908E621 datasheet(39/62 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

908E621

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

Half-Bridge Overvoltage/Undervoltage Protection

The half-bridge outputs are protected against

undervoltage and overvoltage conditions. This protection is

done by the low and high voltage interrupt circuitry. If one of

this flags (LVIF, HVIF) is set, the outputs are automatically

disabled if the VIS bit in the System Control Register

(SYSCTL) is cleared.

The overvoltage and undervoltage status flags are cleared

(and the outputs reenabled) by writing a “1” to the LVIF / HVIF

flags in the Interrupt Flag Register (IFR) or by a reset.

Clearing this flag has no effect as long as the high voltage or

low voltage condition is still present.

Half-Bridge Status and Control Register (HBSCTL)

CRM — Current Recirculation Mode bit

This read/write bit selects the recirculation mode during

PWM.

Reset clears the CRM bit.

1 = recirculation via switched on low-side MOSFET

0 = recirculation via low-side free wheeling diode

HBxOCF — Half Bridges Overcurrent Flag Bit

This read/write bit indicates that an overcurrent condition

on either the LS or the HS FET on HBx has occurred.

Clear HBxOCF and enable Half Bridge by writing a logic

[1] to HBxOCF. Writing a logic [0] to HBxOCF has no effect.

Reset clears the HBxOCF bit.

1 = overcurrent condition on HBx occurred

0 = no overcurrent condition on HBx

High-Side Drivers

The high-side outputs are low resistive high-side switches,

targeted for driving lamps. The high-sides are protected

against overtemperature, overcurrent and overvoltage/

undervoltage.

Figure 23. HS circuitry

HIGH-SIDE OPERATING MODES

The High-sides outputs are enabled if the PSON bit in the

System Control Register (SYSCTL) is set.

Each high-side output is permanently switched on, if the

HSxON bit in the High-Side Output Register (HSOUT) is set.

PWM control of the output is enabled, if the HSxPWM bit

High-Side Output Register (HSOUT) is set. In this operating

mode the high-side MOSFET is on, if the input PWM signal

(PWM terminal) is high.

The below table shows the behavior of the high-side

MOSFETs depending on the HSONx and PWMHSx bits.

Bit7

Bit0

Read

CRM

HB4

OCF

HB3

OCF

HB2

OCF

HB1

OCF

Write

Reset

VSUP

HSx

HS - Driver

charge pump

over-current protection

inrush current limiter

PWM

Control

on/off

Current

Limit

Status

PSON

HSxON

HSxPWM

PWM

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