1-1-3 DC/DC Converter ICs
■Typical Connection Diagram
SPI-8010A
12
B.S
R1
7
L1
C3
D1
11
C1: 220µF/63V
C2: 470µF/25V
C3: 0.1µF
V
IN
V
IN
SWOUT
V0
SPI-8010A
4
CE/SS
Reg Comp AGND
14
R2
C4: 1000pF
C5: 0.1µF
+
+
C1
C7
V
REF
C2
C8
DGND
3
15
I
REF
R3
5
1
C6: 0.047µF
C7: 0.1µF
C4
C5
C6
C8: 0.1µF
GND
GND
R1: 47Ω
L1: 47µH
D1: SPB-G56S
(Sanken)
Diode D1
• Be sure to use a Schottky-barrier diode for D1. 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 L1
• 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 C1, C2
• As large ripple currents flow through C1 and C2, use high-frequency and low-impedance capacitors aiming for switching-mode-power-supply use. Especially
when the impedance of C2 is high, the switching waveform may become abnormal at low temperatures. For C2, 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 R2, R3
• R2 and R3 are the resistors to set the output voltage. Set their values so that IREF becomes approx. 2mA. Obtain R2 and R3 values by the following formula:
(VOUT–VREF) (VOUT–1)
VREF
IREF
1
.
R2=
=
(Ω), R3 =
=
=500(Ω)
.
IREF
2×10–3
2×10–3
To create the optimum operating conditions, place the components as close as possible to each other.
■Ta-PD Characteristics
3.00
100
VO
PD=VO • IO
–1 –VF • IO 1–
ηχ
VIN
2.50
2.00
1.50
1.00
0.50
0
θ
θ
j-a:41.7°C/W(30.8cm2
j-a:47.6°C/W(8.64cm2
)
)
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.
θ
j-a:62.5°C/W(0.84cm2
)
Note 2: Thermal design for D1 must be considered separately.
VO : Output voltage
VIN : Input voltage
IO : Output current
ηχ : Efficiency (%)
VF : Diode D1 forward voltage
SPB-G56S···0.4V(IO=2A)
–30
0
25
50
75
100
125
Ambient Temperature Ta (°C)
ICs
24
ETC [ ETC ]
