Datasheet

TLE42794
Block Description and Electrical Characteristics
Data Sheet 18 Rev. 1.1, 2008-10-09
Reset Output Pull-Up Resistor
R
RO
:
The Reset Output RO is an open collector output requiring an external pull-up resistor. In Table “Electrical
Characteristics Reset Function” on Page 20 a minimum value for the external resistor
R
RO
is given. Keep in
mind to stay within the values specified for the Reset Output RO in Table 4.1 “Absolute Maximum Ratings” on
Page 8
Reset Adjust Function
The undervoltage reset switching threshold can be adjusted according to the application’s needs by connecting
an external voltage divider (
R
ADJ1
, R
ADJ2
) at pin RADJ. For selecting the default threshold connect pin RADJ to
GND.
When dimensioning the voltage divider, take into consideration that there will be an additional current constantly
flowing through the resistors.
With a voltage divider connected, the reset switching threshold
V
RT,new
is calculated as follows:
with
•
V
RT,new
: the desired new reset switching threshold
•
R
ADJ1
, R
ADJ2
: resistors of the external voltage divider
•
V
RADJ,th
: reset adjust switching threshold given in Table “Electrical Characteristics Reset Function” on
Page 20
Figure 6 Block Diagram Reset Function
V
RT new,
R
ADJ 1,
R+
ADJ 2,
R
ADJ 2,
------------------------------------------
V
RADJ th,
×=
GND
QI
BlockDiagram_ResetAdjust.vsd
OR
Supply
RO
V
DST
Int.
Supply
I
D,ch
I
D,dch
V
RADJ,t h
RADJ
Control
D
C
D
Reset
optional
C
Q
VDD
Micro-
Controller
GND
R
ADJ,1
R
ADJ,2
I
RO
I
RADJ
R
RO