L9959 datasheet(26/49 Pages) STMICROELECTRONICS

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Application information

L9959

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DocID027540 Rev 3

to force a transition LOW/HIGH/LOW on DIS pin or a transition HIGH/LOW/HIGH on /ABE

pin.

The errors in the diagnosis register 1 (DIA_REG1) are transferred to the diagnosis register 2

by setting the bit DIACLR1 in the status and configuration register (STATCON_REG) or by

using the enabling -disabling sequence on /ABE or DIS. This will also clear the diagnosis

4.2.1

Current feedback

A feedback current signal is provided at pin CF (Current Feedback). This current is

proportional to the current in the H-Bridge, but does not change its direction. It is measured

in the low-side transistor, which is not switched by PWM. This is determined by the input

DIR or the SDIR register respectively. Therefore, the direction of the current can be seen

from this direction signal.

One current sense monitoring circuit is present and it is connected to the output of the active

LS driver (DIR change mode).

After the DIR transition, the LSx reference output is switched only in the phase in which both

LS drivers are active for recirculation.

In the time-frame between HS turn-off and the start of active freewheeling, (including dead

time and passive freewheeling), the current sense monitors the current flowing in the

previous active LS driver.

This time-frame is not fixed but adaptative to real operative conditions (battery and selected

slew rate mode).

In Table 14: Current feedback (CF) the CF behavior over an external resistor of 5.1k Ohm is

specified. The current out of CF consists of a static offset current and a current proportional

to the current in the select low-side transistor. The voltage at pin CF scales with the resistor

at this pin.

Figure 15. Current feedback and current limiting

Figure 15 Current Feedback and Current Limiting shows the current feedback in case the

OUT1 is controlled by PWM (DIR = 0). In this case, the current is measured through low-

side 2. If the direction is inverted, the current is measured through low-side 1.

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