A4964 datasheet(22/92 Pages) ALLEGRO

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Sensorless Sinusoidal Drive BLDC Controller

A4964

Allegro MicroSystems, LLC

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

FUNCTIONAL DESCRIPTION

The A4964 is a three-phase, sensorless, brushless DC (BLDC)

motor controller for use with external N-channel power MOS-

FETs and is specifically designed for automotive applications.

The motor is driven using 3-phase sinusoidal current drive,

where phase commutation is determined by a proprietary, motor

back-emf (bemf) sensing technique. The motor bemf is sensed

to determine the rotor position without the need for indepen-

dent position sensors. An integrated sensorless startup scheme

includes forwards and reverse pre-rotation (windmill) detection

and syncronization and allows a wide range of motor and load

combinations.

Motor current is provided by six external power N-channel

MOSFETs arranged as a three phase bridge. The A4964 provides

six high current gate drives, three high-side and three low-side,

capable of driving a wide range of MOSFETs. The maximum

MOSFET drive voltage is internally limited under all supply

conditions to protect the MOSFET from excessive gate-source

voltage without the need for an external clamp circuit. The A4964

provides all the necessary circuits to ensure that the gate-source

voltage of both high-side and low-side external MOSFETs are

sufficiently high to achieve full correct conduction at low supply

levels. A low-power sleep state allows the A4964, the power

bridge, and the load to remain connected to a vehicle battery sup-

ply without the need for an additional supply switch.

Three motor control modes are available: closed-loop speed

control, open-loop speed (voltage) control, and current (torque)

control. The motor control mode and the control and configura-

tion parameters can be altered through an SPI-compatible serial

interface and the user-defined power-up parameters can be stored

in non-volatile memory. The A4964 can also operate in a stand-

alone mode, without the need for an external microcontroller,

where the duty cycle of a PWM signal applied to the LIN termi-

nal is used to control the output of the motor.

Startup (inrush) current, and peak motor current is limited by an

integrated fixed frequency PWM current limiter. The maximum

current limit is set by a single external sense resistor and the

active current limit can be modified through the serial interface.

An integrated data acquisition system provides measurement of

the motor voltage, the chip temperature, the motor speed, and an

estimate of the average supply current.

Integrated diagnostics provide indication of undervoltage,

overtemperature, and power bridge faults, and can be configured

to protect the power FETs under most short-circuit conditions.

Detailed diagnostics are available through the serial interface.

Specific functions are described more fully in following sections.

Input and Output Terminal Functions

VBB. Main power supply for internal regulators and charge

pump. The main power supply should be connected to VBB

through a reverse voltage protection circuit and should be

decoupled with ceramic capacitors connected close to the supply

and ground terminals.

VBRG. Sense input to the top of the external MOSFET bridge.

Allows accurate measurement of the voltage at the drain of the

high-side MOSFETs in the bridge.

CP1, CP2. Pump capacitor connections for charge pump. Con-

nect a 470 nF ceramic capacitor between CP1 and CP2.

VREG. Regulated voltage, nominally 11 V, used to supply the

low-side gate drivers and to charge the bootstrap capacitors. A

sufficiently large storage capacitor must be connected to this

terminal to provide the transient charging current.

VLR. VLR regulator output. External logic can be powered by

this node. The voltage can be selected as 3.3 or 5 V. A ceramic

capacitor of at least 1 µF with an ESR of no more than 250 mΩ

should be fitted between the VLR output and GND to ensure

stability.

GND. Analog reference, digital and power ground. Connect to

supply ground—see layout recommendations.

CA, CB, CC. High-side connections for the bootstrap capacitors

and positive supply for high-side gate drivers.

GHA, GHB, GHC. High-side gate-drive outputs for external

N-channel MOSFETs.

SA, SB, SC. Motor phase connections. These terminals sense

the voltages switched across the load. They are also connected to

the negative side of the bootstrap capacitors and are the negative

supply connections for the floating high-side drivers.

GLA, GLB, GLC. Low-side gate-drive outputs for external

N-channel MOSFETs.

CSP, CSM. Differential current sense amplifier inputs. Con-

nect directly to each end of the sense resistor using separate PCB

traces.

A4964 Datasheet(PDF) 22 Page - Allegro MicroSystems

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