BD8150KVT ROHM Co. Ltd., BD8150KVT Datasheet - Page 9

• Manufacturer Part Number: BD8150KVT
• Description: System Power Supplies Power Suuply Ic Series For Tft-lcd Panels
• Manufacturer: ROHM Co. Ltd.

1-8 Load switch MOSFET selection and corresponding soft start (step-up
1-6 Feedback resistance value setting
1-7 Setting soft start time
1-9 RC filter setting for phase compensation
channels only)
Use the following equation to set the feedback resistance value to achieve stability at the specified output voltage.
The INV and NON pins are easily affected by noise, so use as short a pattern layout as possible and make sure that
there is no overlap of the switching lines.
Applying capacitance to the SS pins (pins 55, 56) allows the soft start
time to be set. Refer to Fig. 24 in order to select the appropriate
capacitance. The soft start time will vary depending on the application,
such as frequency, coil, and capacitance, so always verify operation
under actual conditions.
Switching does not exist in the circuits from V
could be damaged by an output short. To prevent this, insert a PMOSFET load switch between the V
a PMOSFET with breakdown voltage between the gate sources and between the drain sources higher than V
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.
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
Output voltage
V
CC
Load switch FET
Fig. 25 Load Switch Circuit Diagram
VO = (R1 + R2) × BG / R2 [V] (Step-up)
VO = −(R1 × BG) / R2 [V] (Inversion)
R2
R1
(a) Step-down
VO
L←
VO = (R1 + R2) × BG / R2 [V] (step-down)
V
CC
INV
L
Switching FET
C
SBDi
Fig. 23 Feedback Resistance Setting
C1
V
CC
R2
R1
C
BG
Vo
(b) Step -up
R1
R2
CC
VO
to VO for normal step-up applications, so the coil or rectification diode
9/16
INV
NON
INV
150 kΩ
100 kΩ
+
5 pF
-
1.00E-01
1.00E-02
1.00E-03
1.00E-04
1.00E-05
ERR
VO
R1
R2
Fig. 26 Soft Start Time for PG Capacitance
1.00E-10
(c) Inverting
100 pF
PG PIN CAPACITOR vs. SOFT START TIME
NON
BG
1.00E-09
DELAY [sec]
FB
Fig. 27 Internal Phase Compensation
1.00E-01
1.00E-02
1.00E-03
1.00E-04
1.00E-05
1.00E-06
Fig. 24 Soft Start Time for SS Capacitance
1.00E-10
1.00E-08
CPG [F]
1.00E-09
DELAY [sec]
RISETIME [sec]
1.00E-07
CSS [F]
1.00E-08
RISETIME [sec]
CC
1.00E-06
and coil. Select
1.00E-07
CC
.
1.00E-06