BD8150KVT-E2 データシートの表示（PDF） - ROHM Semiconductor
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BD8150KVT-E2 Datasheet PDF : 19 Pages
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BD8150KVT
Technical Note
1-8 Load switch MOSFET selection and corresponding soft start (step-up channels only)
Switching does not exist in the circuits from VCC to VO for normal step-up applications, so the coil or rectification diode
could be damaged by an output short. To prevent this, insert a PMOSFET load switch between the VCC and coil.
Select a PMOSFET with breakdown voltage between the gate sources and between the drain sources higher than VCC.
Furthermore, if soft start is to be applied to the load switch, insert a capacitor between the gate sources. Refer to Fig.
26 when selecting the soft start time. Please note that the soft start time depends on the PMOSFET gate capacitance.
L←
Vo
SBDi
C
VCC
PG PIN CAPACITOR vs. SOFT START TIME
1.00E-01
DELAY [sec]
RISETIME [sec]
1.00E-02
1.00E-03
Load switch FET
Switching FET
Fig. 25 Load Switch Circuit Diagram
1.00E-04
1.00E-05
1.00E-10
1.00E-09
1.00E-08
CPG [F]
1.00E-07
1.00E-06
Fig. 26 Soft Start Time for PG Capacitance
1-9 RC filter setting for phase compensation
Phase compensation is required for stabilization in DC/DC converter applications. A built-in phase compensation
circuit makes this possible.
1) When using internal phase compensation, observe the following requirements in designs.
(1) Internally set the switching frequency (1MHz Typ.).
(2) 1 / (2π√LC) = 10 - 30 kHz
(3) 1 / (2πR1C1) = 10 - 100 kHz
VCC
L
C
BG
VCC
C1 R1
R2
NON
+
FB
INV
ERR
-
150 kΩ 100 kΩ
5 pF 100 pF
Fig. 27 Internal Phase Compensation
2) Using external phase compensation
When changing the oscillating frequency and L or C values, insert an RC filter circuit between INV and FB.
(1) (1/2π√LC) 0.5 < 1 / (2πR1C1) < (1/2π√LC) 2
(2) (1/2π√LC) 0.5 < 1 / (2πR4C2) < (1/2π√LC) 2
(3) R3 > R4
(4) (1/2πR4C2) 5 < 1 / (2πR3C3) < fsw / 2
VCC
BG
L
NON
+
C
C1 R1
R3
INV
+ ERR
-
R2
R4 C2
150 kΩ
100 kΩ
C3
FB
100 pF
5 pF
Fig. 28 External Phase Compensation
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© 2009 ROHM Co., Ltd. All rights reserved.
10/18
2009.07 - Rev.B
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