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| 型号： | TPS40074RHL |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | 2 A SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, PQCC20 |
| 封装： | PLASTIC, QFN-20 |
| 文件页数： | 5/37页 |
| 文件大小： | 448K |
| 代理商： | TPS40074RHL |
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VDG03172
RAMP
COMP
SW
VIN
SW
COMP
RAMP
VPEAK
VVALLEY
T2
tON1 > tON2 and d1 > d2
tON2
tON1
d +
tON
T
T1
PROGRAMMING SOFT START
tSTART w 2p
L
COUT (seconds)
(5)
CSS tSS +
ISS
VFB
(6)
PROGRAMMING SHORT CIRCUIT PROTECTION
TPS40074
SLUS617–APRIL 2005
APPLICATION INFORMATION (continued)
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:
Please note: There is a direct correlation between tSTART and the input current required during start-up. The lower
tSTART is, the higher the input current required during start-up since the output capacitance must be charged
faster.
The TPS40074 uses a two-tier approach to short circuit protection. The first tier is a pulse-by-pulse protection
scheme. Short circuit protection is implemented by sensing the voltage drop across the high-side MOSFET while
it is turned on. The MOSFET drain to source voltage is compared to the voltage dropped across a resistor (RILIM)
connected from VDD to the ILIM pin. The voltage drop across this resistor is produced by a constant current sink.
If the voltage drop across the MOSFET exceeds the voltage drop across the ILIM resistor the switching pulse is
immediately terminated. The MOSFET remains off until the next switching cycle is initiated.
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TPS40074RHLR | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd 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 |
| TPS40074RHLRG4 | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd 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 |
| TPS40074RHLT | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd 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 |
| TPS40074RHLTG4 | 功能描述:DC/DC 开关控制器 Mid Input Sync Buck w/Vltg Feed-Fwd 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 |
| TPS40075 | 制造商:TI 制造商全称:Texas Instruments 功能描述:4.5V TO 18V INPUT 10 PIN SYNCHRONOUS BUCK CONTROLLER WITH POWER GOOD |
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