MB39A214APFT-G-JNERE1 Datasheet, PDF (13/56 Pages) Fujitsu Component Limited. – 2ch DC/DC converter IC with PFM/ PWM synchronous rectification

MB39A214A
„ FUNCTION
Bottom detection comparator system for low output voltage ripple
The bottom detection comparator system for low output voltage ripple determines the ON time (t_ON) using
the input voltage (V_IN) and output voltage (V_OUT) to hold the ON state to a specified period. During the OFF
period, the reference voltage (INTREF) is compared with the feedback voltage (FB) using the error
comparator (Error Comp.). When the feedback voltage (FB) is below the reference voltage (INTREF) ,
RS-FF is set and the ON period starts again. Switching is repeated as described above. Error Comp. is used
to compare the reference voltage (INTREF) with the feedback voltage (FB) to control the off-duty condition
in order to stabilize the output voltage.
This system adds the inductor current slope detected during the synchronous rectification period (t_OFF) to
the reference voltage (INTREF) , and generates an output voltage slope during the OFF period, which is
essential for the bottom detection comparator system, in the IC. This enables the stable control operations
under the low output voltage ripple conditions.
y Circuit diagram
VOUT VIN
Bias
Reg.
tON
generator
tON
<Error Comp.>
FB
-
INTREF ₊
RS-FF
R Q ^{RS out}
S
Drive
Logic
+
-
VREF
Slope
Detector
Hi-side
Drive
DRVH
Bias
Lo-side
Drive
DRVL
y Waveforms
DRVH
IL
tON
tOFF
FB
INTREF
VIN
IL
t
VOUT
DS405-00007-1v0-E
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