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42754G

Low Dropout Linear Fixed Voltage Regulator

Infineon Technologies 

TLE42754

Block Description and Electrical Characteristics

5

Block Description and Electrical Characteristics

5.1

Voltage Regulator

The output voltage VQ 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 CQ, 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 8 have to be maintained. For details see also the typical performance graph “Output Capacitor

Series Resistor ESR(CQ) versus Output Current IQ” on Page 13. As the output capacitor also has to buffer load

steps it should be sized according to the application’s needs.

An input capacitor CI is strongly recommended to compensate line influences. Connect the capacitors close to the

component’s terminals.

A protection circuitry prevent 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 VI = 28 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 TLE42754 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

II

I

Saturation Control

Current Limitation

CI

Te m p e r a tu r e

S hutdown

BlockDiagram_VoltageRegulator.vsd

Figure 4 Voltage Regulator

Re g u la te d

Q

IQ

Output Voltage

Bandgap

Re fe r e n ce

GND

} C

ESR

CQ

L OA D

Data Sheet

10

Rev. 1.2, 2014-07-03

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