TLE42694-2 Datasheet, PDF (7/20 Pages) Infineon Technologies AG – Low Dropout Fixed Voltage Regulator

TLE42694-2
Block Description and Electrical Characteristics
4
Block Description and Electrical Characteristics
4.1
Voltage Regulator
The output voltage V_Q is controlled by comparing a portion of it to an internal reference and driving a PNP pass
transistor accordingly. The control loop stability depends on the output capacitor C_Q, the load current, the chip
temperature and the poles/zeros introduced by the integrated circuit. To ensure stable operation, the output
capacitor’s capacitance and its equivalent series resistor ESR requirements given in the table “Functional
Range” on Page 6 have to be maintained. For details see also the typical performance graph “Output Capacitor
Series Resistor ESR(CQ) versus Output Current IQ” on Page 10. As the output capacitor also has to buffer
load steps it should be sized according to the application’s needs.
An input capacitor C_I is strongly recommended to compensate line influences. Connect the capacitors close to the
component’s terminals.
A protection circuitry prevents the IC as well as the application from destruction in case of catastrophic events.
These safeguards contain an output current limitation, a reverse polarity protection as well as a thermal shutdown
in case of overtemperature.
In order to avoid excessive power dissipation that could never be handled by the pass element and the package,
the maximum output current is decreased at input voltages above V_I = 22 V.
The thermal shutdown circuit prevents the IC from immediate destruction under fault conditions (e.g. output
continuously short-circuited) by switching off the power stage. After the chip has cooled down, the regulator
restarts. This leads to an oscillatory behaviour of the output voltage until the fault is removed. However, junction
temperatures above 150 °C are outside the maximum ratings and therefore significantly reduce the IC’s lifetime.
The TLE42694-2 allows a negative supply voltage. In this fault condition, small currents are flowing into the IC,
increasing its junction temperature. This has to be considered for the thermal design, respecting that the thermal
protection circuit is not operating during reverse polarity conditions.
Supply
I_I
I
Saturation Control
Current Limitation
C_I
Temperature
Shutdown
BlockDiagram _VoltageRegulator .vsd
Figure 3 Voltage Regulator
Regulated
Q
IQ
Output Voltage
Bandgap
Reference
GND
CQ
LOAD
Data Sheet
7
Rev. 1.0, 2012-07-03