RT8073
Operation
The RT8073 is a current mode synchronous step-down
DC/DC converter with two integrated power MOSFETs. It
can deliver up to 6A output current from a 2.9V to 5.5V
input supply. The RT8073's current mode architecture
allows the transient response to be optimized over a wide
input voltage and load range. Cycle-by-cycle current limit
provides protection against shorted outputs and soft-start
eliminates input current surge during start-up.
Error Amplifier
The error amplifier adjusts COMP voltage by comparing
the feedback signal (V
FB
) from the output voltage with the
internal 0.8V reference. When the load current increases,
it causes a drop in the feedback voltage relative to the
reference, the COMP voltage then rises to allow higher
inductor current to match the load current.
Oscillator (OSC)
The frequency of the oscillator is adjustable by an external
resistor connected between the RT pin and GND. The
available switching frequency range is from 300kHz to
2MHz.
PGOOD Comparator
When the feedback voltage (V
FB
) rises above 94% or falls
below 106% of reference voltage, the PGOOD open drain
output will be high impedance. The PGOOD open drain
output will be internally pulled low when the feedback
voltage (V
FB
) falls below 90% or rises above 110% of
reference voltage.
Soft-Start (SS)
An internal current source charges an external capacitor
to build the soft-start ramp voltage (V
SS
). The V
FB
voltage
will track the V
SS
during soft-start interval. The chip will
use internal soft-start if the SS pin is floating. The nominal
internal soft-start time is 800μs.
Over Temperature Protection (OTP)
The RT8073 implements an internal over temperature
protection. When junction temperature is higher than
165°C, it will stop switching operation. Once the junction
temperature decreases below 145°C, the RT8073 will
automatically resume switching.
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8073-01
November 2012
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
