Data Sheet

8

Rev. 1.0, 2014-03-13

TLF4277-2

Voltage Regulator

5

Voltage Regulator

5.1

Description Voltage Regulator

The output voltage

V

driving a PNP pass transistor accordingly. The control loop stability depends on the output capacitor

C

capacitor ESR, the load current and the chip temperature. To ensure stable operation, the output capacitor’s

capacitance and its equivalent series resistor ESR requirements given in the Table 2 “Functional Range” on

Page 7 have to be maintained. For stability details please refer to the typical performance graph “Output Capacitor

Series Resistivity

ESR

transients.

An input capacitor

C

Connect the capacitors close to the IC terminals. In general a buffered supply voltage is recommended for the

device. For details see Chapter 9.1.

Protection circuitry prevents the IC as well as the application from destruction in case of catastrophic events. The

integrated safeguards consist of 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,

an integrated safe operation monitor lowers the maximum output current 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 a cycling behavior 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 lifetime.

The TLF4277-2 allows a negative supply voltage. However, several small currents are flowing into the IC

increasing its junction temperature. This reverse current 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

Bandgap

Reference

GND

Q

I

Supply

Regulated

Output Voltage

ADJ

CSO

Load

E.g.

Antenna

Amplitfier

ST

C

ESR

EN

Saturation Control

Current Limitation

Temperature

Shutdown