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參數(shù)資料
| 型號： | LM3075MTC |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | High Efficiency, Synchronous Current Mode Buck Controller |
| 中文描述： | SWITCHING CONTROLLER, 330 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | TSSOP-20 |
| 文件頁數(shù)： | 16/18頁 |
| 文件大?。?/td> | 857K |
| 代理商： | LM3075MTC |
Loop Compensation
(Continued)
The control-output corner frequencies, and thus the desired
compensation corner frequencies, can be determined ap-
proximately by the following equations:
(20)
(21)
Since f
p
is determined by the output network, it shifts with
loading (R
o
) and duty cycle. First determine the range of
frequencies (f
) of the pole across the expected load
range and then place the first compensation zero within that
range.
Example
: R
= 20m
, C
o
= 100uF, R
omax
= 5V/
100mA=50
, R
omin
= 5V/5A = 1
, L = 8 μH.
(22)
(23)
(24)
Once the f
p
range is determined, R
c1
should be calculated
using:
(25)
Where B is the desired gain in V/V at f
(f
z1
), gm is the
transconductance of the error amplifier, and R
1
and R
2
are
the feedback resistors.
A gain value around 10dB (3.3V/V) is generally a good
starting point.
Example
: B = 3.3 V/V, gm = 0.650 μmho, R
1
= 20 k
, R
2
=
60.4 k
:
(26)
Bandwidth varies proportionally to the value of R
c1
. Next,
C
c1
can be determined with the following equation :
(27)
Example
: fpmin = 313Hz, R
c1
= 20k
:
(28)
The value of C
should be within the range determined by
f
. A higher value generally provides a more stable
loop, but too high a value slows the transient response time.
The compensation network also introduces a low frequency
pole that is close to 0Hz. A second pole should also be
placed at f
. This pole can be created with a single capacitor
C
and a shorted R
(see Figure 9). The minimum value for
this capacitor can be calculated by:
(29)
C
c2
may not be necessary, however it does create a more
stable control loop. This is especially important with high
load currents and in current sharing mode.
Example: f
z
= 36kHz, R
c1
= 20k
:
20162331
FIGURE 6. Control-Output Transfer Function
20162332
FIGURE 7. Output-Control Transfer Function
L
www.national.com
16
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| LM3075MTC/NOPB | 功能描述:IC REG CTRLR BUCK PWM CM 20TSSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR) |
| LM3075MTCX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:High Efficiency, Synchronous Current Mode Buck Controller |
| LM3075N/A+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:FM Receiver Circuit |
| LM3075N/B+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:FM Receiver Circuit |
| LM3075N-01/A+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:FM Receiver Circuit |
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