Part # Application Note Motor Control L6204 AN379 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: Using the L6204 a Bipolar stepper and DC motors driver in BCD technology

Part Details:

AN379 APPLICATION NOTE USING THE L6204, A BIPOLAR STEPPER AND DC MOTOR DRIVER IN BCD TECHNOLOGY by E. Balboni Containing two H-bridge drivers, the L6204 is a compact and simple solution for driving two-phase bi-polar stepper motors and in applications where two DC motors must be driven. The L6204 is a DMOS dual full bridge driver mainly designed to drive bipolar stepper motors. All the inputs are TTL/CMOS compatible and each bridge can be enabled by its own dedicated input. The wind-ings current can be regulated by sensing the voltage drop across two low value resistors at the low end of boththe bridge: this is the feedback for the current controller. To feed the gates of the upper DMOS, a peak to peak rectifier charges a capacitor in series with the Power Sup-ply voltage at the optimum DC level defined by an on-board square wave oscillator. The L6204 , with 0.5 A drivecapability without external heatsink up to 70°C, is packaged in a 20 leads PowerDip with four heat transfer pins.The Block diagram of the device is shown in fig.1. Figure 1. Block diagram of the L6204 single chip dual full bridge driver.. GENERAL APPLICATIONS HINTS The L6204 can be used in a very wide range of applications such as the drive of lamps, solenoids, DC motorsor any other inductive loads. The drive of different loads in single-ended configuration is shown in fig.2. The current in the Load Z1, that maybe a DC motor, can flow in both the directions but its peak amplitude cannot be controlled. By means of a change December 2003 1/7 AN379 APPLICATION NOTE of the Duty Cycle of the input signal it is possible to vary in Open Loop Mode the steady state speed of the DCmotor: this is possible because the average current in the winding is dependent from the Duty Cycle. The L/R ratio must be a few times shorter than the minimum DC. In a similar way it can be dimmed a lamp con-nected to the supply (Z2) or to ground (Z3). Very often, when a DC motor is driven, peak current and speed mustbe booth controlled in a Closed Loop Mode. Figure 2. The L6204 is not intended only for Bipolar Stepper applications: here above three different driver configurations are shown. Z1 is a DC motor to be driven in both CW and CCW direction. Z2 can be solenoid like a relay or hammer. Z3 can be an alogen lamp which light intensity is controlled by variable Duty Cycle. This is achieved by the configuration shown in fig.3. The two independent motors can be controlled by only onecontroller (L6506). The sensing resistor (RsA, RsB) generates a voltage proportional to the motor current, that is the feedback forthe current control loop. A second loop, not shown in figure, can control the speed stability while the direction isdefined by the Input state of the L6506. The Enable Input (ENA, ENB) can inhibit one motor or the other whilethe Power Enable acts on both at the same time. D1 and D2 (BAT41 or equivalent), C3 and C4, generates thebootstrap voltage by rectifiing the wave available at pin. 11 of the L6204. When more than one driver is used atthe same Supply Voltage on a common Printed Circuit Board, the bootstrap voltage can be generated only byone of them (master) and used to supply all the other L6204 (slaves) saving diodes and capacitors. R1 C1 (R2 C2) is a snubber network that must be closely connected to the output pins and its use is recom-mended in all the application circuits using the L6204. The values can be calculated as it follows: R = Vs/Ip andC = Ip/(dV/dt), where Vs is the maximum Supply Voltage of the Application, Ip is the peak of the load currentand dV/dt is the Slew Rate accepted as the optimum compromise between speed and transient generation/ra-diation (SR of 200 V/µS are commonly chosen). The network R5C5 sets the operating frequency according tof = 1/(0.69 R5C5) for R5 10Kohm. R3 and R4 are used to protect the comparator input inside the L6506 against 2/7 AN379 APPLICATION NOTE possible negative transitions across the sensing resistor RsA or RsB. The L6204 can be used with paralleledinputs and outputs to double the current capability of the single bridge; for an optimized solution, however, 1.6times the nominal current is recommended instead of two. This configuration is shown in fig.2 to drive the loadZ1. A more complex circuit, in wich one paralleled L6204 drives a DC motor, is shown in fig.4; in this examplethe two chopper of the L6506 are used to implement two functions: 1) Current Control during speed variation atIp max = 0.8A and 2) Current Control during brake and/or direction change at higher current level that dependsfrom the brake repetition (it must be in the Max Ratings limit). The divider R6R7 defines the brake current intensity as V17/Rs while the product (Ip max.) x ( Rs) is the limit ofthe reference voltage V16 for speed control. The Enable function is driven via the L6506 . Since during the braketime the Enable of the L6506 is chopped, the motor current ricirculates via the Supply; because of this a suitablelarge capacitor must be connected in parallel to C2. Figure 3. Bidirectional DC motor drive. The L6204 can drive two motors. 3/7

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