L6699D datasheet(16/38 Pages) STMICROELECTRONICS

16 / 38 page

Application information

L6699

16/38

Doc ID 022835 Rev 2

Note that the “Driving logic…” block sets a minimum deadtime TD_MIN (≈ 230 ns) below

which TD cannot go, to prevent simultaneous conduction of the high-side and the low-side

switch, and also a maximum deadtime TD_MAX to guarantee proper operation of the half

bridge. TD_MAX is internally set at either 700 ns or one fourth of the oscillator cycle,

whichever is shorter.

Figure 9.

Detailed view of deadtime during low-to-high transition of half bridge

midpoint

The actual deadtime TD that can be observed during operation does not depend only on the

adjustment circuit of

Figure 7. This fact can be explained with the aid of the oscilloscope

image shown in

Figure 9.

It illustrates a detailed view of the low-to-high transition of the half bridge midpoint

(waveform labeled HB) along with the high-side gate-drive (HVG), the low-side gate-drive

(LVG) and the oscillator voltage on pin CF (OSC). Obviously, the information that follows

applies to the high-to-low transition as well.

Figure 7.

Adaptive deadtime: principle

schematic

Figure 8.

Relevant timing diagrams

L6699D Datasheet(PDF) 16 Page - STMicroelectronics