33911 datasheet(29/45 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33911

FUNCTIONAL DEVICE OPERATIONS

OPERATIONAL MODES

LOW SIDE OUTPUT PINS LS1 AND LS2

These outputs are two low side drivers intended to drive

relays incorporating the following features:

• PWM capability (software maskable)

• Open load detection

• Current limitation

• Over-temperature shutdown (with maskable interrupt)

• Active clamp (for driving relays)

• High-voltage shutdown (software maskable)

The low side switches are controlled by the bit LS1:2 in the

Low Side Control Register (LSCR).

To protect the device against over-voltage when an

inductive load (relay) is turned off, an active clamp will re-

enable the low side FET if the voltage on the LS1 or LS2 pin

exceeds a certain level.

PWM Capability (direct access)

Each low side driver offers additional (to the SPI control)

direct control via the PWMIN pin.

If both the LS1 and PWMLS1 bits are set in the LSCR, then

the LS1 driver is turned on if the PWMIN pin is high, and

turned off if the PWMIN pin is low. The same applies to the

LS2 and PWMLS2 bits for the LS2 driver.

Figure 18. Low Side Drivers LS1 and LS2

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).

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.

When the drivers operate in current limitation, this is

indicated with the LS1CL and LS2CL bits in the LSSR.

Note: If the drivers are operating in current limitation mode

excessive power might be dissipated.

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 an LS

Interrupt in the Interrupt Source Register (ISR).

If the bit LSM is set in the Interrupt Mask Register (IMR),

then an Interrupt (IRQ) is generated.

A write to the Low Side Control Register (LSCR), when the

over-temperature condition is gone, will re-enable the low

side drivers.

High-voltage Shutdown

In case of a high voltage condition, and if the high-voltage

shutdown is enabed (bit HVSE in the Mode Control Register

(MCR) is set), both low side drivers are shut down.

A write to the LSCR, when the high-voltage condition is

gone, will re-enable the low side drivers.

Sleep And Stop Mode

The low side drivers are disabled in Sleep and Stop Mode.

Also see Table 5, Operating Modes Overview.

LSx

Low Side - Driver

(active clamp)

Open-load Detection

Current Limitation

Over-temperture Shutdown (interrupt maskable)

High-voltage Shutdown (maskable)

PGND

active

clamp

Interrupt

Control

Module

HVSE

Control

on/off

Status

LSx

LSxOP

LSxCL

MOD1:2

PWMIN

VDD

PWMLSx

VDD

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