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參數(shù)資料
| 型號： | TPS54426PWP |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 7.5 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO14 |
| 封裝： | GREEN, PLASTIC, HSSOP-14 |
| 文件頁數(shù)： | 24/26頁 |
| 文件大?。?/td> | 945K |
| 代理商： | TPS54426PWP |
(
)
(
)
2
1
-
×
=
× ×
IN
OUT
OUT LL
IN
V
I
L fsw
V
Tss(ms)=
C6(nF) Vref
Iss( A)
=
C6(nF) 0.765
2
www.ti.com
SLVSAD6B – AUGUST 2010 – REVISED NOVEMBER 2010
OVERVIEW
The TPS54426 is a 4-A synchronous step-down (buck) converter with two integrated N-channel MOSFETs and
auto-skip Eco-mode to improve light lode efficiency. It operates using D-CAP2 mode control. The fast
transient response of D-CAP2 control reduces the output capacitance required to meet a specific level of
performance. Proprietary internal circuitry allows the use of low ESR output capacitors including ceramic and
special polymer types.
DETAILED DESCRIPTION
PWM Operation
The main control loop of the TPS54426 is an adaptive on-time pulse width modulation (PWM) controller that
supports a proprietary D-CAP2 mode control. D-CAP2 mode control combines constant on-time control with
an internal compensation circuit for pseudo-fixed frequency and low external component count configuration with
both low ESR and ceramic output capacitors. It is stable with virtually no ripple at the output.
At the beginning of each cycle, the high-side MOSFET is turned on. The MOSFET is turned off after the internal
one-shot timer expires. The one-shot timer is set by the converter input voltage, VIN, and the output voltage, VO,
to maintain a pseudo-fixed frequency over the input voltage range, hence it is called adaptive on-time control.
The one-shot timer is reset and the high-side MOSFET is turned on again when the feedback voltage falls below
the reference voltage. An internal ramp is added to reference voltage to simulate output ripple, eliminating the
need for ESR induced output ripple from D-CAP2 mode control.
PWM Frequency and Adaptive On-Time Control
TPS54426 uses an adaptive on-time control scheme and does not have a dedicated on board oscillator. The
TPS54426 runs with a pseudo-constant frequency of 700 kHz by using the input voltage and output voltage to
set the on-time one-shot timer. The on-time is inversely proportional to the input voltage and proportional to the
output voltage, therefore, when the duty ratio is VOUT/VIN, the frequency is constant.
Auto-Skip Eco-Mode Control
The TPS54426 is designed with Auto-Skip Eco-mode to increase light load efficiency. As the output current
decreases from heavy load condition, the inductor current is also reduced and eventually comes to point that its
rippled valley touches zero level, which is the boundary between continuous conduction and discontinuous
conduction modes. The rectifying MOSFET is turned off when its zero inductor current is detected. As the load
current further decreases the converter run into discontinuous conduction mode. The on-time is kept almost the
same as is was in the continuous conduction mode so that it takes longer time to discharge the output capacitor
with smaller load current to the level of the reference voltage. The transition point to the light load operation
(1)
Soft Start and Pre-Biased Soft Start
The soft start function is adjustable. When the EN pin becomes high, 2 mA current begins charging the capacitor
which is connected from the SS pin to GND. Smooth control of the output voltage is maintained during start up.
The equation for the slow start time is shown in Equation 2. VFB voltage is 0.765 V and SS pin source current is
2 mA.
(2)
The TPS54426 contains a unique circuit to prevent current from being pulled from the output during startup if the
output is pre-biased. When the soft-start commands a voltage higher than the pre-bias level (internal soft start
becomes greater than feedback voltage VFB), the controller slowly activates synchronous rectification by starting
the first low side FET gate driver pulses with a narrow on-time. It then increments that on-time on a cycle-by-
cycle basis until it coincides with the time dictated by (1-D), where D is the duty cycle of the converter. This
scheme prevents the initial sinking of the pre-bias output, and ensure that the out voltage (VO) starts and ramps
up smoothly into regulation and the control loop is given time to transition from pre-biased start-up to normal
mode operation.
Copyright 2010, Texas Instruments Incorporated
7
Product Folder Link(s) :TPS54426
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TPS54426PWP | 制造商:Texas Instruments 功能描述:IC BUCK SYNC ADJ 14HTSSOP 制造商:Texas Instruments 功能描述:IC, BUCK, SYNC, ADJ, 14HTSSOP 制造商:Texas Instruments 功能描述:IC, BUCK, SYNC, ADJ, 14HTSSOP; Primary Input Voltage:18V; No. of Outputs:1; Output Current:10mA; Voltage Regulator Case Style:HTSSOP; No. of Pins:14; Operating Temperature Min:-40C; Operating Temperature Max:85C; SVHC:No SVHC ;RoHS Compliant: Yes |
| TPS54426PWPR | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 4.5-18V Inp,4A Synch SWIFT Converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| TPS54426RSAR | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 4.5V-18Vin,4A Synch Step-Down SWIFT RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| TPS54426RSAT | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 4.5V-18Vin,4A Synch Step-Down SWIFT RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT |
| TPS54427 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:4.5V to 18 V Input, 4-A Output Single Synchronous Step-Down Switcher with Integrated FET (SWIFTa?￠) |
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