Application Note
27 of 53
V 1.0
2019-04-01
IM393 Application note
IM393 IPM Technical Description
Function and protection circuit
Table 12
Minimum R
SH
and P
SH
Product
Maximum peak current
Minimum shunt resistance,
R
SH
Minimum shunt resistor
power, P
SH
IM393-X6E/F
30 A
16 m
Ω
3 W
IM393-L6E/F
22.5 A
22 m
Ω
2 W
IM393-M6E/F
15 A
33 m
Ω
1.5 W
IM393-S6E/F
9 A
54 m
Ω
1 W
5.1.3
Delay time
The RC filter is necessary in the over-current sensing circuit to prevent malfunction of OC protection caused by
noise. The RC time constant is determined by applying time of noise and the withstand time capability of IGBT.
When the sensing voltage on the shunt resistor exceeds I
TRIP
positive-going threshold (V
IT,TH+
), this voltage is
applied to the ITRIP pin of the IM393-XX via the RC filter. Table 13 shows the specification of the OC protection
reference level. The filter delay time (T
FILTER
) is caused by RC filter time constant, and the input voltage of I
TRIP
pin
rises to the I
TRIP
positive threshold voltage during T
FILTER
.
In addition there is the shutdown propagation delay of I
TRIP
. Please refer to Table 14.
Table 13
Specification of OC protection reference level ‘V
IT,TH+
’
Item
Min.
Typ.
Max.
Unit
I
TRIP
positive going threshold V
IT,TH+
0.44
0.49
0.54
V
Table 14
Internal delay time of OC protection circuit
Item
Condition
Min.
Typ.
Max.
Unit
Shut down
propagation
delay (T
ITRIP
)
IM393-X6E/F
I
out
= 10 A, from V
IT,TH+
to 10 % I
out
-
-
1.5
μs
IM393-L6E/F
I
out
= 7.5 A, from V
IT,TH+
to 10 % I
out
-
-
1.5
μs
IM393-M6E/F
I
out
= 5 A, from V
IT,TH+
to 10 % I
out
-
-
1.5
μs
IM393-S6E/F
I
out
= 3 A, from V
IT,TH+
to 10 % I
out
-
-
1.5
μs
Therefore the total time from over-current event to shut down of all six IGBTs is:
T
TOTAL
= T
FILTER
+ T
ITRIP
(3)
Shut-down propagation delay is inversely proportional to the current range; therefore the T
ITRIP
is reduced at
higher current conditions than those in Table 14. The recommended total delay is less than the 3 μs of safety
operation. Thus, the RC time constant should be set in the range of 1~1.5 µs. Recommended values for the filter
components are R = 1.5 k
Ω
and C = 1 nF.
5.2
Fault output and auto-clear function
As described in the previous section, in the event of an over-current, the RFE pin will get low as the I
TRIP
pin gets
high when the open-drain MOSFET is turned on. When over-current conditions end, the open-drain MOSFET will
be turned off, as illustrated in Figure 18. However, all IGBTs will remain off until RFE voltage can reach a positive-
going threshold. This is called the fault auto-clear function, and is shown as T
FLT-CLR
in Figure 19.
