L9958 datasheet(18/38 Pages) STMICROELECTRONICS

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Current regulation

L9958

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DocID17269 Rev 6

selection can be done "on the fly" by SPI. The corresponding bits are called "VSR" and

"ISR". No external component is needed to select the slew rate range. Only the power

transistors not used for freewheeling can be adjusted, the two others can be controlled with

a preset slew rate.

The couples of value defined to fulfill most of the application requirements are described in

the table below. The required accuracy is ±50 % for an output current from 1A to 8A and

with output voltage up to 19 V. The overall delay implemented between high-side and low-

side transistor switching must be adjusted automatically to avoid any cross-conduction

through one half-bridge in all conditions.

In case of current limitation and any detection that put the bridge in tri-state, the slew rate is

not related anymore to the preset bits "VSR"; "ISR" but to a dedicated faster slew rate

control named "SUPER FAST" mode. The automatic change from SPI selectable to SUPER

FAST slew rate is described hereafter.

Figure 14. Slew rate switching strategy

Table 10. Slew rate control on low side MOS

Range

VSR

ISR

dV/dt (V/μs)

dI/dt (A/μs)

1 (default value)0

0.3

No SR control

Not selectable

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