L99DZ120 datasheet(82/162 Pages) STMICROELECTRONICS

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Application information

L99DZ120

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DocID029145 Rev 4

be driven at the outputs OUT1 and OUT4-6 without external freewheeling diodes. The high-

side drivers OUT7 to OUT15 and OUT_HS are intended to drive resistive loads only.

Therefore only a limited energy (E < 1 mJ) can be dissipated by the internal ESD-diodes in

freewheeling condition. For inductive loads (L > 100 μH) an external freewheeling diode

connected between GND and the corresponding output is required.

4.17

Open-load detection

The open-load detection monitors the load current in each activated output stage. If the load

current is below the open-load detection threshold for t > tOL_OUT the corresponding open-

load bit OUTx_OL (SR 5) is set in the status register.

4.18

Overcurrent detection

An overcurrent condition is detected after a filter time (see Figure 11 and Figure 12) and is

indicated by the status bit OUTx_OC (SR 3). In case of overcurrent, the corresponding

driver switches off to reduce the power dissipation and to protect the integrated circuit. If the

outputs are not configured in recovery mode, the microcontroller has to clear the relevant

status bits to reactivate the corresponding drivers.

4.19

Current monitor

The current monitor sources a current image of the power stage output current at the

current monitor pin CM, which has a fixed ratio (ICMr) of the instantaneous current of the

selected high-side driver. The signal at output CM is blanked for tcmb after switching on the

driver until the correct settlement of the circuitry. The bits CM_SELx (CR 7) define which of

the outputs is multiplexed to the current monitor output CM. The current monitor output

allows a more precise analysis of the actual state of the load rather than the detection of an

open-load or overload condition. For example, it can be used to detect the motor state

(starting, free running, stalled). The current monitor output is enabled after the current-

monitor blanking time, when the selected output is switched on. If this output is off, the

current monitor output is in high impedance mode. The current monitor can be deactivated

by CM_EN (CR 7).

4.20

PWM mode of the power outputs

Description see Section 7.3: Status register overview.

4.21

Cross-current protection

The four half-bridges of the device are cross-current protected by an internal delay time. If

one driver (LS or HS) is turned off, the activation of the other driver of the same half-bridge

will be automatically delayed by the crosscurrent protection time. After the crosscurrent

protection time is expired the slew-rate limited switch-off phase of the driver is changed to a

fast turn-off phase and the opposite driver is turned-on with slew-rate limitation. Due to this

behavior, it is always guaranteed that the previously activated driver is completely turned off

before the opposite driver starts to conduct.

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