AIC1845 ETC2 [List of Unclassifed Manufacturers], AIC1845 Datasheet - Page 10

• Manufacturer Part Number: AIC1845
• Description: Regulated 5V Charge Pump In SOT-23
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

Power Dissipation
When the duty cycle is 0.5, the power loss of
P
P
2. Package Size: A ceramic capacitor with
Table 1 lists the recommended components for
AIC1845 application.
Let’s consider the power dissipation of R
and ESR. Assume that the R
switching element in AIC1845 is equal and ESR
is the equivalent series resistance of C
Fig. 20 and Fig. 21). The approximation of the
power loss of R
Table.1 Bill of Material
Design-
R
ESR
C
C
DS
ator
C
OUT
FLY
−
IN
ON
large volume (0805), gets a lower ESR than
a small one (0603). Therefore, large devices
can improve more transient response than
small ones.
=
=
=
≅
=
=
=
=
I
I
≅
(
2
OUT
2
OUT
I
I
I
I
(
(
2D
2
ON
I
2
OUT
2
OUT
2
ON
0.22µ
2D
2I
IN
Type
I
Part
2.2µ
2.2µ
IN
2D
OUT
-
−
×
×
AVE
)
AVE
)
×
×
2
2
ESR
ESR
(
D(1
×
×
)
D
2
CELMK212BJ-
CELMK212BJ-
CEEMK212BJ
×
2
-224KG (X7R)
225MG (X5R)
225MG (X5R)
2R
Description
ESR
×
DS-ON
×
R
2R
2
-
ESR
2R
DS
DS
D)
×
×
DS
-
-
D
D(1
DS
ON
1
ON
×
×
−
ON
R
-
D
+
×
and ESR are given below:
)
ON
×
1
DS
+
-
D
I
×
D
+
2
OUT
I
D)
×
2
OUT
-
D
ON
+
(
+
D
1
I
Vendor
YUDEN
YUDEN
YUDEN
+
(
I
OUT
TAIYO
TAIYO
TAIYO
I
- 1
+
2
OFF
−
×
I
OUT
×
DS-ON
OFF
2
(
D
(
ESR
D
I
- 1
- 1
OUT
−
)
-
)
2
AVE
2
AVE
D
2
D
×
×
)
of each internal
R
2
×
2R
ESR
[phone]~9
[phone]~9
[phone]~9
×
×
×
DS
- 1
2R
2R
ESR
DS
-
1
ON
D
Phone
DS
FLY
-
DS
ON
×
)
−
-
(1
ON
×
ON
×
(ref to
DS-ON
(1
(1
−
×
×
D)
-
−
(1
(1
D)
D)
−
-
D)
D
)
switching element is
V
V
V
V
In fact, no matter the current is at on state or off
state, it decays exponentially rather than flows
steadily. And the root mean square value of
exponential decay is not equal to that of steady
flow. That is why the approximation comes from.
Let’s treat the charge pump circuit in another
approach and lay the focus on the flying capacitor
C
on state, the voltage across C
The average of V
Similarly, referring to Fig. 21, when the circuit is
at the off state, the voltage of C1 is:
The average of V
The difference of charge stored in C
state and off state is the net charge transferred to
the output in one cycle.
C
C
C
C
1
. Referring to Fig. 20, when the circuit is at the
-
−
-
−
ON
OFF
OFF
ON
V
(t)
P
−
OUT
(t)
−
AVE
V
R
AVE
DS
=
OUT
P
=
−
ESR
V
ON
−
=
IN
=
V
−
=
V
≅
IN
−
=
≅
IN
I
V
I
2
OUT
2
OUT
2R
I
IN
+
I
2
OUT
2
OUT
−
C1
C1
2R
2R
+
DS
×
×
during the on state is:
……………………………(11)
2R
during the off state is:
×
×
−
……………………….(10)
DS
8R
DS
0.5(1
ON
4ESR
ESR
−
DS
−
ON
DS
ON
×
-
ON
I
−
2
ON
−
×
ON
×
×
I
0.5)
I
OFF
0.5(1
×
(t)
ON
1
………………..(12)
I
OFF
is:
-
−
−
ESR
AVE
×
AVE
AIC1845
1
−
R
(t)
0.5)
DS
..........
1
−
+
+
×
between on
ESR
ESR
-
ESR
I
ON
ON
(t)
(7)
×
×
×
I
I
…(9)
ON
I
OFF
10
OFF
−
−
AVE
(t)
AVE