PC33981PNASLASHR2 datasheet(20/24 Pages) MOTOROLA

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33981

MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA

Configuration

The CONF terminal manages the cross-conduction between

the internal MOSFET and the external low-side MOSFET. With

the CONF terminal at 0 V, the two MOSFETs can be

independently controlled. A load can be placed between the

high side and the low side.

With the CONF terminal at 5.0 V, the two MOSFETs cannot

be on at the same time. They are in half-bridge configuration as

shown in the simplified application diagram on page 1. If INHS

and INLS are at 5.0 V at the same time, INHS has priority and

OUT will be at VPWR. If INHS changes from 5.0 V to 0 V with

INLS at 5.0 V, GLS will go to high state as soon as the VGS of

the internal MOSFET is lower than TBD typically. A half-bridge

application could consist in sending PWM signal to the INHS

terminal and 5.0 V to the INLS terminal with the CONF terminal

at 5.0 V.

Figure 11, page 16, illustrates the simplified application

diagram on page 1 with a DC motor and external low side. The

CONF and INLS terminals are at 5.0 V. When INHS is at 5.0 V,

current is flowing in the motor. When INHS goes to 0 V, the load

current recirculates in the external low side.

Bootstrap Supply

Bootstrap supply provides current to recharge the bootstrap

capacitor through the VPWR terminal. A short time is required

after the application of power to the device to charge the

bootstrap capacitor. A typical value for this capacitor is 100 nF.

An internal charge pump allows continuous MOSFET drive.

When the device is in the sleep mode, this bootstrap supply is

off to minimize current consumption.

High-Side Gate Driver

The high-side gate driver switches the bootstrap capacitor

voltage to the gate of the MOSFET. The driver circuit has a low-

impedance drive to ensure that the MOSFET remains OFF in

the presence of fast falling dV/dt transients on the OUT

terminal.

This bootstrap capacitor connected between the power

supply and the CBOOT terminal provides the high pulse current

to drive the device. The voltage across this capacitor is limited

to about 13 V. CBOOT is protected against short by a local

overtemperature sensor.

An external capacitor connected between terminals SR and

GND is used to control the slew rate at the OUT terminal.

Low-Side Gate Driver

The low-side control circuitry is PWM capable. It can drive a

standard MOSFET with an RDS(ON) as low as 4.0 mΩ at a

frequency up to 60 kHz. The VGS is internally clamped at 14 V

typically to protect the gate of the MOSFET. The GLS terminal

is protected against short by a local overtemperature sensor.

Thermal Feedback

The 33981 has an analog feedback output (TEMP terminal)

that provides a value proportional to the temperature of the

GND flag (terminal 13). The controlling microcontroller can

“read” the temperature proportional voltage with its analog-to-

digital converter (ADC). This can be used to provide real-time

monitoring of the PC board temperature to optimize the motor

speed and to protect the whole electronic system. TEMP

terminal value is typically 4.2 V at 25°C with a negative

temperature coefficient of 10 mV/K.

Reverse Battery

The 33981 survives the application of reverse battery voltage

as low as -16 V. Under these conditions, the output’s gate is

enhanced to decrease device power dissipation. No additional

passive components are required. The 33981 survives these

conditions until the maximum junction rating is reached.

In the case of reverse battery in a half-bridge application, a

direct current passes through the external freewheeling diode

and the internal high-side.

As Figure 17 shows, it is essential to protect this power line.

The proposed solution is an external low-side with its gate tied

to battery voltage through a resistor. A high-side in the VPWR

line could be another solution but with a more complex drive.

Figure 17. Reverse Battery Protection

VPWR

VDD

VPWR

MCU

33981

No current

GND

OUT

Diode

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

PC33981PNA/R2 Datasheet(PDF) 20 Page - Motorola, Inc

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