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參數(shù)資料
| 型號： | ISL6529ACB |
| 廠商： | INTERSIL CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Adjustable Precision Shunt Regulator 3-SOT-23 -40 to 125 |
| 中文描述： | SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | PLASTIC, MS-012-AB, SOIC-14 |
| 文件頁數(shù)： | 11/19頁 |
| 文件大?。?/td> | 623K |
| 代理商： | ISL6529ACB |
11
FN9070.5
April 12, 2005
Figure
8
shows an asymptotic plot of the DC-DC converter’s
gain vs. frequency. The actual modulator gain has a high
gain peak dependent on the quality factor (Q) of the output
filter, which is not shown in Figure
8
. Using the above
procedure should yield a compensation gain similar to the
curve plotted. The open loop error amplifier gain bounds the
compensation gain. Check the compensation gain at F
P2
with the capabilities of the error amplifier.
The compensation gain uses external impedance networks
Z
FB
and Z
IN
to provide a stable, high bandwidth (BW)
overall loop. A stable control loop has a gain crossing with
-20dB/decade slope and a phase margin greater than 45
degrees. Include worst case component variations when
determining phase margin.
Linear Regulator Compensation
The linear regulator in the ISL6529 is not internally
compensated and therefore allows the user to optimize
regulator performance with regard to transient load
response. Although the compensation network shown in the
application examples in this data sheet provide conservative
compensation for a variety of loads, performance can be
enhanced with attention to load requirements.
Low ESR capacitors can cause stability concerns in discrete
IC regulators. Even regulators that are internally
compensated can become unstable when these capacitors
are placed across their output. There have been suggestions
to add series resistance to these capacitors to stabilize the
regulator. This approach seems self defeating and throws
away a desirable quality.
Component Considerations
Many unsuspected poles and zeros develop with the
selection of external components and operating conditions
like output MOSFET transistors, output filter capacitors and
load current. These elements will be discussed beginning
with the influence of the MOSFET series output resistance,
the 1/gfs term shown in Figure 7. At low load currents and
low transconductance, the effective output resistance can be
as high as several kilohms. The low MOSFET gfs with
accompanying high series resistance and large values of
output capacitance form a low frequency pole that for many
cases becomes the dominate pole in the system and often
results in a stable no load system. As the load current is
increased, the MOSFET series output resistance is reduced
and moves the output pole into a higher frequency region,
adding phase shift that can result in a marginally stable or
unstable system.
Low output capacitor ESR can result in stability problems as
mentioned above. In contrast, high output capacitor ESR
can improve the system stability. The capacitor and its series
resistance function as a zero, often canceling other poles in
the loop. Figure 9 shows a system simulation with a 300
μ
F,
100m
high ESR output capacitor. A single 10pF capacitor
from input to output of the error amplifier stabilizes the
system for load currents through the 1mA to 3A range.
Contrast this with Figure 10 that shows a Bode plot of
simulations of this regulator operating with a 100
μ
F, 5m
low ESR output capacitor. Note the phase approaching 180°
at high current. This is in contrast to the response previously
shown with the 300
μ
F high ESR capacitor. The 300
μ
F
output capacitor and its ESR provide phase lead to cancel or
offset the pole formed with the MOSFET output resistance
and 300
μ
F capacitance. Also notice that system stability
varies widely with load current. A system can oscillate at no
load and be stable at full load, The converse is also possible.
Oscillation can also occur at load currents between the
current extremes.
FIGURE 8. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN
100
80
60
40
20
0
-20
-40
-60
F
P1
F
Z2
10M
1M
100K
10K
1K
100
10
OPEN LOOP
ERROR AMP GAIN
F
Z1
F
P2
F
LC
F
ESR
COMPENSATION
GAIN
G
FREQUENCY (Hz)
MODULATOR
GAIN
LOOP GAIN
20
VOSC
log
20
--------
log
10
1K
100
10K
100K
1M
10M
FREQUENCY (Hz)
80
60
40
20
0
0
-50
-150
-100
-200
G
P
1mA
1mA
55mA
3A
3A
3A
55mA
1mA
BODE PLOT OF COMPENSATED REGULATOR AT 3 OUTPUT CURRENTS
OUTPUT CAPACITOR
300
μ
F, 100m
FIGURE 9. LOOP RESPONSE WITH ONLY C16 = 10pF
COMPENSATION
ISL6529, ISL6529A
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| ISL6529ACR | 功能描述:IC REG DL BCK/LINEAR SYNC 16-QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
| ISL6529ACR-T | 功能描述:IC REG DL BCK/LINEAR SYNC 16-QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標準包裝:2,500 系列:- 拓撲:降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關:300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* |
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