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參數(shù)資料
| 型號： | TPS51220ARTVR |
| 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, PLASTIC, QFN-32 |
| 文件頁數(shù)： | 17/53頁 |
| 文件大?。?/td> | 1380K |
| 代理商： | TPS51220ARTVR |
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I
LL(DC) + ILL(PEAK) * 0.5
I
IND(RIPPLE)
IN
OUT
IND(RIPPLE)
SW
IN
(V
- V
) × V
1
I
=
×
L ×
V
f
(
)
(
)
LL(PEAK)RAMP
SW
OCL PEAK
I
0.2 - 0.13 t f
I
=
I
LL(DC)
Time
Inductor
Current
I
LL(PEAK)
I
IND(RIPPLE)
0
SLUS897D – DECEMBER 2008 – REVISED FEBRUARY 2010
www.ti.com
normal action of control loop against timing deviation caused by any accidental event such as noise, or the
blanking time, adjusting back to the regulation point. A small amount of jittering does not harm the voltage
regulation. However; if the user wants a further reduction of jitter, using the external clock synchronization
provides adjustable phase shift between channels to avoid overlapping of switching events.
See the PWM
Frequency Control section.
LIGHT LOAD OPERATION
The TPS51220A automatically reduces switching frequency at light load conditions to maintain high efficiency if
Auto Skip or Out-of-Audio 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 reaches a predetermined current, ILL(PEAK), which indicates the
boundary between heavy-load and light-load conditions. Once the top MOSFET is turned on, the TPS51220A
does not allow it to be turned off until it reaches ILL(PEAK). This eventually causes an overvoltage 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 ILL(PEAK)RAMP, which starts from 25% of the overcurrent limit setting (IOCL(PEAK): (see the Current
Protection section) toward 5% of IOCL(PEAK) over one switching cycle to prevent causing large ripple. The
(2)
where
fSW is the PWM switching frequency which is determined by RF resistor setting or external clock
(3)
(4)
Switching frequency versus output current in the light load condition is a function of L, f, VIN and VOUT, but it
decreases almost proportionally to the output current from the ILL(DC), as described in Equation 2; while
maintaining the switching synchronization with the 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, the TPS51220A works on a constant frequency of fSW regardless its load current.
Figure 42. Boundary Between Pulse Skipping and CCM
24
Copyright 2008–2010, Texas Instruments Incorporated
Product Folder Link(s) :TPS51220A
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| TPS51220RHBR | 功能描述:電流型 PWM 控制器 Fixed Freq 99% Duty Cycle Peak Current 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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