參數(shù)資料
型號(hào)： LTC1574
廠商： Linear Technology Corporation
英文描述： High Efficiency Step-Down DC/DC Converters with Internal Schottky Diode(可調(diào)輸出，高效率步降DC/DC變換器（內(nèi)部帶肖特基二極管）)
中文描述： 高效降壓DC / DC轉(zhuǎn)換器的內(nèi)部肖特基二極管（可調(diào)輸出，高效率步降直流/直流變換器（內(nèi)部帶肖特基二極管））
文件頁(yè)數(shù)： 6/8頁(yè)
文件大小： 161K
代理商： LTC1574
6
LTC1574
LTC1574-3.3/LTC1574-5
For C
OUT
, the RMS current rating should be at least:
(
=
300mA
I
I
A
RMS
PEAK
2
RMS
≈
)
Absolute Maximum Ratings and Latchup Prevention
The absolute maximum ratings specify that SW
(Pins 3, 14) can never exceed V
IN
(Pin 5) by more than
0.3V. Normally this situation should never occur. It could,
however, if the output is held up while the supply is pulled
down. A condition where this could potentially occur is
when a battery is supplying power to an LTC1574 regula-
tor and also to one or more loads in parallel with the the
regulator’s V
IN
. If the battery is disconnected while the
LTC1574 regulator is supplying a light load and one of the
parallel circuits is a heavy load, the input capacitor of the
LTC1574 regulator could be pulled down faster than the
output capacitor, causing the absolute maximum ratings
to be exceeded. The result is often a latchup which can be
destructive if V
IN
is reapplied. Battery disconnect is pos-
sible as a result of mechanical stress, bad battery contacts
or use of a lithium-ion battery with a built-in internal
disconnect. The user needs to assess his/her application
to determine whether this situation could occur. If so,
additional protection is necessary.
Prevention against latchup can be accomplished by
simply connecting a Schottky diode across the SW and
V
IN
pins as shown in Figure 7. The diode will normally be
reverse biased unless V
IN
is pulled below V
OUT
at which
time the diode will clamp the (V
OUT
– V
IN
) potential to less
than the 0.6V required for latchup. Note that a low
leakage Schottky should be used to minimize the effect
inductor L1 is chosen for its excellent self-shielding prop-
erties. Open magnetic structures such as drum and rod
cores are to be avoided since they inject high flux levels
into their surroundings. This can become a major source
of noise in any converter circuit.
Design Example
As a design example, assume V
IN
= 9V (nominal),
V
OUT
= 5V and I
OUT
= 350mA maximum. The LTC1574-5
is used for this application with I
PGM
(Pin 6) connected to
V
IN
. The minimum value of L is determined by assuming
the LTC1574-5 is operating in continuous mode.
Figure 6. Continuous Inductor Current
With I
OUT
= 350mA and I
PEAK
= 0.6A (I
PGM
= V
IN
), I
V
= 0.1A.
The peak-to-peak ripple inductor current, I
RIPPLE
, is 0.5A
and is also equal to:
Solving for L in the above equation and with V
D
= 0.5V,
L = 44
μ
H. The next higher standard value of L is 50
μ
H
(example: Coiltronics CTX50-4). The operating frequency,
ignoring voltage across diode V
D
is:
=
111
With the value of L determined, the requirements for C
IN
and C
OUT
are calculated. For C
IN
, its RMS current rating
should be at least:
[
I
V
V
L
RIPPLE
OUT
D
=
+
(
)
4 10
6
A
P-P
f
V
V
kHz
OUT
IN
≈
2.
5
I
I
V
V
V
V
A
mA
RMS
OUT
OUT
IN
OUT
IN
RMS
=
(
)
]
(
)
=
1 2
/
174
I
TIME
I
PEAK
I
V
AVG CURRENT= I
OUT
=
= 350mA
I
PEAK
+ I
V
2
1574 F06
APPLICATIOU
W
U
U
1574 F07
V
IN
V
OUT
LATCHUP
PROTECTION
SCHOTTKY
SW
LTC1574
+
Figure 7. Preventing Absolute Maximum
Ratings from Being Exceeded
相關(guān)PDF資料
PDF描述
LTC1574-3.3 High Efficiency Step-Down DC/DC Converters with Internal Schottky Diode(3.3V,高效率步降DC/DC變換器（內(nèi)部帶肖特基二極管）)
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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LTC1574CS#PBF 功能描述:IC REG BUCK INV ADJ 16SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關(guān):2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁(yè)面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2
LTC1574CS#TR 功能描述:IC REG BUCK INV ADJ 16SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 設(shè)計(jì)資源:Design Support Tool 標(biāo)準(zhǔn)包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 包裝:剪切帶 (CT) 供應(yīng)商設(shè)備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT
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