RT6258B/C
Operation
Overall
The RT6258B/C is an advanced constant on-time (ACOT
TM
)
mode synchronous buck converter. The main control loop
of the RT6258B/C using an ACOT
TM
Power Good
The power good output is an open drain output that requires
a pull-up resistor. PGOOD will be pulled high after soft-
start is over and the output reaches 90% of its set voltage.
There is a 10μs delay built into PGOOD circuitry to prevent
false transition.
mode control which
provides a very fast transient response.
Internal VCC Regulator
The RT6258B/C includes a 5V linear regulator (VCC). The
VCC regulator steps down input voltage to supply both
internal circuitry and gate drivers. Do not connect the VCC
pin to external loads.
LDO
The RT6258B/C includes a 3.3V/5V 100mA linear
regulators (LDO). When VOUT is higher than the switch
over threshold 3.1V (RT6258B) or 4.7V (RT6258C), an
automatic circuit will change the power source of linear
regulator from VIN path to VOUT path.
Soft-Start
The RT6258B/C provides an internal soft-start function to
prevent large inrush current and output voltage overshoot.
The typical soft-start duration is around 0.6ms.
Over-Current Limit
The RT6258B/C current limit is fixed 9A and it is a cycle-
by-cycle
“valley”
type, measuring the inductor current
through the synchronous rectifier during the off-time while
the inductor current ramps down. If output voltage drops
below the output under-voltage protection level, the
RT6258B/C will stop switching to avoid excessive heat.
Output Over-Voltage Protection (OVP) and Under-
Voltage Protection (UVP)
The RT6258B/C includes output over-voltage protection
(OVP) and output under-voltage protection (UVP). If the
output voltage rises above OVP threshold or drops below
UVP threshold for longer than 20μs (typical), the OVP or
UVP function is triggered.
Copyright
©
2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6258B/C-02
October 2019
www.richtek.com
5
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
