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參數資料
| 型號： | TPS65170RHDT |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩壓器 |
| 英文描述： | 4.2 A SWITCHING REGULATOR, 900 kHz SWITCHING FREQ-MAX, PQCC28 |
| 封裝： | 5 X 5 MM, GREEN, PLASTIC, QFN-28 |
| 文件頁數： | 8/35頁 |
| 文件大小： | 4698K |
| 代理商： | TPS65170RHDT |
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IN
LOGIC
DCM
SW
IN
V
I
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V
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SLVSA27 – OCTOBER 2009
www.ti.com
A capacitor can also be connected in parallel with the top resistor, as illustrated in Figure 24. The effect of this
capacitor is to slow down the speed with which the transistor turns on, thereby limiting inrush current. (Note that
the capacitor also slows down the speed with which the transistor turns off, and therefore the speed with which it
can respond to error conditions.)
Even when trying to limit inrush current, the capacitor must not be too large or the output voltage will rise so
slowly the condition will be interpreted as an error (see Power Supply Sequencing in Detail later in this data
sheet). Typical values are 10nF to 100nF, depending on the transistor used for the isolation switch and the value
of the gate-drive resistors.
Note that even in applications that do not use an isolation switch, an external pull-up resistor (typically 100k
Ω)
connected between the GD and VIN is required.
BUCK CONVERTER
The buck converter is a non-synchronous type that runs at a fixed frequency of 750kHz. The converter features
integrated soft-start (0.66ms), bootstrap, and compensation circuits to minimize external component count. The
buck converter's internal block diagram is shown in Figure 25 and a typical application circuit in Figure 26.
The output voltage of the buck converter is internally programmed to 3.3V and is enabled as soon as VIN
exceeds the UVLO threshold. For best performance, the buck converter's FB pin should be connected directly to
the positive terminal of the output capacitor(s).
The buck converter can operate in either continuous conduction mode (CCM) or discontinuous conduction mode
(DCM), depending on the load current. At medium and high load currents, the inductor current is always greater
than zero and the converter operates in CCM; at low load currents, the inductor current is zero during part of
each switching cycle, and the converter operates in DCM. The switch node waveforms for CCM and DCM
operation are shown in Figure 11 and Figure 12. Note that the ringing seen during DCM operation occurs
because of parasitic capacitance in the PCB layout and is quite normal for DCM operation. However, there is
very little energy contained in the ringing waveform and it does not significantly affect EMI performance.
Equation 10 can be used to calculate the load current below which the buck converter operates in DCM
(10)
The buck converter uses a skip mode to regulate VLOGIC at very low load currents. This mode allows the
converter to maintain its output at the required voltage while still meeting the requirement of a minimum on time.
The buck converter enters skip mode when its feedback voltage exceeds the skip mode threshold (1% above the
normal regulation voltage). During skip mode, the buck converter switches for a few cycles, then stops switching
for a few cycles, and then starts switching again and so on, for as long as the feedback voltage is above the skip
mode threshold. Output voltage ripple can be a little higher during skip mode (see Figure 13).
16
Copyright 2009, Texas Instruments Incorporated
Product Folder Link(s) :TPS65170
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| TPS65171RHAR | 功能描述:LCD 驅動器 Compact LCD Bias RoHS:否 制造商:Maxim Integrated 數位數量:4.5 片段數量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| TPS65175ARSHR | 制造商:Texas Instruments 功能描述:LCD BIAS CHIP AND LEVEL SHIFTE 制造商:Texas Instruments 功能描述:IC BIAS PWR SUPP FOR LCD 56VQFN 制造商:Texas Instruments 功能描述:Fully Programmable LCD Bias IC |
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| TPS65175RSHR | 功能描述:LCD 驅動器 Fully Programmable LCD Bias IC RoHS:否 制造商:Maxim Integrated 數位數量:4.5 片段數量:30 最大時鐘頻率:19 KHz 工作電源電壓:3 V to 3.6 V 最大工作溫度:+ 85 C 最小工作溫度:- 20 C 封裝 / 箱體:PDIP-40 封裝:Tube |
| TPS65176RHDR | 功能描述:其他電源管理 LCD BIAS IC FOR TV RoHS:否 制造商:Texas Instruments 輸出電壓范圍: 輸出電流:4 mA 輸入電壓范圍:3 V to 3.6 V 輸入電流: 功率耗散: 工作溫度范圍:- 40 C to + 110 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel |
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