RT6206B
Output Voltage Setting
Latch off Mode UVP
The resistive divider allows the FB pin to sense the output
voltage as shown in Figure 4.
The Latch off Under-Voltage Protection (UVP) function is
provided for the TSSOP-14 (Exposed Pad) package. When
the protection function is triggered, the IC will shutdown
in Latch-Off Mode. The IC stops switching, leaving both
switches open, and is latched off. To restart operation,
toggle EN or power the IC off and then on again.
V
OUT
R1
FB
RT6206B
R2
Inductor Selection
GND
The inductor value and operating frequency determine the
ripple current according to a specific input and an output
voltage. The ripple current ΔIL increases with higher VIN
and decreases with higher inductance.
Figure 4. Output Voltage Setting
The output voltage is set by an external resistive divider
according to the following equation. It is recommended to
V
f L
VOUT
V
IN
OUT
1
IL =
use 1% tolerance or better divider resistors.
R1
VOUT = 0.765(1
)
Having a lower ripple current reduces not only the ESR
losses in the output capacitors but also the output voltage
ripple. High frequency with small ripple current can achieve
highest efficiency operation. However, it requires a large
inductor to achieve this goal. For the ripple current
selection, the value of ΔIL = 0.2(IMAX) will be a reasonable
starting point. The largest ripple current occurs at the
highest VIN. To guarantee that the ripple current stays
below the specified maximum, the inductor value should
be chosen according to the following equation :
R2
Under-Voltage Lockout Protection
The RT6206B has Under-Voltage Lockout Protection
(UVLO) that monitors the voltage of VIN pin. When the
VIN voltage is lower than UVLO threshold voltage, the
RT6206B will be turned off in this state. This is non-latch
protection.
Over-Temperature Protection
V
f I
V
OUT
V
IN(MAX)
OUT
The RT6206B equips an Over-Temperature Protection
(OTP) circuitry to prevent overheating due to excessive
power dissipation. The OTP will shut down switching
operation when junction temperature exceeds 150°C.
Once the junction temperature cools down by
approximately 25°C the main converter will resume
operation. To keep operating at maximum, the junction
temperature should be prevented from rising above 150°C.
L =
1
L(MAX)
Input and Output Capacitors Selection
The input capacitance, CIN, is needed to filter the
trapezoidal current at the source of the high-side MOSFET.
Alow ESR input capacitor with larger ripple current rating
should be used for the maximum RMS current. The RMS
current is given by :
Hiccup Mode UVP
V
V
V
IN
V
OUT
OUT
I
= I
1
RMS
OUT(MAX)
IN
AHiccup Mode Under-Voltage Protection (UVP) function
is provided for the SOP-8 (Exposed Pad) and WDFN-10L
3x3 packages. When the FB voltage drops below half of
the feedback reference voltage, VFB, the UVP function
will be triggered and the RT6206B will shut down for a
period of time before recovering automatically. The Hiccup
Mode UVP can reduce input current in short-circuit
conditions.
This formula has a maximum at VIN = 2VOUT, where
IRMS = IOUT / 2. This simple worst-case condition is
commonly used for design because even significant
deviations do not offer much relief.
Choose a capacitor rated at a higher temperature than
required. Several capacitors may also be paralleled to
meet size or height requirements in the design. For the
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is a registered trademark of Richtek Technology Corporation.
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12
DS6206B-02 March 2017
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
