Features

Able to drive two winding of the bipolar step motor

motor or two DC motors

The output current of each winding is as high as 1.2A [123 ]

Wide voltage range: 12V to 40V

Four Elephant Limited current control, suitable for

Micro -step and DC motor control

Precision PWM control

[

[ 123] No need to circulate the diode

TTL/CMOS compatible input

cross -conducting protection

Hot shutdown

Instruction ] L6258E

is a capability to drive bipolar winding in BCD technology to drive bipolar winding in BCD technology. Two DC motors are controlled by two -way control. L6258E and some external components form a complete control and drive circuit. It has a high high -efficiency phase shift and cutting waves at the lowest current control of the low -current ripple, making the device the ideal choice and DC motor for the steprons. The power level is a dual -DMOS full bridge that can maintain a voltage of up to 40V, including the capacity of each winding in the continuous mode of the current diode re -cycle output current is 1.2A, the peak startup current is as high as 1.5A.A thermal protection circuit disabled output. Limit

Electric characteristics (vs 40V; vdd 5V; tj 25 °; unless there are other regulations.)

] Electric characteristics (continued)

(vs 40V; vdd 5V; tj 25 °; unless there are other regulations.)

1. Chopping The wave frequency is twice the FOSC value.

2. Except for disable input, all logic inputs are like this.

Functional description

This circuit is used to drive two windows of dual -pole step motor or two DC motors. The current control is adjusted by the switch mode. In this system, the direction and amplitude of the load current depends on the phase and duty cycle between the two outputs of the current control loop. The L6258E power grade is composed of the power DMO configured by the bridge as shown in Figure 4. Among them, the bridge output OUT_A and OUT_B are driven to the ground end through the high level input terminal and the high level of the input end, and the same input. The zero current conditions are obtained by using the signal of μA and medium to drive the two semi -bridge in the same phase, and the occupation ratio is 50%. In this case, the output of the two semi -bridge continuously switches the power supply (VS) and ground between the power supply, but the pressure difference between the load is equal to zero. Figure 4 shows the timing diagram and load current working conditions of these two outputs.

Next, we consider positive currentThe direction of the inflow load is from the exit of A when we think that the current of the flow load is negative from the outside to the outside. At present, we only need to increase the duty cycle of the IN 号 A signal, and reduce the duty cycle signal of IN 峎 B. We input the positive current input load. In this way, the two outputs are different. The current can be carried out by the diagonal lines composed of T1 and T4. When the output is driven to VS and the output terminal, the current is circulated to the two outputs. At that time, the two outputs of T1 and T2 are connected to the ground. Due to the low voltage on the recycling load, the current discharge time constant generated from the current charging time constant is greater than the oblique bridge formed by the current charging time. In this way, the load current is positive, and the average amplitude depends on the duty cycle of the two driving signals. Figure 4 shows that the timing chart in the case of positive load current is opposite. If we want to drive the negative current to enter the load, we must reduce the duty cycle of the input A signal and increase the duty cycle of the input B signal. In this way, we get the phase shift between the two output so that the current flows in when the output is driven to the ground, the diagonal bridge output formed by T2 and T3 is driven to VS, and we will have the same current current In the case of the previous cycle conditions, the two outputs are driven to VS or ground. Therefore, in this case, the load current is always negative, and the average amplitude always depends on the duty cycle ratio of the two driving signals. Figure 4 shows the timing diagram of negative load current. Figure 5 shows the device frame diagram of the entire current control loop.

Reference voltage

The voltage applied to the VREF pin is the reference voltage of the internal DAC, and the sensor resistance value. According to the following relationship:

, RS sensing resistance value

Input logic (I0-I1-I2-I3)

According to the following table Select the current in the motor winding group:

The current control loop

The current control circuit is a cross -guided amplifier working in PWM mode. Motor current is a programmatic DAC voltage function. In order to control the output current, the current control adjusts the two output OUT U A and OUT U B. A sensing resistor RS RS and the motor winding can be generated in order to generate a voltage of a voltage feedback and programming value. The duty -ratio of the two output is the output of the large -device through comparative errors, with two triangular wave benchmarks. In order to use the previously explained duty -ratio modulation driver output bridge driver's signal of each output (OUTA and OUTB) is a triangle wave signal generated by using these two methods as a reference, Tri_0 and Tri_180 have the same amplitude. The same average (VR), but each phase shift is 180 °. Two triangular wave references are applied to the first triangle wave input comparator and firstThe non -inverse input end of the comparator. The other two inputs of the comparator are connected to the output of the error amplifier output terminal by the difference between the difference between the DAC of the programming. The reset Figure 6 shows the comparison between the above signals.

