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參數(shù)資料
| 型號： | LTC3405AES6 |
| 英文描述： | Analog IC |
| 中文描述： | 模擬IC |
| 文件頁數(shù)： | 10/16頁 |
| 文件大小： | 239K |
| 代理商： | LTC3405AES6 |
10
LTC3405A
3405af
APPLICATIOU
Although all dissipative elements in the circuit produce
losses, two main sources usually account for most of the
losses in LTC3405A circuits: V
IN
quiescent current and I
2
R
losses. The V
IN
quiescent current loss dominates the
efficiency loss at very low load currents whereas the I
2
R
loss dominates the efficiency loss at medium to high load
currents. In a typical efficiency plot, the efficiency curve at
very low load currents can be misleading since the actual
power lost is of no consequence as illustrated in Figure 4.
W
U
U
2. I
2
R losses are calculated from the resistances of the
internal switches, R
SW
, and external inductor R
L
. In
continuous mode, the average output current flowing
through inductor L is “chopped” between the main
switch and the synchronous switch. Thus, the series
resistance looking into the SW pin is a function of both
top and bottom MOSFET R
DS(ON)
and the duty cycle
(DC) as follows:
R
SW
= (R
DS(ON)TOP
)(DC) + (R
DS(ON)BOT
)(1 – DC)
The R
DS(ON)
for both the top and bottom MOSFETs can
be obtained from the Typical Performance Charateristics
curves. Thus, to obtain I
2
R losses, simply add R
SW
to
R
L
and multiply the result by the square of the average
output current.
Other losses including C
IN
and C
OUT
ESR dissipative
losses and inductor core losses generally account for less
than 2% total additional loss.
Thermal Considerations
In most applications the LTC3405A does not dissipate
much heat due to its high efficiency. But, in applications
where the LTC3405A is running at high ambient
temperature with low supply voltage and high duty
cycles, such as in dropout, the heat dissipated may
exceed the maximum junction temperature of the part. If
the junction temperature reaches approximately 150
°
C,
both power switches will be turned off and the SW node
will become high impedance.
To avoid the LTC3405A from exceeding the maximum
junction temperature, the user will need to do some
thermal analysis. The goal of the thermal analysis is to
determine whether the power dissipated exceeds the
maximum junction temperature of the part. The tempera-
ture rise is given by:
T
R
= (P
D
)(
θ
JA
)
where P
D
is the power dissipated by the regulator and
θ
JA
is the thermal resistance from the junction of the die to the
ambient temperature.
Figure 4. Power Lost vs Load Current
LOAD CURRENT (mA)
0.1
P
10
1000
1
0.1
0.01
0.001
0.0001
3405A F04
1
100
V
OUT
= 1.8V
V
IN
= 3.6V
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.3V
1. The V
IN
quiescent current is due to two components:
the DC bias current as given in the electrical character-
istics and the internal main switch and synchronous
switch gate charge currents. The gate charge current
results from switching the gate capacitance of the
internal power MOSFET switches. Each time the gate is
switched from high to low to high again, a packet of
charge, dQ, moves from V
IN
to ground. The resulting
dQ/dt is the current out of V
IN
that is typically larger than
the DC bias current. In continuous mode, I
GATECHG
=
f(Q
T
+ Q
B
) where Q
T
and Q
B
are the gate charges of the
internal top and bottom switches. Both the DC bias and
gate charge losses are proportional to V
IN
and thus
their effects will be more pronounced at higher supply
voltages.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3405AES6#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 1.5 MHz 6-SOT-23 制造商:Linear Technology 功能描述:BUCK 0.3A 1.8V 1.5MHZ 6TSOT23 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 1.5 MHz, 6-SOT-23 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 1.5 MHz, 6-SOT-23; Primary Input Voltage:5.5V; No. of Outputs:1; Output Voltage:800mV; Output Current:300mA; No. of Pins:6; Operating Temperature Min:-40C; Operating Temperature Max:85C; MSL:MSL 1 - Unlimited ;RoHS Compliant: Yes |
| LTC3405AES6#TR | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 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:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC3405AES6#TRM | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 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:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
| LTC3405AES6#TRMPBF | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 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:- 產(chǎn)品培訓(xùn)模塊:High Efficiency Current Mode Switching Regulators CMOS LDO Regulators 特色產(chǎn)品:BD91x Series Step-Down Regulators 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:降壓（降壓） 輸出類型:兩者兼有 輸出數(shù):2 輸出電壓:3.3V，0.8 V ~ 2.5 V 輸入電壓:4.5 V ~ 5.5 V PWM 型:電流模式 頻率 - 開關(guān):1MHz 電流 - 輸出:1.5A 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:20-VFQFN 裸露焊盤 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:VQFN020V4040 產(chǎn)品目錄頁面:1373 (CN2011-ZH PDF) 其它名稱:BD9152MUV-E2TR |
| LTC3405AES6#TRPBF | 功能描述:IC REG BUCK SYNC ADJ .3A SOT23-6 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:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
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