MB39A214APFT-G-JNERE1 Datasheet, PDF (29/56 Pages) Fujitsu Component Limited. – 2ch DC/DC converter IC with PFM/ PWM synchronous rectification

MB39A214A
Setting switching frequency
The switching frequency is set at the FREQ pin. As for the setting process, see the switching frequency
control function table.
Setting over current limitation
The over current limitation value can be set by adjusting the over current limitation setting resistor value
connected to the ILIM pin.
Calculate the resistor value by the following formula.
R_LIM =
10⁶
¯
R_{ON_Sync} ¯ (I_LIM −
ΔI_L
2
)
R_LIM
I_LIM
ΔI_L
R_{ON_Sync}
: Over current limitation value setting resistor [Ω]
: Over current limitation value [A]
: Ripple current peak-to-peak value of inductor [A]
: ON resistance of low-side FET [Ω]
RLIM
ILIM
Inductor current
ILIM
ΔIL
Over current
limitation value
IOUT
0
Time
If the rate of inductor saturation current is small, the inductor value decreases and the ripple current of
inductor increase when the over-current flows. At that time there is a possibility that the limited output
current increases or is not limited, because the bottom of inductor current is detected. It is necessary to use
the inductor that has enough large rate of inductor saturation current to prevent the overlap current.
DS405-00007-1v0-E
29