LM3423MHBKBSTEV/NOPB National Semiconductor, LM3423MHBKBSTEV/NOPB Datasheet - Page 11

• Manufacturer Part Number: LM3423MHBKBSTEV/NOPB
• Description: BOARD EVAL BUCK BOOST LM3423
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM3423MHBKBSTEV/NOPB

• Current - Output / Channel: 1A
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 35V
• Features: Dimmable
• Voltage - Input: 4.5 ~ 35V
• Utilized Ic / Part: LM3423
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM3423MHBKBSTEV

SWITCHING FREQUENCY
An external resistor (R
the switch node (where D1, Q1, and L1 connect), in combi-
nation with a capacitor (C
sets the off-time (t
buck-boost topologies, the V
tually constant switching frequency (f
For a buck topology, R
however the V
switching frequency. Instead, constant ripple operation can
be achieved. Changing the connection of R
V
Adding a PNP transistor as shown in
constant ripple over varying V
The switching frequency is defined:
Buck (Constant Ripple vs. V
Buck (Constant Ripple vs. V
Boost and Buck-boost
For all topologies, the C
1 nF and should be located very close to the LM3421/23.
SW
to V
IN
will provide a constant ripple over varying V
IN
proportionality will not ensure a constant
OFF
) as shown in
T
) connected between the RCT pin and
T
T
T
) between the RCT and AGND pins,
and C
capacitor is recommended to be
IN
O
IN
O
.
proportionality ensures a vir-
)
)
T
are also used to set t
Figure
SW
Figure 3
).
T
FIGURE 4. LED Current Sense Circuitry
2. For boost and
in
Figure 2
will provide
from
OFF
IN
,
.
11
FIGURE 2. Off-timer Circuitry for Boost and Buck-boost
FIGURE 3. Off-timer Circuitry for Buck Regulators
Regulators
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