PBL3770A ERICSSON | Alldatasheet

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Technical content

Figure 1. Block diagram.

Description

PBL 3770A is a bipolar monolithic circuit intended to control and drive the current in one winding of a stepper motor. It is a high power version of PBL 3717 and special care has been taken to optimize the power handling capability without suffering in reliability. The circuit consists of a LS-TTL compatible logic input stage, a current sensor, a monostable multivibrator and a high power H-bridge output stage. The circuit is pin-compatible with the PBL 3717 industry-standard driver. Two PBL 3770A and a small number of external components form a complete control and drive unit for LS-TTL or microprocessor-controlled stepper motor systems. Key Features

  • Half-step and full-step operation.
  • Switched mode bipolar constant current drive
  • Wide range of current control 5 -1800 mA.
  • Wide voltage range 10 - 45 V.
  • Designed for unstabilized motor supply voltage.
  • Current levels can be selected in steps or varied continuously.
  • Thermal overload protection. GND VCC M A M B Phase I V R & &&& Monostable t = 0.69 • R • C Current Sensor Output Stage off T T Schmitt Trigger Time Delay C T E PBL 3770A 1 ≥1 ≥1≥1 VMMVMM PBL 3770A

Figure 2. Definition of symbols.

Electrical Characteristics

Electrical characteristics over recommended operating conditions. CT = 820 pF, RT = 56 kohm. Ref. Parameter Symbol fig. Conditions Min Typ Max Unit General Supply current I CC 2V MM = 20 to 40 V, I0 = I1 = HIGH. 30 40 mA VMM = 20 to 40 V, I0 = I1 = LOW, 48 65 mA fs = 23 kHz Total power dissipation P D fs = 28 kHz, IM = 1000 mA, VMM = 36 V 1.9 2.3 W Note 2, 4. f s = 24 kHz, IM = 1000 mA, VMM = 12 V 1.7 2.1 W Note 2, 4. f s = 28 kHz, IM = 1300 mA, VMM = 36 V 2.7 3.2 W Note 3, 4. f s = 28 kHz, IM = 1500 mA, VMM = 36 V 3.5 W Note 3, 4. Turn-off delay t d 3T a = +25°C, dVC /dt ≥ 50 mV/µs. 2.5 µs Thermal shutdown junction temperature 170 °C Logic Inputs Logic HIGH input voltage V IH 2 2.0 V Logic LOW input voltage V IL 2 0.8 V Logic HIGH input current I IH 2V I = 2.4 V 20 µA Logic LOW input current I IL 2V I = 0.4 V -0.4 mA Analog Inputs Comparator threshold voltage VCH 2V R = 5.0 V, I0 = I1 = LOW 400 415 430 mV Comparator threshold voltage VCM 2V R = 5.0 V, I0 = HIGH, I1 = LOW 240 250 265 mV Comparator threshold voltage VCL 2V R = 5.0 V, I0 = LOW, I1 = HIGH 70 80 90 mV Input current I C 2 -20 µA Motor Outputs Lower transistor saturation voltage IM = 1000 mA 0.5 0.8 V IM = 1300 mA 0.8 1.3 V Lower diode forward voltage drop I M = 1000 mA 1.3 1.6 V IM = 1300 mA 1.5 1.8 V Upper transistor saturation voltage IM = 1000 mA 1.1 1.3 V IM = 1300 mA 1.3 1.6 V Output leakage current I 0 = I1 = HIGH, Ta = +25°C 100 µA Monostable Cut off time t off 3V MM = 10 V, ton ≥ 5 µs 2 73 13 5 µs Thermal Characteristics Ref. Parameter Symbol Fig. Conditions Min Typ Max Unit Thermal resistance Rth J-C DIL package. 11 °C/W RthJ-A 15 DIL package. Note 2. 40 °C/W RthJ-C PLCC package. 9 °C/W RthJ-A 15 PLCC package. Note 2. 35 °C/W RthJ-C SO package. 11 °C/W RthJ-A 15 SO package. 40 °C/W Notes 1. All voltages are with respect to ground. Currents are positive into, negative out of specified terminal. 2. All ground pins soldered onto a 20 cm2 PCB copper area with free air convection. Ta = +25°C. 4. Not covered by final test program.

