MM912F634CV2AP datasheet(86/335 Pages) FREESCALE

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Functional Description and Application Information

Low Side Drivers - LSx

MM912F634

Freescale Semiconductor

4.12.4

Functional Description

The Low Side switches are controlled by the bits LS1:2 in the Low Side Control Register (LSCR). In order to control the Low

Sides, the LSCEN register has to be correctly written once after RESET or VROV.

To protect the device against over-voltage when an inductive load (relay) is turned off an active clamp circuit is implemented.

4.12.4.1

Voltage Regulator Over-voltage Protection

NOTE

The over-voltage threshold has to be trimmed at system power up. Please refer to

Section 4.25.1.2.3, “Trimming Register 2 (CTR2)" for details. The default trim is worst case

and may have disabled the LS function already. An initial LS enable would be needed.

To protect the application for an unintentional activation of the drivers in case of a voltage regulator over-voltage failure, the Low

Side Drivers will automatically shut down in case of an over-voltage on one of the two regulators.

The shutdown is fully handled in the analog section of the driver. This will secure the feature in case the digital logic is damaged

due to the over-voltage condition.

Once an over-voltage condition on one of the voltage regulators occurs, the LSx control bits in the Low Side Control Register

(LSCR) will be reset to 0. The Voltage Regulator Over-voltage Condition Bit (VROVC) in the Voltage Status Register (VSR) will

stay set as long as the condition is present. If the Voltage Regulator Over-voltage Interrupt was enabled (VROVIE=1), the VROV-

Interrupt will be issued. Reading the Voltage Regulator Over-voltage Condition Bit (VROVC) in the Voltage Status Register (VSR)

will clear the interrupt. To issue another VROV - Interrupt, the condition has to vanish and be present again.

To re-enable the Low Side Drivers after a Voltage Regulator Over-voltage condition occurred, first the LSCEN register has to be

written with “0x05” - this information is processed through the main digital blocks, and would secure a minimum functionality

before enabling the LS drivers again. In a second step, the LSx Control Bits in the Low Side Control Register (LSCR) must be

enabled again after the over-voltage condition has vanished (VROVC=0).

4.12.4.2

Open Load Detection

Each Low Side driver signals an open load condition if the current through the Low Side is below the open load current threshold.

The open load condition is indicated with the bit LS1OP and LS2OP in the Low Side Status Register (LSSR).

4.12.4.3

Current Limitation

Each Low Side driver has a current limitation. In combination with the over-temperature shutdown, the Low Side drivers are

protected against over-current and short-circuit failures.

The driver operates in current limitation, and is indicated with the bits LS1CL and LS2CL in the Low Side Status Register (LSSR).

Note: If the drivers is operating in current limitation mode excessive power might be dissipated.

4.12.4.4

Over-temperature Protection (LS Interrupt)

Both Low Side drivers are protected against over-temperature. In case of an over-temperature condition, both Low Side drivers

are shut down and the event is latched in the Interrupt Control Module. The shutdown is indicated as LS Interrupt in the Interrupt

Source Register (ISR).

If the bit LSM is set in the Interrupt Mask Register (IMR) than an Interrupt (IRQ) is generated.

A write to the Low Side Control Register (LSCR) will re-enable the Low Side drivers when the over-temperature condition is gone.

4.12.5

PWM Capability

See Section 4.13, “PWM Control Module (PWM8B2C)".

MM912F634CV2AP Datasheet(PDF) 86 Page - Freescale Semiconductor, Inc

MM912F634CV2AP Datasheet(HTML) 86 Page - Freescale Semiconductor, Inc

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