R1232D RICOH [RICOH electronics devices division], R1232D Datasheet - Page 11

• Manufacturer Part Number: R1232D
• Description: PWM STEP-DOWN DC/DC CONVERTER WITH SYNCHRONOUS RECTIFIER
• Manufacturer: RICOH [RICOH electronics devices division]

OUTPUT CURRENT AND SELECTION OF EXTERNAL COMPONENTS
are respectively described as R
In the continuous mode, when Equation 1 is solved for ton and assumed that the solution is tonc
When the ton=tonc, the mode is the continuous mode.
When P-channel Tr. of L
(Wherein, Ripple Current P-P value is described as I
When P-channel Tr. of L
Put Equation 4 to Equation 3 and solve for ON duty of P-channel transistor, Don=ton/(toff+ton),
Ripple Current is as follows;
wherein, peak current that flows through L, and L
Consider ILmax, condition of input and output and select external components.
The above explanation is directed to the calculation in an ideal case in continuous mode.
tonc=t×V
V
L×I
D
I
ILmax=I
RP
IN
ON
=(V
=V
RP
=(V
/toff=V
OUT
IN
OUT
−V
OUT
+(R
OUT
−R
OUT
+I
F
/V
ONP
+V
RP
ONN
−R
IN
/2 .......................................................................................................... Equation 7
+R
OUT
............................................................................................................. Equation 2
X
X
×I
ONP
is ON:
is "OFF"(N-channel Tr. is "ON"):
OUT
L
+R
)×I
×I
ONP
+R
OUT
ONN
OUT
L
−R
and R
×I
+L×I
×I
OUT
OUT
L
×I
RP
....................................................................................... Equation 4
)/(V
OUT
ONN
/ton .............................................................................. Equation 3
)×D
IN
, and the DC resistor of the inductor is described as R
+R
ON
ONN
/fosc/L .............................................................. Equation 6
×I
X
Tr. is as follows;
OUT
RP
−R
, ON resistance of P-channel Tr. and N-channel Tr. of L
ONP
×I
OUT
) ........................................... Equation 5
L
.)
R1232D
X
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