33981 查看數據表（PDF） - Motorola => Freescale

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33981

High-Frequency, High-Current, Self-Protected High-Side Switch (4.0 mΩ up to 60 kHz)

Motorola => Freescale 

Freescale Semiconductor, Inc.

SYSTEM/APPLICATION INFORMATION

INTRODUCTION

The 33981 is a high-frequency self-protected silicon 4.0 mΩ

RDS(ON) high-side switch used to replace electromechanical

relays, fuses, and discrete devices in power management

applications. The 33981 can be controlled by pulse-width

modulation (PWM) with a frequency up to 60 kHz. It is designed

for harsh environments, and it includes self-recovery features.

The 33981 is suitable for loads with high inrush current, as

well as motors and all types of resistive and inductive loads. A

dedicated parallel input is available for an external low-side

control with protection features and cross-conduction

management.

FUNCTIONAL DESCRIPTION

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.

The 33981 will go to the normal operating mode when the EN

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

disabled typically 20 µs after the EN transitions to logic [1] to

enable the charge of the bootstrap capacitor.

Fault Logic

This 33981 indicates the faults below as they occur by

driving the FS terminal to logic [0]:

• Overtemperature

• Overcurrent fault on OUT

• Overload fault on the external low-side MOSFET

The FS terminal will return to logic [1] when the

overtemperature fault condition is removed. The two other

faults are latched.

Undervoltage

The latched faults are reset when the VPWR voltage is below

VPWR(UV).

Overtemperature Fault

The 33981 incorporates overtemperature detection and

shutdown circuitry on OUT. Overtemperature detection also

protects the bootstrap circuit (CBOOT terminal) and the low-side

gate driver (GLS terminal). Overtemperature detection occurs

when OUT is in the ON or OFF state and GLS is at high or low

level.

For OUT, an overtemperature 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, shows an overtemperature on OUT.

An overtemperature fault on the bootstrap circuit or 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 indefinitely until the offending load is removed. FS

terminal transition to logic [1] will be disabled typically 15 µs

after to enable the charge of the bootstrap capacitor.

Figure 13, page 17, shows an overtemperature on the

bootstrap circuit or on the low-side gate drive. As the

temperature increases, TEMP voltage decreases until thermal

shutdown.

Overtemperature faults force the TEMP terminal to 0 V.

Overcurrent Fault on High Side

The OUT terminal has a 100 A overcurrent high-detection

level for maximum device protection. If at any time the current

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

will go to 0 V. The OUT terminal is reset by a logic [0] at the

INHS terminal for at least 200 µs. When INHS goes to 0 V,

CSNS goes to 5.0 V.

In Figure 11, page 16, the OUT terminal is short-circuited to

0 V. When the current reaches IOCH, OUT is turned OFF within

10 µs 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 VGLS > VGSH

and VDLS > VDSH for at least 2.5 µs, the GLS terminal goes to

0 V and the OCLS internal current source is disconnected and

OCLS goes to 0 V. The GLS terminal and the OCLS terminal

are reset by a logic [0] at the INLS terminal for at least 200 µs.

When connected to an external resistor, the OCLS terminal

with its internal current source sets the VDSH level. By changing

the external resistance, the protection level can be adjusted

depending on low-side characteristics. A 3.3 kΩ resistor gives

a VDSH level of 3.3 V typical.

This protection circuitry measures the voltage between the

drain of the low side (DLS terminal) and the 33981 ground

(GND terminal). It also uses the voltage across the external

resistance connected to the OCLS terminal and the GND

terminal. For this reason it is key that the low-side source, the

33981 ground, and the external resistance ground connection

are connected together in order to prevent false error detection

due to ground shifts.

MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA

For More Information On This Product,

Go to: www.freescale.com

33981

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