In the case of VDAC equal to zero, the cross -guidance circuit is balanced at the VR value, so the output of the two comparators is the signal with the same phase and 50%duty ratio. cycle. As we have mentioned, in this case, the two outputs of OUT_A and OUT_B are driven from VS to grounding at the same time; and the differential voltage shell of the load is zero, and there is no current flow in the motor winding.

There is a positive differential voltage on VDAC (see Figure 5), and the cross -guided circuit will be unbalanced and respecting the virtual reality. In this case, the output voltage of the error amplifier is greater than the VR, and the first output comparator is a square wave with a square wave with a duty cycle of more than 50%is a square wave with a duty cycle of less than 50%. The duty cycle obtained at the output end of the two comparators is the same, but for 50%of the level, one is positive and the other is negative. In this case, the two driving signals generated by driving the two output switching currents from the OUT U A flow through the motor winding from the OUT U A, and then flow to OUT 帴 B. For negative differences and voltage VDACs, the cross -guidance circuit will be the virtual reality of negative imbalance. In this case, the output of the first comparator is that the duty cycle is less than 50%, and the output of the second comparator is more than 50%of the square waves with higher duty cycle. The duty cycle obtained at the output of the two comparators is always the same. In this case, the two drive signals generated by the two outputs were driven to output the current from the U winding to the motor.

The current control loop compensation

In order to have a flexible system that can drive motors with different electrical characteristics, the non -inverse input and output of the error placing the large device. Connecting an external RC compensation network on these pins, you can adjust the gain and bandwidth of the current control loop

Open ring transmission function analysis

Fragics: see Figure 5.

Input parameters:

vs 24 volts

ll 12 hours

rl 12Ωrs 0.33Ωrc to be calculated

CC to be calculated

GS cross -guide gain 1/rb

GIN cross -guided gain 1/ra

amplitude. TRIA_0_180 Reference value 1.6V (Peak-Peak)

Ra 40kΩrb 20kΩvr Internal reference value is equal to VDD/2 (typical value. 2.5 伏)

These data refer to a typical typical data. The application will be used as a stability of the current control circuit during the analysis process. The box diagram shows L6258The schematic diagram of the internal current control loop in E input voltage is PWM working mode VDAC. The relationship between the two variables is given by the following formula:

VDAC is the definition of the load current value Control voltage

GIN is the gain of the input cross -guided amplifier (1/RA)

GS is the gain of the sensor transgender amplifier (1/RB)

RS is connected to the output end to detect the resistance current of the load current. In this configuration, the input voltage and the induction resistance from the sensing resistance, and then the error amplifier between the two signals is amplifier to obtain the error signal control of the control output stage duty cycle. Load current. Obviously, there must be a good current control loop, and the error amplifier must have high DC gains and large bandwidth.

gain and bandwidth must be selected according to the many parameters of the application, such as the characteristics of load and power supply. The most important thing is that the stability must always be guaranteed. There is a very flexible system, and it is possible to adapt to the system in any application. The error amplifier must use the connected RC network for compensation output and negative input. In order to evaluate the stability of the system, we must consider the current control loop: ALOOP Acer · ACPW · A load · ACSENSE is the attenuation of the mass of the load block with the block of the block added with the block of errors, power and sensor amplifiers. The same formula represented by DB can be written like this: ALOOPDB Acerdb+ACPWDB+A load database+AcsenseDB now we can start analyzing the dynamic characteristics of each separate block. Special attention to the error placed.

Power amplifier

The power amplifier is not a linear amplifier, but the full bridge configuration phase of the circuit full bridge in the PWM mode. The output occupation ratio changes obtain the amplifier and two triangular wave reference TRI-0 and TRI-U180 through a comparative error voltage. Because all current control circuits are reference VR reference, the result is that when the output voltage error placing the large velocity is equal to the VR voltage, the two output output terminal A and the output end B have the same voltage phase and the duty cycle; the output of the error amplifier output will Increased voltage to VR voltage, the occupation ratio of the OUT U A increased, and the OUT U B's duty cycle decreased the same percentage; on the contrary, the voltage of the error amplifier was reduced to the VR voltage, and the occupation ratio of the OUT 廑 U A decreased. OUT OUT降 The increase of the same percentage of the duty ratio of 降 B.

