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參數資料
| 型號： | TPS65257RHAT |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩壓器 |
| 英文描述： | 4 A SWITCHING REGULATOR, 2200 kHz SWITCHING FREQ-MAX, PQCC40 |
| 封裝： | 6 X 6 MM, GREEN, PLASTIC, VQFN-40 |
| 文件頁數： | 17/34頁 |
| 文件大小： | 2100K |
| 代理商： | TPS65257RHAT |
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VOUT
Burst
Skipping
IL
IOUT
_
RIP
S
OUT
RIPPLE
OUT
K
T
V
C
=
0.35
S
IN
OUT
IN
T
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SLVSB32
– SEPTEMBER 2011
Low Power/Pulse Skipping Operation
When a buck synchronous converter operates at light load or standby conditions, the switching losses are the
dominant source of power losses. Under these load conditions, TPS65257 uses a pulse skipping modulation
technique to reduce the switching losses by keeping the power transistors in the off-state for several switching
cycles, while maintaining a regulated output voltage. Figure 45 shows the output voltage and load plus the
inductor current.
Figure 45. Low Power/Pulse Skipping
During the burst mode, the converter continuously charges up the output capacitor until the output voltage
reaches a certain limit threshold. The operation of the converter in this interval is equivalent to the peak inductor
current mode control. In each switch period, the main switch is turned on until the inductor current reaches the
peak current limit threshold. As the load increases the number of pulses increases to make sure that the output
voltage stays within regulation limits. When the load is very light the low power controller has a zero crossing
detector to allow the low side mosfet to operate even in light load conditions. The transistor is not disabled at
light loads. A zero crossing detection circuit will disable it when inductor current reverses. During the whole
process the body diode does not conduct but is used as blocking diode only.
During the skipping interval, the upper and lower transistors are turned off and the converter stays in idle mode.
The output capacitors are discharged by the load current until the moment when the output voltage drops to a
low threshold.
The choice of output filter will influence the performance of the low power circuit. The maximum ripple during low
power mode can be calculated as:
(12)
Where KRIP is 1.4 for Buck1 and 0.7 for Buck2 and Buck3. TS can be calculated as:
(13)
USB Switch
The USB switch is enabled (active high) with the USB_EN pin. The switch has a typical resistance of 100m
and
has a fold-back current limit that is typically 25% lower than the overcurrent detection point. If a continuous
short-circuit condition is applied to the USB switch output, the USB switch will shut-down once its temperature
reaches 130
°C, allowing for the buck converters to operate unaffected. Once the USB switch cools down it will
restart automatically.
24
Copyright
2011, Texas Instruments Incorporated
Product Folder Link(s): TPS65257
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| TPS65258EVM | 功能描述:電源管理IC開發工具 TPS65258 EVAL MOD RoHS:否 制造商:Maxim Integrated 產品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| TPS65258RHAR | 功能描述:PMIC 解決方案 3 DC-DC CONVERTERS RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| TPS65258RHAT | 功能描述:PMIC 解決方案 3 DC-DC CONVERTERS RoHS:否 制造商:Texas Instruments 安裝風格:SMD/SMT 封裝 / 箱體:QFN-24 封裝:Reel |
| TPS65261-1RHBR | 功能描述:Buck Switching Regulator IC Positive Adjustable 0.6V 3 Output 3A, 2A 32-VFQFN Exposed Pad 制造商:texas instruments 系列:- 包裝:剪切帶（CT） 零件狀態:有效 功能:降壓 輸出配置:正 拓撲:降壓 輸出類型:可調式 輸出數:3 電壓 - 輸入（最小值）:4.5V 電壓 - 輸入（最大值）:18V 電壓 - 輸出（最小值/固定）:0.6V 電壓 - 輸出（最大值）:18V 電流 - 輸出:3A，2A 頻率 - 開關:250kHz ~ 2MHz 同步整流器:是 工作溫度:-40°C ~ 85°C（TA） 安裝類型:表面貼裝 封裝/外殼:32-VFQFN 裸露焊盤 供應商器件封裝:32-VQFN（5x5） 標準包裝:1 |
| TPS65261-1RHBT | 功能描述:IC REG BCK ADJ 3A/2A TRPL 32VQFN 制造商:texas instruments 系列:- 包裝:剪切帶（CT） 零件狀態:在售 功能:降壓 輸出配置:正 拓撲:降壓 輸出類型:可調式 輸出數:3 電壓 - 輸入（最小值）:4.5V 電壓 - 輸入（最大值）:18V 電壓 - 輸出（最小值/固定）:0.6V 電壓 - 輸出（最大值）:18V 電流 - 輸出:3A，2A 頻率 - 開關:250kHz ~ 2MHz 同步整流器:是 工作溫度:-40°C ~ 85°C（TA） 安裝類型:表面貼裝 封裝/外殼:32-VFQFN 裸露焊盤 供應商器件封裝:32-VQFN（5x5） 標準包裝:1 |
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