L6506 L6506D ® CURRENT CONTROLLER FOR STEPPING MOTORS DESCRIPTION The L6506/D is a linear integrated circuit designed to sense and control the current in stepping motors and similar devices. When used in conjunction with the L293, L298, L7150, L6114/L6115, the chip set forms a constant current drive for an inductive load and performs all the interface function from the control logic thru the power stage. Two or more devices may be synchronized using the sync pin. In this mode of operation the oscillator in the master chip sets the operating frequency in all chips. DIP18 SO20 ORDERING NUMBERS: L6506 L6506D BLOCK DIAGRAM (pin’s number referred to DIP-18) July 2003 1/8 L6506 -L6506D PIN CONNECTIONS (top view) DIP18 SO20 ABSOLUTE MAXIMUM RATINGS Symbol Value Unit VCC Vi Supply Voltage Input Signals 10 7 V V Ptot Total Power Dissipation (Tamb = 70°C) for DIP18 Total Power Dissipation (Tamb = 70ÉC) for SO20 Junction Temperature 1 0.8 W W 150 °C -40 to 150 °C Tj Tstg Parameter Storage Temperature THERMAL DATA Symbol Rth j-amb Parameter Thermal Resistance Junction-ambient Max. DIP18 SO20 Unit 80 100 °C/W ELECTRICAL CHARACTERESTICS (VCC = 5.0V, Tamb = 25°C; unless otherwise noted) Symbol VCC ICC Parameter Supply Voltage Quiescent Supply Current Test Conditions Min. Typ. 4.5 VCC = 7V Max. Unit 7 25 V mA Max. Unit COMPARATOR SECTION Symbol Parameter VIN VIO Input Voltage Range Input Offset Voltage IIO Input Offset Current IIB Input Bias Current Response time 2/8 Test Conditions Vsense Inputs VIN = 1.4V VREF = 1.4V VSENS = 0 to 5V Min. Typ. –0.3 0.8 3 V ±5.0 mV ±200 nA 1 µA 1.5 µs L6506 - L6506D ELECTRICAL CHARACTERISTICS (continued) COMPARATOR SECTION PERFORMANCE (Over Operating Temperature Range) Symbol Parameter VIO Input Offset Voltage IIO Input Offset Curent Test Condtions Min. Typ. VIN = 1.4V Max. Unit ±20 mV ±500 nA Max. Unit Vs V 0.8 V V 0.4 V LOGIC SECTION (Over Operating Temperature Range - TTL compatible inputs & outputs) Symbol Parameter VIH VIL Input High Voltage VOH Output High Voltage VOL Ouptut Low Voltage IOH Ouput Source Current - Outputs 1-4 Test Condtions Min. Typ. 2 Input Low Voltage VCC = 4.75V IOH = 400µA VCC = 4.75V IOH = 4mA 2 VCC = 4.75V 2.75 3.5 0.25 mA OSCILLATOR Symbol fosc VthL VthH Ri Parameter Test Condtions Frequency Range Min. Lower Threshold Voltage Higher Threshold Voltage Internal Discharge Resistor CIRCUIT OPERATION The L6506 is intended for use with dual bridge drivers, such as the L298, quad darlington arrays, such as the L7150, quad DMOS array such as L6114L6115, or discrete power transistors to drive stepper motors and other similar loads. The main function of the device is to sense and control the current in each of the load windings. A common on-chip oscillator drives the dual chopper and sets the operating frequency for the pulse width modulated drive. The RC network on pin 1 sets the operating frequency which is given by the equation : 1 f= for R > 10 K 0.69 RC The oscillator provides pulses to set the two flipflops which in turn cause the outputs to activate the drive. When the current in the load winding reaches the programmed peak value, the voltage across the sense resistor (Rsense) is equal to Vref and the corresponding comparator resets its flip-flop interrupting the drive current until the next oscillator pulse occurs. The peak current in each winding is programmed by selecting the value of the sense resis- Typ. 5 Max. Unit 70 KHz 0.33 VCC 0.66 VCC 0.7 1 V V 1.3 kΩ tor and Vref. Since separate inputs are provided for each chopper, each of the loads may be programmed independently allowing the device to be used to implement microstepping of the motor. Lower threshold of L6506’s oscillator is 1/3 VCC. Upper threshold is 2/3 VCC and internal discharge resistor is 1 KΩ ± 30 %. Ground noise problems in multiple configurations can be avoided by synchronizing the oscillators. This may be done by connecting the sync pins of each of the devices with the oscillator output of the master device and connecting the R/C pin of the unused oscillators to ground. The equations for the active time of the sync pulse (T2), the inactive time of the sync signal (T1) and the duty cycle can be found by looking at the figure 1 and are : R1 RIN T2 = 0.69 C1 (1) R1 + RIN T1 = 0.69 R1 C1 DC = T2 T1 + T2 (2) (3) 3/8 L6506 -L6506D (5) Looking at equation 1 it can easily be seen that the minimum pulse width of T2 will occur when the value of R1 is at its minimum and the value of R1 at its maximum. Therefore, when evaluating equation 4 the minimum value for R1 of 700Ω (1 KΩ – 30 %) should be used to guarantee the required pulse width. APPLICATIONS INFORMATION The circuits shown in figure 2 use the L6506 to implement constant current drives for stepper motors. Figure 2 shows the L6506 used with the L298 to drive a 2 phase bipolar motor. The peak current can be calculated using the equation : Vref Ipeak = Rsense The L6506 may be used to implement either full step or half step drives. In the case of 2 phase bipolar stepper motor applications, if a half step drive is used, the bridge requires an additional input to disable the power stage during the half step. If used in conjunction with the L298 the enable inputs may be used for this purpose. By substituting equations 1 and 2 into equation 3 and solving for the value of R1 the following equations for the external components can be derived : 1 (4) R1 = ( – 2) RIN DC C1 = T1 0.69 R1 Figure 1 : Oscillator Circuit and Waveforms. The circuit of Fig.2 can be used in applications requiring different peak and hold current values by modifying the reference voltage. For quad darlington array in 4 phase unipolar motor applications half step may be implemented using the 4 phase inputs. The L6506 may also be used to implement microstepping of either bipolar or unipolar motors. 4/8 L6506 - L6506D Figure 2 : Application Circuit Bipolar Stepper Motor Driver. (pin’s number referred to DIP18) 5/8 L6506 -L6506D mm DIM. MIN. a1 0.254 B 1.39 TYP. inch MAX. MIN. TYP. MAX. OUTLINE AND MECHANICAL DATA 0.010 1.65 0.055 0.065 b 0.46 0.018 b1 0.25 0.010 D 23.24 0.915 E 8.5 0.335 e 2.54 0.100 e3 20.32 0.800 F 7.1 0.280 I 3.93 0.155 L 3.3 Z 1.27 0.130 DIP18 6/8 1.59 0.050 0.063 L6506 - L6506D mm inch OUTLINE AND MECHANICAL DATA DIM. MIN. TYP. MAX. MIN. TYP. MAX. A 2.35 2.65 0.093 0.104 A1 0.1 0.3 0.004 0.012 B 0.33 0.51 0.013 0.020 C 0.23 0.32 0.009 0.013 D 12.6 13 0.496 0.512 E 7.4 7.6 0.291 0.299 e 1.27 0.050 H 10 10.65 0.394 0.419 h 0.25 0.75 0.010 0.030 L 0.4 1.27 0.016 0.050 SO20 K 0˚ (min.)8˚ (max.) L h x 45˚ A B e A1 K C H D 20 11 E 1 0 1 SO20MEC 7/8 L6506 -L6506D Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. 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