RT9068
4
DS9068-06 March 2017www.richtek.com
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Copyright 2017 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
Operation
The RT9068 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 50mA of output current with a maximum dropout
voltage of 300mV. Its 30μA 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 RT9068 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
RT9068's internal dividers are placed between SENSE and
GND and have a divider resistance of about 1MΩ.
Current Limit Protection
The RT9068 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 155°C (typ.). Once the junction
temperature cools down by approximately 5°C, the
regulator will automatically resume operation.
Reverse-Battery Protection
The RT9068 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 500Ω 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 RT9068 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 RT9068 SHDN input is an active-high input that turns
off the output transistor and reduces the quiescent current
to 2μA typical. Connect SHDN to a voltage below 0.6V for
normal operation.