TLE6389_07 Datasheet, PDF (29/38 Pages) Infineon Technologies AG – Step-Down DC/DC Controller

TLE 6389
7.4
SI_Enable
Connecting SI_ENABLE to 5V causes SI_GND to have low impedance. Thus the SI
comparator is in operation and can be used to monitor the battery voltage. SO output
signal is valid. Connecting SI_ENABLE to GND causes SI_GND to have high
impedance. Thus the SI comparator is not able to monitor the battery voltage. SO output
signal is invalid.
7.5
Battery sense comparator - voltage divider
The formula to calculate the resistor divider for the sense comparator is basically the
same as for the feedback divider in section before. With the selected resistor R_SI2, the
desired threshold of the input voltage V_{IN, UV} and the lower sense threshold V_{SI, low} the
resistor R_SI1 is given to:
R_SI1
=
R_SI2
⋅


V-----_{I--N---,---U---V--}
V_{SI, low}
–
1_
For high accuracy and low ohmic resistor divider values the On-resistance of the
SI_GND NMOS (typ. 100Ω) has to be added to R_SI2.
7.6
Undervoltage reset - delay time
The diagram below shows the typical behavior of the reset output in dependency on the
input voltage V_IN, the output voltage V_VOUT or V_FB.
Datasheet Rev. 2.1
29
2007-08-13