R1215D002F RICOH [RICOH electronics devices division], R1215D002F Datasheet - Page 11

• Manufacturer Part Number: R1215D002F
• Description: STEP-UP DC/DC CONTOLLER
• Manufacturer: RICOH [RICOH electronics devices division]

continuous. The continuous current through the inductor is described as Iconst, then,
follows:
and external components should be selected.
components is not included. The actual maximum output current is between 50% and 80% of the calculation.
Especially, when the IL
for V
In the continuous mode, the deviation of the current is equal between on time and off time.
Further, the electric power, P
When I
In this moment, the peak current, ILxmax flowing through the inductor and the driver Tr. is described as
With the formula 4,6, and ILxmax is,
Therefore, peak current is more than I
In the formula 7, peak current ILxmax at discontinuous mode can be calculated. Put Iconst=0 in the formula.
The explanation above is based on the ideal calculation, and the loss caused by L
OUT
, Vf (as much as 0.3V) of the diode should be considered.
OUT
I
I
ILx
ILx
V
OUT
OUT
IN
becomes more than formula 5, the current flows through the inductor, then the mode becomes
max
max
=
=
=
t
f
f
ON
OSC
OSC
=
=
L /
×
×
Iconst
V
X
=
V
V
OUT
is large, or V
IN
IN
(
V
2
2
/
OUT
V
×
×
+
IN
t
t
V
ON
ON
−
AV
×
IN
2
2
V
I
is equal to output electric power, V
OUT
×
/
/
IN
{
{
t
2
2
)
ON
×
+
IN
×
×
L /
toff
L
L
V
is low, the loss of V
IN
×
×
OUT
...................................................................................... Formula 7
×
(
(
L /
V
V
. Considering the value of ILxmax, the condition of input and output,
t
ON
OUT
OUT
................................................................................ Formula 4
/(
−
−
2
V
V
×
IN
IN
) L
)
)
}
}
................................................................. Formula 8
+
=
V
V
IN
IN
IN
2
×
is generated with the on resistance of the switch. As
×
Iconst
t
ON
/(
2
OUT
/
V
×
OUT
L
× I
×
OUT
V
................................. Formula 6
OUT
, thus,
)
....................... Formula 5
X
switch and external
R1215D
11