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參數(shù)資料
| 型號(hào)： | A8450KLB |
| 廠商： | Allegro MicroSystems, Inc. |
| 英文描述： | Automotive Multioutput Voltage Regulator |
| 中文描述： | 汽車Multioutput穩(wěn)壓器 |
| 文件頁數(shù)： | 11/15頁 |
| 文件大小： | 549K |
| 代理商： | A8450KLB |
11
A8450KLB-DS, Rev. 1
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
A8450
Automotive Multioutput Voltage Regulator
For electrolytic output capacitors, a low-ESR type is recom-
mended, with a minimum voltage rating of 10 V. However,
because ESR decreases with voltage, the most cost-effective
choice may be a capacitor with a higher voltage rating.
Regulator Output Capacitors (C3 and C4)
. The output
capacitors used with the 3.3 V regulator (C3) and the 1.2 V
to 3.3 V adjustable regulator (C4), should be 1 μF or greater
X7R (5% tolerance) ceramic or equivalent capacitors, with
a maximum capacitance change of ±15% over a temperature
range of –55oC to 125oC.
The ESR of these capacitors does not affect the outputs of
the corresponding regulators. If a greater capacitance is used,
the regulators have improved ripple rejection at frequencies
greater than 100 kHz.
Pass Transistors (Q1 and Q2)
. The pass transistors
used to implement the 3.3 V regulator and the 1.2 V to 3.3 V
adjustable regulator must ensure the following:
Stable operation.
The cutoff frequency for the control
loops of the regulators is 100 kHz. Transistors must be
selected that have gain bandwidth product, f
T
(kHz), and
beta, h
FE
(A), ratings such that
f
T
h
FE
> 100 kHz
Adequate base drive.
It is acceptable to use a lower level
of current gain, h
FE
, for lower total load currents, I
LOAD
.
The lower limit for I
LOAD
is limited by the minimum base
current for the A8450, I
BD(min)
, and the minimum h
FE
of
the pass transistor, such that
I
LOAD
= I
BD(min)
×
h
FE(min)
Note that h
FE
is dependant on operating temperature.
Lower temperatures decrease h
FE
, affecting the current
capacity of the transistor.
Packaged for sufficient power dissipation.
In order to
ensure appropriate thermal handling, the design of the ap-
plication must take into consideration the thermal charac-
teristics of the PCB where the A8450 and pass transistors
are mounted, the ambient temperature, and the power
dissipation characteristics of the transistor packages. In
general, the power dissipation, P
D
(mW), is estimated by
P
D
= (
V
REG
–
V
OUT
)
×
I
LOAD
For a typical application where V
REG
= 5.8 V, V
OUT
=
2.5 V, and I
LOAD
= 190 mA
P
D
= (5.8 – 2.5)
×
190 = 627 mW
Adjusting Pass Transistor Power Dissipation
Transistors are manufactured in a wide variety of pack-
age types, and the thermal dissipation efficiencies of the
packages can vary greatly. In general, increasing thermal
efficiency can also increase cost substantially. Selecting the
package to closely match operating conditions is important to
optimizing application design and cost.
Even when using a thermally-enhanced package, it remains
difficult to provide high current to a load at high ambient
operating temperatures. Depending on the load requirements,
using drop resistors, as shown in figure 5, may be necessary
to protect the pass transistor from overheating.
The output current-limiting resistors, RCL (corresponding
to R3 and R4), will drop between 175 mV and 225 mV at
the highest current output, I
LOAD
. Assuming no additional
resistance, the voltage dropped, V
DROP
(mV), on each pass
Figure 5. Placement of drop resistors for thermal protection; example
shown is for the 3.3 V regulator.
VREG
CL33
V33BD
V33
V
CE
RCL
V
OUTV33
I
LOAD
A8450
V
DROP
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|---|---|
| A8450KLB-T | 功能描述:IC REG QD BUCK/LINEAR 24-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（2），線性（LDO）（1） 功能:任何功能 輸出數(shù):3 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動(dòng)器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:4.5 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:28-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:* 包裝:帶卷 (TR) 其它名稱:ISL6402IVZ-TTR |
| A8450KLB-T | 制造商:Allegro MicroSystems 功能描述:Voltage Regulator IC |
| A8450KLBTR | 功能描述:IC REG QD BUCK/LINEAR 24-SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（2），線性（LDO）（1） 功能:任何功能 輸出數(shù):3 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動(dòng)器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:4.5 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:28-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:* 包裝:帶卷 (TR) 其它名稱:ISL6402IVZ-TTR |
| A8450KLBTR-T | 功能描述:IC REG QD BUCK/LINEAR 24-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 + 切換式 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 拓?fù)?降壓（降壓）同步（3），線性（LDO）（2） 功能:任何功能 輸出數(shù):5 頻率 - 開關(guān):300kHz 電壓/電流 - 輸出 1:控制器 電壓/電流 - 輸出 2:控制器 電壓/電流 - 輸出 3:控制器 帶 LED 驅(qū)動(dòng)器:無 帶監(jiān)控器:無 帶序列發(fā)生器:是 電源電壓:5.6 V ~ 24 V 工作溫度:-40°C ~ 85°C 安裝類型:* 封裝/外殼:* 供應(yīng)商設(shè)備封裝:* 包裝:* |
| A845DSC | 制造商:Pentair Technical Products / Hoffman 功能描述:DSC Box 8.00x4.00x4.75 Gray, 8.00x4.00x3.75, Steel |
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