Datasheet
LT8640/LT8640-1
5
Rev.C
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TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency at 3.3V
OUT
Efficiency vs Frequency
Burst Mode Operation Efficiency
vs Inductor Value
Reference Voltage
12V
IN
to 3.3V
OUT
Efficiency
vs Frequency
Efficiency at 5V
OUT
LOAD CURRENT (A)
0.5
60
EFFICIENCY (%)
POWER LOSS (W)
65
75
80
85
100
95
1.5
2.5
3
8640 G02
70
90
0
0.35
1.05
1.40
1.75
2.80
2.45
0.70
2.10
1 2
3.5
4 4.5
5
1MHz, L = 2.2μH
2MHz, L = 1μH
3MHz, L = 1μH
L = WE–LHMI1040
EFFICIENCY
POWER LOSS
Efficiency at 5V
OUT
Efficiency at 3.3V
OUT
8640 G03
LOAD CURRENT (A)
0 0.5
50
EFFICIENCY (%)
POWER LOSS (W)
60
55
65
75
80
85
100
95
1.5
2.5
3
70
90
0
0.6
0.3
1.2
1.5
1.8
2.1
3.0
2.7
0.9
2.4
1 2
3.5
4 4.5
5
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
f
SW
= 1MHz
L = IHLP3232DZ-01, 3.3μH
EFFICIENCY
POWER LOSS
8640 G04
LOAD CURRENT (A)
0 0.5
50
EFFICIENCY (%)
POWER LOSS (W)
60
55
65
75
80
85
100
95
1.5
2.5
3
70
90
0
0.3
0.6
0.9
1.5
1.8
2.1
3.0
2.7
1.2
2.4
1 2
3.5
4 4.5
5
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
f
SW
= 1MHz
L = IHLP3232DZ-01, 2.2μH
EFFICIENCY
POWER LOSS
LOAD CURRENT (mA)
40
EFFICIENCY (%)
50
60
70
80
8640 G05
30
20
10
0
90
100
0.01
0.1
1
10
100
1000
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
f
SW
= 1MHz
L = IHLP3232DZ-01, 4.7μH
LOAD CURRENT (mA)
40
EFFICIENCY (%)
50
60
70
80
8640 G06
30
20
10
0
90
100
0.01
0.1
1
10
100
1000
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
f
SW
= 1MHz
L = IHLP3232DZ-01, 4.7μH
SWITCHING FREQUENCY (MHz)
0
96
94
92
90
88
84
86
82
80
1.5 2.5 3
8640 G07
0.5 1
2
EFFICIENCY (%)
V
IN
= 12V
V
OUT
= 3.3V
I
LOAD
= 2A
L = IHLP3232DZ-01, 4.7μH
INDUCTOR VALUE (µH)
1
65
EFFICIENCY (%)
70
75
80
85
90
95
2 3 4 5 6 7
8640 G08
8
V
IN
= 12V
V
IN
= 24V
V
OUT
= 5V
I
LOAD
= 10mA
L = IHLP3232DZ-01
TEMPERATURE (°C)
–50
REFERENCE VOLAGE (V)
0.971
0.973
0.975
150
8640 G09
0.969
0.967
0.965
0.961
0
50
100
–25
25
75
125
0.963
0.979
0.977
EFFICIENCY
POWER LOSS
L = WE–LHMI1040
1MHz, L = 3.3µH
2MHz, L = 2.2µH
3MHz, L = 1µH
LOAD CURRENT (A)
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
60
65
70
75
80
85
90
95
100
0
0.38
0.75
1.13
1.50
1.88
2.25
2.63
3.00
EFFICIENCY (%)
POWER LOSS (W)
vs Frequency
12V
IN
to 5V
OUT
Efficiency
8640 G01
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