參數(shù)資料
型號(hào): LTC3833EUDC#PBF
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PQCC20
封裝: 3 X 3 MM, LEAD FREE, PLASTIC, QFN-20
文件頁(yè)數(shù): 19/36頁(yè)
文件大?。?/td> 513K
代理商: LTC3833EUDC#PBF
LTC3833
26
3833f
APPLICATIONS INFORMATION
When making adjustments to improve efficiency, the input
current is the best indicator of changes in efficiency. If you
make a change and the input current decreases, then the
efficiency has increased. If there is no change in input
current there is no change in efficiency.
Power losses in the switching regulator will reflect as a
longer than ideal on-time. This efficiency accounted on-
time in continuous mode can be calculated as:
tON(REAL)
tON(IDEAL)
Efficiency
Design Example
Consider a step-down converter with VIN=6Vto24V,VOUT
= 1.2V, IOUT(MAX) = 15A, and f = 350kHz (see Figure 9).
The regulated output voltage is determined by:
VOUT = 0.6V 1+
RFB2
RFB1
Using a 20k resistor from VOSNS+ to VOSNS–, the top
feedback resistor is also 20k.
The frequency is programmed by:
RT k
[ ]= 41550
f kHz
[ ]
– 2.2
=
41550
350
– 2.2
≈116.5k
Select the nearest standard value of 115k.
Theminimumon-timeoccursformaximumVINandshould
be greater than 20ns which is the best that the LTC3833
can achieve. The minimum on-time for this application is:
tON(MIN) =
VOUT
VIN(MAX) f
=
1.2V
24V 350kHz
≈143ns
Set the inductor value to give 40% ripple current at maxi-
mum VIN:
L
=
1.2V
350kHz 40% 15A
1–
1.2V
24V
≈ 0.54H
Select 0.56μH which is the nearest standard value.
VIN
VOUT
PGOOD
RUN
VRNG
SENSE
SENSE+
RPGD
100k
INTVCC
RITH
47.5k
RT
115k
RDCR
3.09k
LTC3833
RFB2
20k
RFB1
20k
COUT1
330F
2.5V
×2
MT
MB
COUT2
100F
×2
L1
0.56H
TG
SW
DB
CSS
0.1F
RDIV1
52.3k
RDIV2
10k
CITH1
470pF
CITH2 47pF
3833 F09
VIN
6V TO 24V
VOUT
1.2V
15A
CDCR
0.1F
CB 0.1F
CVCC
4.7F
CIN1: SANYO 25SVPD82M
COUT1: SANYO 2R5TPE330M9
DB: CENTRAL CMDSH-3
L1: VISHAY IHLP4040DZ-056H
MB: RENESAS RJK0330DPB
MT: RENESAS RJK0305DPB
TRACK/SS
ITH
RT
MODE/PLLIN
EXTVCC
SGND
BOOST
INTVCC
BG
PGND
VOSNS+
VOSNS–
CIN2
10F
CIN1
82F
25V
+
350kHz
Figure 9. 1.2V, 15A, 350kHz Step-Down Converter
Efficiency
LOAD CURRENT (A)
0.1
60
EFFICIENCY
(%)
80
100
1
10
100
3833 F09b
40
50
70
90
30
20
VIN = 12V
VOUT = 1.2V
PULSE-SKIPPING
MODE
FORCED
CONTINUOUS
MODE
相關(guān)PDF資料
PDF描述
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