參數(shù)資料
型號： L5980TR
廠商： STMICROELECTRONICS
元件分類： 穩(wěn)壓器
英文描述： 1.6 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
封裝： 3 X 3 MM, 1.08 MM HEIGHT, ROHS COMPLIANT, VFQFPN-8
文件頁數(shù)： 42/42頁
文件大?。?/td> 1188K
代理商： L5980TR
L5980
Functional description
Doc ID 13003 Rev 6
9/42
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 250 kHz; it can be increased as
shown in Figure 6 by external resistor connected to ground.
To improve the line transient performance
keeping 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
Clock
Generator
Ramp
Generator
FSW
Sawtooth
Clock
Synchronization
SYNCH
相關(guān)PDF資料
PDF描述
L5983 1.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
L5983TR 1.5 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
L5986A 3.9 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
L5986ATR 3.9 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
L5986TR 3.9 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO8
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
L5980TR-CUT TAPE 制造商:ST 功能描述:L5980 Series 15 V 250 kHz 0.7 A Step Down Switching Regulator - VFQFPN-8
L5981 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1A 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
L5981_08 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:1 A step-down switching regulator
L5981TR 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1a Step-Down Switching 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
L5983 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.5A STEP-DOWN 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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