61

ICs

SPI-8001TW/SPI-8002TW/SPI-8003TW

■Typical Connection Diagram

GND

3

SWout1

R5

C4

C1

C6

+

24

SS1

6

11

DGND1

5

15

SS2

DGND2

12

7

13

SWout2

10

R6

C5

C/E

AGND

Ch2

Ch1

14

1, 9

Di2

L2

C3

C8

+

GND

Di1

L1

C2

R1

R2

R3

R4

C7

+

SPI-8000TW

Diodes Di1, Di2

• Be sure to use Schottky-barrier diodes for Di1 and Di2.

If other diodes like fast recovery diodes are used, IC may be destroyed because of the reverse voltage generated by the recovery voltage or ON voltage.

Choke coils L1, L2

• 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 2.0A, take care concerning heat radiation from the choke coil caused by magnetic saturation due to

overload or short-circuited load.

Capacitors C1, C2, C3

• As large ripple currents flow through C1, C2 and C3, use high-frequency and low-impedance capacitors suitable for switching mode power supplies.

Especially when the impedance of C2 and C3 are high, the switching waveforms may become abnormal at low temperatures. For C2 and C3, do not use

capacitors with extremely low equivalent series resistance (ESR) such as OS capacitors or tantalum capacitors, which may cause abnormal oscillation.

Resistors R1, R2, R3, R4

shown below.

1

R1=

=

(Ω), R2=

=

1(KΩ)

To create the optimum operating conditions, place the components as close as possible to each other.

C1

: 220 µF/50V

C2, C3

: 470 µF/25V

C4, C5

: 1 µF

C6, C7, C8 : 0.1 µF

Note 1: The efficiency depends on the input voltage and the output current. Therefore, obtain the value from the efficiency graph and substitute the percent-

age in the formula above.

ηχ : Efficiency (%)

100

ηχ

–25

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

025

50

75

100

125 135 150

69.2°C/W (0.84 cm

52.3°C/W (3.34 cm

42.6°C/W (8.64 cm

35.8°C/W (30.8 cm

(Copper Laminate Area)

θ j-a

38.2°C/W (15.6 cm

=

.

.

GND

3

SWout1

R5

C5

C1

C4

C9

R7

+

24

SS1

6

12

DGND1

5

16

SS2

DGND2

13

7

14

SWout2

11

R6

C6

C/E

AGND

Ch2

Ch1

15

1, 9

10

Di2

L2

C3

C8

+

GND

Di1

L1

C2

R1

R2

R3

R4

C7

+

8

SPI-8003TW

R5, R6

: 1kΩ

L1, L2

: 47 µH

Di1, Di2

: SJPB-H6

(Sanken)

C1

: 220 µF/50V

C2, C3

: 470 µF/25V

C4

: 1 µF/50V

C5, C6

: 1 µF/10V

C7, C8

: 0.1 µF/50V

C9

: 100pF/10V

L1, L2

: 47 µH

R2, R4

: 1kΩ

R5, R6

: 1kΩ

Di1, Di2

: SJPB-H6 (Sanken)