Figure 3. Pin configurations. 11 1 0 M B Motor output B, Motor current flows from MA to MB when Phase is high. parallel between T and Ground. 3 3,14 12,4 V MM Motor supply voltage, 10 to 40 V. Pin 3(12) and pin 14(4) should be wired together. 4-7, 4,5, 1-3,9, GND Ground and negative supply. Note these pins are used for heatsinking. ground plane for efficient heat sinking. 86 1 8 V CC Logic voltage supply normally +5 V. 97 1 9 I 1 Logic input. It controls, together with the I0 input, the current level in the output stage. The controlable levels are fixed to 100, 60, 20, 0%. Motor current flows from MA to MB when the phase input is high. 11 9 21 I 0 Logic input. It controls, together with the I1 input, the current level in the output stage. The controlable levels are fixed to 100, 60, 20, 0%. resistor, filtered through a RC Network. the output current. Input resistance: typically 6.8 kΩ ± 20%. A Motor output A, Motor current flows from MA to MB when Phase is high. 20 16 8 E Common emitter. Connect the Sence resistor between this pin and ground.

winding of a 2-phase stepper motor.

  • Input logic
  • Current sense
  • Single-pulse generator
  • Output stage Input logic Phase input. The phase input determines the direction of the current in the motor winding. High input forces the current from terminal M A to MB and low input from terminal MB to MA. A Schmitt trigger provides noise immunity and a delay circuit eliminates the risk of cross conduction in the output stage during a phase shift. Half- and full-step operation is possible. Current level selection. The status of I0 and I1 inputs determines the current level in the motor winding. Three fixed current levels can be selected according to the table below. Motor current I 0 I1 High level 100% L L Medium level 60% H L Low level 20% L H Zero current 0% H H The specific values of the different current levels are determined by the reference voltage V R together with the value of the sensing resistor RS. The peak motor current can be calculated as follows: im = (VR • 0.080) / RS [A], at 100% level The motor current can also be continuously varied by modulating the voltage reference input. Current sensor The current sensor contains a reference voltage divider and three comparators for measuring each of the selectable current levels. The motor current is sensed as a voltage drop across the current sensing resistor, RS, and compared with one of the voltage references from the divider. When the two voltages are equal, the compara-tor triggers the single-pulse generator. Only one comparator at a time is activa-ted by the input logic. Single-pulse generator The pulse generator is a monostable multivibrator triggered on the positive edge of the comparator output. The multivibrator output is high during the pulse time, t off , which is determined by the timing components RT and CT. toff = 0.69 • RT • CT The single pulse switches off the power feed to the motor winding, causing the winding to decrease during t off . If a new trigger signal should occur during toff , it is ignored. Output stage The output stage contains four transistors and two diodes, connected in an H-bridge. Note that the upper recirculation diodes are connected to the circuit externally. The two sinking transistors are used to switch the power supplied to the motor winding, thus driving a constant current through the winding. See figures 5 and 6. Overload protection The circuit is equipped with a thermal shut-down function, which will limit the junction temperature. The output current will be reduced if the maximum permis- sible junction temperature is exceeded. It should be noted, however, that it is not short circuit protected. Operation When a voltage V MM is applied across the motor winding, the current rise follows the equation: i R = Winding resistance L = Winding inductance t = time (see figure 6, arrow 1) The motor current appears across the external sensing resistor, R S, as an analog voltage. This voltage is fed through a low-pass filter, R C C C , to the voltage comparator input (pin 10). At the moment the sensed voltage rises above the comparator threshold voltage, the monostable is triggered and its output turns off the conducting sink transistor. The polarity across the motor winding reverses and the current is forced to circulate through the appropriate upper protection diode back through the source transistor (see figure 6, arrow 2). After the monostable has timed out, the current has decayed and the analog

Figure 4. Definition of terms.