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參數(shù)資料
| 型號： | TPS51427ARHBT |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | DUAL SWITCHING CONTROLLER, PQCC32 |
| 封裝： | 5 X 5 MM, GREEN, PLASTIC, QFN-32 |
| 文件頁數(shù)： | 4/42頁 |
| 文件大小： | 2131K |
| 代理商： | TPS51427ARHBT |
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DETAILED DESCRIPTION
BASIC PWM OPERATION
LIGHT LOAD CONDITIONS
(
)
f
VIN
VOUT
OUT(LL)
SW
VIN
V
1
I
2
L
V
-
=
÷
÷
÷
è
è
(1)
SLUS843B – MAY 2008 – REVISED SEPTEMBER 2008 .................................................................................................................................................. www.ti.com
The main control loop of the TPS51427A is designed as an adaptive on-time pulse width modulation (PWM)
controller. It supports a proprietary D-CAP mode that uses internal compensation circuitry and is suitable for a
minimal external component count configuration when an appropriate amount of ESR at the output capacitor(s) is
allowed. D-CAP mode can also enable stable operation when using capacitors with low ESR, such as specialty
polymer capacitors.
The basic operation of D-CAP mode can be described in this way: At the beginning of each cycle, the
synchronous high-side MOSFET turns on or goes to an ON state. This MOSFET turns off, or returns to an OFF
state, after an internal one-shot timer expires. The one-shot timer is determined by VIN and VOUT and keeps the
frequency fairly constant over the input voltage range under steady-state conditions; it is an adaptive on-time
control or fixed-frequency emulated on-time control. The MOSFET turns on again when the following two
conditions occur:
Feedback information, monitored at the VFB1/VOUT2 voltage, indicates insufficient output voltage; and
the inductor current information indicates that current is below the overcurrent limit.
Operating in this manner, the controller regulates the output voltage. The synchronous low-side or the rectifying
MOSFET is turned on each OFF state to keep the conduction loss minimum.
The TPS51427A supports three selectable operating modes: PWM-only, Out-Of-Audio (OOA), and Auto-Skip.
If the SKIPSEL pin is connected to GND, Auto-Skip mode is selected. This mode enables a seamless transition
to the reduced frequency operation under light load conditions so that high efficiency is maintained over a wide
range of load current. This frequency reduction is achieved smoothly and without an increase in VOUT ripple or
load regulation.
Auto-Skip operation can be described in this way: As the output current decreases from a heavy load condition,
the inductor current is also reduced. Eventually, the inductor current reaches the point that its valley equals zero
current; that is, the boundary between continuous conduction and discontinuous conduction modes. The
rectifying MOSFET turns off when this zero inductor current is detected. Because the output voltage remains
higher than the reference voltage at this point, both high-side and low-side MOSFETs are turned off and wait for
the next cycle. As the load current decreases further, the converter runs in discontinuous conduction mode and
takes longer to discharge the output capacitor below the reference voltage. Note that the ON time remains the
same as that in the heavy load condition. On the other hand, when the output current increases from a light load
to a heavy load, the switching frequency increases to the preset value as the inductor current reaches the
continuous conduction limit. The transition load point to the light load operation IOUT(LL) (that is, the threshold
between continuous conduction and discontinuous conduction mode) can be calculated as shown in Equation 1:
Where fSW is the PWM switching frequency. Switching frequency versus output current under a light load
condition is a function of L, fSW, VIN, and VOUT, but decreases at a near-proportional rate to the output current
from the IOUT(LL) threshold. For example, the frequency is approximately 60 kHz at IOUT(LL)/5 if the PWM switching
frequency is 300 kHz.
PWM-only mode is selected if the SKIPSEL pin is connected to 5 V. The rectifying MOSFET does not turn off
when the inductor current reaches zero. The converter runs in forced continuous conduction mode over the
entire load range. System designers may want to use this mode to avoid certain frequencies under light load
conditions but do so at the cost of lower efficiency. However, keep in mind that the output has the capability to
both source and sink current in this mode. If the output terminal is connected to a voltage source that is higher
than the regulator target value, the converter sinks current from the output and boosts the charge into the input
capacitors. This operation may cause an unexpected high voltage at VIN and may damage the power FETs.
If SKIPSEL pin is connected to VREF2 or left floating, OOA mode operation is selected.
12
Copyright 2008, Texas Instruments Incorporated
Product Folder Link(s): TPS51427A
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS51427ARHBTG4 | 功能描述:DC/DC 開關(guān)控制器 Dual D-Cap Synch Step Down Cntrlr 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 |
| TPS51427RHBR | 功能描述:DC/DC 開關(guān)控制器 Dual D-Cap Synch Step Down Cntrlr 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 |
| TPS51427RHBRG4 | 功能描述:DC/DC 開關(guān)控制器 Dual D-Cap Sync Step Down Cntrlr 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 |
| TPS51427RHBT | 功能描述:DC/DC 開關(guān)控制器 Dual D-Cap Synch Step Down Cntrlr 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 |
| TPS51427RHBTG4 | 功能描述:DC/DC 開關(guān)控制器 Dual D-Cap Sync Step Down Cntrlr 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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