LM3424MH/NOPB National Semiconductor, LM3424MH/NOPB Datasheet - Page 31

• 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

1. OPERATING POINT
Solve for V
Solve for D, D', D
2. SWITCHING FREQUENCY
Solve for R
The closest standard resistor is 14.3 kΩ therefore f
The chosen component from step 2 is:
3. AVERAGE LED CURRENT
Solve for R
Assume R
The closest standard resistor for R
R
HSP
is actually 1 kΩ therefore I
CSH
O
T
SNS
:
and r
:
= 12.4 kΩ and solve for R
MAX
D
:
, and D
MIN
:
LED
SNS
is:
is actually 0.1Ω and for
HSP
:
SW
is:
31
The chosen components from step 3 are:
4. THERMAL FOLDBACK
Find the resistances corresponding to T
BK
datasheet. Assuming R
R
Solve for R
The chosen components from step 4 are:
5. INDUCTOR RIPPLE CURRENT
Solve for L1:
The closest standard inductor is 33 µH therefore Δi
Determine minimum allowable RMS current rating:
The chosen component from step 5 is:
NTC-BK
= 24.3 kΩ and R
= 24.3 kΩ.
GAIN
:
NTC-END
REF1
= 7.15 kΩ) from the manufacturer's
= R
REF2
= 49.9 kΩ, then R
BK
and T
www.national.com
END
L-PP
(R
BIAS
is:
NTC-
=