STK672-120 Sanyo Semicon Device, STK672-120 Datasheet - Page 6

• Manufacturer Part Number: STK672-120
• Description: Two-Phase Stepping Motor Driver (Square Wave Drive) Output Current: 2.4 A
• Manufacturer: Sanyo Semicon Device

• Thermal design
T1: Motor rotation operation time
T2: Motor hold operation time
T3: Motor current off time
T2 may be reduced, depending on the application.
T0: Single repeated motor operating cycle
IO1 and IO2: Motor current peak values
Due to the structure of motor windings, the phase current is a positive and negative current with a pulse form.
Note that figure 3 presents the concepts here, and that the on/off duty of the actual signals will differ.
If the value calculated in formula (I) above is under 1.5 W, then there will be no need to use a heat sink for ambient
temperatures Ta up to 60°C. See figure 6 for operating substrate temperature rise data when a heat sink is not attached.
If a heat sink is to be used, to lower Tc if P
the heat sink.
While formulas (I) and (II) above are adequate for thermal design, note that figure 5 is merely a single example of one
operating mode for a single motor. For example, while figure 5 shows a 2-phase excitation motor, if 1-2 phase excitation
is used with a 500-Hz clock frequency, the drive will be turned off for 25% of the time and the loss P
75% of that in figure 5.
It is extremely difficult for Sanyo to calculate the internal average power dissipation P
conditions. After performing the above rough calculations, always install the hybrid IC in an actual end product and
verify that the substrate temperature Tc does not rise above 105°C.
[Operating range in which a heat sink is not used]
Thermal design that lowers this hybrid IC’s operating substrate temperature can be effective in improving end product
quality. The size of the heat sink required by this hybrid IC varies with the average power dissipation P
P
Since there are periods when current flows and periods when the current is off during actual motor operation, P
cannot be determined from the data presented in figure 5. Therefore, we calculate P
operation consists of repetitions of the operation shown in figure 3.
The hybrid IC internal average power dissipation P
P
(Here, P1 is the P
D
D
increases as the output current increases, as shown in figure 5.
= (T1 P1 + T2 P2 + T3) T0
Tcmax: Maximum operating substrate temperature = 105°C
Ta: The hybrid IC ambient temperature
c - a = (Tc max–Ta) PD
Motor phase current
(sink side)
D
for IO1 and P2 is the P
(II)
(I)
Figure 3 Motor Current Timing
D
D
increases, use formula (II) and the graph in figure 7 to determine the size of
for IO2)
D
STK672-120
can be calculated from the following formula.
D
D
for all possible end product
assuming that actual motor
D
will be reduced to
D
. The value of
No. 6042-6/9
D