LM3424MH/NOPB National Semiconductor, LM3424MH/NOPB Datasheet - Page 26

• Manufacturer Part Number: LM3424MH/NOPB
• Description: IC LED DVR BUCK/BOOST 20-TSSOP
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: High Power, Constant Currentr

Specifications of LM3424MH/NOPB

• Constant Current: Yes
• Topology: Flyback, PWM, SEPIC, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Automotive
• Type - Secondary: High Brightness LED (HBLED)
• Frequency: 2MHz
• Voltage - Supply: 4.5 V ~ 75 V
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP Exposed Pad, 20-eTSSOP, 20-HTSSOP
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 1A
• Internal Switch(s): Yes
• Efficiency: 96%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Other names: LM3424MH

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The minimum allowable inductor RMS current rating (I
can be calculated as:
Buck
Boost and Buck-boost
6. LED RIPPLE CURRENT
Set the nominal LED ripple current (Δi
the output capacitance (C
Buck
Boost and Buck-boost
To set the worst case LED ripple current, use D
solving for C
mended to use a minimum of 40 µF of output capacitance to
improve performance.
The minimum allowable RMS output capacitor current rating
(I
Buck
Boost and Buck-boost
7. PEAK CURRENT LIMIT
Set the peak current limit (I
path sense resistor (R
CO-RMS
) can be approximated:
O
. Remember, when PWM dimming it is recom-
LIM
):
O
):
LIM
) by solving for the transistor
LED-PP
), by solving for
MAX
L-RMS
when
)
26
8. SLOPE COMPENSATION
For all topologies, the preferred method to set slope compen-
sation is to ensure any duty cycle is attainable for the nominal
V
9. LOOP COMPENSATION
Using a simple first order peak current mode control model,
neglecting any output capacitor ESR dynamics, the neces-
sary loop compensation can be determined.
First, the uncompensated loop gain (T
be approximated:
Buck
Boost and Buck-boost
Where the pole (ω
Buck
Boost
Buck-boost
And the RHP zero (ω
Boost
Buck-boost
O
and chosen L by solving for R
P1
) is approximated:
Z1
) is approximated:
SLP
:
U
) of the regulator can