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参数资料
| 型号： | LM25119PSQX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | DUAL SWITCHING CONTROLLER, QCC32 |
| 封装： | 5 X 5 MM, LLP-32 |
| 文件页数： | 7/24页 |
| 文件大小： | 694K |
| 代理商： | LM25119PSQX |
30126214
FIGURE 5. Maximum Duty Cycle vs Switching Frequency
Thermal Protection
Internal thermal shutdown circuitry is provided to protect the
integrated circuit in the event the maximum junction temper-
ature is exceeded. When activated, typically at 165°C, the
controller is forced into a low power reset state, disabling the
output driver and the VCC bias regulators. This feature is de-
signed to prevent catastrophic failures from overheating and
destroying the device.
Application Information
EXTERNAL COMPONENTS
The procedure for calculating the external components is il-
lustrated with the following design example. Only the values
for the 3.3V output are calculated since the procedure is the
same for the 1.8V output. The circuit shown in Figure 14 is
configured for the following specifications:
CH1 output voltage, V
OUT1 = 3.3V
CH2 output voltage, V
OUT2 = 1.8V
CH1 maximum load current, I
OUT1 = 8A
CH2 maximum load current, I
OUT2 = 8A
Minimum input voltage, V
IN(MIN) = 6V
Maximum input voltage, V
IN(MAX) = 36V
Switching frequency, f
SW = 230kHz
Some component values were chosen as a compromise be-
tween the 3.3V and 1.8V outputs to allow identical compo-
nents to be used on both outputs. This design can be
reconfigured in a dual-channel interleaved configuration with
a single 3.3V output which requires identical power channels.
TIMING RESISTOR
R
T sets the switching frequency of each regulator channel.
Generally, higher frequency applications are smaller but have
higher losses. Operation at 230kHz was selected for this ex-
ample as a reasonable compromise between small size and
high efficiency. The value of R
T for 230kHz switching fre-
quency can be calculated as follows:
(7)
A standard value or 22.1k
was chosen for R
T. The internal
oscillator frequency is twice the switching frequency and is
about 460kHz.
OUTPUT INDUCTOR
The inductor value is determined based on the operating fre-
quency, load current, ripple current and the input and output
voltages.
30126215
FIGURE 6. Inductor Current
Knowing the switching frequency, maximum ripple current
(I
PP), maximum input voltage and the nominal output voltage
(V
OUT), the inductor value can be calculated:
(8)
The maximum ripple current occurs at the maximum input
voltage. Typically, I
PP is 20% to 40% of the full load current.
When operating in the diode emulation mode configuration,
the maximum ripple current should be less than twice the
minimum load current. For full synchronous operation, higher
ripple current is acceptable. Higher ripple current allows for a
smaller inductor size, but places more of a burden on the out-
put capacitor to smooth the ripple current. For this example,
a ripple current of 25% of 8A was chosen as a compromise
for the 1.8V output.
(9)
The nearest standard value of 6.8
μH was chosen for L. Using
the value of 6.8H for L, calculate I
PP again. This step is nec-
essary if the chosen value of L differs significantly from the
calculated value.
(10)
(11)
CURRENT SENSE RESISTOR
Before determining the value of current sense resistor (R
S), it
is valuable to understand the K factor, which is the ramp slope
multiple chosen for slope compensation. The K factor can be
varied from 1 to 3 in practice and is defined as:
15
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LM25119
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM25119PSQX/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 |
| LM25119QPSQ/NOPB | 制造商:Texas Instruments 功能描述: 制造商:Texas Instruments 功能描述:IC REG CTRLR BUCK PWM CM 32-LLP 制造商:Texas Instruments 功能描述:LM25119QPSQ/NOPB |
| LM25119QPSQX/NOPB | 制造商:Texas Instruments 功能描述:IC REG CTRLR BUCK PWM CM 32-LLP 制造商:Texas Instruments 功能描述:Dual Synchronous Buck Controller |
| LM2512 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Mobile Pixel Link Level 0, 24-Bit RGB Display Interface Serializer with Dithering and Look Up Table Option |
| LM-2512 | 制造商:ROHM 制造商全称:Rohm 功能描述:16 x 32 matrix display |
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