TLF1963 Datasheet, PDF (19/24 Pages) Infineon Technologies AG – Low Dropout Linear Voltage Post Regulator

TLF1963
Application Information
6.2
Output Capacitance and Transient Response
The TLF1963 is designed to be stable with a wide range of output capacitors. The ESR of the output capacitor
affects stability, most notably with small capacitors. A minimum output capacitor of 10 µF with an ESR in the range
of 10 mΩ to 3 Ω is recommended to prevent oscillations. Larger values of output capacitance can decrease the
peak deviations and provide improved transient response for larger load current changes.
6.3
Overload Recovery
The TLF1963 has a safe operating area protection. The device protects itself by limiting the output current to a
maximum and prevent it self against destruction due to overload or short circuits conditions. In this cases the
current is limited and the resulting output voltage decreases according to the load down to 0V in a short circuit
condition.
The TLF1963 can supply the application for all input voltages between 2.5 V up to 20V with currents up to 1.5 A.
Of course it needs to be ensured, that the junction temperature stays within the operating range up to 150 °C. For
startup conditions with a high load current the TLF1963 is able to start up properly without exeeding the safe
operating area. Even imediatly after removal of a short circuit failure case the device is able to start if the load
current is very high. The characteristic of the current limitation can by seen in the typical perfomance graphs on
Page 15.
6.4
Output Voltage Noise
The TLF1963 has been designed to provide low output voltage noise over the 10 Hz to 100 kHz bandwidth while
operating at full load. Output voltage noise is typically 40 µV_RMS over this frequency bandwidth. For higher output
voltages (generated by using a resistor divider), the output voltage noise will be gained up accordingly.
Higher values of output voltage noise may be measured when care is not exercised with regards to circuit layout
and testing. Crosstalk from nearby traces can induce unwanted noise onto the output of the TLF1963. Power
supply ripple rejection must also be considered, because the TLF1963 does not have unlimited power supply
ripple rejection and will pass a small portion of the input noise through to the output.
6.5
Protection Features
The TLF1963 has several protection features which makes him ideal for use in battery-powered circuits. In addition
to the normal protection features associated with monolithic regulators, such as current limiting and thermal
limiting, the device is protected against reverse input voltages and reverse output voltages.
Current limit protection and thermal overload protection are intended to protect the device against current overload
conditions at the output of the device. For normal operation, the junction temperature should not exceed 150 °C.
The input of the device will withstand reverse voltages of 20 V. Current flow out of the device will be limited to less
than 2 mA in case of an input voltage of -20 V at the Input and no negative voltage will appear at the output. The
device will protect both itself and the load. This provides protection against batteries that can be plugged in
backward.
The output of the TLF1963 can be pulled below ground without damaging the device. If the input is left open circuit
or grounded, the output can be pulled below ground by 20 V. The output will act like an open circuit, no current
will flow out of the pin. If the input is powered by a voltage source, the output will source the short-circuit current
of the device and will protect itself by thermal limiting. In this case, grounding the EN pin will turn off the device
and stop the output from sourcing the short-circuit current.
The ADJ pin of the adjustable device can be pulled above or below ground by as much as 7 V without damaging
the device. If the input is left open circuit or grounded, the ADJ pin will act like an open circuit when pulled below
ground and like a resistor (typically 4 kΩ) in series with a diode when pulled above ground.
In situations where the ADJ pin is connected to a resistor divider that would pull the ADJ pin above its 7 V clamp
voltage if the output is pulled high, the ADJ pin input current must be limited to less than 5 mA. For example, a
resistor divider is used to provide a regulated 1.5V output from the 1.21 V reference when the output is forced to
Data Sheet
19
Rev. 1.0, 2012-11-08