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參數(shù)資料
| 型號： | TPS61251DSGT |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | SWITCHING REGULATOR, 3500 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | 2 X 2 MM, PLASTIC, WSON-8 |
| 文件頁數(shù)： | 2/23頁 |
| 文件大?。?/td> | 587K |
| 代理商： | TPS61251DSGT |
OUT(CL)
IN(DC)
I
= (1 D)
I
-
g
IN
OUT
V
D
1
V
h
=
-
g
SLVSAF7 – SEPTEMBER 2010
www.ti.com
DETAILED DESCRIPTION
OPERATION
The TPS61251 Boost Converter operates as a quasi-constant frequency adaptive on-time controller. In a typical
application the frequency will be 3.5 MHz and is defined by the input to output voltage ratio and does not vary
from moderate to heavy load currents. At light load the converter will automatically enter Power Save Mode and
operates in PFM (Pulse Frequency Modulation) mode. During PWM operation the converter uses a unique fast
response quasi-constant on-time valley current mode controller scheme which offers excellent line and load
regulation and the use of small ceramic input capacitors.
Based on the VIN/VOUT ratio, a simple circuit predicts the required on-time. At the beginning of the switching
cycle, the low-side NMOS switch is turned-on and the inductor current ramps up to a peak current that is defined
by the on-time and the inductance. In the second phase, once the peak current is reached, the current
comparator trips, the on-timer is reset turning off the switch, and the current through the inductor then decays to
an internally set valley current limit. Once this occurs, the on-timer is set to turn the boost switch back on again
and the cycle is repeated.
The TPS61251 directly and accurately controls the average input current through intelligent adjustment of the
valley current limit, allowing an accuracy of ±10%. Together with an external bulk capacitor the TPS61251 allows
an application to be interfaced directly to its load, without overloading the input source due to appropriate set
average input current limit .
High values of output capacitance are mainly achieved by putting capacitors in parallel. This reduces the overall
series resistance (ESR) to very low values. This results in almost no voltage ripple at the output and therefore
the regulation circuit has no voltage drop to react on. Nevertheless to guarantee accurate output voltage
regulation even with very low ESR the regulation loop can switch to a pure comparator regulation scheme.
During this operation the output voltage is regulated between two thresholds. The upper threshold is defined by
the programmed output voltage and the lower value is about 10 mV lower. If the upper threshold is reached the
off-time is increased to reduce the current in the inductor. Therefore the output voltage will slightly drop until the
lower threshold is tripped. Now the off-time will be reduced to increase the current in the inductor to charge up
the output voltage to the steady-state value. The current swing during this operation mode is strongly depending
on the current drawn by the load but will not exceed the programmed current limit. The output voltage during
comparator operation stays within the specified accuracy with minimum voltage ripple.
This architecture with adaptive slope compensation provides excellent transient load response and requiring
minimal output filtering. Internal softstart and loop compensation simplifies the design process while minimizing
the number of external components.
CURRENT LIMIT OPERATION
The current limit circuit employs a valley current sensing scheme. Current limit detection occurs during the
off-time through sensing of the voltage drop across the synchronous rectifier. The output voltage is reduced as
the power stage of the device operates in a constant current mode. The maximum continuous output current
(IOUT(CL)), before entering current limit (CL) operation, can be defined by Equation 1 as shown below:
(1)
The duty cycle (D) can be estimated by following Equation 2
(2)
SOFTSTART
The TPS61251 has an internal charging circuit that controls the current during the output capacitor charging and
prevents the converter from inrush current that exceeds the set current limit. For typical 100 s the current is
ramped to the set current limit. After reaching the current limit threshold the output capacitor is charged with a
constant current until the programmed output voltage is reached. During the phase where VIN > VOUT the
rectifying switch is controlled by the current limit circuit and works as a linear regulator in constant current mode.
If then VIN = VOUT the converter starts switching and boosting up the voltage to its nominal output voltage by still
10
Copyright 2010, Texas Instruments Incorporated
Product Folder Link(s): TPS61251
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS61251DSGT | 制造商:Texas Instruments 功能描述:IC BOOST DC/DC CONV ADJ 3V-6.5V OUTPUT 制造商:Texas Instruments 功能描述:IC, BOOST DC/DC CONV, ADJ 3V-6.5V OUTPUT, 1.5A, 8-QFN |
| TPS61251EVM-517 | 功能描述:電源管理IC開發(fā)工具 TPS61251 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 |
| TPS61252 | 制造商:TAOS 制造商全稱:TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS 功能描述:TINY 1.5-A BOOST CONVERTER WITH ADJUSTABLE INPUT CURRENT LIMIT |
| TPS61252DSGR | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3.5MHz1.5A92% Eff Boost Converter 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 |
| TPS61252DSGT | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 3.5MHz1.5A92% Eff Boost Converter 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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