bd9017kv ROHM Co. Ltd., bd9017kv Datasheet - Page 12

• Manufacturer Part Number: bd9017kv
• Description: Step-down,high-efficiency Switching Regulator Controller Type
• Manufacturer: ROHM Co. Ltd.

(10)Schottky barrier diode selection
○
BD9017KV
c
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2009 ROHM Co., Ltd. All rights reserved.
<Reference> Measurement of open loop of the DC/DC converter
(9)MOSFET selection
To measure the open loop of the DC/DC converter, use the gain phase analyzer or FRA to measure the frequency characteristics.
⑦ Phase compensation provided by secondary (dual) phase lead
Once the phase-lead frequency is determined, it should be set close to the LC resonance frequency.
This technique simplifies the phase topology of the DCDC Converter. Therefore, it might need a certain amount
of trial-and-error process. There are many factors (The PCB board layout, Output Current, etc.)that can affect
the DCDC characteristics. Please verify and confirm using practical applications.
Output
voltage
Load
0
DC/DC converter
V
V
0
GSM1
GSM2
Vo
controller
V
CC
R1
R2
Fig. 30
V
V
V
DS
DS
CC
Fig. 32
Maximum load
C1
Fig. 31
I
L
FB
+
R3
+
Adequate phase margin
Inadequate phase margin
V
Fig. 29
①
②
A
R
V
①
②
O
C2
Vm
Vo
R
L
Vo
COMP
t
<Procedure>
1.Check to ensure output causes no oscillation at the maximum load in
2.Isolate ① and ② and insert Vm
3.Measure (probe) the oscillation of ① to that of ②.
※Please contact us if you have any questions regarding phase compensation
Furthermore, the phase margin can also be measured with the load
responsiveness. Measure variations in the output voltage when
instantaneously changing the load from no load to the maximum load.
Even though ringing phenomenon is caused, due to low phase margin,
no ringing takes place. Phase margin is provided. However, no specific
phase margin can be probed.
closed loop.
(with amplitude of approximately.100mVpp).
12/17
・The shoot-through may happen when the input parasitic
FET uses Nch MOS
・V
・V
・V
・Allowable current＞voltage current + ripple current
※Should be at least the over current protection value
※Select a low ON-resistance MOSFET for highest efficiency
・ Reverse voltage V
・ Allowable current＞voltage current + ripple current
※Should be at least the over current protection value
※Select a low forward voltage, fast recovery diode for
capacitance of FET is extremely big. Less than or equal to
1200pF input parasitic capacitance is recommended. Please
confirm operation on the actual application since this
character is affected by PCB layout and components.
highest efficiency
DS
GSM1
GSM2
＞Vcc
Phase lead fz1 =
Phase lead fz2 =
LC resonance frequency fr =
＞Voltage between BOOT and SW pins
＞VREG5
R
＞Vcc
2πR1C1
2πR3C2
1
1
2π√LC
Technical Note
2009.09 - Rev.C
1
[Hz]
[Hz]
[Hz]