ST L6506, L6506D User Manual

	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

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L6506 -L6506D

PIN CONNECTIONS (top view)

DIP18

SO20

ABSOLUTE MAXIMUM RATINGS

Symbol	Parameter	Value	Unit
VCC	Supply Voltage	10	V
Vi	Input Signals	7	V
Ptot	Total Power Dissipation (Tamb = 70°C) for DIP18	1	W
	for SO20	0.8	W
Tj	Junction Temperature	150	°C
Tstg	Storage Temperature	-40 to 150	°C
THERMAL DATA

Symbol	Parameter		DIP18	SO20	Unit
Rth j-amb	Thermal Resistance Junction-ambient	Max.	80	100	°C/W

ELECTRICAL CHARACTERESTICS (VCC = 5.0V, Tamb = 25°C; unless otherwise noted)

Symbol	Parameter	Test Conditions	Min.	Typ.	Max.	Unit
VCC	Supply Voltage		4.5		7	V
ICC	Quiescent Supply Current	VCC = 7V			25	mA

COMPARATOR SECTION

Symbol	Parameter	Test Conditions	Min.	Typ.	Max.	Unit
VIN	Input Voltage Range	Vsense Inputs	–0.3		3	V
VIO	Input Offset Voltage	VIN = 1.4V			±5.0	mV
IIO	Input Offset Current				±200	nA
IIB	Input Bias Current				1	μA
	Response time	VREF = 1.4V VSENS = 0 to 5V		0.8	1.5	μs

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L6506 - L6506D

ELECTRICAL CHARACTERISTICS (continued)

COMPARATOR SECTION PERFORMANCE (Over Operating Temperature Range)

Symbol	Parameter	Test Condtions	Min.	Typ.	Max.	Unit
VIO	Input Offset Voltage	VIN = 1.4V			±20	mV
IIO	Input Offset Curent				±500	nA

LOGIC SECTION (Over Operating Temperature Range - TTL compatible inputs & outputs)

Symbol	Parameter	Test Condtions	Min.	Typ.	Max.	Unit
VIH	Input High Voltage		2		Vs	V
VIL	Input Low Voltage				0.8	V
VOH	Output High Voltage	VCC = 4.75V	2	3.5		V
		IOH = 400μA
VOL	Ouptut Low Voltage	VCC = 4.75V		0.25	0.4	V
		IOH = 4mA
IOH	Ouput Source Current - Outputs	VCC = 4.75V	2.75			mA
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OSCILLATOR

Symbol	Parameter	Test Condtions	Min.	Typ.	Max.	Unit
fosc	Frequency Range		5		70	KHz
VthL	Lower Threshold Voltage			0.33 VCC		V
VthH	Higher Threshold Voltage			0.66 VCC		V
Ri	Internal Discharge Resistor		0.7	1	1.3	kΩ

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

:

f =	1	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-

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 :

T2 = 0.69 C1		R1 RIN		(1)
		R1 + RIN
T1 = 0.69 R1 C1				(2)
DC =	T2			(3)
	T1 + T2

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