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參數(shù)資料
| 型號： | LTC3851EUD#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.05 A SWITCHING CONTROLLER, 790 kHz SWITCHING FREQ-MAX, PQCC16 |
| 封裝： | 3 X 3 MM, LEAD FREE, PLASTIC, MO-220WEED-2, QFN-16 |
| 文件頁數(shù)： | 7/28頁 |
| 文件大?。?/td> | 325K |
| 代理商： | LTC3851EUD#TRPBF |
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LTC3851
15
3851fb
0V to 0.8V on the TK/SS pin. The total soft-start time can
be calculated as:
t
SOFT-START = 0.8
C
SS
1.0A
Regardless of the mode selected by the MODE/PLLIN pin,
the regulator will always start in pulse-skipping mode up
to TK/SS = 0.64V. Between TK/SS = 0.64V and 0.72V, it
will operate in forced continuous mode and revert to the
selected mode once TK/SS > 0.72V. The output ripple
is minimized during the 80mV forced continuous mode
window.
When the regulator is congured to track another supply,
the feedback voltage of the other supply is duplicated by a
resistor divider and applied to the TK/SS pin. Therefore, the
voltage ramp rate on this pin is determined by the ramp rate
of the other supply’s voltage. Note that the small soft-start
capacitor charging current is always owing, producing
a small offset error. To minimize this error, one can select
the tracking resistive divider value to be small enough to
make this error negligible.
In order to track down another supply after the soft-start
phase expires, the LTC3851 must be congured for forced
continuous operation by connecting MODE/PLLIN to
INTVCC.
Output Voltage Tracking
The LTC3851 allows the user to program how its output
ramps up and down by means of the TK/SS pins. Through
this pin, the output can be set up to either coincidentally or
ratiometrically track with another supply’s output, as shown
in Figure 3. In the following discussions, VMASTER refers to
a master supply and VOUT refers to the LTC3851’s output
as a slave supply. To implement the coincident tracking
in Figure 3a, connect a resistor divider to VMASTER and
connect its midpoint to the TK/SS pin of the LTC3851. The
ratio of this divider should be selected the same as that of
the LTC3851’s feedback divider as shown in Figure 4a. In
this tracking mode, VMASTER must be higher than VOUT.
To implement ratiometric tracking, the ratio of the resistor
divider connected to VMASTER is determined by:
V
OUT
V
MASTER
=
R2
R4
R3
+R4
R1
+R2
So which mode should be programmed? While either
mode in Figure 4 satises most practical applications,
the coincident mode offers better output regulation.
This concept can be better understood with the help of
Figure 5. At the input stage of the error amplier, two
common anode diodes are used to clamp the equivalent
reference voltage and an additional diode is used to match
the shifted common mode voltage. The top two current
sources are of the same amplitude. In the coincident
APPLICATIONS INFORMATION
TIME
(3a) Coincident Tracking
VMASTER
VOUT
OUTPUT
VOL
TAGE
VMASTER
VOUT
TIME
3851 F03
(3b) Ratiometric Tracking
OUTPUT
VOL
TAGE
Figure 3. Two Different Modes of Output Voltage Tracking
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3851IGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,000 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:50% 電源電壓:9 V ~ 10 V 降壓:無 升壓:是 回掃:是 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:8-TSSOP（0.173"，4.40mm 寬） 包裝:帶卷 (TR) |
| LTC3851IGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3851IMSE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3851IMSE#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3851IMSE-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
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