L99DZ80EP datasheet(32/68 Pages) STMICROELECTRONICS

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Application information

L99DZ80EP

32/68

DocID18260 Rev 6

Application information

3.1

Dual power supply: VS and VCC

The power supply voltage VS supplies the power drivers and the Power-MOS gate drivers.

For supplying the high-side drivers for the power- and gate-driver outputs, an internal

charge-pump is used. The SPI interface and the logic circuitry is supplied by VCC.

Due to the independent VCC supply the control and status information are not lost, if there

are spikes or glitches on the power supply voltage.

3.2

Wake up and Active mode/standby mode

After power up of VS and VCC the device operates in standby-mode. Pulling the signal CSN

to low level wakes the device up and the analog part is activated (active mode). After at

least 10 µs, the first SPI communication is valid and the EN-bit can be used to set the EN-

mode.

The device can be set into active mode writing a ‘1’ into the EN-register. If the EN-register is

not set to ‘1’, the device goes back to standby mode typical 256 µs after the rising edge of

CSN and all latched data are cleared. In standby mode the current at VS (VCC) is less than

6 µA (5 µA) for CSN = high (DO in 3-state). It is recommended to switch all outputs off

before entering standby mode.

3.3

Charge pump

The charge pump uses two external capacitors, which are switched with a frequency of

typically 125 kHz. The output of the charge pump has a current limitation. In standby mode

and after a thermal shutdown has been triggered the charge pump is disabled. If the charge

pump output voltage remains too low for longer than TCP, the power-MOS outputs, the EC-

control are switched off and the H-Bridge gate drivers are switched to resistive low. The

CP_LOW bit has to be cleared through a software reset to reactivate the drivers.

3.4

Diagnostic functions

All diagnostic functions (overcurrent, open-load, power supply overvoltage /undervoltage,

temperature warning and thermal shutdown) are internally filtered. The condition has to be

valid for at least the associated filter time before the corresponding status bit in the status

registers is set. The filters are used to improve the noise immunity of the device. The open-

load and temperature warning functions are intended for information purpose and do not

change the state of the output drivers. On contrary, the overcurrent condition disables the

corresponding driver and thermal shutdown disables all drivers. Without setting the

overcurrent recovery bits in the input data register, the microcontroller has to clear the

overcurrent status bits to reactivate the corresponding drivers.

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