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參數(shù)資料
| 型號： | TPS54354MPWPREP |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 6.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | GREEN, PLASTIC, HTSSOP-16 |
| 文件頁數(shù)： | 2/35頁 |
| 文件大小： | 1132K |
| 代理商： | TPS54354MPWPREP |
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Extending Slow-Start Time
Use n in Table 2.
CSS (F) = 5.55
103
n
Tss (ms)
(4)
Switching Frequency (RT)
RT (kW) +
46000
s (kHz) * 35.9
(5)
180° Out-of-Phase Synchronization (SYNC)
SLVS684A – JANUARY 2007 – REVISED JULY 2009 ....................................................................................................................................................... www.ti.com
In applications that use large values of output capacitance, there may be a need to extend the slow-start time to
prevent the startup current from tripping the current limit. The current-limit circuit is designed to disable the
high-side MOSFET and reset the internal voltage reference for a short amount of time when the high-side
MOSFET current exceeds the current-limit threshold. If the output capacitance and load current cause the startup
current to exceed the current-limit threshold, the power-supply output will not reach the desired output voltage.
To extend the slow-start time and to reduce the startup current, an external resistor and capacitor can be added
to the ENA pin. The slow-start capacitance is calculated using the following equation:
The RSS resistor must be 2 k and the slow-start capacitor must be less than 0.47 F.
The TPS5435x has an internal oscillator that operates at twice the PWM switching frequency. The internal
oscillator frequency is controlled by the RT pin. Grounding RT sets the PWM switching frequency to a default
frequency of 250 kHz. Floating RT sets the PWM switching frequency to 500 kHz.
Connecting a resistor from RT to AGND sets the frequency according to the following equation (also see
RT controls the SYNC pin functions. If RT is floating or grounded, SYNC is an output. If the switching frequency
has been programmed using a resistor from RT to AGND, SYNC functions as an input.
The internal voltage-ramp charging current increases linearly with the set frequency and keeps the feed-forward
modulator constant (Km = 8), regardless of the frequency set point.
Table 3.
SWITCHING FREQUENCY
SYNC PIN
RT PIN
250 kHz, internally set
Generates SYNC output signal
AGND
500 kHz, internally set
Generates SYNC output signal
Float
Terminate to quiet ground
Externally set from 250 kHz to 700 kHz
R = 215 k
to 69 k
with 10-k
resistor
Set RT resistor equal to 90% to 110% of external
synchronization frequency. When using a dual setup (see
Figure 27 for example), if the master 35x device RT pin is
Externally synchronized frequency
Synchronization signal
left floating, use a 110-k
resistor to tie the slave RT pin
to ground. Conversely, if the master 35x device RT pin is
grounded, use a 237-k
resistor to tie the slave RT pin to
ground.
The SYNC pin is configurable as an input or as an output, as noted in the previous section. When operating as
an input, SYNC is a falling-edge-triggered signal (see Figure 3, Figure 4, and Figure 19). When operating as an
output, the signal's falling edge is approximately 180° out of phase with the rising edge of the PH pins. Thus, two
TPS5435x devices operating in a system can share an input capacitor and draw ripple current at twice the
frequency of a single unit.
When operating the two TPS5435x devices 180° out of phase, the total RMS input current is reduced, thus,
reducing the amount of input capacitance needed and increasing efficiency.
When synchronizing a TPS5435x to an external signal, the timing resistor on the RT pin must be set so that the
oscillator is programmed to run at 90% to 110% of the synchronization frequency.
10
Copyright 2007–2009, Texas Instruments Incorporated
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相關(guān)代理商/技術(shù)參數(shù) |
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| TPS54354PWP | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 4.5 to 20V Inp 3-A Synch PWM Switch 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(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| TPS54354PWPG4 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 4.5 to 20V Inp 3-A Synch PWM Switch RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| TPS54354PWPR | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 4.5 to 20V Inp 3-A Synch PWM Switch RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| TPS54354PWPRG4 | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 4.5 to 20V Inp 3-A Synch PWM Switch RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| TPS54355 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:4.5V TO 20 V INPUT 3-A OUTPUT SYNCHRONOUS PWM SWITCHER WITH INTEGRATED FET |
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