DS6203B Datasheet, PDF (5/22 Pages) Richtek Technology Corporation – 5A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter with VID Control

RT6203B
Shutdown, Start-Up and Enable (EN)
The enable input (EN) has a logic-low level of 0.4V. When
V_EN is below this level the IC enters shutdown mode and
supply current drops to less than 10μA. When V_EN exceeds
its logic-high level of 2V the IC is fully operational. Unlike
many competing devices, EN is a high voltage input that
can be safely connected to V_IN (up to 18V) for automatic
start-up.
Input Under-Voltage Lockout
In addition to the enable function, the RT6203B feature an
Under-Voltage Lockout (UVLO) function that monitors the
internal linear regulator output (PVCC). To prevent
operation without fully-enhanced internal MOSFET
switches, this function inhibits switching when V_CC drops
below the UVLO falling threshold. The IC resumes
switching when V_CC exceeds the UVLO rising threshold.
Soft-Start (SS)
The RT6203B soft-start uses an external pin (SS) to clamp
the output voltage and allow it to slowly rise. After V_EN is
high and V_IN exceeds its UVLO threshold, the IC begins
to source 6μA from the SS pin. An external capacitor at
SS is used to adjust the soft-start timing. Following below
equation to get the minimum capacitance range in order
to avoid UV occurs.
t=
C_OUT  V_OUT  0.75 1.2
I_LIM  Load Current  0.8
C_SS

t  6A
V_REF
Do not leave SS unconnected. During start-up the SS
capacitor is charged and the RT6203B operates in
discontinuous switching mode with very small pulses. This
prevents negative inductor currents and keeps the circuit
from sinking current. Therefore, the output voltage may
be pre-biased to some positive level before start-up. Once
the V_SS ramp charges enough to raise the internal reference
above the feedback voltage, switching will begin and the
output voltage will smoothly rise from the pre-biased level
to its regulated level. After V_SS rises above about 2.2V
output over- and under-voltage protections are enabled and
the RT6203B begins continuous-switching operation.
Internal Regulator (PVCC)
An internal linear regulator (PVCC) produces a 5V supply
from V_IN. The 5V power supplies the internal control circuit,
such as internal gate drivers, PWM logic, reference, analog
circuitry, and other blocks. 1μF ceramic capacitor for
decoupling and stability is required.
Over-Temperature Protection
The RT6203B includes an Over-Temperature Protection
(OTP) circuitry to prevent overheating due to excessive
power dissipation. The OTP will shut down switching
operation when the junction temperature exceeds 150°C.
Once the junction temperature cools down by
approximately 20°C the IC will resume normal operation
with a complete soft-start. For continuous operation,
provide adequate cooling so that the junction temperature
does not exceed 150°C.
Copyright ©2016 Richtek Technology Corporation. All rights reserved.
DS6203B-00 September 2016
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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