參數(shù)資料
型號(hào)： LT1432
廠商： Linear Technology Corporation
英文描述： 5V High Efficiency Step-Down Switching Regulator Controller
中文描述： 5V的高效率降壓型開關(guān)穩(wěn)壓控制器
文件頁(yè)數(shù)： 10/28頁(yè)
文件大?。?/td> 611K
代理商： LT1432
10
LT1432
U
S
A
O
PPLICATI
U
U
1A/DIV
Note that the switch output voltage is nearly identical to
the 12V input during switch on time, a necessary require-
ment for high efficiency, and indicative of an efficient
switch topology. Also note the fast, clean edges on the
switching waveforms, an additional requirement for high
efficiency. The “overlap time” of switch current and volt-
age, which leads to AC switching losses, is only 10ns.
Figure 4 shows the same waveforms when load current
has been reduced to 0.25A, and Figure 5 is at 25mA (note
the scale change for current in Figure 5). The regulator is
now into discontinuous mode as shown by the fact that
switch current has no initial jump, but starts its upward
slope from zero. This implies that the inductor current has
dropped to zero during switch off time, and that is shown
by the “ringing” waveform on the rising edge of switch
voltage. The switch has not yet been turned on, but the
voltage at its output rises and rings as the “input” end of
the inductor tries to settle to the same voltage as its
“output” end (5V).
This ringing is not an oscillation.It is the result of stored
energy in the catch diode capacitance. This energy is
transferred to the inductor as the inductor voltage at-
tempts to rise to 5V. The inductor and diode capacitance
tank circuit continues to ring until the stored energy is
dissipated by losses in the core and parasitic resistances.
The relatively undamped nature in this case is good
because it shows low losses and that translates to high
efficiency. EMI is not increased by operating in this mode.
Figure 6 shows input capacitor current (1A/DIV) with I
OUT
= 2A. The theoretical peak-to-peak value (ignoring sloping
waveforms) is equal to output current, and this is indeed
what the top waveform shows. The RMS value is approxi-
mately equal to one half output current. This is a major
consideration because the physical size of a capacitor with
1A ripple current rating may make it the largest component
in the regulator (see output capacitor section). Clever
desigers may hit on the idea of utilizing battery impedance
or remote input capacitors to divert some of the current
away from the actual local capacitor to reduce its size. This
is not too practical as shown by the middle waveform in
Figure 6, which shows input capacitor current when an
additional large capacitor is added about 6" away from the
local capacitor. The wiring inductance and parasitic resis-
tance limit the shunting effect and local capacitor current
is reduced only slightly. the bottom waveform shows input
capacitor current with output current reduced to 0.25A.
Figure 7 shows output capacitor ripple current at loads of
2A, 0.25A, and 25mA respectively starting from the top.
Note that ripple current is independent of load current until
the load drops well into the discontinuous region. The
small steps superimposed on the triangular ripple are
caused by loading of the diode which pumps the power
supply capacitor on the LT1271. Amplitude of the ripple
current is about 0.7Ap-p in this case, or approximately
0.5A/DIV
5
μ
s/DIV
Figure 6. Input Capacitor Current
Figure 7. Output Capacitor Ripple Current
5
μ
s/DIV
相關(guān)PDF資料
PDF描述
LT1432-3.3 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LT1432CN8 5V High Efficiency Step-Down Switching Regulator Controller
LT1432CN8-3.3 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LT1432CS8 5V High Efficiency Step-Down Switching Regulator Controller
LT1432CS8-3.3 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT1432-3.3 制造商:LINER 制造商全稱:Linear Technology 功能描述:3.3V High Efficiency Step-Down Switching Regulator Controller
LT1432CN8 制造商:LINER 制造商全稱:Linear Technology 功能描述:5V High Efficiency Step-Down Switching Regulator Controller
LT1432CN8-3.3 功能描述:IC REG CTRLR BUCK PWM 8-DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR)
LT1432CS8 制造商:Linear Technology 功能描述:
LT1432CS8-3.3 制造商:LINER 制造商全稱:Linear Technology 功能描述:3.3V High Efficiency Step-Down Switching Regulator Controller
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