BM6112FV-C
Short Circuit Protection (SCP) Function – continued
Collector or drain voltage (VDESAT) at which desaturation protection function operates and the blanking time (tBLANK
)
determined by external component can be calculated by the formula below.
푅3 +푅2
푉퐷퐸푆퐴푇 = 푉
×
– 푉
[V]
푆퐶퐷퐸푇
퐹퐷1
푅3
푅3+푅2+푅1
푅3
푉
> 푉
×
[V]
퐶퐶2푀퐼푁
푆퐶퐷퐸푇
푅2+푅1
푅3+푅2+푅1
푅3
ꢆ
ꢇꢈꢉꢊꢋ
푡퐵퐿퐴푁퐾 = − 푅3+푅2+푅1 × ꢀꢁ × ꢂ퐵퐿퐴푁퐾 ꢃ 6.5 × ꢄ0ꢅ12 × ln(ꢄ −
×
)
[s]
(
)
ꢆ
ꢈꢈꢌ
where:
푉퐷퐸푆퐴푇 is the collector or drain voltage at which desaturation protection function operates.
푉퐹퐷1 is the forward voltage of the diode.
푉
is the Short Circuit Detection Voltage.
푆퐶퐷퐸푇
푉퐶퐶2푀퐼푁 is the minimum Output-side Positive Supply Voltage.
푡퐵퐿퐴푁퐾 is the blanking time.
ꢀꢄ is the resistance 1 to determine the 푉퐷퐸푆퐴푇, 푉퐶퐶2푀퐼푁 and 푡퐵퐿퐴푁퐾
ꢀꢍ is the resistance 2 to determine the 푉퐷퐸푆퐴푇, 푉퐶퐶2푀퐼푁 and 푡퐵퐿퐴푁퐾
ꢀꢁ is the resistance 3 to determine the 푉퐷퐸푆퐴푇, 푉퐶퐶2푀퐼푁 and 푡퐵퐿퐴푁퐾
.
.
.
ꢂ퐵퐿퐴푁퐾 is the capacitance to determine the 푡퐵퐿퐴푁퐾
.
Reference Value
R2
VDESAT
R1
R3
4.0 V
4.5 V
5.0 V
5.5 V
6.0 V
6.5 V
7.0 V
7.5 V
8.0 V
8.5 V
9.0 V
9.5 V
10.0 V
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
15 kΩ
39 kΩ
6.8 kΩ
6.8 kΩ
5.1 kΩ
5.1 kΩ
5.1 kΩ
6.8 kΩ
6.8 kΩ
7.5 kΩ
8.2 kΩ
6.8 kΩ
10 kΩ
6.8 kΩ
9.1 kΩ
43 kΩ
36 kΩ
39 kΩ
43 kΩ
62 kΩ
68 kΩ
82 kΩ
91 kΩ
82 kΩ
130 kΩ
91 kΩ
130 kΩ
Figure 59. Block Diagram for DESAT
25/35
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