The gain of this block is defined by the amplitude of the two triangular wave references; more precisely, the gain of the power amplifier block is the amplitude of the two reference signals. In fact, changes in the output voltage of the error amplifier will generate a larger duty cycle. When the amplitude of the two triangles is low, the cycle of the two output output is reference. When the input voltage is equal to the amplitude, the maximum value of the duty ratio is 100%in the two triangle reference system. The transmission function of this module includes the output duty cycleThe amplitude of the triangle reference.

In addition, Tri_0 and TRI_180 as a triangle, it is clear Gain.

Load attenuation

The load block is added with an equivalent circuit (resistance and inductance) plus induction resistance by the motor winding. We will consider the influence of the BEMF voltage of the motor in the next chapter. The input of this module is the PWM voltage of the power amplifier. As an output, we have the voltage on the induction resistance generated by the current flow into the motor winding. The relationship between these two variables is:

The equivalent resistance of the RL motor winding

RS sensor resistor

] Due to the inductance of the motor LL, the load has a pole, the frequency is:

Before analyzing the error placing module and sensing cross -guided module, we must consider: [123 123 ]

ALOOPDB AXDB+BXDB

AX | DB ACPW | DB+A load | db

and bx | db accept ] This means that AX | DB is the sum of the power amplifier and load block; the maximum decibel (29,5)+(-31.4) -1.9 decibel AX transmission function of the AX transmission function is:

The BODE diagram of the AX | DB function shows the DC gain of -1.9db and the pole of 163Hz. Now it is obvious (due to the negative gain of the AX function), the BX function must have a high DC gain to increase the total open ring gain and increase the bandwidth.

Error amplifier and sensor amplifier

As mentioned earlier, the gain of these two blocks is: BXDB Acerrdb+AcsenseDb as the sensor resistance between the BX block and the error amplifier input terminal The voltage voltage output is the same, and the voltage gain is obtained from the following formulas:

The typical application circuit is shown in Figure 11.

Note: In order to avoid the disabled ""DC feedback"" in order to avoid the decline of the current peak, a ""DC feedback"" will be added to an error amplifier. Figure 11 (R1-11).

Interference

Since the circuit uses switch mode current adjustment, a good capacitor (100NF) can be reduced to the influence of the wiring inductance. Packaging between (needle feet) 1,36,18,19) Absorb a small amount of induction energyquantity. It should be noted that in addition to the electrolyte, this kind of capacitor usually requires poor capacitors under high frequency. Usually it is located in the component. 19) During the rapid current attenuation or the phase period, the current re -circulating path changes. The range value of the capacitor is between several μF and 100 μF. It must be selected depends on application parameters such as motor inductance and load current amplitude. Between logical power and grounding, it is also recommended to use 100NF decoupling capacitors. EA_IN1 and EA_IN2 pins execute high impedance lines. We must pay attention to avoid coupling noise on the signal. It is recommended to connect the component to this pin near L6258E, surround them with ground track, and keep the device quickly switch output as much as possible. Remember to avoid the peak output current during the start/closing of the power supply. No sensing resistance is the best way to achieve sensing. Regardless of whether this is possible, some metal membrane resistors of the same value can be connected in parallel. Two input terminals (induction A and induction B) for sensing winding motor current should be directly connected to the sensor RS terminals, and the RS and two inductive inputs should be as short as possible.

Note: Connect the disable pins to the voltage source of low impedance (u0026 lt; 300Ω) to reduce the minimum interference and disable the output current of the OUT1A (pin 5) capacitor coupling (pin 6) 123]

Electric selection

Some steps of the iron heart loss of some step motors are very high, which is not suitable for the current regulations of the switch mode. In addition, the design of some step motors is not running continuously at the maximum current. Because the circuit can drive the constant current through the motor, the temperature may exceed during low and high -speed operation.

Unused input

Unused inputs should be connected to the appropriate voltage level to obtain the highest degree of resistance

PCB design precautions

We recommend abide by the following layout rules to avoid grounding and abnormal recycling current. The bypass capacitors of power and logic power supply must be as close to IC as much as possible. Separate logic and power grounding on the PCB board, and the grounding of the internal charge pump circuit to avoid the traces of the ground power signal of the logic signal through the ground power signal. Because the integrated circuit uses the circuit board as a heat sink, the area of u200bu200bthe heat dissipation copper tablets must be on the requirements of the AMB of Hong Kong Radio AMB.