L9952GXP datasheet(20/68 Pages) STMICROELECTRONICS

20 / 68 page

Description

L9952GXP

20/68

Doc ID 13518 Rev 5

2.12

V1, V2 fail

The V1, and V2 regulator output voltages are monitored.

In case of a drop below the V1, V2 – fail thresholds (V1,2 < 2V,typ for t > 2us), the V1,2 - fail

bits are latched. The fail bits are cleared by a dedicated SPI command.

If 4ms after turn on of the regulator the V1,2 voltage is below the V1,2 fail thresholds,

(independent for V1,2 ), the L9952GXP will identify a short circuit condition at the related

regulator output and the regulator will be switched off.

In case of a V1 failure the device enters VBAT - standby mode automatically.

In case of a V2 failure the SHT5V2 bit (SR0 Bit12) is set.

2.13

Low side driver outputs Rel1, Rel2

The outputs Rel1, Rel2 (RDSon = 2 Ω typ. @25 °C) are specially designed to drive relay

loads.

Typical relays used have the following characteristics:

Relay type 1:

–

closed armature: R = 160

Ω +10%, L= 300mH

–

open armature: R = 160

Ω +10%, L= 240mH

Relay type 2:

–

closed armature: R= 220

Ω +10%, L= 420mH

–

open armature: R= 220

Ω +10%, L= 330mH

The outputs provide an active output zener clamping (40V) feature for the demagnetisation

of the relay coil, even though a load dump condition exists. In case of watchdog failure the

relay drivers will be switched off and the low side driver control bits are cleared.

Note:

Due to relays bouncing, high dV/dt and/or dI/dt transients may occur on the low side driver

outputs. In case high currents are switched (for example window lift motor), due to parasitic

capacitive inductive coupling from load side of relays to the relays coils, the Absolute

Maximum Ratings of the Low Side driver outputs may be exceeded. In order to avoid this, it

is recommended to place a 10nF capacitor at the Rel1, Rel2 outputs to GND.

If a hard short circuit to VBAT is possible at the "Low Side Driver" outputs, an RC network is

required with TRC > 1µs, R ≥ 1 Ω (see block diagram, the value is given for an output short

circuit of given di/dt = 5A/µs).

2.14

PWM inputs

The inputs PWM 1,2 can be used to control the output drivers Out1..4 and OUT_HS with a

PWM signal. Each PWM input can be mapped individually to each of the above listed

outputs according to the SPI settings.

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