參數(shù)資料
型號(hào): LM2574-12BWM
廠商: MICREL INC
元件分類(lèi): 穩(wěn)壓器
英文描述: 52kHz Simple 0.5A Buck Regulator
中文描述: 1.8 A SWITCHING REGULATOR, 63 kHz SWITCHING FREQ-MAX, PDSO14
封裝: SOIC-14
文件頁(yè)數(shù): 20/24頁(yè)
文件大小: 397K
代理商: LM2574-12BWM
LM2574
20
MOTOROLA ANALOG IC DEVICE DATA
R1
47 k
LM2574–XX
5
2
and
4
3
Gnds
Pins
ON/OFF
R2
47 k
+Vin
+Vin
C1
0.1
μ
F
Cin
22
μ
F
NOTE
: This picture does not show the complete circuit.
Figure 32. Delayed Startup Circuitry
Undervoltage Lockout
Some applications require the regulator to remain off until
the input voltage reaches a certain threshold level. Figure 33
shows an undervoltage lockout circuit applied to a buck
regulator. A version of this circuit for buck–boost converter is
shown in Figure 34. 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:
Vth
VZ1
1.0
R2
R1
10 k
Z1
1N5242B
R2
10 k
Q1
2N3904
R3
47 k
Cin
22
μ
F
LM2574–XX
5
2
and
4
3
Gnds
Pins
ON/OFF
+Vin
+Vin
NOTE
: This picture does not show the complete circuit.
Figure 33. Undervoltage Lockout Circuit for
Buck Converter
R2
15 k
Z1
1N5242
R1
15 k
Q1
2N3904
R3
68 k
Cin
22
μ
F
LM2574–XX
5
2
and
4
3
Gnds
Pins
ON/OFF
+Vin
+Vin
–Vout
NOTE
: This picture does not show the complete circuit (see Figure 27).
Figure 34. Undervoltage Lockout Circuit for
Buck–Boost Converter
Adjustable Output, Low–Ripple Power Supply
A 0.5 A output current capability power supply that
features an adjustable output voltage is shown in Figure 35.
This regulator delivers 0.5 A into 1.2 to 35 V output. The
input voltage ranges from roughly 3.0 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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