stk672-080-e Sanyo Semiconductor Corporation, stk672-080-e Datasheet - Page 14

• Manufacturer Part Number: stk672-080-e
• Description: Unipolar Constant-current Chopper External Excitation Pwm Circuit With Built-in Microstepping Controller Stepping Motor Driver Sine Wave Drive Output Current 2.8a No Heat Sink*
• Manufacturer: Sanyo Semiconductor Corporation

Thermal Design
<Hybrid IC Average Internal Power Loss Pd>
The main elements internal to this hybrid IC with large average power losses are the current control devices, the
regenerative current diodes, and the current detection resistor. Since sine wave drive is used, the average power loss
during microstepping drive can be approximated by applying a waveform factor of 0.64 to the square wave loss during
2 phase excitation.
The losses in the various excitation modes are as follows.
2 phase excitation
1-2 phase excitation
W1-2 phase excitation Pd W1-2EX = 0.64 · {(Vsat+Vdf) ·
2W1-2 phase excitation Pd 2W1-2EX = 0.64 · {(Vsat+Vdf) ·
4W1-2 phase excitation Pd 4W1-2EX = 0.64 · {(Vsat+Vdf) ·
Here, t1 and t3 can be determined from the same formulas for all excitation methods.
However, the formula for t2 differs with the excitation method.
2 phase excitation
W1-2 phase excitation t2 =
t1 =
fclock : CLK input frequency (Hz)
Vsat
Vdf
I OH
t1
t2
t3
R
+
−
0.35
L
: The voltage drop of the power MOSFET and the current detection resistor (V)
: The voltage drop of the body diode and the current detection resistor (V)
: Phase current peak value (A)
: Phase current rise time (s)
: Constant-current operating time (s)
: Phase switching current regeneration time (s)
· n (1 –
Pd 2EX = (Vsat+Vdf) ·
Pd 1-2EX = 0.64 · {(Vsat+Vdf) ·
t2 =
R +
V
t3
CC
fclock
0.35
fclock
Motor Phase Current Model Figure (2 Phase Excitation)
1
7
2
t1
· I OH )
– t1
– (t1+t3)
fclock
STK672-080-E
2
t2
· I OH · t2 +
fclock
1-2 phase excitation
t3 =
4W1-2 phase excitation
2W1-2 phase excitation
fclock
4
fclock
fclock
8
16
16
−
· I OH · t2 +
R
L
·I OH · t2 +
·I OH · t2 +
·I OH · t2 +
I
V CC 1 : Supply voltage applied to the motor (V)
L
R
· n (
OH
·
2
fclock
: Motor inductance (H)
: Motor winding resistance (Ω)
I
OH
I
I
OH
OH
I
I
t2 =
V
·R
OH
OH
· (Vsat · t1+Vdf · t3)
CC
·
4
fclock
+
·
t2 =
8
fclock
16
16
·
·
fclock
fclock
V
1
fclock
I OH
CC
+
0.35
3
1
fclock
A13270
· (Vsat · t1+Vdf · t3)}
+
15
· (Vsat · t1+Vdf · t3)}
· (Vsat · t1+Vdf · t3)}
· (Vsat · t1+Vdf · t3)}
0.35
– t1
– t1
)
No.6507-14/18