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參數資料
| 型號： | LTC3851AEMSE-1#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.05 A SWITCHING CONTROLLER, 810 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件頁數： | 8/30頁 |
| 文件大?。?/td> | 0K |
| 代理商： | LTC3851AEMSE-1#PBF |
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LTC3851A-1
16
3851a1fa
0V to 0.8V on the TK/SS pin. The total soft-start time can
be calculated as:
tSOFT-START = 0.8
CSS
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 configured to track another supply,
the feedback voltage of the other supply is duplicated by a
resistordividerandappliedtotheTK/SSpin.Therefore,the
voltageramprateonthispinisdeterminedbytheramprate
of the other supply’s voltage. Note that the small soft-start
capacitor charging current is always flowing, 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 LTC3851A-1 must be configured for
forced continuous operation by connecting MODE/PLLIN
to INTVCC.
Output Voltage Tracking
The LTC3851A-1 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 co-
incidentally 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
LTC3851A-1’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
theLTC3851A-1.Theratioofthisdividershouldbeselected
the same as that of the LTC3851A-1’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:
VOUT
VMASTER
=
R2
R4
R3 +R4
R1+R2
So which mode should be programmed? While either
mode in Figure 4 satisfies 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 LTC3851A-1’s error
amplifier, two common anode diodes are used to clamp
applicaTions inForMaTion
Figure 3. Two Different Modes of Output Voltage Tracking
TIME
(3a) Coincident Tracking
VMASTER
VOUT
OUTPUT
VOL
TAGE
VMASTER
VOUT
TIME
3851A1 F03
(3b) Ratiometric Tracking
OUTPUT
VOL
TAGE
3851A1
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| LTC3851AEUD#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-QFN 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: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) |
| LTC3851AEUD#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-QFN 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: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) |
| LTC3851AEUD-1#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-QFN 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: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) |
| LTC3851AEUD-1#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 16-QFN 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: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) |
| LTC3851AHMSE#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: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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