tle4678 Infineon Technologies Corporation, tle4678 Datasheet - Page 16

• Manufacturer Part Number: tle4678
• Description: Low Drop Out Linear Voltage Regulator 5 V Fixed Output Voltage
• Manufacturer: Infineon Technologies Corporation

Reset Reaction Time
In case the output voltage of the regulator drops below the output undervoltage lower reset threshold
delay capacitor
threshold
Additionally to the delay capacitor discharge time
reaction rime
with
•
•
•
Reset Ouput “RO”
The reset output “RO” is an open collector output with an integrated pull-up resistor. In case a lower-ohmic “RO”
signal is desired, an external pull-up resistor to the output “Q” can be connected. Since the maximum “RO” sink
current is limited, the optional external resistor
Reset Output “RO” Low for
In case of an undervoltage reset condition reset output “RO” is held “low” for
is 0 V. This is achieved by supplying the reset circuit from the output capacitor.
Reset Adjust Function
The undervoltage reset switching threshold can be adjusted according to the application’s needs by connecting
an external voltage divider (
GND. The reset adjustment range is given in
When dimensioning the voltage divider, take into consideration that there will be an additional current constantly
flowing through the resistors.
with
•
•
•
Datasheet
t
t
t
typical performance graphs.
V
R
V
rr,total
rr,int
rr,d
RT,new
ADJ,1
RADJ,th
t
With a voltage divider connected, the reset switching threshold
V
: Delay capacitor discharge time. For a capacitor
rr,total
: Internal reset reaction time; see
RADJ,th
: Total reset reaction time
,
V
: Desired reset switching threshold.
R
: Reset adjust switching threshold given in
DST,lo
ADJ,2
=
t
t
rr,total
rr,int
C
, the reset output “RO” will be set to “low”.
(
: Resistors of the external voltage divider, see
R
D
+
ADJ,1
is discharged rapidly. Once the delay capacitor’s voltage has reached the lower delay switching
becomes:
t
rr,d
+
R
ADJ,2
R
ADJ1
V
) /
Q
,
R
R
ADJ,2
1 V
ADJ2
) at pin “RADJ”. For selecting the default threshold connect pin “RADJ” to
Item
Item
7.2.16.
R
RO,ext
t
rr,d
7.2.6.
, an internal reaction time
Item
must not below as specified in
16
C
D
7.2.5.
different from the value specified in
Figure
V
6.
RT,new
V
is calculated as follows
Q
t
rr,int
1 V, even if the input voltage
applies. Hence, the total reset
Item
7.2.8.
Rev. 1.0, 2008-07-31
Item
Reset Function
7.2.17, see
V
TLE4678
RT,new
V
RT,lo
, the
=
(3)
(4)
V
I