TS4270 datasheet(3/9 Pages) TSC

3 / 9 page

Preliminary

TS4270

5V Ultra Low Dropout Fixed Voltage Regulator

3/9

Version: A07

Block Diagram

Application Description

The IC regulates an input voltage in the range of 5.5V < VI <36V to VOnom = 5.0V Up to 26V it produces a regulated

output current of more than 550mA. Above 26V the save-operating-area protection allows operation up to 36V with a

regulated output current of more than 300mA. Over voltage protection limits operation at 42V. The over voltage

protection hysteresis restores operation if the input voltage has dropped below 36V. A reset signal is generated for an

output voltage of VO<4.5V. The delay for power-on reset can be set externally with a capacitor.

Design Notes for External Components

An input capacitor CI is necessary for compensation of line influences. The resonant circuit consisting of lead

inductance and input capacitance can be damped by a resistor of approx.1Ω Win series with CI. An output capacitor CO

is necessary for the stability of the regulating circuit. Stability is guaranteed at values of CO ≥ 22uF and ESR of < 3Ω.

Circuit Description

The control amplifier compares a reference voltage, which is kept highly accurate by resistance adjustment, to a

voltage that is proportional to the output voltage and drives the base of a series transistor via a buffer. Saturation

control as a function of the load current prevents any over-saturation of the power element. If the output voltage

decreases below 4.5V, an external capacitor CD on pin 4 (Reset Delay) will be discharged by the reset generator. If the

voltage on this capacitor drops below VDLR, a reset signal is generated on pin 2 (Reset Output), i.e. reset output is set

low. If the output voltage rises above 4.5V, CD will be charged with constant current. After the power-on-reset time the

voltage on the capacitor reaches VDU and the reset output will be set high again. The value of the power-on-reset time

can be set within a wide range depending of the capacitance of CD.

The IC also incorporate a number of internal circuits for protection against:

•

Overload

•

Over Voltage

•

Over temperature

•

Reverse Polarity

TS4270 Datasheet(PDF) 3 Page - Taiwan Semiconductor Company, Ltd