L9945 datasheet(23/144 Pages) STMICROELECTRONICS

23 / 144 page

Symbol

Parameter

Test condition

Min.

Max.

Unit

ISDO_Leak

Tri state leakage current

NCS = HIGH;

VSDO = VIO – 0.3 V

-5

µA

NCS = HIGH;

VSDO = VIO

µA

VOV_SDO

Over voltage detection threshold at SDO

output (for reverse supply protection)

Prevent output from damage; avoid back supply to

VIO; no hysteresis required

VIO + 0.05 VIO + 0.2

tOV_SDO_fil

Overvoltage detection analog filter time

100

700

tOFF_PROT_OV

Overvoltage detection HS turn OFF/ON

time at SDO.

Includes analog filter time and comparator reaction

time until 50% IOVpeak_SDO_HS

0.5

μs

IOVpeak_SDO_HS

Maximum possible peak reverse current

at SDO HS before protection Turn Off

VSDO = 36 V; VIO = 3 V; limited by RDSON only;

HS channel On

250

Note:

The SDO pin electrical characteristics are also reported in the SPI table. SDO PCB trace must be routed

carefully in order avoid spikes on SDO pin, which may generate an overvoltage failure. A pull-down resistor in

the [10 - 47] kΩ range on SDO pin is also recommended.

5.3

Reset

The device is reset by the following two events:

Power On Reset (POR)

•

0 ≤ VDD5 ≤ VPOR:

–

Logic is reset;

–

Outputs are in three-state, diagnostics regulators for open load detection are OFF;

–

No violation of leakage current requirements;

–

Charge pump is disabled.

•

VPOR ≤ VDD5 ≤ 4.5 V:

–

SPI functional (if VIO is stable);

–

Internal oscillator is functional and the logic is working correctly;

–

The outputs can switch according to the control;

–

Regulators for open load detection may provide wrong diagnostic;

–

Overcurrent shutdown is active but thresholds may be inaccurate.

NRES assertion:

•

NRES input is active low;

•

It is typically connected to the VDD5 reset of the ECU power supply;

•

NRES is internally pulled up: in case of NRES pin left unconnected, NRES is inactive;

•

Open load failure detection is inactive during NRES assertion;

•

Charge pump is disabled while NRES is asserted.

Both POR and NRES events are latched and readable via SPI:

•

After POR, the n_POR_LATCH is set and can be cleared via SPI readout;

•

When NRES is active, NRES_LATCH is set and can be cleared via SPI readout.

The two reset events are ORed, so that full functionality is achieved only when both POR and NRES are

released.

The default configuration for the outputs after reset is Low-Side with NFET. Channels are three-stated until the

output is enabled through the en_OUT_xx bit.

After configuration and enable, all outputs follow the control signal as long as reset (NRES, POR) is not active. In

case of a reset all outputs will be immediately disabled and all diagnostic and protection information will be lost.

L9945

Functional description

DS12275 - Rev 10

page 23/144

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