BD9006F 查看數據表（PDF） - ROHM Semiconductor
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BD9006F Datasheet PDF : 18 Pages
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BD9006F, BD9006HFP, BD9007F, BD9007HFP
Technical Note
D1
CIN
L1
C1
Co
R4 C2
R1
R2
CIN
D1
L1
C3
Co
Fig.25 BD9006F Reference Layout Pattern
Fig.26 BD9006HFP Reference Layout Pattern
※As shown above ,design the GND pattern as large as possible within inner layer.
※Gray zones indicate GND.
500
450
400
350
300
250
200
150
100
50
0
100
200
300
OSCILATING FREQUENCY SETTEING
RESISTANCE:RT[kΩ]
Fig.27 RT Resistance Values vs.
Oscillating Frequency
RT[kΩ]
27
30
33
36
39
43
47
51
56
62
68
75
82
91
fosc[kHz]
537
489
449
415
386
353
324
300
275
250
229
209
192
174
RT[kΩ]
100
110
120
130
150
160
180
200
220
240
270
300
330
360
fosc[kHz]
160
146
134
124
108
102
91
82
75
69
61
55
50
46
※ The values in the graph for oscillating frequency are Typical values, and variance of±5%
forBD9006F/HFP and ±20% for BD9007F/HFP should be considered.
●Phase Compensation setting procedure
1．Application stability conditions
The following section describes the stability conditions of the negative feedback system.
Since the DC/DC converter application is sampled according to the switching frequency, GBW (frequency at 0-dB gain) of
the overall system should be set to 1/10 or less of the switching frequency. The following section summarizes the
targeted characteristics of this application.
・At a 1 (0-dB) gain, the phase delay is 150˚ or less (i.e. the phase margin is 30˚ or more).
・The GBW for this occasion is 1/10 or less of the switching frequency.
Responsiveness is determined with restrictions on the GBW. To improve responsiveness, higher switching frequency
should be provided.
Replace a secondary phase delay (-180˚) with a secondary phase lead by inserting two-phase leads, to ensure the
stability through the phase compensation. Furthermore, the GBW (i.e., frequency at 0-dB gain) is determined according
to phase compensation capacitance provided for the error amplifier. Consequently, in order to reduce the GBW, increase
the capacitance value.
(1) Typical integrator (low pass filter)
(2) Open loop characteristics of integrator
Feedback R
FB
A
C
Gain A
[dB]
0
Phase 0
[ °] 90
-180
(a)
-20dB/decade
Point (a)
fa=
1
2πRCA
[Hz]
GBW(b)
f
-90°
Ph位as相e マmaーrgジinン
-180°
Point (b)
fb=GBW=
1
2πRC
[Hz]
f
Since the error amplifier is provided with (1) or (2) phase compensation, the low pass filter is applied. In the case of the
DC/DC converter application, the R becomes a parallel resistance of the feedback resistance.
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© 2009 ROHM Co., Ltd. All rights reserved.
12/17
2009.05 - Rev.A
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