LM3410XSD National Semiconductor, LM3410XSD Datasheet - Page 15

• Manufacturer Part Number: LM3410XSD
• Description: IC, LED DRIVER, POWERWISE 1.6MHZ
• Manufacturer: National Semiconductor

Specifications of LM3410XSD

• Led Driver Application: Backlighting, LED Flash Driver
• No. Of Outputs: 1
• Output Current: 2.8A
• Output Voltage: 24V
• Input Voltage: 2.7V To 5.5V
• Dimming Control Type: PWM
• Topology: Boost, SEPIC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The LM3410 conduction loss is mainly associated with the
internal power switch:
The value for R
junction temperature you wish to analyze. As an example, at
125°C and R
Switching losses are also associated with the internal power
switch. They occur during the switch on and off transition pe-
riods, where voltages and currents overlap resulting in power
loss.
The simplest means to determine this loss is to empirically
measuring the rise and fall times (10% to 90%) of the switch
at the switch node:
V
3V
5V
3V
5V
IN
Typical Switch-Node Rise and Fall Times
FIGURE 11. LM3410 Switch Current
P
P
DSON
P
SWR
SWF
COND-NFET
P
DSON
(small ripple approximation)
COND-NFET
= 250 mΩ (See typical graphs for value).
= 1/2(V
= 1/2(V
V
P
12V
12V
18V
should be equal to the resistance at the
5V
OUT
SW
P
IND
= I
= P
OUT
OUT
= I
= I
2
SW-rms
SWR
or
or
IN
IN
x I
x I
2
2
R
IN
IN
x R
+ P
DCR
x f
x R
x f
10nS
t
6nS
6nS
8nS
RISE
DSON
SWF
SW
SW
DSON
x t
x t
x D
FALL
RISE
x D
)
)
30038542
t
4nS
5nS
7nS
8nS
FALL
15
Quiescent Power Losses
I
1.5 mA.
R
Example Efficiency Calculation:
Operating Conditions:
5 x 3.3V LEDs + 190mV
Quiescent Power Loss:
Switching Power Loss:
Internal NFET Power Loss:
Diode Loss:
V
Inductor Power Loss:
R
Q
D
SET
DCR
is the quiescent operating current, and is typically around
= 0.45V
Power Loss
= 75 mΩ
P
P
ΣP
SWR
SWF
P
COND
CONDUCTION
R
V
t
L
t
TABLE 1. Operating Conditions
I
f
FALL
V
RISE
DSON
V
= 1/2(V
LED
= 1/2(V
DCR
I
OUT
SW
I
D
IN
Q
IN
D
P
P
+ P
SW
P
DIODE
IND
P
SW
= P
Q
OUT
OUT
R
= I
= I
= I
+ P
DSON
= V
SWR
P
I
REF
IN
IN
Q
x I
Q
x I
IN
2
DIODE
x V
= 310 mA
D
2
= I
IN
IN
x R
+ P
≊
= 225 mΩ
x D x R
x I
Q
x f
x f
IN
16.7V
LED
DCR
SWF
x V
SW
+ P
= 10 mW
SW
IN
= 23 mW
x t
= 7 mW
x t
IND
= 80 mW
DSON
FALL
RISE
+ P
1.60MHz
= 17 mW
225mΩ
)
)
16.7V
50mA
0.45V
75mΩ
0.31A
10nS
10nS
Q
3.3V
3mA
0.82
≊
≊
= P
40 mW
40 mW
LOSS
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