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參數(shù)資料
| 型號： | L5985TR |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | 2A step-down switching regulator |
| 中文描述： | 第2A降壓型開關(guān)穩(wěn)壓器 |
| 文件頁數(shù)： | 8/36頁 |
| 文件大?。?/td> | 757K |
| 代理商： | L5985TR |
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L5985
Functional description
8/36
4.1
Oscillator and Synchronization
Figure 4
shows the block diagram of the oscillator circuit. The internal oscillator provides a
constant frequency clock. Its frequency depends on the resistor externally connect to FSW
pin. In case the FSW pin is left floating the frequency is 250KHz; it can be increased as
shown in
Figure 6
by external resistor connected to ground.
To improve the line transient performance, and to keep the PWM gain constant versus the
input voltage, the voltage feed forward is implemented by changing the slope of the
sawtooth according to the input voltage change (see
Figure 5
.a).
The slope of the sawtooth also changes if the oscillator frequency is increased by the
external resistor. In this way a frequency feed forward is implemented (
Figure 5
.b) in order to
keep the PWM gain constant versus the switching frequency (see
Section 5.4
for PWM gain
expression).
On the SYNCH pin the synchronization signal is generated. This signal has a phase shift of
180° with respect to the clock. This delay is useful when two devices are synchronized
connecting the SYNCH pin together. When SYNCH pins are connected, the device with
higher oscillator frequency works as Master, so the Slave device switches at the frequency
of the Master but with a delay of half a period. This minimizes the RMS current flowing
through the input capacitor [see L5988D Data sheet].
Figure 4.
Oscillator circuit block diagram
The device can be synchronized to work at higher frequency feeding an external clock
signal. The synchronization changes the sawtooth amplitude, changing the PWM gain
(
Figure 5
.c). This changing has to be taken into account when the loop stability is studied.
To minimize the change of the PWM gain, the free running frequency should be set (with a
resistor on FSW pin) only slightly lower than the external clock frequency. This pre-adjusting
of the frequency will change the sawtooth slope in order to get negligible the truncation of
sawtooth, due to the external synchronization.
Clock
Generator
Ramp
Generator
FSW
Sawtooth
Clock
Synchronization
SYNCH
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| L5991D | PRIMARY CONTROLLER WITH STANDBY |
| L5993 | CONSTANT POWER CONTROLLER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| L5986 | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2.5 A buck switching regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| L5986A | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2.5 A STEP-DOWN SWITCH REG RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| L5986ATR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 Step-down switch regulator, 2.5A RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| L5986TR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 2.5 A Step-down Switch Regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| L5987 | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3 A buck switching regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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