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参数资料
| 型号： | LM3153MHX-2.5 |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封装： | TSSOP-14 |
| 文件页数： | 6/20页 |
| 文件大小： | 479K |
| 代理商： | LM3153MHX-2.5 |
8. C
VCC, and CBST and CEN
C
VCC should be placed directly at the VCC pin with a recom-
mended value of 1 F to 2.2 F. For input voltage ranges that
include voltages below 8V a 1 F capacitor must be used for
C
VCC. CBST creates a voltage used to drive the gate of the
high-side FET. It is charged during the SW off-time. The rec-
ommended value for C
BST is 0.47 F. The EN bypass capac-
itor, C
EN, recommended value is 1000 pF when driving the EN
pin from open drain type of signal.
Design Example
30053261
FIGURE 4. Design Example Schematic
1. Define Power Supply Operating Conditions
a. V
OUT = 3.3V
b. V
IN-MIN = 6V, VIN-TYP = 12V, VIN-MAX = 24V
c. Typical Load Current = 12A, Max Load Current = 15A
d. Soft-Start time t
SS = 5 ms
2. Determine which IC Controller to Use
The LM3151 and LM3152 allow for the full input voltage
range. However, from buck converter basic theory, the higher
switching frequency will allow for a smaller inductor. There-
fore, the LM3152-3.3 500 kHz part is chosen so that a smaller
inductor can be used.
3. Determine Inductor Required
a. ET = (24-3.3) x (3.3/24) x (1000/500) = 5.7 V s
b. From the inductor nomograph a 12A load and 5.7 V s cal-
culation corresponds to a L44 type of inductor.
c. Using the inductor designator L44 in Table 1 the Coilcraft
HA3778-AL 1.65 H inductor is chosen.
4. Determine Output Capacitance
The voltage rating on the output capacitor should be greater
than or equal to the output voltage. As a rule of thumb most
capacitor manufacturers suggests not to exceed 90% of the
capacitor rated voltage. In the case of multilayer ceramics the
capacitance will tend to decrease dramatically as the applied
voltage is increased towards the capacitor rated voltage. The
capacitance can decrease by as much as 50% when the ap-
plied voltage is only 30% of the rated voltage. The chosen
capacitor should also be able to handle the rms current which
is equal to:
For this design the chosen ripple current ratio, r = 0.3, repre-
sents the ratio of inductor peak-to-peak current to load current
Iout. A good starting point for ripple ratio is 0.3 but it is ac-
ceptable to choose r between 0.25 to 0.5. The nomographs
in this datasheet all use 0.3 as the ripple current ratio.
I
rmsco = 1A
t
ON = (3.3V/12V) / 500 kHz = 550 ns
Minimum output capacitance is:
C
Omin = 70 / (fS
2
x L)
C
Omin = 70 / (500 kHz
2
x 1.65 H) = 169 F
The maximum ESR allowed to prevent over-voltage protec-
tion during normal operation is:
ESR
max = (80 mV x L) / ET
ESR
max = (80 mV x 1.65 H) / 5.7 V s
ESR
max = 23 m
The minimum ESR must meet both of the following criteria:
ESR
min ≥ (15 mV x L) / ET
www.national.com
14
LM3151/LM3152/LM3153
相关PDF资料 |
PDF描述 |
|---|---|
| LM3153MHE-2.5 | SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PDSO14 |
| LM3152MH-5.0 | SWITCHING CONTROLLER, 500 kHz SWITCHING FREQ-MAX, PDSO14 |
| LM3151MHE-2.5 | SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO14 |
| LM3153MHE-5.0 | SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PDSO14 |
| LM3151MHX-2.5 | SWITCHING CONTROLLER, 250 kHz SWITCHING FREQ-MAX, PDSO14 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3153MHX-3.3 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:SIMPLE SWITCHER? CONTROLLER, High Input Voltage Synchronous Step-Down |
| LM3153MHX-3.3/NOPB | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| LM316 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:OPERATIONAL AMPLIFIERS |
| LM316A | 制造商:NSC 制造商全称:National Semiconductor 功能描述:OPERATIONAL AMPLIFIERS |
| LM316AH | 制造商:NSC 制造商全称:National Semiconductor 功能描述:OPERATIONAL AMPLIFIERS |
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