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參數(shù)資料
型號: TPS51221RTVRG4
廠商: TEXAS INSTRUMENTS INC
元件分類: 穩(wěn)壓器
英文描述: DUAL SWITCHING CONTROLLER, 333 kHz SWITCHING FREQ-MAX, PQCC32
封裝: 5 X 5 MM, GREEN, PLASTIC, QFN-32
文件頁數(shù): 15/39頁
文件大小: 829K
代理商: TPS51221RTVRG4
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RF-Resistance-kW
f
-Frequency-kHz
SW
LIGHT LOAD OPERATION
I
LL(DC) + ILL(PEAK) * 0.5
I
IND(RIPPLE)
(2)
I
IND(RIPPLE) +
1
L
SW
V
IN * VOUT
V
OUT
V
IN
(3)
SLVS786A – NOVEMBER 2007 – REVISED MARCH 2009............................................................................................................................................... www.ti.com
The TPS51221 does NOT support switching frequency change on-the-fly. (neither from the switching frequency
set by the RF resistor to the external clock, nor vice versa)
Figure 39. Switching Frequency vs RF
The TPS51221 automatically reduces switching frequency at light load condition to maintain high efficiency if
Auto Skip or OOA mode is selected by SKIPSELx. This reduction of frequency is achieved by skipping pulses.
As the output current decreases from heavy load condition, the inductor current is also reduced and eventually
comes to the point that its peak touches a predetermined current, ILL(PEAK), which indicates the boundary between
heavy-load and light-load conditions. Once the top MOSFET is turned on, the TPS51221 does not allow turning it
off until it touches ILL(PEAK). This eventually causes an over-voltage condition to the output, and pulse skipping.
From the next pulse after zero-crossing is detected, ILL(PEAK) is limited by the ramp-down signal which starts from
25% of the over-current limit setting (IOCL(PEAK): see the CURRENT PROTECTION section) toward 5% of
IOCL(PEAK), over one switching cycle to prevent causing a large ripple. The transition load point to the light load
operation ILL(DC) can be calculated as follows;
where fSW is the PWM switching frequency as determined by RF resistor setting or external clock. Switching
frequency versus output current in the light load condition is a function of L, f, Vin and Vout; but it decreases
almost proportional to the output current from the ILL(DC) given above however, as the switching is synchronized
with clock. Due to the synchronization, the switching waveform in boundary load condition (close to ILL(DC)),
appears as a sub-harmonic oscillation; however, it is the intended operation.
If SKIPSELx is tied to GND, TPS51221 works at the constant frequency of fSW, regardless of its load current.
22
Copyright 2007–2009, Texas Instruments Incorporated
Product Folder Link(s): TPS51221
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
TPS51221RTVT 功能描述:電流型 PWM 控制器 Fixed Freq Notebook Sys Pwr Dual Cntrlr RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
TPS51221RTVTG4 功能描述:電流型 PWM 控制器 Fixed Freq Notebook Sys Pwr Cntrlr RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
TPS51222 制造商:TI 制造商全稱:Texas Instruments 功能描述:Fixed Frequency, 99% Duty Cycle Peak Current Mode Notebook System Power Controller
TPS51222RTVR 功能描述:電流型 PWM 控制器 Fixed-Freq,Notebook Sys Pwr Cntrlr RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
TPS51222RTVT 功能描述:電流型 PWM 控制器 Fixed-Freq,Notebook Sys Pwr Cntrlr RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
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