1-1-2 Switching Mode Regulator ICs
sTypical
Connection Diagram
SPI-8010A
12
B.S
11
R1
L1
C3
V
IN
4
C1
V
IN
CE/SS
C7
SPI-8010A
SW
OUT
7
D1 R2
C9
V
0
+
Reg Comp AGND
5
C4
C5
14
C6
1
DGND V
REF
3
+
C2
C8
15
R3
I
REF
GND
GND
C1: 220
µ
F/63V
C2: 470
µ
F/25V
C3: 0.1
µ
F
C4: 1000pF
C5: 0.1
µ
F
C6: 0.047
µ
F
C7: 0.1
µ
F
C8: 0.1
µ
F
C9: 6800pF
R1: 47Ω
L1: 47
µ
H
D1: SPB-G56S
(Sanken)
Diode D
1
• Be sure to use a Schottky-barrier diode for D
1
. If other diodes like fast recovery diodes are used, ICs may be destroyed because of the reverse voltage
generated by the recovery voltage or ON voltage.
Choke coil L
1
• If the winding resistance of the choke coil is too high, the efficiency may drop below the rated value.
• As the overcurrent protection starting current is about 4.5A, take care concerning heat radiation from the choke coil caused by magnetic saturation due to
overload or short-circuited load.
Capacitors C
1
, C
2
• As large ripple currents flow through C
1
and C
2
, use high-frequency and low-impedance capacitors aiming for switching-mode-power-supply use. Especially
when the impedance of C
2
is high, the switching waveform may become abnormal at low temperatures. For C
2
, do not use a capacitor with an extremely low
equivalent series resistance (ESR) such as an OS capacitor or a tantalum capacitor, which may cause an abnormal oscillation.
Resistors R
2
, R
3
• R
2
and R
3
are the resistors to set the output voltage. Set their values so that I
REF
becomes approx. 2mA. Obtain R
2
and R
3
values by the following formula:
R2=
V
REF
(V
OUT
–V
REF
) (V
OUT
–1)
1
. 500(Ω)
=
(Ω), R3 =
=
=
.
I
REF
2×10
–3
I
REF
2×10
–3
To create the optimum operating conditions, place the components as close as possible to each other.
sT
a
-P
D
Characteristics
3.00
P
D
=V
O
• I
O
Power Dissipation P
D
(W)
2.50
θ
j-a:41.7°C/W(30.8cm
2
)
θ
j-a:47.6°C/W(8.64cm
2
)
100
V
O
–1 –V
F
• I
O
1–
ηχ
V
IN
2.00
θ
j-a:62.5°C/W(0.84cm
2
)
1.50
Note 1: The efficiency depends on the input voltage and the output cur-
rent. Therefore, obtain the value from the efficiency graph and
substitute the percentage in the formula above.
Note 2: Thermal design for D
1
must be considered separately.
V
O
: Output voltage
V
IN
: Input voltage
I
O
: Output current
ηχ
: Efficiency (%)
V
F
: Diode D
1
forward voltage
SPB-G56S···0.4V(I
O
=2A)
1.00
0.50
0
–30
0
25
50
75
100
125
Ambient Temperature T
a
(°C)
58
ICs
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