Datasheet

ELECTRICAL CHARACTERISTICS (continued)
COMPARATOR SECTION PERFORMANCE (Over OperatingTemperature Range)
Symbol Parameter Test Condtions Min. Typ. Max. Unit
V
IO
Input Offset Voltage V
IN
= 1.4V ±20 mV
I
IO
Input Offset Curent ±500 nA
CIRCUIT OPERATION
The L6506is intendedfor use with dual bridge driv-
ers, such as the L298, quad darlington arrays, such
as the L7150, quad DMOS array such as L6114-
L6115,or discretepowertransistorstodrive stepper
motorsand othersimilar loads.The mainfunctionof
thedeviceis to senseandcontrolthecurrent ineach
of the load windings.
Acommonon-chiposcillatordrives thedualchopper
and setstheoperatingfrequencyfor thepulsewidth
modulateddrive. The RC network on pin 1 sets the
operatingfrequency which is given by the equation
:
1
f = for R > 10 K
0.69 RC
The oscillator provides pulses to set the two flip-
flops which in turncause the outputsto activate the
drive. When the current in the load winding reaches
the programmed peak value, the voltageacross the
sense resistor (R
sense
) is equal to V
ref
and the cor-
responding comparatorresets its flip-flop interrupt-
ing thedrive current untilthenextoscillatorpulse oc-
curs. The peak current in each winding is pro-
grammed by selecting the value of thesense resis-
tor and V
ref
. Since separateinputs are provided for
each chopper, each of the loads may be pro-
grammed independently allowing the device to be
used to implement microstepping of the motor.
Lowerthresholdof L6506’soscillatoris 1/3 V
CC
.Up-
per threshold is 2/3 V
CC
and internal discharge re-
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
eachof the devices with the oscillator output of the
masterdeviceand connectingthe R/C pinof the un-
used oscillators to ground.
The equations for the active time of the sync pulse
(T2), theinactivetime of thesyncsignal(T1)andthe
dutycyclecanbefoundbylookingatthefigure1and
are :
R1 R
IN
T2 = 0.69 C1 (1)
R1 + R
IN
T1 = 0.69 R1 C1 (2)
T2
DC = (3)
T1 + T2
LOGIC SECTION (Over OperatingTemperature Range - TTL compatible inputs & outputs)
Symbol Parameter Test Condtions Min. Typ. Max. Unit
V
IH
Input High Voltage 2 V
s
V
V
IL
Input Low Voltage 0.8 V
V
OH
Output High Voltage V
CC
= 4.75V
I
OH
= 400µA
2 3.5 V
V
OL
Ouptut Low Voltage V
CC
= 4.75V
I
OH
= 4mA
0.25 0.4 V
I
OH
Ouput Source Current - Outputs
1-4
V
CC
= 4.75V 2.75 mA
OSCILLATOR
Symbol Parameter Test Condtions Min. Typ. Max. Unit
f
osc
Frequency Range 5 70 KHz
V
thL
Lower Threshold Voltage 0.33 V
CC
V
V
thH
Higher Threshold Voltage 0.66 V
CC
V
R
i
Internal Discharge Resistor 0.7 1 1.3 kΩ
L6506 - L6506D
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