Datasheet
LM2679
SNVS026N –MARCH 2000–REVISED APRIL 2013
www.ti.com
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.
Specifications 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 Parameter Conditions Min Typ Max Units
DEVICE PARAMETERS
I
Q
Quiescent Current V
FEEDBACK
= 8V 4.2 6 mA
For 3.3V, 5.0V, and ADJ Versions
V
FEEDBACK
= 15V
For 12V Versions
V
ADJ
Current Limit Adjust
1.181/1.169 1.21 1.229/1.246 V
Voltage
I
CL
Current Limit R
ADJ
= 5.6KΩ,
(1)
5.5/5.3 6.3 7.6/8.1 A
I
L
Output Leakage V
IN
= 40V, Softstart Pin = 0V
mA
Current V
SWITCH
= 0V 1.0 1.5
mA
V
SWITCH
= −1V 6 15
R
DS(ON)
Switch On-Resistance I
SWITCH
= 5A 0.12 0.14/0.225 Ω
f
O
Oscillator Frequency Measured at Switch Pin 225 260 280 kHz
D Duty Cycle Maximum Duty Cycle 91 %
Minimum Duty Cycle 0 %
I
BIAS
Feedback Bias V
FEEDBACK
= 1.3V 85 nA
Current ADJ Version Only
V
SFST
Softstart Threshold
0.53 0.63 0.74 V
Voltage
I
SFST
Softstart Pin Current Softstart Pin = 0V 3.7 6.9 μA
θ
JA
Thermal Resistance NDZ Package, Junction to Ambient
(2)
65
θ
JA
NDZ Package, Junction to Ambient
(3)
45
θ
JC
NDZ Package, Junction to Case 2
θ
JA
KTW Package, Junction to Ambient
(4)
56 °C/W
θ
JA
KTW Package, Junction to Ambient
(5)
35
θ
JA
KTW Package, Junction to Ambient
(6)
26
θ
JC
KTW Package, Junction to Case 2 ++
θ
JA
NHM Package, Junction to Ambient
(7)
55
°C/W
θ
JA
NHM Package, Junction to Ambient
(8)
29
(1) The peak switch current limit is determined by the following relationship: I
CL
=37,125/ R
ADJ
.
(2) Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads in a
socket, or on a PC board with minimum copper area.
(3) Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads
soldered to a PC board containing approximately 4 square inches of (1 oz.) copper area surrounding the leads.
(4) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.136 square inches (the
same size as the DDPAK package) of 1 oz. (0.0014 in. thick) copper.
(5) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.4896 square inches
(3.6 times the area of the DDPAK package) of 1 oz. (0.0014 in. thick) copper.
(6) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board copper area of 1.0064 square
inches (7.4 times the area of the DDPAK 3 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.
(7) Junction to ambient thermal resistance for the 14-lead VSON mounted on a PC board copper area equal to the die attach paddle.
(8) Junction to ambient thermal resistance for the 14-lead VSON 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 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.
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