L9958 datasheet(16/38 Pages) STMICROELECTRONICS

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Current regulation

L9958

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Doc ID 17269 Rev 5

Current regulation

To protect the actuator and limit power dissipation, a two-level chopper current limitation is

integrated as shown in figure below. The current is measured by sense cells integrated in

the low-side switches. As soon the upper current limit “IH” is reached, both low-side drivers

are switched on to allow free-wheeling recirculation, until the lower current limit “IL” is

reached. During the current regulation, all the slew rate controls are disabled in order to

minimize the power dissipation. Four current limit levels can be set by the SPI control bits 0

and 1. In order to achieve very precise current threshold and ripple, an external resistance is

required (1 % accuracy on all temp range/lifetime) to generate a current reference. Detailed

values for current thresholds and ripple are reported in Table 9.

Figure 11.

Current limitation

4.1

Temperature-dependent current regulation

In order to reduce power dissipation and thus the junction temperature, above a

temperature Twarn = 160 °C, current regulation high limit linearly decreases with

temperature, to reach about 2.5 A at Tsd = 175 °C (shutdown temperature).

When this thermal threshold is reached during a current limitation phase, the information is

stored and latched in a coding of bits called "Twarn". This bit can be reset only if the settings

conditions (Tj > Twarn and ILIM = 0) are not present anymore. This feature is mainly used to

reduce the power dissipation and thus the junction temperature.

Table 9.

Current limitation programmability

CL_2

CL_1

Current limit (typical values)

2.5 A

4 A

6.6 A (default value)

8.6 A

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