MIC2017 Micrel Semiconductor, MIC2017 Datasheet - Page 13

• Manufacturer Part Number: MIC2017
• Description: (MIC2007 / MIC2017) Adjustable Current Limit Power Distribution Switch
• Manufacturer: Micrel Semiconductor

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Micrel
Application Information
Setting I
The MIC2007/2017’s current limit is user programmable
and controlled by a resistor connected between the I
pin and Ground. The value of this resistor is determined
by the following equation:
or
Example:
Looking in the Electrical specifications we will find CLF
at I
the typical value of CLF at an I
Applying the equation above:
Designers should be aware that variations in the
measured I
because of small differences between individual ICs
(inherent in silicon processing) resulting in a spread of
I
value of CLF to calculate R
spread by using the minimum and maximum values of
CLF and the calculated value of R
October 2005
LIMIT
LIMIT
values. In the example above we used the typical
= 1A. For the sake of this example, we will say
LIMIT
R
I
LIMIT
LIMIT
SET
(the closest standard 1% value)
(Ω) = Current Limit Factor (V)
I
I
Set I
= Current Limit Factor (CLF)
LIMIT_MIN
LIMIT_MIN
for a given R
R
LIMIT
SET
R
R
SET
SET
(Ω) = 235 V
= 210V = 1.12A
= 260V = 1.39A
= 1.25A
I
LIMIT
187Ω
= 188 Ω
= 187 Ω
187Ω
SET
R
SET
. We can determine I
1.25 A
(A)
SET
SET
OUT
resistor, will occur
.
of 1A is 235V.
LIMIT
LIMIT
’s
13
Giving us a maximum I
of:
or
I
The
designed to act as a constant current source to the load.
As the load tries to pull more than the allotted current,
V
increases. When V
I
power supply and to limit internal heating of the
MIC2007/2017.
When measuring I
dependence in mind. Otherwise, the measurement data
may appear to indicate a problem when none really
exists. This voltage dependence is illustrated in Figures
4 and 5.
In Figure 4, output current is measured as V
below V
below V
remains constant throughout the remainder of the test.
In Figure 5, this test is repeated but with V
exceeding 1V.
When V
limiting circuitry responds by decreasing I
seen in Figure 5. In this demonstration, V
controlled and I
applications, V
Ohm’s law by the load and the limiting current.
LIMIT
LIMIT
OUT
vs. I
to reduce the drain of fault current on the system’s
drops and the input to output voltage differential
MIC2007/2017’s
IN
IN
IN
OUT
, with the test terminating when V
I
.
LIMIT_MIN
1.12A
- V
measured
Observe that once I
OUT
OUT
OUT
OUT
IN
> 1V, the MIC2007/2017’s current
is the measured quantity. In real life
is determined in accordance with
1.25A ±11%
-V
I
it is important to bear this voltage
LIMIT
LIMIT_TYP
OUT
1.25A
current
exceeds 1V, I
variation over temperature
I
limiting
LIMIT_MAX
LIMIT
1.39A
MIC2007/MIC2017
is reached I
OUT
OUT
M9999-102805
OUT
drops below
OUT
circuitry
, as can be
OUT
IN
is pulled
is being
- V
is 1V
OUT
OUT
is