L6506
®
CURRENT CONTROLLER FOR STEPPING MOTORS
DESCRIPTION
The L6506/D is a linear integrated circuit designed
to sense and c ontrol the cu rr ent in steppin g m ot o rs
and simila r dev ic es . When use d i n conjuncti on with
the L293, L298, L7150, L6114/L6115, the chip set
forms a const ant c ur re nt dri v e for an inductive loa d
and performs all the int erface function f rom the con trol logic thru t he p ower stage.
Two or more devices may be synchronized using
the sync pi n. In this m ode of oper ation t he os cil lator
in the master chi p sets the opera ting frequency in all
chips.
BLOCK DIAGRAM (pin’s number refer red to DIP-18)
L6506D
DIP18 SO20
ORDERING NUMBERS:
L6506 L6506D
July 2003
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L6506 -L65 06D
PIN CONNECTIONS (top view)
DIP18 SO20
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
V
P
T
T
Supply Voltage 10 V
CC
Input Signals 7 V
i
Total Power Dissipation (T
tot
= 70°C) for DIP18
amb
Total Power Dissipation (Tamb = 70ÉC) for SO20
Junction Temperature 150
j
Storage Temperature -40 to 150
stg
1
0.8
THERMAL DATA
Symbol Parameter DIP18 SO20 Unit
R
th j-amb
ELECT RI CAL CHARACTERES T ICS (V
Thermal Resistance Junction-ambient Max. 80 100
= 5.0V, T
CC
= 25°C; unless otherwise noted)
amb
C/W
°
Symbol Parameter Test Conditions Min. Typ. Max. Unit
CC
Supply Vo lta ge 4.5 7 V
CC
Quiesce nt Su ppl y Cur ren t VCC = 7V 25 mA
V
I
COMPARATOR SECTION
Symbol Parameter Test Conditions Min. Typ. Max. Unit
V
V
I
I
Input Voltage Range V
IN
Input Offset Voltage VIN = 1.4V
IO
Input Offset Current
IO
Input Bias Current 1
IB
Response time V
Inputs –0.3 3 V
sense
5.0
±
200
±
= 1.4V V
REF
= 0 to 5V 0.8 1.5
SENS
W
W
C
°
C
°
mV
nA
µ
µ
A
s
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L6506 - L6506D
ELECT RI CAL CHARACTERISTICS (continued)
COMPARATOR SECTION PERF ORMANCE (O v er Oper at in g T em pe ra tu re Rang e)
Symbol Parameter Test Condtions Min. Typ. Max. Unit
V
LOGIC SECTION (Over Operating Temp era t ure Ran ge - TT L c om patible inputs & o utput s )
Symbol Parameter Test Condtions Min. Typ. Max. Unit
V
V
V
OSCILLATOR
Symbol Parameter Test Condtions Min. Typ. Max. Unit
f
V
V
Input Offset Voltage VIN = 1.4V
IO
Input Offset Curent
I
IO
Input High Voltage 2 V
IH
V
Input Low Voltage 0.8 V
IL
Output High Voltage VCC = 4.75V
OH
= 400µA
I
OH
Ouptut Low Voltage VCC = 4.75V
OL
I
Ouput Source Current - Outputs
OH
1 - 4
Frequency Range 5 70 KHz
osc
Lower Threshold Voltage 0.33 V
thL
Higher Threshold Voltage 0.66 V
thH
Internal Discharge Resistor 0.7 1 1.3
R
i
I
= 4mA
OH
VCC = 4.75V 2.75 mA
2 3.5 V
0.25 0.4 V
CC
CC
±
20
±
500
s
mV
nA
V
V
V
k
Ω
CIRCUIT OPERATION
The L6506 is intende d for use with dua l b ridge drivers, suc h as the L298 , qua d darl ingto n array s, s uch
as the L7150, quad DMOS array such as L6114L6115, or d iscrete power transistor s to drive stepper
motors and other similar loads. T he main functi on of
the device is to sen se and control the cu rrent in each
of the load windings.
A common on-chip oscill ator drives the dual chopper
and sets t he opera ting freque ncy for the p ulse wi dth
modulated driv e. The RC network on pin 1 sets the
operating fr eque nc y whic h is given by t he e quat i on
:
f = for R > 10 K
1
0.69 RC
The oscillator provides pulses to set the two flipflops which in t urn caus e the outputs t o acti vate t he
drive. When the current in the lo ad winding re aches
the programm ed peak val ue, the vo ltage acr oss the
sense resistor (R
) is equal to V
sense
and the cor-
ref
responding comparator resets its flip-flop interrupting the drive cur rent until the next oscil lator pulse occurs. The peak current in each winding is programmed by sele cting th e value of the s ense r esis-
tor and V
. Since sepa rate inputs are provid ed fo r
ref
each chopper, each of the loads may be programmed independently allowing the device to be
used to implement microstepping of the motor.
Lower thres hold of L6506 ’s oscillator is 1/3 V
per threshold is 2/3 V
and internal discharge re-
CC
CC
. Up-
sistor 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 wit h the osc illator output of the
master dev ice and connecting the R/C pin of the unused osci lla to rs t o gr oun d.
The equations for the active time of the sync pulse
(T2), the i nactive time of the sync signal ( T1) and the
duty cyc le can be found by looking at the fi gure 1 and
are :
R1 R
T2 = 0.69 C1 (1)
R1 + R
IN
IN
T1 = 0.69 R1 C1 (2)
DC = (3)
T2
T1 + T2
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L6506 -L65 06D
By substituting equations 1 and 2 into equation 3
and solving for the value of R1 the following equations for the ex ter nal c om ponents can be der iv ed :
R1 = ( – 2) R
1
DC
C1 = (5)
0.69 R1
IN
T1
(4)
Figure 1 : Oscillator Cir c uit and Waveform s .
Looking at eq uat io n 1 it can easi ly be se en t ha t the
minimum pulse wid th 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.
APPLICAT IONS I NFORMATI ON
The circuits s how n in fi gure 2 us e the L6506 to im plement cons tant c urrent drives for s teppe r mot ors.
Figure 2 shows the L6506 used with the L298 to
drive a 2 phas e bipolar mot or. The peak current can
be calculated using the equa ti on :
V
=
R
ref
sense
I
peak
The circuit of Fig.2 can be used in applications requiring different peak and hold current values by
modifying t he r efer enc e v olt a ge.
The L6506 ma y be used to implemen t 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 bri dge req uir es an additional input to disable the power stage du ring the ha lf step . If used in
conjunctio n w ith the L298 the e nable input s may be
used for this purpose.
For quad darlin gton array in 4 phase unipo lar motor
applications half step may be implemented using
the 4 phase in puts .
The L6506 may also be used to implement microsteppi ng of either bipolar or un ipolar motors.
4/8
L6506 - L6506D
Figure 2 : Applicatio n Ci rc ui t Bipolar Stepp er Mot or Dr iv er . (p in’s number referred t o DIP 18)
5/8
L6506 -L65 06D
DIM.
MIN. TYP. MAX. MIN. TYP. MAX.
a1 0.254 0.010
B 1.39 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 0.130
Z 1.27 1.59 0.050 0.063
mm inch
OUTLINE AND
MECHANICAL DATA
DIP18
6/8
L6506 - L6506D
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
K 0˚ (min.)8˚ (max.)
mm inch
OUTLINE AND
MECHANICAL DATA
SO20
B
e
D
1120
110
L
h x 45˚
A
K
A1
C
H
E
SO20MEC
7/8
L6506 -L65 06D
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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 STMicr oelectronic s.
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