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| 型号： | TPS54140DGQR |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, 2500 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | GREEN, PLASTIC, MSOP-10 |
| 文件页数： | 13/46页 |
| 文件大小： | 1778K |
| 代理商： | TPS54140DGQR |
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Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
RT kOhm
sw kHz 1.0888
206033
(
) =
(
)
(11)
0
200
400
600
800
1000
100
200
300
400
500
600
700
800
900
1000
RT/CLK-ClockResistance-kW
f
-SwitchingFrequency-kHz
s
V =12V,
T =25°C
I
J
0
500
1000
1500
2000
2500
0
25
50
75
100
125
150
175
200
f
-SwitchingFrequency-kHz
s
RT/CLK-ClockResistance-kW
V =12V,
T =25°C
I
J
Overcurrent Protection and Frequency Shift
SLVS889 – OCTOBER 2008 .............................................................................................................................................................................................. www.ti.com
DETAILED DESCRIPTION (continued)
The switching frequency of the TPS54140 is adjustable over a wide range from approximately 300kHz to
2500kHz by placing a resistor on the RT/CLK pin. The RT/CLK pin voltage is typically 0.5V and must have a
resistor to ground to set the switching frequency. To determine the timing resistance for a given switching
frequency, use Equation 11 or the curves in Figure 39 or Figure 40. To reduce the solution size one would
typically set the switching frequency as high as possible, but tradeoffs of the supply efficiency, maximum input
voltage and minimum controllable on time should be considered.
The minimum controllable on time is typically 130ns and limits the maximum operating input voltage.
The maximum switching frequency is also limited by the frequency shift circuit. More discussion on the details of
the maximum switching frequency is located below.
SWITCHING FREQUENCY
vs
RT/CLK RESISTANCE HIGH FREQUENCY RANGE
RT/CLK RESISTANCE LOW FREQUENCY RANGE
Figure 39. High Range RT
Figure 40. Low Range RT
The TPS54140 implements current mode control which uses the COMP pin voltage to turn off the high side
MOSFET on a cycle by cycle basis. Each cycle the switch current and COMP pin voltage are compared, when
the peak switch current intersects the COMP voltage, the high side switch is turned off. During overcurrent
conditions that pull the output voltage low, the error amplifier will respond by driving the COMP pin high,
increasing the switch current. The error amplifier output is clamped internally, which functions as a switch current
limit.
To increase the maximum operating switching frequency at high input voltages the TPS54140 implements a
frequency shift. The switching frequency is divided by 8, 4, 2, and 1 as the voltage ramps from 0 to 0.8 volts on
VSENSE pin.
The device implements a digital frequency shift to enable synchronizing to an external clock during normal
startup and fault conditions. Since the device can only divide the switching frequency by 8, there is a maximum
input voltage limit in which the device operates and still have frequency shift protection.
During short-circuit events (particularly with high input voltage applications), the control loop has a finite minimum
controllable on time and the output has a very low voltage. During the switch on time, the inductor current ramps
to the peak current limit because of the high input voltage and minimum on time. During the switch off time, the
inductor would normally not have enough off time and output voltage for the inductor to ramp down by the ramp
up amount. The frequency shift effectively increases the off time allowing the current to ramp down.
20
Copyright 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS54140
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| TPS54140EVM-429 | 功能描述:电源管理IC开发工具 1.5A,25-42V In SWIFT Cnvrtr Eval Mod RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| TPS54140-Q1 | 制造商:TI 制造商全称:Texas Instruments 功能描述:1.5-A 42-V STEP-DOWN SWIFTa?￠ DC/DC CONVERTER WITH Eco-modea?￠ CONTROL |
| TPS54140QDGQRQ1 | 功能描述:直流/直流开关调节器 AC 3.5-42V Inp,1.5A RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| TPS54140QDRCRQ1 | 功能描述:直流/直流开关调节器 AC 3.5-42V Inp,1.5A RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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