RT9074 datasheet(4/16 Pages) RICHTEK

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RT9074

DS9074-01

December 2014

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Operation

The RT9074 is a high input-voltage linear regulator

specifically designed to minimize external components.

The input voltage range is from 4.5V to 60V. The device

supplies 100mA of output current with a maximum dropout

voltage of 300mV. Its 30

μA quiescent and 2μA shutdown

currents make it ideal for use in battery-powered

applications. Unlike many PNP LDO regulators, ground

current does not increase much in dropout conditions.

Output Transistor

The RT9074 includes a built-in PNP output transistor

configured for low dropout voltage. The output transistor

blocks reverse current if the output voltage is held higher

than the input voltage (such as in battery-backup

applications) so no additional output blocking diode is

needed.

Error Amplifier

The Error Amplifier compares the output feedback voltage

from an internal feedback voltage divider (fixed output

versions) or FB (adjustable output versions) to an internal

reference voltage and controls the PNP output transistor's

base current to maintain output voltage regulation. The

RT9074's internal dividers are placed between SENSE and

GND and have a divider resistance of about 1M

Ω.

Current Limit Protection

The RT9074 provides a current limit function to prevent

damage during output over-load or shorted-circuit

conditions. The output current is detected by an internal

current-sense transistor.

Over-Temperature Protection

The over temperature protection function will turn off the

PNP output transistor when the internal junction

temperature exceeds 150

°C (typ.). Once the junction

temperature cools down by approximately 20

°C, the

regulator will automatically resume operation.

Reverse-Battery Protection

The RT9074 inputs (VIN and SHDN) can withstand reverse

voltages as high as

−60V. Both the IC and the load are

protected, as long as the load impedance is 500

Ω or less.

In these conditions, the output voltage is guaranteed to

be no more negative than

−1V with the maximum negative

input voltage. In battery-powered applications, no

additional protection against battery reversal is typically

needed.

Reverse-Output Protection

The RT9074 protects against current flow to the input (VIN)

when the output voltage exceeds VIN. This simplifies

battery and capacitive

“keep-alive” circuits since they

need no additional output blocking diode.

Shutdown Input (8 Pin Versions)

The RT9074 SHDN input is an active-high input that turns

off the output transistor and reduces the quiescent current

to 2

μA typical. Connect SHDN to a voltage below 0.6V for

normal operation.

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