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PDF AN020 Data sheet ( Hoja de datos )
| Número de pieza | AN020 | |
| Descripción | The Power Management of PDA | |
| Fabricantes | AIC | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AN020 (archivo pdf) en la parte inferior de esta página. Total 7 Páginas | ||
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AN020
The Power Management of PDA—The Application
of SEPIC Circuit
Introduction
The PDA (Personal Digital Assistant) appeals to an
increasing number of users because of its multifunction
such as: Wireless Communication, Organizer, Mobile
Phone, Handwriting Recognition, Web Access, Flash
Memory, and Data/fax Modem. The users can choose
their favorites among various brands according to their
individual requirement. And the efficiency and the
duration of the battery used in the products are critical
to the users.
From the designers’ point of view, the circuit for power
management becomes obviously substantial. Here
goes the block diagram of circuit in PDA.
Referred to Fig.1, it is easily seen that there are two
possible combinations for input.
One way is to combine 2 Ni-MH cells and a 6V adapter.
The combination causes the input voltage ranging from
1.8V to 2.6V. The other way is to put a Li-Ion battery
and an adapter together. That results in a range from
2.4V to 4.3V for the input voltage. To have a regulated
3.3V input voltage for the controller, the voltage
obtained from battery needs another treatment. The
conventional method is to boost the battery voltage
and then reduce it to what we expect. In this manner,
regulated voltages are obtained from the battery
steadily, regardless of the original level of the battery.
described above. For example, there would be an
increase of the number of elements and space, higher
cost, reduced reliability, and low efficiency of power
transfer. This article introduces a better approach to
achieve a regulated voltage. The benefits of the
simplified circuit with low cost and high efficiency may
result from this approach.
Operation Principle
A. The Description of the Circuit
Referred to Fig. 2, the SEPIC (Single End Primary
Inductor Circuit) meets the requirement for the
output voltage to tolerate any levels of voltage from
input. You might have heard of ”SEPIC”, yet the
corresponding operation theory, design guide, and
application are not often employed in the literature.
We provide insight of the circuit for your design.
As shown in Fig.2, L1 and L2 are chokes. They can
be coupled or uncoupled. C1 and C2 are aluminum
electrolytic capacitors. M1 is MOSFET and D1 is the
power diode. When M1 turns on, D1 is off and VIN
and C1 provide energy to L1, L2, respectively. In
turn, as M1 turns off, D1 is on. L1 charges C1. L1
and L2 provide electric energy to C2 and load from
magnetic energy stored before. In steady state, the
average voltage of L1 and L2 is zero and that of C1
is VIN.
Nevertheless, there are some defects in the method
April, 2001
1
1 page  
AN020
C1= D × TS × IIN ,
D VC1
C1=
0.53 ×11.1× 0.71
3.3 × 0.05
=25.3µF,
Let C1 be 47µF/10V/Low ESR
Step 3: Selection of M1 and D1
M1: voltage stress> VIN + VOUT = 4.5 + 3.3 = 7.8V ,
Current stress>
Current stress>
IIN
×
2
DMAX
×
1
1
+K
=
0.71×
2
0.53
×
1
1+ 0.5
=1.78A
Where
k=
IP1
IP2
,
1>k>0
Let it approximate 0.5.
IP2
IP1
Fig.6 The Current of M1
M1 is chosen to be CEM4410（30V/10A）
D1: voltage stress>VIN+VOUT=4.5+3.3=7.8V,
Current stress equals to M1
D1 is SB220 (20V/2A)
The whole circuit is shown below.
VIN
+
C1
220µF
VOUT
C6
0.1µF
C5 +
220µF
D1
581
C7
0.1µF
L2
L1
68µH
R3
10
105 C8
Q1
CET6030L
68µH
U1
1 SD
VOUT 8
2 VIN
LBI 7
3
EXT
LBO 6
4
GND
FB 5
AIC1630A
Fig.7 The SEPIC Circuit of AIC1630A
R1
510K
R2
120K
5
5 Page | ||
| Páginas | Total 7 Páginas | |
| PDF Descargar | [ Datasheet AN020.PDF ] | |
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