參數(shù)資料
型號(hào)： TPS40056PWPG4
廠商： TEXAS INSTRUMENTS INC
元件分類： 穩(wěn)壓器
英文描述： SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16
封裝： PLASTIC, HTSSOP-16
文件頁(yè)數(shù)： 3/32頁(yè)
文件大?。?/td> 747K
代理商： TPS40056PWPG4
TPS40056
SLVS612 APRIL 2006
11
www.ti.com
APPLICATION INFORMATION
PROGRAMMING SOFT START
TPS40056 uses a closed-loop approach to ensure a controlled ramp on the output during start-up. Soft-start
is programmed by charging an external capacitor (CSS) via an internally generated current source. The voltage
on CSS is fed into a separate non-inverting input to the error amplifier (in addition to FB and EA_REF). The loop
is closed on the lower of the CSS voltage or the the external reference voltage EA_REF. Once the CSS voltage
rises above the external reference voltage, regulation is based on the external reference. To ensure a controlled
ramp-up of the output voltage the soft-start time should be greater than the L-CO time constant as described
in equation (10).
t
START w 2p
L
C
O
(seconds)
There is a direct correlation between tSTART and the input current required during start-up. The faster tSTART,
the higher the input current required during start-up. This relationship is describe in more detail in the section
titled, Programming the Current Limit which follows. The soft-start capacitance, CSS, is described in
equation (11).
For applications in which the VIN supply ramps up slowly, (typically between 50 ms and 100 ms) it may be
necessary to increase the soft-start time to between approximately 2 ms and 5 ms to prevent nuisance UVLO
tripping. The soft-start time should be longer than the time that the VIN supply transitions between 8 V and 9 V.
C
SS +
2.3
mA
0.7 V
t
START
(Farads)
PROGRAMMING CURRENT LIMIT
The TPS40056 uses a two-tier approach for overcurrent protection. The first tier is a pulse-by-pulse protection
scheme. Current limit is implemented on the high-side MOSFET by sensing the voltage drop across the
MOSFET when the gate is driven high. The MOSFET voltage is compared to the voltage dropped across a
resistor connected from VIN pin to the ILIM pin when driven by a constant current sink. If the voltage drop across
the MOSFET exceeds the voltage drop across the ILIM resistor, the switching pulse is immediately terminated.
The MOSFET remains off until the next switching cycle is initiated.
The second tier consists of a fault counter. The fault counter is incremented on an overcurrent pulse and
decremented on a clock cycle without an overcurrent pulse. When the counter reaches seven (7) a restart is
issued and seven soft-start cycles are initiated. Both the upper and lower MOSFETs are turned off during this
period. The counter is decremented on each soft-start cycle. When the counter is decremented to zero, the
PWM is re-enabled. If the fault has been removed the output starts up normally. If the output is still present the
counter counts seven overcurrent pulses and re-enters the second-tier fault mode. See Figure 3 for typical
overcurrent protection waveforms.
The minimum current limit setpoint (ILIM) depends on tSTART, CO, VO, and the load current at turn-on (IL).
I
LIM +
C
O
V
O
t
START
) I
L
(Amperes)
(10)
(11)
(12)
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TPS40057 制造商:TI 制造商全稱:Texas Instruments 功能描述:WIDE INPUT SYNCHRONOUS BUCK CONTROLLER
TPS40057PWP 功能描述:DC/DC 開(kāi)關(guān)控制器 Wide Input Sync Buck src/sink w/prebias RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK
TPS40057PWP 制造商:Texas Instruments 功能描述:CONTROLLER IC
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