S-8365AAABA-M5T1Y2 Datasheet, PDF (20/63 Pages) Seiko Instruments Inc – PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER

STEP-UP, SUPER-SMALL PACKAGE, 1.2 MHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8365/8366 Series
Rev.2.1_01
 External Parts Selection
1. Inductor
The recommended L value of the S-8365/8366 Series is 2.2 μH for 1.2 MHz products and 3.3 μH for 600 kHz
products.
Note the following when changing the inductance.
The inductance (L) has a strong influence on the maximum output current (IOUT) and efficiency (η).
The inductor peak current (IPK) increases when L is decreased, which improves the circuit stability and increases
the IOUT users can obtain. If L is decreased further, the ability of the external transistor to drive the current becomes
insufficient, reducing the efficiency and decreasing IOUT.
The loss due to the IPK of the switching transistor is decreased by increasing L and the efficiency maximizes at a
certain L value. If L is increased further, the loss due to the serial resistance of the inductor increases, lowering the
efficiency.
Caution
When selecting an inductor, be careful about its allowable current. If a current exceeding the
allowable current flows through the inductor, magnetic saturation occurs, substantially lowering
the efficiency and destroying ICs due to large current. Therefore, select an inductor such that IPK
does not exceed the allowable current. The following equations express IPK in the ideal statuses
in the discontinuous and continuous modes :
IPK =
IPK =
2 × IOUT × (VOUT + VD^*2 − VIN)
fOSC^*1 × L
VOUT + VD^*2
VIN
× IOUT +
(VOUT + VD^*2 − VIN) × VIN
2 × (VOUT + VD^*2) × fOSC^*1 × L
(Discontinuous mode)
(Continuous mode)
*1. fOSC : oscillation frequency
*2. VD is the forward voltage of a diode. The reference value is 0.4 V.
However, current exceeding the above equation flows because conditions are practically not ideal.
Perform sufficient evaluation with actual application.
Manufacture
TDK Corporation
Coilcraft, Inc.
Taiyo Yuden Co., Ltd.
Sumida Corporation
Table 13 Typical Inductors (for Small Low-Profile Devices)
Product Name
VLF3010ST-2R2M
VLF3010ST-3R3M
VLS252010-2R2M
VLS252010-3R3M
LPS3008-222ML
LPS3008-332ML
NR3010T2R2M
NR3010T3R3M
CDRH2D11BNP-2R2N
CDRH2D11BNP-3R3N
L Value
2.2 μH
3.3 μH
2.2 μH
3.3 μH
2.2 μH
3.3 μH
2.2 μH
3.3 μH
2.2 μH
3.3 μH
DC Resistance
0.092 Ω max.
0.130 Ω max.
0.190 Ω max.
0.304 Ω max.
0.175 Ω max.
0.285 Ω max.
0.114 Ω max.
0.168 Ω max.
0.0955 Ω max.
0.154 Ω max.
Rated
Current
1.1 A max.
0.88 A max.
1.2 A max.
1.0 A max.
1.1 A max.
0.88 A max.
1.1 A max.
0.87 A max.
1.4 A max.
1.0 A max.
Dimensions (L × W × H)
[mm]
2.8 × 3.0 × 1.0
2.8 × 3.0 × 1.0
2.5 × 2.0 × 1.0
2.5 × 2.0 × 1.0
3.0 × 3.0 × 0.8
3.0 × 3.0 × 0.8
3.0 × 3.0 × 1.0
3.0 × 3.0 × 1.0
3.0 × 3.0 × 1.2
3.0 × 3.0 × 1.2
Manufacture
TDK Corporation
Coilcraft, Inc.
Taiyo Yuden Co., Ltd.
Table 14 Typical Inductors (for Large Current, High Step-up Rate)
Product Name
LTF5022T-2R2M
LTF5022T-3R3M
LPS6225-222ML
LPS6225-332ML
NR6028T2R2M
L Value
2.2 μH
3.3 μH
2.2 μH
3.3 μH
2.2 μH
DC Resistance
0.040 Ω max.
0.060 Ω max.
0.045 Ω max.
0.055 Ω max.
0.020 Ω max.
Rated
Current
3.4 A max.
2.7 A max.
4.1 A max.
3.6 A max.
4.2 A max.
Dimensions (L × W × H)
[mm]
5.0 × 5.2 × 2.2
5.0 × 5.2 × 2.2
6.0 × 6.0 × 2.4
6.0 × 6.0 × 2.4
6.0 × 6.0 × 2.8
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