L9949

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tors and one grounded resistive load can be driven with its three half bridges, one full bridge and one highside

driver power outputs. The integrated standard serial peripheral interface (SPI) controls all operation modes (for-

ward, reverse, brake and high impedance). All diagnostic informations are available via the SPI.

Dual Power Supply: VS and VCC

The power supply voltage VS supplies the full bridge, the half bridges and the highside driver. An internal

charge-pump are used to drive the highside switches. The logic supply voltage VCC (stabilized 5V) is used for

the logic part and the SPI of the device. Due to the independent logic supply voltage the control and status in-

formation will not be lost, if there are temporary spikes or glitches on the power supply voltage. In case of power-

on (VCC increases from undervoltage to VVCC OFF = 4.2V) the circuit is initialized by an internally generated

power-on-reset (POR). If the voltage VCC decreases under the minimum threshold (VVCC ON = 3.4V), the out-

puts are switched to tristate (high impedance) and the status registers are cleared.

Standby-Mode

The standby mode of the L9949 is activated by setting the bits 12 and 13 of the Input Data Register to zero. All

latched data will be cleared and the inputs and outputs are switched to high impedance. In the standby mode

the current at VS (VCC) is less than typ. 6µA (40µA) for CSN = high (DO in tristate). By switching the VCC voltage

a very low quiescent current can be achieved. If one of the bits 12 and 13 are set to high, the device will be

switched to active mode.

Inductive Loads

Each half bridge is built by internally connected highside and a lowside power DMOS transistor. Due to the built-

in reverse diodes of the output transistors inductive loads can be driven at the outputs OUT1 to OUT5 without

external free-wheeling diodes. The highside driver OUT6 is intended to drive resistive loads only hence only a

limited energie (E<1mJ ) can be dissipated by the internal ESD-diode in freewheeling condition. For inductive

loads (L>100

µH) an external free-wheeling diode connected to GND and OUT6 is needed.

Diagnostic Functions

All diagnostic functions (over/open load, power supply over-/undervoltage, temperature warning and thermal

shutdown) are internally filtered and the condition has to be valid for at least 10µs (0.5ms, respectively) before

the corresponding status bit in the status registers will be set. The filters are used to improve the noise immunity

of the device. The open load and temperature warning function are intended for information purpose and will

not change the state of the output drivers. In contrast, the overload and thermal shutdown condition will disable

the corresponding driver (overload) or all drivers (thermal shutdown), respectively. The microcontroller has to

clear the status bits to reactivate the corresponding drivers. This is to avoid an uncontrolled switching behaviour

of the device which may result in a heavy noise on the GND and VS lines in case of an fault condition (e.g. short

to GND or VS).

Overvoltage and Undervoltage Detection

If the power supply voltage VS rises above the overvoltage threshold VSOV OFF (max. 22V), the outputs OUT1

to OUT6 are switched to high impedance state to protect the load. If the supply voltage recovers to normal op-

erating voltage, the device will return to the programmed state (lockout bit 14 = 0). When the voltage VS drops

below the undervoltage threshold VSUV OFF (min. 6V), the output stages are switched to high impedance to

avoid the operation of the power devices without sufficient gate driving voltage (increased power dissipation). If

the supply voltage VS and the internal charge-pump recovers to normal operating voltage the system returns to

the programmed state (lockout bit 14 = 0). If the lockout bit 14 is set, the automatic turn-on of the drivers is de-

activated. The microcontroller needs to clear the status bits to reactivate the drivers.

DESCRIPTION (continued)