STK672-210 Sanyo Semicon Device, STK672-210 Datasheet - Page 6

• Manufacturer Part Number: STK672-210
• Description: Two-Phase Stepping Motor Driver Output Current: 1.4 A
• Manufacturer: Sanyo Semicon Device

Thermal Design
The size of the heat sink required for the STK672-210 depends on the motor output current I
characteristics of the motor, the excitation mode, and the basic drive frequency.
The thermal resistance ( c-a) of the required heat sink can be determined from the following formula.
For example, the required area for a heat sink made from 2 mm thick aluminum can be determined from the graph at the
right below. Note that the ambient temperature is greatly influenced by the ventilation and air flow patterns within the
application. This means that the size of the heat sink must be determined with care so that the STK672-210 back surface
(aluminum substrate) temperature Tc in the mounted state never exceeds, under any conditions that might occur, the
temperature Tc = 105 °C.
STK672-210 Average Internal Power Dissipation Pd
Of the devices that contribute to the STK672-210 average internal power supply, the devices with the largest power
dissipation are the current control devices, the diodes that handle the regenerative current, the current detection resistor,
and the predriver circuit.
The following presents formulas for calculating the power dissipation for the different excitation (drive) modes.
2 phase excitation mode
1-2 phase excitation mode
Motor hold mode
Tcmax: The STK672-210 substrate temperature (°C)
Ta: The STK672-210 ambient temperature (°C)
Pd: The average internal power dissipation in the STK672-210 (W)
Pd
Pd
Pd
c – a = —————— (°C/W)
20
16
12
2EX
1-2EX
HOLDEX
8
4
0
Vsat: Ron voltage drop + shunt resistor combined voltage
Vdf: FET internal diode Vdf + shunt resistor combined voltage
Clock: Input clock CLK (the reference frequency prior to splitting into 4 phases)
0
= (Vsat + Vdf) 0.5 Clock I
= (Vsat + Vdf) 0.25 Clock I
IC internal average power dissipation, Pd — W
2
Tc max – Ta
= (Vsat + Vdf) I
4
Figure 1 Motor Output Current Waveform Model (Commutation Current)
Pd
6
8
c-a — Pd
t1
c-a=
10
OH
Tc max--Ta
12
Pd
14
No Fin
23.0[ C / W]
Tc max=105 C
OH
16
( C / W)
40 C
50 C
60 C
OH
ITF01880
t2 + 0.5 Clock I
18
t2 + 0.25 Clock I
STK672-210
20
t2
OH
100
1.0
10
7
5
3
2
7
5
3
2
10
OH
(Vsat t1 + Vdf t3)
(Vsat t1 + Vdf t3)
2
3
Heat sink area, S — cm
t3
5
7
c-a — S
100
0A
ITF02290
OH
I OH
2
(A), the electrical
2
3
No Fin
23.0[ C / W]
Mounted vertically
Convection cooling
No.7464-6/8
5
ITF01881
7
1000