UNITRODE UC1717, UC2717, UC3717 Technical data

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UC1717

UC2717

UC3717

Stepper Motor Drive Circuit

FEATURES

∙Half-step and Full-step Capability

∙Bipolar Constant Current Motor Drive

∙Built-in Fast Recovery Schottky Commutating Diodes

∙Wide Range of Current Control 5-1000mA

∙Wide Voltage Range 10-45V

∙Designed for Unregulated Motor Supply Voltage

∙Current Levels can be Selected in Steps or Varied Continuously

∙Thermal Overload Protection

DESCRIPTION

The UC3717 has been designed to control and drive the current in one winding of a bipolar stepper motor. The circuit consists of an LS- TTL-compatible logic input, a current sensor, a monostable and an output stage with built-in protection diodes. Two UC3717s and a few external components form a complete control and drive unit for LSTTL or micro-processor controlled stepper motor systems.

The UC1717 is characterized for operation over the full military temperature range of -55°C to +125°C, the UC2717 is characterized for -25°C to +85°C, and the UC3717 is characterized for 0°C to +70°C.

ABSOLUTE MAXIMUM RATINGS (Note 1)

Voltage

Logic Supply, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	7V
Output Supply, VM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	45V
Input Voltage
Logic Inputs (Pins 7, 8, 9). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6V
Analog Input (Pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	Vcc
Reference Input (Pin 11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	15V
Input Current

Logic Inputs (Pins 7, 8, 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA Analog Inputs (Pins 10, 11). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA Output Current (Pins 1, 15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1A Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C Storage Temperature Range, TS . . . . . . . . . . . . . . . . . . -55°C to +150°C

Note 1: All voltages are with respect to ground, Pins 4,5, 12, 13. Pin numbers refer to DIL-16 package. Currents are positive into, negative out of the specified terminal.

Note 2: Consult Packaging Section of Databook for information on thermal limitations and considerations of package.

BLOCK DIAGRAM

7/95

							UC1717
							UC2717
CONNECTION DIAGRAMS							UC3717
CONNECTION DIAGRAMS
DIL-16 (TOP VIEW)				PLCC-20 (TOP VIEW)	PACKAGE PIN FUNCTION
DIL-16 (TOP VIEW)				PLCC-20 (TOP VIEW)	FUNCTION			PIN
J or N Package				Q Package	FUNCTION			PIN
J or N Package				Q Package	N/C			1
					N/C			1
					BOUT			2
					Timing			3
					VM			4
					Gnd			5
					N/C			6
					Gnd			7
					VCC			8
					I1			9
					Phase			10
					N/C			11
					I0			12
					Current			13
					VR			14
					Gnd			15
					N/C			16
					Gnd			17
					Vm			18
					AOUT			19
					Emitters			20
RECOMMENDED OPERATING CONDITIONS
PARAMETER	MIN	TYP	MAX	UNITS
Supply Voltage, VCC	4.75	5	5.25	V
Supply Voltage, VM	10		40	V
Output Current. IM	20		800	mA
Rise Time Logic Inputs, tR			2	ms
Fall Time Logic Inputs, tF			2	ms
Ambient Temperature, TA
UC1717	-55		125	°C
UC2717	-25		85	°C
UC3717	0		70	°C
ELECTRICAL CHARACTERISTICS Unless otherwise specified, these specifications apply for VCC = 5V, TA = TJ.
PARAMETER			TEST CONDITIONS		MIN	TYP	MAX	UNITS
Supply Current, ICC							25	mA
High-Level Input Voltage, Pins 7, 8, 9					2.0			V
Low-Level Input Voltage, Pins 7, 8, 9							0.8	V
High-Level Input Current, Pins 7, 8, 9	VI = 2.4V						20	mA
Low Level Input Current, Pins 7, 8, 9	VI = 0.4V				-0.4			mA
Comparator Threshold Voltage	IO = 0, I1 = 0, VR = 5.0V				390	420	440	mV
	IO = 1, I1 = 0, VR = 5.0V				230	250	270	mV
	IO = 0, I1 = 1, VR = 5.0V				65	80	90	mV
Comparator Input Current					-20		20	mA
Output Leakage Current	IO = 1, I1 = 1, TA = +25°C						100	mA
Total Saturation Voltage Drop	IM = 500mA						4.0	V
Total Power Dissipation	IM = 500mA, fS = 30kHz					1.4	2.1	W
	IM = 800mA, fS = 30kHz					2.9	3.1	W
Cut Off Time, tOFF	VM = 10V, tON³ 5ms (See Figure 5 and 6)				25	30	35	ms
Turn Off Delay, tD	TA = +25°C; dVc/dt ³ 50mV/ms (See Figure 5 and 6)					1.6	2.0	ms
Thermal Shutdown Junction Temperature					+160		+180	°C

UC1717

UC2717

UC3717

Figure 1

Figure 2: Typical Source Saturation Voltage vs Output Current

FUNCTIONAL DESCRIPTION

The UC3717 drive circuit shown in the block diagram includes the following functions:

(1)Phase Logic and H-Bridge Output Stage

(2)Voltage Divider with three Comparators for current control

(3)Two Logic inputs for Digital current level select

(4)Monostable for off time generation

Input Logic: If any of the logic inputs are left open, the circuit will treat it as a high level input.

Phase Input: The phase input terminal, pin 18, controls the direction of the current through the motor winding. The Schmidt-Trigger input coupled with a fixed time delay assures noise immunity and eliminates cross conduction in the output stage during phase changes. A low level on the phase input will turn Q2 on and enable Q3 while a high level will turn Q1 on and enable Q4. (See Figure 7).

Output Stage: The output stage consists of four Darlington transistors and associated diodes connected in an H-Bridge configuration. The diodes are needed to provide a current path when the transistors are being switched. For fast recovery, Schottky diodes are used

Figure 3: Typical Sink Saturation Voltage vs Output Current

Figure 4: Typical Power Losses vs Output Current

Figure 5: Connections and Component Values as in Figure 6.

across the source transistors. The Schottky diodes allow the current to circulate through the winding while the sink transistors are being switched off. The diodes across the sink transistors in conjunction with the Schottkys provide the path for the decaying current during phase reversal. (See Figure 7).

PHASE INPUT	Q1, Q4	Q2, Q3
Low	Off	On
High	On	Off

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