If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Input Supply Voltage
Softstart Pin Voltage
Switch Voltage to Ground
Boost Pin Voltage
Feedback Pin Voltage
Power Dissipation
ESD (Note 2)
45V
−0.1V to 6V
−1V to V
IN
V
SW
+ 8V
−0.3V to 14V
Internally Limited
2 kV
Operating Ratings
Supply Voltage
Junction Temperature Range (T
J
)
8V to 40V
−40˚C to 125˚C
Electrical Characteristics
LM2679-3.3
Symbol
V
OUT
η
Parameter
Output Voltage
Efficiency
Limits appearing in
bold type face
apply over the entire junction temperature
range of operation, −40˚C to 125˚C. Specifications appearing in normal type apply for T
A
= T
J
= 25˚C. R
ADJ
= 5.6KΩ
Conditions
V
IN
= 8V to 40V, 100mA
≤
I
OUT
≤
5A
V
IN
= 12V, I
LOAD
= 5A
Typical
(Note 3)
3.3
82
Min
(Note 4)
3.234/3.201
Max
(Note 4)
3.366/3.399
Units
V
%
LM2679-5.0
Symbol
V
OUT
η
Parameter
Output Voltage
Efficiency
Conditions
V
IN
= 8V to 40V, 100mA
≤
I
OUT
≤
5A
V
IN
= 12V, I
LOAD
= 5A
Typical
(Note 3)
5.0
84
Min
(Note 4)
4.900/4.850
Max
(Note 4)
5.100/5.150
V
%
Units
LM2679-12
Symbol
V
OUT
η
Parameter
Output Voltage
Efficiency
Conditions
V
IN
= 15V to 40V, 100mA
≤
I
OUT
≤
5A
V
IN
= 24V, I
LOAD
= 5A
Typical
(Note 3)
12
92
Min
(Note 4)
11.76/11.64
Max
(Note 4)
12.24/12.36
V
%
Units
LM2679-ADJ
Symbol
V
FB
η
Parameter
Feedback
Voltage
Efficiency
Conditions
V
IN
= 8V to 40V, 100mA
≤
I
OUT
≤
5A
V
OUT
Programmed for 5V
V
IN
= 12V, I
LOAD
= 5A
Typ
(Note 3)
1.21
84
Min
(Note 4)
1.186/1.174
Max
(Note 4)
1.234/1.246
V
%
Units
3
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LM2679
All Output Voltage Versions
Electrical Characteristics
Limits appearing in
bold type face
apply over the entire junction temperature range of operation, −40˚C to 125˚C. Specifica-
tions appearing in normal type apply for T
A
= T
J
= 25˚C. Unless otherwise specified V
IN
=12V for the 3.3V, 5V and Adjustable
versions and V
IN
=24V for the 12V version.
Symbol
I
Q
Parameter
Quiescent
Current
V
FEEDBACK
= 8V
For 3.3V, 5.0V, and ADJ Versions
V
FEEDBACK
= 15V
For 12V Versions
V
ADJ
I
CL
I
L
Current Limit
Adjust Voltage
Current Limit
Output Leakage
Current
Switch
On-Resistance
Oscillator
Frequency
Duty Cycle
Feedback Bias
Current
Softstart
Threshold
Voltage
Softstart Pin
Current
Thermal
Resistance
Softstart Pin = 0V
T Package, Junction to Ambient
(Note 6)
T Package, Junction to Ambient
(Note 7)
θ
JC
θ
JA
θ
JA
θ
JA
θ
JC
θ
JA
θ
JA
T Package, Junction to Case
S Package, Junction to Ambient
(Note 8)
S Package, Junction to Ambient
(Note 9)
S Package, Junction to Ambient
(Note 10)
S Package, Junction to Case
SD Package, Junction to Ambient
(Note 11)
SD Package, Junction to Ambient
(Note 12)
29
2
55
˚C/W
++
26
35
2
56
˚C/W
45
R
ADJ
= 5.6KΩ, (Note 5)
V
IN
= 40V, Softstart Pin = 0V
V
SWITCH
= 0V
V
SWITCH
= −1V
I
SWITCH
= 5A
Measured at Switch Pin
Maximum Duty Cycle
Minimum Duty Cycle
I
BIAS
V
SFST
V
FEEDBACK
= 1.3V
ADJ Version Only
1.21
6.3
1.0
6
0.12
260
91
0
85
225
1.181/1.169
5.5/5.3
1.229/1.246
7.6/8.1
1.5
15
0.14/0.225
280
V
A
mA
mA
Ω
kHz
%
%
nA
Conditions
Typ
4.2
Min
Max
6
Units
mA
DEVICE PARAMETERS
R
DS(ON)
f
O
D
0.63
0.53
0.74
V
I
SFST
θ
JA
θ
JA
3.7
65
6.9
µA
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4
LM2679
All Output Voltage Versions
Electrical Characteristics
(Continued)
Note 1:
Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions under which of the device is
guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test condition, see the electrical
Characteristics tables.
Note 2:
ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 3:
Typical values are determined with T
A
= T
J
= 25˚C and represent the most likely norm.
Note 4:
All limits are guaranteed at room temperature (standard type face) and at
temperature extremes (bold type face).
All room temperature limits are 100%
tested during production with T
A
= T
J
= 25˚C. All limits at temperature extremes are guaranteed via correlation using standard standard Quality Control (SQC)
methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 5:
The peak switch current limit is determined by the following relationship: I
CL
=37,125/ R
ADJ
.
Note 6:
Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with
1
⁄
2
inch leads in a socket, or on a PC
board with minimum copper area.
Note 7:
Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with
1
⁄
2
inch leads soldered to a PC board
containing approximately 4 square inches of (1 oz.) copper area surrounding the leads.
Note 8:
Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.136 square inches (the same size as the
TO-263 package) of 1 oz. (0.0014 in. thick) copper.
Note 9:
Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.4896 square inches (3.6 times the area
of the TO-263 package) of 1 oz. (0.0014 in. thick) copper.
Note 10:
Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board copper area of 1.0064 square inches (7.4 times
the area of the TO-263 package) of 1 oz. (0.0014 in. thick) copper. Additional copper area will reduce thermal resistance further. See the thermal model in Switchers
Made Simple
®
software.
Note 11:
Junction to ambient thermal resistance for the 14-lead LLP mounted on a PC board copper area equal to the die attach paddle.
Note 12:
Junction to ambient thermal resistance for the 14-lead LLP mounted on a PC board copper area using 12 vias to a second layer of copper equal to die
attach paddle. Additional copper area will reduce thermal resistance further. For layout recommendations, refer to Application Note AN-1187.
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