Datasheet

V
OUT1
RT/SD
FB
VIN
SW
RTN
BST
N
P
C2
R
FB2
R
FB1
R
T
C4
C3
Input
LM5006
R3
C1
GND
VCC
V
IN
GND
UV
R
UV2
R
UV1
UVO
R
UVO
UV STATUS
LG
Q1
C5
V
OUT2
D1
N
S
L1
SHUT
DOWN
V
OUT2
= (V
OUT1
x
N
S
N
P
) - V
D1
FB
SW
L1
LM5006
R3
C2
V
OUT
R
FB2
R
FB1
LM5006
SNVS646B –FEBRUARY 2011–REVISED MARCH 2013 www.ti.com
Figure 40. Alternate Minimum Output Ripple
Secondary Output
A secondary slave output voltage can be produced by replacing the inductor (L1) with an inductor which has a
second winding, and using a MOSFET for synchronous rectification (Q1) rather than a diode. The synchronous
rectification option is required to ensure the circuit is in continuous conduction mode at all values of the main
output’s load current. This ensures the secondary output voltage is correct for all load conditions. See Figure 41.
The approximate secondary output voltage (V
OUT2
) is:
where
• N
P
and N
S
are the number of primary and secondary turns
• V
D1
is the drop across D1 (23)
Figure 41. Generate a Secondary Output
PC Board Layout
The LM5006 regulation, over-voltage, and current limit comparators are very fast, and respond to short duration
noise pulses. Layout considerations are therefore critical for optimum performance. The layout must be as neat
and compact as possible, and all of the components must be as close as possible to the associated pins. The
two major current loops have currents which switch very fast, and so the loops should be as small as possible to
minimize conducted and radiated EMI. The first loop is formed by C1, through VIN to the SW pin, L1, C2, and
back to C1. The second loop is formed by L1, C2, D1 (or Q1), and back to L1. Since a current equal to the load
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