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參數資料
| 型號： | TPS54328DDA |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 穩壓器 |
| 英文描述： | 5.7 A SWITCHING REGULATOR, 700 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | GREEN, PLASTIC, MS-012BA, SOP-8 |
| 文件頁數： | 17/19頁 |
| 文件大小： | 497K |
| 代理商： | TPS54328DDA |
(
)
(
)
2
1
-
×
=
× ×
IN
OUT
OUT LL
IN
V
I
L fsw
V
C6(nF) x V
C6(nF) x 0.765
REF
t
(ms) =
=
SS
I
( A)
2
SS
m
www.ti.com
SLVSAN2 – NOVEMBER 2010
OVERVIEW
The TPS54328 is a 3-A synchronous step-down (buck) converter with two integrated N-channel MOSFETs. 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 TPS54328 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 even with virtually no ripple at the output.
At the beginning of each cycle, the high-side MOSFET is turned on. This MOSFET is turned off after internal one
shot timer expires. This one shot 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
TPS54328 uses an adaptive on-time control scheme and does not have a dedicated on board oscillator. The
TPS54328 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 TPS54328 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 TPS54328 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) :TPS54328
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相關代理商/技術參數 |
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| TPS54328DDAR | 功能描述:直流/直流開關轉換器 4.5V-18Vin,3A Synch Step-Down SWIFT RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| TPS54328DRCR | 功能描述:直流/直流開關轉換器 4.5V-18V Inp 3A Sync SD DCAP Md Cnvrtr RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| TPS54328DRCT | 功能描述:直流/直流開關轉換器 4.5V-18V Inp 3A Sync SD DCAP Md Cnvrtr RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| TPS54328EVM-686 | 功能描述:電源管理IC開發工具 TPS54328 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 |
| TPS54329 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:4.5V to 18V Input, 3-A SYNCHRONOUS STEP DOWN CONVERTER |
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