STK672-210-E

No. 7464-7/10

t1: The time until the winding current reaches its rated current (IOH)

t2: The time in the constant-current control (PWM) region

t3: The time from the point a phase signal is cut until the back EMF current is dissipated.

t1 = (–L/(R + 0.77)) In (1 – ((R + 0.77)/VCC1) × IOH)

t3 = (–L/R) In ((VCC1 + 0.77) / (IOH × R + VCC1 + 0.77))

VCC1: Motor supply voltage (V)

L: Motor inductance (H)

R: Motor winding resistance (

Ω)

IOH: Set motor output current wave height (A)

The constant-current control time t2, and the time T (= t1 + t2 + t3) that the phase signal is on in each excitation mode

are as follows.

2 phase excitation mode: t2 = (2/Clock) – (t1 + t3)

1-2 phase excitation mode: t2 = (3/Clock) – t1

Determine the values for Vsat and Vdf by substitution using the graphs for Vsat vs IOH and Vdf vs IOH for the set

current value for IOH. Then judge whether or not a heat sink is required from the determined average power dissipation

for the STK672-210-E by comparison with the

ΔTc vs. Pd graph.

Note that it is necessary to check the temperature rise in the actual application system case, since the STK672-210-E

substrate temperature Tc changes with the air convection conditions around the STK672-210-E when a heat sink

without fins is used.

ITF02291

0

0.5

1.0

1.5

2.0

2.5

Output current, IO - A

Vsat - IO

0

1.0

1.5

2.0

2.5

3.0

3.5

0.5

ITF02292

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

Output current, If - A

Vdf - If

0.4

1.7

0

0.1

0.2

0.3

0.8

0.5

0.6

0.7

1.5

1.6

1.4

1.2

1.3

1.1

0.9

1.0

Tc

=1

05

°C

25

°C

10

5°C

Tc

=2

5°C

ITF02294

0

20

40

60

80

100

120

Substrate temperature, Tc - °C

IIH - Tc

1000

7

5

3

2

100

7

5

3

2

10

1.0

7

5

3

2

ITF02293

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

Motor current, IOH - A

Vref - IOH

0.10

0.45

0.40

0

0.05

0.20

0.15

0.35

0.30

0.25

IIH

IIL