33981B datasheet(13/37 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33981

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

The 33981 has 2 operating modes: Sleep and Normal

depending on EN input.

SLEEP MODE

Sleep mode is the state of the 33981 when the EN is

logic [0]. In this mode, OUT, the gate driver for the external

MOSFET, and all unused internal circuitry are off to minimize

current draw.

NORMAL MODE

The 33981 will go to the normal operating mode when the

EN pin is logic [1]. The INHS and INLS commands will be

disabled tON after the EN transitions to logic [1] to enable the

charge of the bootstrap capacitor.

PROTECTION AND DIAGNOSTIC FEATURES

UNDERVOLTAGE

The 33981 incorporates undervoltage protection. In case

of VPWR<VPWR(UV), the OUT is switched OFF until the power

supply rises to VPWR(UV)+VPWR(UVHYS). The latched fault are

reset below VPWR(UV).

OVERTEMPERATURE FAULT

The 33981 incorporates over temperature detection and

shutdown circuitry on OUT. Overtemperature detection also

protects the low-side gate driver (GLS pin). Overtemperature

detection occurs when OUT is in the ON or OFF state and

GLS is at high or low level.

For OUT, an over temperature fault condition results in

OUT turning OFF until the temperature falls below TSD. This

cycle will continue indefinitely until the offending load is

removed. Figure 12, page 16 and Figure 18, page 20 show an

over temperature on OUT.

An over temperature fault on the low-side gate drive

results in OUT turning OFF and the GLS going to 0 V until the

temperature falls below TSD. This cycle will continue until the

offending load is removed. FS pin transition to logic [1] will be

disabled typically tON after to enable the charge of the

bootstrap capacitor.

Overtemperature faults force the TEMP pin to 0 V.

OVERCURRENT FAULT ON HIGH SIDE

The OUT pin has an overcurrent high-detection level

called IOCH for maximum device protection. If at any time the

current reaches this level, OUT will stay OFF and the CSNS

pin will go to 0 V. The OUT pin is reset (and the fault is

delatched) by a logic [0] at the INHS pin for at least tRST(diag).

When INHS goes to 0 V, CSNS goes to 5.0 V.

In Figure 16, page 19, the OUT pin is short-circuited to 0 V.

When the current reaches IOCH, OUT is turned OFF within

tOCH owing to internal logic circuit.

OVERLOAD FAULT ON LOW SIDE

This fault detection is active when INLS is logic [1]. Low-

side overload protection does not measure the current

directly but rather its effects on the low-side MOSFET. When

Table 5. Operating Modes

Condition

CONF

INHS

INLS

OUT

GLS

Comments

Sleep

Device is in Sleep mode. The OUT and low-side gate are OFF.

Normal

Normal mode. High side and low side are controlled

independently. The high side and the low side are both on.

Normal

Normal mode. High side and low side are controlled

independently. The high side and the low side are both off.

Normal

Normal mode. Half-bridge configuration. The high side is off

and the low side is on.

Normal

Normal mode. Half-bridge configuration. The high side is on

and the low side is off.

Normal

PWM

PWM_bar

Normal mode. Cross-conduction management is activated.

Half-bridge configuration.

H = High level

L = Low level

x = Don’t care

PWM_bar = Opposite of pulse-width modulation signal.

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