L9969S datasheet(37/70 Pages) STMICROELECTRONICS

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3.2.6.8

Undervoltage shutdown

In case of undervoltage on VS, L9969 reacts by shutting down. The diagnosis of VS undervoltage is also available

on SPI registers; in fact undervoltage on VS does not reset the SPI interface. The involved parameters in

undervoltage shutdown are reported in Table 22.

5 V < VBATT < 18 V, 4.5 V < VDD < 5.5 V, TJ= -40 °C to 150 °C, unless otherwise specified.

Table 22. Undervoltage shutdown parameters

Symbol

Parameter

Condition

Min

Typ

Max

Unit

VUF_OFF

Undervoltage at VS, switch off threshold

3.1

3.8

4.5

VUF_ON

Undervoltage at VS, switch on threshold

3.3

4.0

4.7

VUF_HYS

Undervoltage at VS, hysteresis

100

1000

tUF

Filter time detection undervoltage VS

1,5

µs

3.2.6.9

Open Load diagnosis in active mode

Open Load diagnosis is possible when outputs are switched off by DIS or NABE but also during active operation,

in case the feature is enabled via CONFIG_REG.OLDA = 1. However, default value for the open load diagnosis

during active operation is: disabled (CONFIG_REG.OLDA = 0).

Figure 24 shows how this could be achieved.

Figure 24. Open Load diagnosis in active mode

In active mode, by default the Open Load diagnostic is deactivated. If one has sent the command

CONFIG_REG.OLDA mode = 1, the Open Load diagnostic in active mode (OLDA) is activated. In Figure 24,

at the beginning, the OLDA is deactivated. The load is assumed to have an inductive component. The current

in the load is toggled by the signal PWM. If the PWM signal is low, one has the free-wheeling of the inductive

component of the load via the low-side transistors. At the beginning of the free-wheeling phase, the inductivity

must free-wheel. Therefore it is generating a negative voltage on the OUTx. This voltage is detected internally the

HBR. As long as there is a negative voltage at the beginning of the free-wheeling phase, no open load fault has

occurred. If there is no negative voltage at the beginning of the free-wheeling phase, there is an open load (or a

simple resistor connected as load, where this principle does not work).

L9969x

Functional behavior in detail

DS14029 - Rev 3

page 37/70

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