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参数资料
| 型号： | LT1573I |
| 厂商： | Linear Technology Corporation |
| 英文描述： | Low Dropout PNP Regulator Driver |
| 中文描述： | 低压差稳压器驱动进步党 |
| 文件页数： | 10/16页 |
| 文件大小： | 200K |
| 代理商： | LT1573I |
10
LT1573
Thermal Considerations
The thermal characteristics of several components need
to be considered; the LT1573, the pass transistor and
resistor R
D
. Power dissipation should be calculated based
on the worst-case conditions seen by each component
during normal operation.
1.
Power Dissipation of the LT1573:
The worst-case
power dissipation in the LT1573 is a function of drive
current, supply voltage and the value of R
D
. Worst-case
dissipation for the LT1573 occurs when the drive cur-
rent is equal to approximately one half of its maximum
value. The worst-case power dissipation in the LT1573
can be calculated by the following formula:
(
4
minimum R for latch-off function
where,
V
IN
= the maximum input voltage to the circuit
V
BE
= the minimum emitter/base voltage of the PNP
pass transistor
Following the previous design example for selecting
resistor R
D
, the power dissipation of LT1573 is calcu-
lated from Eq (2):
(
( )
For some operating conditions R
D
may be replaced with
a short. This is possible in applications where the
operating requirements (input voltage and drive cur-
rent) 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
LT1573:
P
D
= (V
IN
– V
BE
)(I
DRIVE
)
where,
V
IN
= the maximum input voltage
V
BE
= the minimum emitter/base voltage of the PNP
I
DRIVE
= the required maximum drive current
P
V
V
R
R
D
IN
BE
D
D
=
)
>
2
(2)
P
W
D
=
)
=
5 5 0 65
4 24
0 25
2
.
(3)
2.
Power Dissipation of the Resistor R
D
:
The worst-case
power dissipation in resistor R
D
needs to be calculated
so that the power rating of the resistor can be deter-
mined. The worst-case power dissipation in this resis-
tor will occur when the drive current is at a maximum.
The power dissipation can be calculated from the fol-
lowing formula:
P
V
V
V
R
RD
IN
BE
DRIVE
D
=
(
)
2
(4)
where,
V
IN
= the maximum input voltage
V
BE
= the minimum emitter/base voltage of the PNP
V
DRIVE
= the voltage at the LT1573 DRIVE pin
= V
SAT
of the DRIVE pin in the worst case
Following the previous design example, the power
dissipation of resistor R
D
is calculated from Eq (4):
(
24
3.
Power Dissipation of the PNP Transistor:
The worst-
case power dissipation in the PNP pass transistor is
simply equal to:
P
PNP
= (V
IN
– V
OUT
)(I
OUT
)
where,
V
IN
= the maximum input voltage
I
OUT
= the maximum output current
Following the previous design example, the power
dissipation of PNP transistor is calculated from Eq (5):
P
PNP
= (5.5 – 3.3)(5) = 11W
The LT1573 series regulators have internal thermal
limiting designed to protect the device during overload
conditions. For continuous normal load conditions,
the maximum junction temperature rating of 125
°
C
must not be exceeded. It is important to give careful
consideration to all sources of thermal resistance from
junction to ambient. For surface mount devices, heat
sinking is accomplished by using the heat spreading
P
W
RD
=
)
=
5 5 0 65 0 39
0 83
2
(5)
APPLICATIOU
W
U
U
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| LT1573IS8 | 功能描述:IC REG CTRLR SGL POS ADJ 8-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性晶体管驱动器 系列:- 产品培训模块:More Information on LDOs 标准包装:2,500 系列:- 类型:正，固定式 输出数:2 输出电压:2.8V，3.3V 电流 - 电源:12mA 输入电压:5 V ~ 22 V 工作温度:0°C ~ 70°C 封装/外壳:16-SOIC（0.154"，3.90mm 宽） 供应商设备封装:16-SOIC 包装:带卷 (TR) |
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| LT1573IS8#TR | 功能描述:IC REG CTRLR SGL POS ADJ 8SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性晶体管驱动器 系列:- 产品培训模块:More Information on LDOs 标准包装:2,500 系列:- 类型:正，固定式 输出数:2 输出电压:2.8V，3.3V 电流 - 电源:12mA 输入电压:5 V ~ 22 V 工作温度:0°C ~ 70°C 封装/外壳:16-SOIC（0.154"，3.90mm 宽） 供应商设备封装:16-SOIC 包装:带卷 (TR) |
| LT1573IS8#TRPBF | 功能描述:IC REG CTRLR SGL POS ADJ 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性晶体管驱动器 系列:- 产品培训模块:More Information on LDOs 标准包装:2,500 系列:- 类型:正，固定式 输出数:2 输出电压:2.8V，3.3V 电流 - 电源:12mA 输入电压:5 V ~ 22 V 工作温度:0°C ~ 70°C 封装/外壳:16-SOIC（0.154"，3.90mm 宽） 供应商设备封装:16-SOIC 包装:带卷 (TR) |
| LT1575 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Ultrafast Transient Response, Low Dropout Regulators Adjustable and Fixed |
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