lm2612atlx National Semiconductor Corporation, lm2612atlx Datasheet - Page 15

• Manufacturer Part Number: lm2612atlx
• Description: Ic Conv Dc/dc Stp-dwn 10microsmd
• Manufacturer: National Semiconductor Corporation

Application Information
SETTING THE OUTPUT VOLTAGE
The LM2612 features pin-selectable output voltage to elimi-
nate the need for external feedback resistors. Select an
output voltage of 1.05V, 1.3V, 1.5V or 1.8V by configuring the
VID0 and VID1 pins, as directed in Table 1.
VID0 and VID1 are digital inputs. They may be set high by
connecting to VDD or low by connecting to SGND. Option-
ally, VID0 and VID1 may be driven by digital gates that
provide over 1.3V for a high state and less than 0.4V for a
low state to ensure valid logic levels. The VID0 and VID1
inputs each have an internal 1.8 µA pull-down that pulls them
low for a default 1.5V output when left unconnected. Leaving
these pins open is acceptable, but setting the pins high or
low is recommended.
For low-cost applications, an unshielded bobbin inductor is
suggested. For noise critical applications, a toroidal or
shielded-bobbin inductor should be used. A good practice is
to lay out the board with overlapping footprints of both types
for design flexibility. This allows substitution of a low-noise
toroidal inductor, in the event that noise from low-cost bobbin
models is unacceptable.
The saturation current rating is the current level beyond
which an inductor loses its inductance. Beyond this rating,
DO1608C-103
DO1606T-103
UP1B-100
UP0.4CB-100
ELL6GM100M
ELL6PM100M
P1174.103T
P0770.103T
CDRH5D18-100
CDRH4D28-100
CDC5D23-100
NP05D B100M
NP04S B100N
SLF6025T-100M1R0
SLF6020T-100MR90
A918CY-100M
A915AY-100M
Model
TABLE 1. VID0 and VID1 Output Voltage Selection Settings
TABLE 2. Suggested Inductors and Their Suppliers
Coilcraft
Coilcraft
Coiltronics
Coiltronics
Panasonic
Panasonic
Pulse Engineering
Pulse Engineering
Sumida
Sumida
Sumida
Taiyo Yuden
Taiyo Yuden
TDK
TDK
Toko
Toko
V
Vendor
OUT
1.05
1.8
1.5
1.3
(V)
VID0
0
0
1
1
15
Logic Level
INDUCTOR SELECTION
A 10µH inductor with a saturation current rating greater than
the max current limit of the device is recommended for most
applications. The inductor’s resistance should be less than
0.3Ω for good efficiency. Table 2 lists suggested inductors
and suppliers.
the inductor loses its ability to limit current through the PFET
switch to a ramp and allows the switch current to increase
rapidly. This can cause poor efficiency, regulation errors or
stress to DC-DC converters like the LM2612. Saturation
occurs when the magnetic flux density from current through
the windings of the inductor exceeds what the inductor’s
core material can support with energy storage in a corre-
sponding magnetic field.
VID1
1
0
0
1
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