L6201 - L6202 - L6203
Quiescent Energy
The last contribution to the energy dissipation is
due to the quiescent supply current and is given by:
E
QUIESCENT
= I
QUIESCENT
⋅
V
s
⋅
T
Total Energy Per Cycle
E
TOT
= E
OFF/ON
+ E
LD
+ E
COM
+
+ E
ON/OFF
+ E
QUIESCENT
The Total Power Dissipation P
DIS
is simply :
P
DIS
= E
TOT
/T
T
r
= Rise time
T
LD
= Load drive time
T
f
= Fall time
T
d
= Dead time
T = Period
T = T
r
+ T
LD
+ T
f
+ T
d
motor.
The L6506 senses the voltage across the sense
resistor R
S
to monitor the motor current: it com-
pares the sensed voltage both to control the
speed and during the brake of the motor.
Between the sense resistor and each sense input
of the L6506 a resistor is recommended; if the
connections between the outputs of the L6506
and the inputs of the L6203 need a long path, a
resistor must be added between each input of the
L6203 and ground.
A snubber network made by the series of R and C
must be foreseen very near to the output pins of
the I.C.; one diode (BYW98) is connected be-
tween each power output pin and ground as well.
The following formulas can be used to calculate
the snubber values:
R
≅
V
S
/l
p
C = l
p
/(dV/dt) where:
V
S
is the maximum Supply Voltage foreseen on
the application;
I
p
is the peak of the load current;
dv/dt is the limited rise time of the output voltage
(200V/µs is generally used).
If the Power Supply Cannot Sink Current, a suit-
able large capacitor must be used and connected
near the supply pin of the L6203. Sometimes a
capacitor at pin 17 of the L6506 let the application
better work. For motor current up to 2A max., the
L6202 can be used in a similar circuit configura-
tion for which a typical Supply Voltage of 24V is
recommended.
DC Motor Speed Control
Since the I.C. integrates a full H-Bridge in a single
package it is idealy suited for controlling DC mo-
tors. When used for DC motor control it performs
the power stage required for both speed and di-
rection control. The device can be combined with
a current regulator like the L6506 to implement a
transconductance amplifier for speed control, as
shown in figure 17. In this particular configuration
only half of the L6506 is used and the other half
of the device may be used to control a second
Figure 17:
Bidirectional DC Motor Control
12/20
STMICROELECTRONICS [ STMICROELECTRONICS ]
