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参数资料
| 型号： | LT1871EMS-7 |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | PLASTIC, MSOP-10 |
| 文件页数： | 3/32页 |
| 文件大小： | 461K |
| 代理商： | LT1871EMS-7 |
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LTC1871-7
11
18717fc
OPERATION
can cause the LTC1871-7 to exceed its maximum junc-
tion temperature rating. The junction temperature can be
estimated using the following equations:
IQ(TOT) ≈ IQ + f QG
PIC = VIN (IQ + f QG)
TJ = TA + PIC RTH(JA)
The total quiescent current IQ(TOT) consists of the static
supply current (IQ) and the current required to charge and
discharge the gate of the power MOSFET. The 10-pin MSOP
package has a thermal resistance of RTH(JA) = 120°C/W.
As an example, consider a power supply with VIN =10V.
The switching frequency is 200kHz, and the maximum
ambient temperature is 70°C. The power MOSFET chosen
is the FDS3670(Fairchild), which has a maximum RDS(ON)
of 35mΩ (at room temperature) and a maximum total
gate charge of 80nC (the temperature coefcient of the
gate charge is low).
IQ(TOT) = 600μA + 80nC 200kHz = 16.6mA
PIC = 10V 16.6mA = 166mW
TJ = 70°C + 120°C/W 166mW = 89.9°C
TJRISE = 19.9°C
This demonstrates how signicant the gate charge current
can be when compared to the static quiescent current in
the IC.
To prevent the maximum junction temperature from being
exceeded, the input supply current must be checked when
operating in a continuous mode at high VIN. A tradeoff
between the operating frequency and the size of the power
MOSFET may need to be made in order to maintain a reliable
IC junction temperature. Prior to lowering the operating
frequency, however, be sure to check with power MOSFET
manufacturers for their latest-and-greatest low QG, low
RDS(ON) devices. Power MOSFET manufacturing tech-
nologies are continually improving, with newer and better
performance devices being introduced almost yearly.
Output Voltage Programming
The output voltage is set by a resistor divider according
to the following formula:
VO =1.230V 1+
R2
R1
The external resistor divider is connected to the output
as shown in Figure 1, allowing remote voltage sensing.
Figure 7. Bypassing the LDO Regulator and Gate Driver Supply
–
+
1.230V
R2
R1
P-CH
7V
DRIVER
GATE
CVCC
4.7μF
X5R
CIN
INPUT
SUPPLY
6V TO 30V
GND
PLACE AS CLOSE AS
POSSIBLE TO DEVICE PINS
M1
18717 F07
INTVCC
VIN
GND
LOGIC
6V-RATED
POWER
MOSFET
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相关代理商/技术参数 |
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|---|---|
| LT1871EMS-7-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage,Current Mode Boost, Flyback and SEPIC Controller |
| LT1871EMS-7-TR | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage,Current Mode Boost, Flyback and SEPIC Controller |
| LT1871EMS-7-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage,Current Mode Boost, Flyback and SEPIC Controller |
| LT1871IMS-7 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage,Current Mode Boost, Flyback and SEPIC Controller |
| LT1871IMS-7-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage,Current Mode Boost, Flyback and SEPIC Controller |
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