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參數(shù)資料
| 型號： | TPS62225DDCR |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.4 A SWITCHING REGULATOR, 1850 kHz SWITCHING FREQ-MAX, PDSO5 |
| 封裝： | GREEN, PLASTIC, TSOT-23, 5 PIN |
| 文件頁數(shù)： | 2/24頁 |
| 文件大?。?/td> | 676K |
| 代理商： | TPS62225DDCR |
DETAILED DESCRIPTION
OPERATION
POWER-SAVE MODE OPERATION
I
skip v
66 mA )
Vin
160 W
I
peak +
66 mA )
Vin
80 W
SLVS491E – SEPTEMBER 2003 – REVISED FEBRUARY 2009....................................................................................................................................... www.ti.com
The TPS6222x is a synchronous step-down converter operating with typically 1.25-MHz fixed frequency pulse
width modulation (PWM) at moderate to heavy load currents and in power-save mode operating with pulse
frequency modulation (PFM) at light load currents.
During PWM operation, the converter uses a unique fast response, voltage mode, controller scheme with input
voltage feed forward. This achieves good line and load regulation and allows the use of small ceramic input and
output capacitors. At the beginning of each clock cycle initiated by the clock signal (S), the P-channel MOSFET
switch is turned on, and the inductor current ramps up until the comparator trips and the control logic turns off the
switch. The current limit comparator also turns off the switch in case the current limit of the P-channel switch is
exceeded. Then, the N-channel rectifier switch is turned on and the inductor current ramps down. The next cycle
is initiated by the clock signal, again turning off the N-channel rectifier and turning on the P-channel switch.
The GM amplifier and input voltage determines the rise time of the sawtooth generator; therefore, any change in
input voltage or output voltage directly controls the duty cycle of the converter. This gives a very good line and
load transient regulation.
As the load current decreases, the converter enters the power-save mode operation. During power-save mode,
the converter operates with reduced switching frequency in PFM mode and with a minimum quiescent current to
maintain high efficiency. Two conditions allow the converter to enter the power-save mode operation. One is
when the converter detects discontinuous conduction mode. The other is when the peak switch current in the
P-channel switch goes below the skip current limit. The typical skip current limit can be calculated as:
During the power-save mode, the output voltage is monitored with the comparator (comp) by the thresholds
comp low and comp high. As the output voltage falls below the comp low threshold set to 0.8% typical above
Vout, the P-channel switch turns on. The P-channel switch is turned off as the peak switch current is reached.
The typical peak switch current can be calculated:
The N-channel rectifier is turned on and the inductor current ramps down. As the inductor current approaches
zero, the N-channel rectifier is turned off and the P-channel switch is turned on again, starting the next pulse.
The converter continues these pulses until the comp high threshold (set to typically 1.6% above Vout) is reached.
The converter enters a sleep mode, reducing the quiescent current to a minimum. The converter wakes up again
as the output voltage falls below the comp low threshold. This control method reduces the quiescent current
typically to 15
A and reduces the switching frequency to a minimum, thereby achieving high converter efficiency
at light load. Setting the skip current thresholds to typically 0.8% and 1.6% above the nominal output voltage at
light load current results in a dynamic output voltage achieving lower absolute voltage drops during heavy load
transient changes. This allows the converter to operate with a small output capacitor of just 10
F and still have a
low absolute voltage drop during heavy load transient changes. See Figure 14 for detailed operation of the
power-save mode.
10
Copyright 2003–2009, Texas Instruments Incorporated
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| TPS62227DDCTG4 | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 1.2V Out 400mA 95% Eff Step-Down Cnvrtr 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: 安裝風格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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