L99MOD50XP datasheet(22/42 Pages) STMICROELECTRONICS

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Application information

L99MOD50XP

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DS12615 Rev 4

supply voltage VS recovers (control register 3: bit 4=0) to normal operating voltage then the

outputs stages return to the programmed state. If the undervoltage/overvoltage recovery

disable bit is set (control register 3: bit 4=1), the automatic turn-on of the drivers is

deactivated.

The microcontroller needs to clear the status bits to reactivate the drivers. It is

recommended to set bit1 control register 3 to avoid a possible high current oscillation in

case of a shorted output to GND and low battery voltage.

3.6

Overvoltage and undervoltage detection at VCC

In case of power-on (VCC increases from undervoltage to VPOR OFF = 2.9 V) the circuit is

initialized by an internally generated power-on-reset (POR). If the voltage VCC decreases

below the minimum threshold (VPOR ON = 2.0 V), the outputs are switched to tristate (high

impedance) and the status registers are cleared.

3.7

Temperature warning and thermal shutdown

If the junction temperature rises above Tj TW, a temperature warning flag is set after at least

32 μs and it can be read via the SPI. If the junction temperature increases above the second

threshold Tj SD, the thermal shutdown bit is set and the power DMOS transistors of all output

stages are switched off to protect the device after at least 32 μs.

The temperature warning and thermal shutdown flags are latched and the bits must be

cleared by the microcontroller. This is possible only if the temperature has decreased below

trigger temperature. If the thermal shutdown bit has been cleared the output stages are

reactivated.

3.8

Inductive loads

Each half bridge is built by internally connected high-side and low-side power DMOS

transistors. Due to the built-in reverse diodes of the output transistors, inductive loads can

be driven at the outputs OUT1 to OUT6 without external free-wheeling diodes. The high-

side drivers OUT7 to OUT11 are intended to drive resistive loads. 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 free-wheeling diode connected between GND

and the corresponding output is required.

3.9

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 at least 1 ms (tdOL) the corresponding

open load bit is set in the status register. Due to mechanical/electrical inertia of typical loads

a short activation of the outputs (e.g. 3 ms) can be used to test the open load status without

changing the mechanical/electrical state of the loads.

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