A6985F datasheet(32/77 Pages) STMICROELECTRONICS

部件名	A6985F

功能描述	38 V 500 mA synchronous step-down switching regulator

PDF	77 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

32 / 77 page

Functional description

A6985F

32/77

DocID027738 Rev 2

Figure 21. Valley current sense operation in overcurrent condition

Figure 21 shows the switching frequency reduction during the valley current sense

operation in case of extremely low duty cycle (VIN =38 V, fSW = 2 MHz short-circuit

condition).

In a worst case scenario (like Figure 21) 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



A6985F 数据表(PDF) 32 Page - STMicroelectronics