TLE4678-2

Voltage Regulator

Data Sheet

9

Rev. 1.0, 2014-03-03

5

Voltage Regulator

5.1

Description Voltage Regulator

The output voltage

V

transistor accordingly. Saturation control as a function of the load current prevents any oversaturation of the pass

element. The control loop stability depends on the output capacitor

C

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 chapter Chapter 4.2 have to be maintained. For

details see also the typical performance graph “Output Capacitor Series Resistor

ESR

Also, the output capacitor shall be sized to buffer load transients.

An input capacitor

C

Connect the capacitors close to the IC terminals.

Protection circuitry prevent the IC as well as the application from destruction in case of catastrophic events. These

safeguards contain output current limitation, reverse polarity protection as well as 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

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 behavior of the output voltage until the fault is removed. However, a junction

temperature above 150 °C is outside the maximum rating and therefore reduces the IC lifetime.

The TLE4678-2 allows a negative supply voltage. However, several 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 condition.

Figure 3

Block Diagram Voltage Regulator Circuit

Figure 4

Output Voltage vs. Input Voltage

C

ESR

Bandgap

Reference

GND

Q

I

BlockDiagram_VoltageRegulator.vsd

Saturation Control

Current Limitation

Temperature

Shutdown

LOAD

Supply

Regulated

Output Voltage

V

t

Diagram_Output-InputVoltage.svg

V

Q,nom

V

I

V

dr

V

Q

d

V

Q

d

t

I

load

d

V

Q

d

t

≈

I

I

load

≈

V

I(ext),min