參數(shù)資料
型號: ML4871CS-3
英文描述: High Current Boost Regulator
中文描述: 高電流升壓穩(wěn)壓器
文件頁數(shù): 6/9頁
文件大小: 237K
代理商: ML4871CS-3
6
ML4871
OUTPUT CAPACITOR
The output capacitor filters the pulses of current from the
switching regulator. Since the switching frequency will
vary with inductance, the minimum output capacitance
required to reduce the output ripple to an acceptable level
will be a function of the inductor used. Therefore, to
maintain an output voltage with less than 100mV of ripple
at full load current, use the following equation:
C
L
V
OUT
OUT
=
44
(2)
The output capacitor’s Equivalent Series Resistance (ESR)
and Equivalent Series Inductance (ESL), also contribute to
the ripple. Just after the NMOS transistor, Q1, turns off, the
current in the output capacitor ramps quickly to between
0.5A and 1.5A. This fast change in current through the
capacitor’s ESL causes a high frequency (5ns) spike to
appear on the output. After the ESL spike settles, the output
still has a ripple component equal to the inductor
discharge current times the ESR. To minimize these effects,
choose an output capacitor with less than 10nH of ESL
and 100m
W
of ESR.
Suitable tantalum capacitors can be obtained from the
following vendors:
AVX
(207) 282-5111
Kemet
(846) 963-6300
Sprague
(207) 324-4140
Figure 5. Efficiency vs. I
OUT
Using the Circuit of Figure 8
Figure 4. I
OUT
vs. VIN Using the Circuit of Figure 8
DESIGN CONSIDERATIONS
(Continued)
Figure 6. No Load Input Current vs. V
IN
1000
800
600
400
200
0
I
VIN (V)
1.0
2.0
3.0
5.0
4.0
VOUT = 3.3V
VOUT = 5V
90
80
70
60
E
IOUT (mA)
1
10
100
1000
VOUT = 3.3V
VOUT = 5V
VIN = 2.4V
90
60
30
0
I
VIN (V)
1.0
2.0
3.0
5.0
4.0
VOUT = 3.3V
VOUT = 5V
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