L9953LXP datasheet(20/35 Pages) STMICROELECTRONICS

20 / 35 page

Application information

L9953LXP

20/35

Doc ID 16185 Rev 3

Application information

3.1

Dual power supply: VS and VCC

The power supply voltage VS supplies the half bridges and the highside drivers. An internal

charge-pump is used to drive the highside switches. The logic supply voltage VCC

(stabilized 5 V) is used for the logic part and the SPI of the device.

Due to the independent logic supply voltage the control and status information will not be

lost, if there are temporary spikes or glitches on the power supply voltage. In case of power-

on (VCC increases from under voltage to VPOR Off = 4.2 V) the circuit is initialized by an

internally generated power-on-reset (POR). If the voltage VCC decreases under the

minimum threshold (VPOR ON = 3.4 V), the outputs are switched to 3-state (high impedance)

and the status registers are cleared.

3.2

Standby mode

The standby mode of the L9953LXP is activated by clearing the bit 23 of the input data

impedance. In the standby mode the current at VS (VCC) is less than 6 µA (50µA) for

CSN = high (DO in 3-state). By switching the VCC voltage a very low quiescent current can

be achieved. If bit 23 is set, the device will be switched to active mode.

3.3

Inductive loads

Each half bridge is built by an 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

drivers OUT6 to OUT8 are intended to drive resistive loads. Hence only a limited energy

(E<1mJ) can be dissipated by the internal ESD diodes in freewheeling condition. For

inductive loads (L>100µH) an external free-wheeling diode connected to GND and the

corresponding output is needed.

3.4

Diagnostic functions

All diagnostic functions (over/open-load, power supply over-/under voltage, temperature

warning and thermal shutdown) are internally filtered and the condition has to be valid for at

least 32 µs (open-load: 1ms, 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. Open-

load and temperature warning function are intended for information purpose and will not

change the state of the output drivers. On contrary, the overload condition will disable the

corresponding driver (over-current) and overtemperature will switch off all drivers (thermal

shutdown). Without setting the over-current recovery bits in the input data register, the

microcontroller has to clear the over-current status bits to reactivate the corresponding

drivers.

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