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參數(shù)資料
| 型號： | LT1123 |
| 廠商： | Linear Technology Corporation |
| 元件分類： | 基準電壓源/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)： | 5/12頁 |
| 文件大?。?/td> | 206K |
| 代理商： | LT1123 |
5
LT1123
U
S
A
O
PPLICATI
IU
U
R
D
is used to limit the drive current available to the PNP
and to limit the power dissipation in the LT1123. Limiting
the drive current to the PNP will limit the output current of
the regulator which will minimize the stress on the regu-
lator circuit under overload conditions. R
D
is chosen
based on the operating requirements of the circuit, prima-
rily dropout voltage and output current.
DROPOUT VOLTAGE
The dropout voltage of an LT1123 based regulator circuit
is determined by the V
CE
saturation voltage of the discrete
PNP when it is driven with a base current equal to the
available drive current of the LT1123. The LT1123 can sink
up to 150mA of base current (150mA typ., 125mA min.)
when output voltage is up near the regulating point (5V).
The available drive current of the LT1123 can be reduced
by adding a resistor (R
D
) in series with the drive pin (see
the section below on current limit). The MJE1123 is
specified for dropout voltage (V
CE
sat.) at several values of
output current and up to 120mA of base drive current. The
chart below lists the operating points that can be guaran-
output at 5V. The drive pin of the LT1123 can only sink
current; R
B
is required to provide pullup on the base of the
PNP. R
B
must be sized so that the voltage drop caused by
the minimum drive pin current is less than the emitter/
base voltage of the external PNP at light loads. The
recommended value for R
B
is 620
. For circuits that are
required to run at junction temperatures in excess of
100
°
C the recommended value of R
B
is 300
.
Dropout Voltage
DROPOUT VOLTAGE
TYP
0.16V
0.13V
0.25V
0.2V
0.45V
MAX
0.3V
0.25V
0.4V
0.35V
0.75V
20mA
50mA
1A
1A
2A
1A
4A
120mA
DRIVE CURRENT
OUTPUT CURRENT
R
D
R
B
620
V
IN
V
OUT
= 5V
10μF ALUM
LT1123 F01
+
DRIVE
LT1123
GND
FB
MJE1123
Figure 1. Basic Regulator Circuit
teed by the combined data sheets of the LT1123 and
MJE1123. Figure 2 illustrates the chart in graphic form.
Although these numbers are only guaranteed by the data
sheet at 25
°
C, Dropout Voltage vs Temperature (Figure 3)
clearly shows that the dropout voltage is nearly constant
over a wide temperature range.
Figure 3. Dropout Voltage vs Temperature
CASE TEMPERATURE (°C)
20
D
0.55
0.65
0.75
80
LT1123 F03
0.45
0.35
40
60
100
0.25
0.15
0.05
120
I
C
= 4A, I
B
= 0.12A
I
C
= 2A, I
B
= 0.05A
I
C
= 1A, I
B
= 0.02A
Figure 2. Maximum Dropout Voltage
0
D
0.75
1.0
4
LT1123 F02
0.50
0.25
1
2
3
0
OUTPUT CURRENT (A)
BASED ON
MJE1123 SPECS
I
DRIVE
= 20mA
I
DRIVE
= 120mA
I
DRIVE
= 50mA
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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 - 線性晶體管驅動器 系列:- 產品培訓模塊:More Information on LDOs 標準包裝: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） 供應商設備封裝: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 - 線性晶體管驅動器 系列:- 產品培訓模塊:More Information on LDOs 標準包裝: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） 供應商設備封裝:16-SOIC 包裝:帶卷 (TR) |
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