參數(shù)資料
型號(hào)： LTC1878
廠商： Linear Technology Corporation
英文描述： High Efficiency Monolithic Synchronous Step-Down Regulator(高效率,單片同步步降穩(wěn)壓器)
中文描述： 高效率單片同步降壓型穩(wěn)壓器（高效率，單片同步步降穩(wěn)壓器）
文件頁(yè)數(shù)： 8/16頁(yè)
文件大?。?/td> 228K
代理商： LTC1878
8
LTC1878
INPUT VOLTAGE (V)
2.5
0
M
200
400
600
800
1200
3.5
4.5
5.5
6.5
1878 F01
7.5
1000
V
OUT
= 1.5V
V
OUT
= 3.3V
V
OUT
= 2.5V
L = 10
μ
H
Figure 1. Maximum Output Current vs Input Voltage
Figure 2. Maximum Inductor Peak Current vs Duty Cycle
Dropout Operation
When the input supply voltage decreases toward the
output voltage, the duty cycle increases toward the maxi-
mum on-time. Further reduction of the supply voltage
forces the main switch to remain on for more than one
cycle until it reaches 100% duty cycle. The output voltage
will then be determined by the input voltage minus the
voltage drop across the internal P-channel MOSFET and
the inductor.
Low Supply Operation
The LTC1878 is designed to operate down to an input
supply voltage of 2.65V although the maximum allowable
output current is reduced at this low voltage. Figure 1
shows the reduction in the maximum output current as a
function of input voltage for various output voltages.
Another important detail to remember is that at low input
supply voltages, the R
DS(ON)
of the P-channel switch
increases. Therefore, the user should calculate the power
dissipation when the LTC1878 is used at 100% duty cycle
with a low input voltage (see Thermal Considerations in
the Applications Information section).
Slope Compensation and Inductor Peak Current
Slope compensation provides stability in constant fre-
quency architectures by preventing subharmonic oscilla-
tions at high duty cycles. It is accomplished internally by
adding a compensating ramp to the inductor current
signal at duty cycles in excess of 40%. As a result, the
maximum inductor peak current is reduced for duty cycles
>40%. This is shown in the decrease of the inductor peak
current as a function of duty cycle graph in Figure 2.
DUTY CYCLE (%)
0
M1100
1000
900
800
700
600
80
1878 F02
20
40
60
100
V
IN
= 3.3V
OPERATIOU
APPLICATIOU
The basic LTC1878 application circuit is shown on the first
page. External component selection is driven by the load
requirement and begins with the selection of L followed by
C
IN
and C
OUT
.
W
U
U
Inductor Value Calculation
The inductor selection will depend on the operating fre-
quency of the LTC1878. The internal nominal frequency is
550kHz, but can be externally synchronized from 400kHz
to 700kHz.
The operating frequency and inductor selection are inter-
related in that higher operating frequencies allow the use
of smaller inductor and capacitor values. However, oper-
ating at a higher frequency generally results in lower
efficiency because of increased internal gate charge losses.
The inductor value has a direct effect on ripple current. The
ripple current
I
L
decreases with higher inductance or
frequency and increases with higher V
IN
or V
OUT
.
相關(guān)PDF資料
PDF描述
LTC1911-15 Low Noise, High Efficiency, Inductorless Step-Down DC/DC Converter
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LTC1878EMS8 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類(lèi)型:升壓（升壓） 輸出類(lèi)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(kāi)關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無(wú) 工作溫度:-40°C ~ 85°C 安裝類(lèi)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
LTC1878EMS8#PBF 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:250 系列:- 類(lèi)型:降壓（降壓） 輸出類(lèi)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(kāi)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(lèi)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(chēng):296-25628-2
LTC1878EMS8#TR 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類(lèi)型:升壓（升壓） 輸出類(lèi)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(kāi)關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無(wú) 工作溫度:-40°C ~ 85°C 安裝類(lèi)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
LTC1878EMS8#TRPBF 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 類(lèi)型:升壓（升壓） 輸出類(lèi)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(kāi)關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無(wú) 工作溫度:-40°C ~ 85°C 安裝類(lèi)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
LTC1878EMS8PBF 制造商:Linear Technology 功能描述: 制造商:Linear Technology 功能描述:DC-DC Converter Step-Down 2.65-6V MSOP8
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