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参数资料
| 型号： | LM2575D2TR4-3.3 |
| 厂商： | ON SEMICONDUCTOR |
| 元件分类： | 稳压器 |
| 英文描述： | 3.2 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PSSO5 |
| 封装： | PLASTIC, D2PAK-5 |
| 文件页数： | 13/62页 |
| 文件大小： | 1103K |
| 代理商： | LM2575D2TR4-3.3 |
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LM2575
3–132
MOTOROLA ANALOG IC DEVICE DATA
Design Recommendations:
The same design rules as for the previous inverting
buck–boost converter can be applied. The output capacitor
Cout must be chosen larger than would be required for a
standard buck converter. Low input voltages or high output
currents require a large value output capacitor (in the range
of thousands of
F). The recommended range of inductor
values for the negative boost regulator is the same as for
inverting converter design.
Another important point is that these negative boost
converters cannot provide current limiting load protection in
the event of a short in the output so some other means, such
as a fuse, may be necessary to provide the load protection.
Delayed Startup
There are some applications, like the inverting regulator
already mentioned above, which require a higher amount of
startup current. In such cases, if the input power source is
limited, this delayed startup feature becomes very useful.
To provide a time delay between the time the input voltage
is applied and the time when the output voltage comes up,
the circuit in Figure 30 can be used. As the input voltage is
applied, the capacitor C1 charges up, and the voltage across
the resistor R2 falls down. When the voltage on the ON/OFF
pin falls below the threshold value 1.4 V, the regulator starts
up. Resistor R1 is included to limit the maximum voltage
applied to the ON/OFF pin, reduces the power supply noise
sensitivity, and also limits the capacitor C1 discharge current,
but its use is not mandatory.
When a high 50 Hz or 60 Hz (100 Hz or 120 Hz
respectively) ripple voltage exists, a long delay time can
cause some problems by coupling the ripple into the ON/OFF
pin, the regulator could be switched periodically on and off
with the line (or double) frequency.
Figure 30. Delayed Startup Circuitry
R1
47 k
LM2575–XX
1
3
5
Gnd
ON/OFF
R2
47 k
+Vin
C1
0.1
F
Cin
100
F
NOTE:
This picture does not show the complete circuit.
Undervoltage Lockout
Some applications require the regulator to remain off until
the input voltage reaches a certain threshold level. Figure 31
shows an undervoltage lockout circuit applied to a buck
regulator. A version of this circuit for buck–boost converter is
shown in Figure 32. Resistor R3 pulls the ON/OFF pin high
and keeps the regulator off until the input voltage reaches a
predetermined threshold level, which is determined by the
following expression:
V
th [
V
Z1 )
1
) R2
R1
V
BE
(Q1)
Figure 31. Undervoltage Lockout Circuit for
Buck Converter
R2
10 k
Z1
1N5242B
R1
10 k
Q1
2N3904
R3
47 k
Vth ≈ 13 V
Cin
100
F
LM2575–5.0
1
3
5
Gnd
ON/OFF
+Vin
NOTE:
This picture does not show the complete circuit.
Figure 32. Undervoltage Lockout Circuit for
Buck–Boost Converter
R2
15 k
Z1
1N5242B
R1
15 k
Q1
2N3904
R3
68 k
Vth ≈ 13 V
Cin
100
F
LM2575–5.0
1
3
5
Gnd
ON/OFF
+Vin
Vout = –5.0 V
NOTE:
This picture does not show the complete circuit.
Adjustable Output, Low–Ripple Power Supply
A 1.0 A output current capability power supply that
features an adjustable output voltage is shown in Figure 33.
This regulator delivers 1.0 A into 1.2 V to 35 V output. The
input voltage ranges from roughly 8.0 V to 40 V. In order to
achieve a 10 or more times reduction of output ripple, an
additional L–C filter is included in this circuit.
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相关代理商/技术参数 |
参数描述 |
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| LM2575EP | 制造商:NSC 制造商全称:National Semiconductor 功能描述:SIMPLE SWITCHER 1A Step-Down Voltage Regulator |
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| LM2575HVM12 | 制造商:Texas Instruments 功能描述:* |
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| LM2575HVM-12/NOPB | 功能描述:IC REG BUCK 12V 1A 24-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:SIMPLE SWITCHER® 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:3.3V 输入电压:4.5 V ~ 24 V PWM 型:- 频率 - 开关:- 电流 - 输出:125mA 同步整流器:无 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-6 包装:Digi-Reel® 供应商设备封装:SOT-6 其它名称:MAX1836EUT33#TG16DKR |
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