TDE1890V View Datasheet(PDF) - STMicroelectronics
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TDE1890V Datasheet PDF : 12 Pages
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TDE1890 - TDE1891
APPLICATION INFORMATION
DEMAGNETIZATION OF INDUCTIVE LOADS
An internal zener diode, limiting the voltage
across the Power MOS to between 50 and 60V
(Vcl), provides safe and fast demagnetization of
inductive loads without external clamping devices.
The maximum energy that can be absorbed from
an inductive load is specified as 1J (at
Tj = 85°C).
To define the maximum switching frequency three
points have to be considered:
1) The total power dissipation is the sum of the
On State Power and of the Demagnetization
Energy multiplied by the frequency.
2) The total energy W dissipated in the device
during a demagnetization cycle (figg. 2, 3) is:
W = Vcl
L
RL
[Io
–
Vcl – Vs
RL
log
1
+
Vs
Vcl – Vs
]
Where:
Vcl = clamp voltage;
L = inductive load;
RL = resistive load;
Vs = supply voltage;
IO = ILOAD
3) In normal conditions the operating Junction
temperature should remain below 125°C.
If the demagnetization energy exceeds the rated
value, an external clamp between output and +VS
must be externally connected (see fig. 5).
The external zener will be chosen with Vzener
value lower than the internal Vcl minimum rated
value and significantly (at least 10V) higher than
the voltage that is externally supplied to pin 10,
i.e. than the supply voltage.
Alternative circuit solutions can be implemented
to divert the demagnetization stress from the
TDE1890/1, if it exceeds 1J. In all cases it is rec-
ommended that at least 10V are available to de-
magnetize the load in the turn-off phase.
A clamping circuit connected between ground and
the output pin is not recommended. An interrup-
tion of the connection between the ground of the
load and the ground of the TDE1890/1 would
leave the TDE1890/1 alone to absorb the full
amount of the demagnetization energy.
Figure 2: Inductive Load Equivalent Circuit
5/12
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