Electronic Components Datasheet Search |
|
PBL37761 Datasheet(PDF) 7 Page - Ericsson |
|
PBL37761 Datasheet(HTML) 7 Page - Ericsson |
7 / 8 page PBL 3776/1 7 Figure 9. Typical upper transistor satura- tion voltage vs. output current. To achieve the best utilization of the motor driver combination it is important to find the correct operation conditions in terms of motor voltage, winding current and stepping mode to fit the motor type and the motor winding. To find the correct operation conditions for a certain application the following procedure can be used. 1. If low noise and low resonance’s or high resolution is required, use half step or even better modified half step, quarter step, etc. In order to implement modified Figure 8. Typical lower transistor saturation voltage vs. output current. by a higher current. A compromise has to be made. Select a motor with the lowest possible winding resistance and inductance, that still gives the required torque, and use as high supply voltage as possible, without exceeding the maximum recommended 40 V. Check that the chopping duty cycle does not exceed 50% at maximum current. Thermal shutdown The circuit is equipped with a thermal shutdown function that turns the outputs off at a chip (junction) temperature above 160 °C. Normal operation is resumed when the temperature has decreased about 20 °C. Programming Figure 10 shows the different input and output sequences for full-step, half-step and modified halfstep operations. Full-step mode. Both windings are energized at all the time with the same current, I M1 = IM2. To make the motor take one step, the current direction (and the magnetic field direction) in one phase is reversed. The next step is then taken when the other phase current reverses. The current changes go through a sequence of four different states which equal four full steps until the initial state is reached again. Half-step mode. In the half-step mode, the current in one winding is brought to zero before a complete current reversal VCE Sat (V) I M (A) 0 0.20 0.40 1.2 0.8 0.4 0 0.2 0.6 1.0 VCE Sat (V) I M (A) 0 0.20 0.40 0.4 0 0.2 0.6 connected together close to the main filtering capacitor at the power supply. • Decouple the supply voltages close to the PBL 3776/1 circuit. Use a ceramic capacitor in parallel with an electrolytic type for both V CC and VBB. Route the power supply lines close together. • Do not place sensitive circuits close to the driver. Avoid physical current loops, and place the driver close to both the motor and the power supply connector. The motor leads could preferably be twisted or shielded. Motor selection The PBL 3776/1 is designed for two- phase bipolar stepper motors, i.e. motors that have only one winding per phase. The chopping principle of the PBL 3776/1 is based on a constant frequency and a varying duty cycle. This scheme imposes certain restrictions on motor selection. Unstable chopping can occur if the chopping duty cycle exceeds approximately 50%. See figure 3 for definitions. To avoid this, it is necessary to select a motor with a low winding resistance and inductance, i.e. windings with fewer turns. It is not possible to use a motor that is rated for the same voltage as the actual supply voltage. Only rated current needs to be considered. Typical motors to be used together with the PBL 3776/1 in a high current application, have a voltage rating of 0.5 to 6 V, while the supply voltage usually ranges from 12 to 40 V. Low inductance, especially in combination with a high supply voltage, enables high stepping rates. However, to give the same torque capability at low speed, the reduced number of turns in the winding in the low resistive, low inductive motor must be compensated half step or modes with better resolution an external sequence generator must be used. See the testboard manual for TB 313i testboard for more information. If the required stepping rate is high or if low cost is more important than low noise use full step mode. 2. Set the motor supply voltage and the winding currents to their maximum values (limited by the motor or the driver). Run the motor in the application at the lowest frequency with maximum load. 3. Decrease the current, by decreasing the Vref voltage, until the motor phases out, then raise the current with the selected torque margin, 25 to 50% as a guideline. This sets a first approximation of the suitable current level. 4. Run the motor at the highest frequency with maximum load. Decrease the motor voltage until the motor phases out. Increase the motor voltage with 15 to 30% as a guideline to find a first estimation of the required motor voltage. To get an even better estimation continue to adjust the current in the low frequency range and the voltage in the high frequency range. This is a very simplified method for finding the correct operating conditions for the motor but it will be helpful in most cases. If the motor fails to run in the high frequency range at maximum voltage a motor with lower winding resistance should be selected. If the problems occur in the low frequency range a larger motor or a gearbox will have to be used. |
Similar Part No. - PBL37761 |
|
Similar Description - PBL37761 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |