DS12667 Rev 6

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L99MOD51XP

Application information

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4.10

PWM input

Each driver has a corresponding PWM enable bit which can be programmed by the SPI

interface. If the PWM enable bit is set, the outputs OUT1 to OUT5 are controlled by the

logically AND-combination of the signal applied to the PWM input and the output control bit

in input data register1.

4.11

Cross-current protection

The three 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 is

delayed automatically by the cross-current protection time. After the cross-current 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 totally turned-off before the

opposite driver starts to conduct.

4.12

Programmable softstart function to drive loads with higher

inrush current

Loads with start-up currents higher than the over-current limits (e.g. inrush current of lamps,

start current of motors and cold resistance of heaters) can be driven by using the

programmable softstart function (i.e. overcurrent recovery mode). Each driver has a

corresponding over-current recovery bit. If this bit is set, the device switches-on

automatically the outputs again after a programmable recovery time. The duty cycle in over-

current condition can be programmed by the SPI interface to be about 12% or 25%. The

PWM modulated current will provide sufficient average current to power up the load (e.g.

heat up the bulb) until the load reaches operating condition.

The device itself cannot distinguish between a real overload and a non linear load like a light

bulb. A real overload condition can only be qualified by time. As an example the

microcontroller can switch on light bulbs by setting the over-current Recovery bit for the first

50 ms. After clearing the recovery bit the output will be automatically disabled if the overload

condition still exits.

Figure 9. Example of programmable softstart function for inductive loads