MIC2009YM6-TR Datasheet, PDF (23/30 Pages) Micrel Semiconductor – Fixed and Adjustable Current Limiting Power Distribution Switches

Micrel, Inc.
Application Information
Setting I_LIMIT
The MIC2009/2019’s current limit is user programmable
and controlled by a resistor connected between the
I_LIMIT pin and GND. The value of this resistor is
determined by the following equation:
I_LIMIT
=
CurrentLimitFactor(CLF)
R _SET
or
R _SET
=
CurrentLimitFactor(CLF)
I_LIMIT (A)
For example: Set I_LIMIT = 1.25A
Looking in the Electrical specifications we will find CLF
at I_LIMIT = 1A.
Min
Typ
Max
Units
190
243
293
V
Table 1. CLF at I_LIMIT = 1A
For the sake of this example, we will say the typical
value of CLF at an I_OUT of 1A is 243V. Applying the
equation above:
R_SET (Ω) =
243V
1.25A
= 194.4Ω
R_SET = 196Ω
(the closest standard 1% value)
Designers should be aware that variations in the
measured I_LIMIT for a given R_SET resistor, will occur
because of small differences between individual ICs
(inherent in silicon processing) resulting in a spread of
I_LIMIT values. In the example above we used the typical
value of CLF to calculate R_SET. We can determine
I_LIMIT’s spread by using the minimum and maximum
values of CLF and the calculated value of R_SET.
I_{LIMIT_MIN}
=
190V
196Ω
=
0.97A
I_{LIMIT_MAX}
=
293V
196Ω
= 1.5A
MIC20xx Family
Giving us a maximum I_LIMIT variation over temperature
of:
I_{LIMIT_MIN}
0.97A (-22%)
I_{LIMIT_TYP}
1.25A
I_{LIMIT_MAX}
1.5A (+20%)
I_OUT
0.1A
0.2A
0.3A
0.4A
0.5A
0.6A
0.7A
0.8A
0.9A
R_SET
1928Ω
993Ω
673Ω
511Ω
413Ω
346Ω
299Ω
263Ω
235Ω
I_{LIMIT_MIN}
0.063A
0.137A
0.216A
0.296A
0.379A
0.463A
0.548A
0.634A
0.722A
I_{LIMIT_MAX}
0.136A
0.265A
0.391A
0.515A
0.637A
0.759A
0.880A
1.001A
1.121A
Table 2. MIC20x9A R_SET Table
I_OUT
0.2A
0.3A
0.4A
0.5A
0.6A
0.7A
0.8A
0.9A
1A
1.1A
1.2A
1.3A
1.4A
1.5A
R_SET
1125Ω
765Ω
582Ω
470Ω
395Ω
341Ω
300Ω
268Ω
243Ω
222Ω
204Ω
189Ω
176Ω
165Ω
I_{LIMIT_MIN}
0.127A
0.202A
0.281A
0.361A
0.443A
0.526A
0.610A
0.695A
0.781A
0.868A
0.956A
1.044A
1.133A
1.222A
I_{LIMIT_MAX}
0.267A
0.390A
0.510A
0.629A
0.746A
0.861A
0.976A
1.089A
1.202A
1.314A
1.426A
1.537A
1.647A
1.757A
Table 3. MIC20x9 R_SET Table
August 2011
23
M9999-080211-D