MLX16305 Datasheet, PDF (18/29 Pages) Melexis Microelectronic Systems – Interlock switch sensor interface IC

MLX16305
Interlock switch sensor interface IC
12. Overcurrent Limitation
The MLX16305 has a built-in overcurrent limitation as protection against destruction and overheating. It
also allows detecting short circuits to Ground on any of the SENSE channels.
The voltage regulator will enter current limitation when the voltage over the external Rref
resistance (VRREF) is between VREF and VREF + 3V:
VREF < VRREF(limit activated) < VREF + 3V
The current limitation is realized by reducing the
forced output voltage on the SENSE pin
(VSENSE), until VRREF drops below the limitation
threshold.
The graph shows the trends of Isense (~VRREF)
and Vsense for an example where:
Vref = 5V and Rref=1kΩ.
As the Rsense ‘load’ drops from normal operating
range down to a short circuit condition Isense is
theoretically clamped between 40 and 80mA,
depending on Ioffset:
IsenselimMin = (VRef/Rref – (Ioffsetmax=1mA) )*10
IsenselimMax = (Vref+3)/Rref *10
Remark
• Under any condition, including during
current limitation it is guaranteed that
Vmeasout < Vref +0.5V
[mA]
90
80
70
60
50
40
30
20
10
0 _Current
limiting
[V]
6
5
4
IsenseMax
IsenseMin
3
VsenseMax
VsenseMin
2
1
Rsense
0
Operating range
The current limiting should also be taken into
account to set the minimum allowable operating [mA]
current.
50
Isense Limit (Vsup)
The graph on the right shows the minimum Isense
limits for Rref = 1kOhm for different values of
minimum Vsup:
• Zone c is due to the current limiting
• Zone d is due to Isense Max specification
o da: 30mA
o db: 40mA
o dc: 45mA
Remark that Zone c will shift to the right when
increasing Rref, and to the left with reducing Rref
2c
45
40
2b
35
1
8V
9V
30
12V
2a
16V
25
20V
20
Vref[V]
3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8
3901016305
Rev. 005
Page 18 of 29
Data Sheet
Oct/06