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參數(shù)資料
| 型號： | TPS54318RTET |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 5.5 A SWITCHING REGULATOR, 2000 kHz SWITCHING FREQ-MAX, PQCC16 |
| 封裝： | 3 X 3 MM, PLASTIC, QFN-16 |
| 文件頁數(shù)： | 8/36頁 |
| 文件大?。?/td> | 1388K |
| 代理商： | TPS54318RTET |
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VSENSE
COMP
VO
R1
R3
C1
C2
R2
CO RO
gm
225 uA/V
0.8 V
PowerStage
13.0 A/V
PH
RESR
COUT
RL
b
a
c
SLVS975 – SEPTEMBER 2009 ......................................................................................................................................................................................... www.ti.com
SMALL SIGNAL MODEL FOR LOOP RESPONSE
Figure 30 shows an equivalent model for the TPS54318 control loop which can be modeled in a circuit simulation
program to check frequency response and dynamic load response. The error amplifier is a transconductance
amplifier with a gm of 225
μA/V. The error amplifier can be modeled using an ideal voltage controlled current
source. The resistor Ro and capacitor Co model the open loop gain and frequency response of the amplifier. The
1-mV AC voltage source between the nodes a and b effectively breaks the control loop for the frequency
response measurements. Plotting a/c shows the small signal response of the frequency compensation. Plotting
a/b shows the small signal response of the overall loop. The dynamic loop response can be checked by
replacing the RL with a current source with the appropriate load step amplitude and step rate in a time domain
analysis.
Figure 30. Small Signal Model for Loop Response
SIMPLE SMALL SIGNAL MODEL FOR PEAK CURRENT MODE CONTROL
Figure 30 is a simple small signal model that can be used to understand how to design the frequency
compensation. The TPS54318 power stage can be approximated to a voltage controlled current source (duty
cycle modulator) supplying current to the output capacitor and load resistor. The control to output transfer
function is shown in Equation 7 and consists of a dc gain, one dominant pole and one ESR zero. The quotient of
the change in switch current and the change in COMP pin voltage (node c in Figure 30) is the power stage
transconductance. The gm for the TPS54318 is 13 A/V. The low frequency gain of the power stage frequency
response is the product of the transconductance and the load resistance as shown in Equation 8. As the load
current increases and decreases, the low frequency gain decreases and increases, respectively. This variation
with load may seem problematic at first glance, but the dominant pole moves with load current [see Equation 9].
The combined effect is highlighted by the dashed line in the right half of Figure 31. As the load current
decreases, the gain increases and the pole frequency lowers, keeping the 0-dB crossover frequency the same
for the varying load conditions which makes it easier to design the frequency compensation.
16
Copyright 2009, Texas Instruments Incorporated
Product Folder Link(s) :TPS54318
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PDF描述 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS54318RTET | 制造商:Texas Instruments 功能描述:Voltage Regulator IC 制造商:Texas Instruments 功能描述:IC, SYNC STEP-DOWN SWITCHER, QFN-16 |
| TPS54319 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:2.95-V to 6-V Input, 3-A Output, 2-MHz, Synchronous Step-Down Switcher With Integrated FETs ( SWIFTa?￠) |
| TPS54319_1 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:2.95-V to 6-V Input, 3-A Output, 2-MHz, Synchronous Step-Down Switcher With Integrated FETs ( SWIFTa?￠) |
| TPS54319EVM-626 | 功能描述:電源管理IC開發(fā)工具 Evaluation Module for TPS54319 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 |
| TPS54319RTE | 制造商:TI 制造商全稱:Texas Instruments 功能描述:2.95-V to 6-V Input, 3-A Output, 2-MHz, Synchronous Step-Down Switcher With Integrated FETs ( SWIFT?) |
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