LM3407EVAL National Semiconductor, LM3407EVAL Datasheet - Page 8

• Manufacturer Part Number: LM3407EVAL
• Description: BOARD EVALUATION FOR LM3407
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3407EVAL

• Current - Output / Channel: 350mA
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 4.5V
• Features: Dimmable
• Voltage - Input: 4.5 ~ 30V
• Utilized Ic / Part: LM3407
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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PULSE LEVEL MODULATION (PLM)
The LM3407 incorporates the innovative Pulse Level Modu-
lation technique. With an external 1% thick film resistor con-
nected to the ISNS pin, the converter output voltage can
adjust automatically as needed to deliver constant current
within 10% accuracy to a serially connected LED string of dif-
ferent number and type. Pulse Level Modulation is a novel
method to provide precise constant current control with high
efficiency. It allows the use of low side current sensing and
facilitates true average output current regulation regardless
FIGURE 1. Operating Waveforms of a Floating Buck Converter
8
of the input voltage and inductor value. Pulse Level Modula-
tion can be treated as a process that transforms a trapezoidal
pulse chain into a square pulse chain with an amplitude equal
to the center of inductor current ramp. Figure 2 shows the
waveform of the converter in steady state. In the figure, I
the inductor current and I
pin. V
sistor R
and is a reference pulse that is synchronized and has an
identical pulse width to V
ISNS
ISNS
is the voltage drop across the current sensing re-
. V
MSL
is the center of the inductor current ramp
ISNS
LX
is the switch current into the LX
.
30046619
L1
is