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參數(shù)資料
| 型號： | LTC1871HMS |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.05 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 3/36頁 |
| 文件大?。?/td> | 519K |
| 代理商： | LTC1871HMS |
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LTC1871
11
1871fe
APPLICATIONS INFORMATION
Programming the Operating Frequency
The choice of operating frequency and inductor value is
a tradeoff between efciency and component size. Low
frequency operation improves efciency by reducing
MOSFET and diode switching losses. However, lower
frequency operation requires more inductance for a given
amount of load current.
The LTC1871 uses a constant frequency architecture that
can be programmed over a 50kHz to 1000kHz range with
a single external resistor from the FREQ pin to ground, as
shown in Figure 1. The nominal voltage on the FREQ pin is
0.6V, and the current that ows into the FREQ pin is used
to charge and discharge an internal oscillator capacitor. A
graph for selecting the value of RT for a given operating
frequency is shown in Figure 6.
INTVCC Regulator Bypassing and Operation
An internal, P-channel low dropout voltage regulator pro-
duces the 5.2V supply which powers the gate driver and
logic circuitry within the LTC1871, as shown in Figure 7.
The INTVCC regulator can supply up to 50mA and must be
bypassed to ground immediately adjacent to the IC pins
with a minimum of 4.7μF tantalum or ceramic capacitor.
Good bypassing is necessary to supply the high transient
currents required by the MOSFET gate driver.
For input voltages that don’t exceed 7V (the absolute
maximum rating for this pin), the internal low dropout
regulator in the LTC1871 is redundant and the INTVCC pin
can be shorted directly to the VIN pin. With the INTVCC
pin shorted to VIN, however, the divider that programs the
regulated INTVCC voltage will draw 10μA of current from
the input supply, even in shutdown mode. For applications
that require the lowest shutdown mode input supply cur-
rent, do not connect the INTVCC pin to VIN. Regardless of
whether the INTVCC pin is shorted to VIN or not, it is always
necessary to have the driver circuitry bypassed with a
4.7μF tantalum or low ESR ceramic capacitor to ground
immediately adjacent to the INTVCC and GND pins.
In an actual application, most of the IC supply current is
used to drive the gate capacitance of the power MOSFET.
As a result, high input voltage applications in which a
large power MOSFET is being driven at high frequencies
can cause the LTC1871 to exceed its maximum junction
Figure 6. Timing Resistor (RT) Value
FREQUENCY (kHz)
100
R
T(kΩ)
300
1000
1871 F06
10
100
200
1000
900
800
700
600
500
400
0
Figure 7. Bypassing the LDO Regulator and Gate Driver Supply
+
–
+
1.230V
R2
R1
P-CH
5.2V
DRIVER
GATE
CVCC
4.7μF
CIN
INPUT
SUPPLY
2.5V TO 30V
GND
PLACE AS CLOSE AS
POSSIBLE TO DEVICE PINS
M1
1871 F07
INTVCC
VIN
GND
LOGIC
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| LTC1871HMS#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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) |
| LTC1871HMS#TRPBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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) |
| LTC1871HMSPBF | 制造商:Linear Technology 功能描述:PWM Controller Current Mode MSOP10 |
| LTC1871IMS | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP RoHS:否 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) |
| LTC1871IMS#PBF | 功能描述:IC REG CTRLR BST FLYBK CM 10MSOP 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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