------------ TMASKHS



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