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參數(shù)資料
| 型號： | LT1123 |
| 廠商： | Linear Technology Corporation |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Cap-Free, NMOS, 150mA Low Dropout Regulator with Reverse Current Protection |
| 中文描述： | 無電容，NMOS管，150mA的低壓差穩(wěn)壓器的反向電流保護 |
| 文件頁數(shù)： | 8/12頁 |
| 文件大小： | 206K |
| 代理商： | LT1123 |
8
LT1123
U
S
A
O
PPLICATI
U
U
THERMAL
RESISTANCE
requirements (input voltage and drive current) are at the
low end and the output will not be shorted. For R
D
= 0 the
following formula may be used to calculate the maximum
power dissipation in the LT1123.
P
D
= (V
IN
– V
BE
)(I
DRIVE
)
where V
IN
= maximum input voltage
V
BE
= emitter/base voltage of PNP
I
DRIVE
= required maximum drive current
The maximum junction temperature rise above ambient
for the LT1123 will be equal to the worst case power
dissipation multiplied by the thermal resistance of the
device. The thermal resistance of the device will depend
upon how the device is mounted, and whether a heat sink
is used. Measurements show that one of the most effective
ways of heat sinking the TO-92 package is by utilizing the
PC board traces attached to the leads of the package. The
table below lists several methods of mounting and the
measured value of thermal resistance for each method. All
measurements were done in still air.
Package alone.............................................................................. 220
°
C/W
Package soldered into PC board with plated through
holes only..............................................................................175
°
C/W
Package soldered into PC board with 1/4 sq. in. of copper trace
per lead .................................................................................145
°
C/W
Package soldered into PC board with plated through holes in
board, no extra copper trace, and a clip-on type heat sink:
Thermalloy type 2224B.............................................. 160
°
C/W
Aavid type 5754.......................................................... 135
°
C/W
The maximum operating junction temperature of the
LT1123 is 125
°
C. The maximum operating ambient
temperature will be equal to 125
°
C minus the maximum
junction temperature rise above ambient.
The worst case power dissipation in R
D
needs to be
calculated so that the power rating of the resistor can be
determined. The worst case power in the resistor will
occur when the drive current is at a maximum. Figure 8
plots the required power rating of R
D
versus supply
voltage and resistor value. Power dissipation can be
calculated using the following formula:
D
=
(
Figure 8. Power in R
D
V
IN
(V)
6
R
D
)
8
1k
LT1123 F08
10
100
7
15
14
13
12
11
10
9
5
1W
0.5W
0.25W
2W
where V
BE
= emitter/base voltage of the PNP pass
transistor
V
DRIVE
= voltage at the drive pin of the LT1123
= V
SAT
of the drive pin in the worst case
The worst case power dissipation in the PNP pass transis-
tor is simply equal to:
P
MAX
= (V
IN
– V
OUT
)(I
OUT
)
where V
IN
= Maximum V
IN
I
OUT
= Maximum I
OUT
The thermal resistance of the MJE1123 is equal to:
70
°
C/W Junction to Ambient (no heat sink)
1.67
°
C/W Junction to Case
The PNP will normally be attached to either a chassis or a
heat sink so the actual thermal resistance from junction to
ambient will be the sum of the PNP's junction to case
thermal resistance and the thermal resistance of the heat
sink or chassis. For non-standard heat sinks the user will
need to determine the thermal resistance by experiment.
The maximum junction temperature rise above ambient
for the PNP pass transistor will be equal to the maximum
power dissipation times the thermal resistance, junction
to ambient, of the PNP. The maximum operating junction
temperature of the MJE1123 is 150
°
C. The maximum
operating ambient temperature for the MJE1123 will be
equal to 150
°
C minus the maximum junction temperature
rise.
P
V – V
– V
R
R
BE
DRIVE
2
)
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| LT1123CST#PBF | 功能描述:IC REG CTRLR SGL 5V SOT223 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性晶體管驅(qū)動器 系列:- 產(chǎn)品培訓(xùn)模塊:More Information on LDOs 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:正，固定式 輸出數(shù):2 輸出電壓:2.8V，3.3V 電流 - 電源:12mA 輸入電壓:5 V ~ 22 V 工作溫度:0°C ~ 70°C 封裝/外殼:16-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC 包裝:帶卷 (TR) |
| LT1123CST#TR | 功能描述:IC REG CTRLR SGL 5V SOT223 RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性晶體管驅(qū)動器 系列:- 產(chǎn)品培訓(xùn)模塊:More Information on LDOs 標(biāo)準(zhǔn)包裝:2,500 系列:- 類型:正，固定式 輸出數(shù):2 輸出電壓:2.8V，3.3V 電流 - 電源:12mA 輸入電壓:5 V ~ 22 V 工作溫度:0°C ~ 70°C 封裝/外殼:16-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:16-SOIC 包裝:帶卷 (TR) |
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