參數(shù)資料
型號： TPS40074RHLT
廠商： TEXAS INSTRUMENTS INC
元件分類： 穩(wěn)壓器
英文描述： 2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC20
封裝： GREEN, PLASTIC, QFN-20
文件頁數(shù)： 5/41頁
文件大小： 765K
代理商： TPS40074RHLT
www.ti.com
VDG03172
RAMP
COMP
SW
VIN
SW
COMP
RAMP
VPEAK
VVALLEY
T2
tON1 > tON2 and d1 > d2
tON2
tON1
d +
t
ON
T
T1
PROGRAMMING SOFT START
t
START w 2p
L
C
OUT
(seconds)
(5)
C
SS
t
SS +
I
SS
V
FB
(6)
SLUS617B – APRIL 2005 – REVISED OCTOBER 2006
APPLICATION INFORMATION (continued)
Figure 9 shows the effect of changing input voltage on the duty cycle, and how that change takes place. The
pulse width modulator (PWM) ramp input is generated using a current that is proportional to the current into the
KFF pin. The TPS40074 holds this pin at a constant 400 mV, so connecting a resistor from KFF to the input
power supply causes a current to flow into the KFF pin that is proportional to the input voltage. The slope of the
ramp signal to the PWM is therefore proportional to the input voltage. This allows the duty cycle to change with
variations in Vin without requiring much response from the error amplifier, resulting in very good line transient
response. Another benefit is essentially constant PWM gain over the entire input voltage operating range. This
makes the output control loop easier to design for a wide input range converter.
Figure 9. Voltage Feed-Forward and PWM Duty Cycle Waveforms
TPS40074 uses a closed-loop approach to ensure a controlled ramp on the output during start-up. Soft-start is
programmed by connecting an external capacitor (CSS) from the SS pin to GND. This capacitor is charged by a
fixed current, generating a ramp signal. The voltage on SS is level shifted down approximately 1 V and fed into a
separate non-inverting input to the error amplifier. The loop is closed on the lower of the level shifted SS voltage
or the 700-mV internal reference voltage. Once the level shifted SS voltage rises above the internal reference
voltage, output voltage regulation is based on the internal reference. To ensure a controlled ramp-up of the
output voltage the soft-start time should be greater than the L-COUT time constant or:
where
L is the value of the filter inductor
COUT is the value of the output capacitance
tSTART is the output ramp up-time
For a desired soft-start time, the soft-start capacitance, CSS, can be found from:
To ensure correct start up of the converter, the soft-start time is limited and can be calculated using Equation 7.
13
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
TPS40074RHLTG4 功能描述:DC/DC 開關(guān)控制器 Mid Input Sync Buck w/Vltg Feed-Fwd RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
TPS40075 制造商:TI 制造商全稱:Texas Instruments 功能描述:4.5V TO 18V INPUT 10 PIN SYNCHRONOUS BUCK CONTROLLER WITH POWER GOOD
TPS40075EVM-001 功能描述:電源管理IC開發(fā)工具 15A 12V In 1.5V Out Eval Mod RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
TPS40075RHLR 功能描述:DC/DC 開關(guān)控制器 Wide Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
TPS40075RHLRG4 功能描述:DC/DC 開關(guān)控制器 Wide Input Synch Buck Controller RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
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