NSC LM2676T-5.0, LM2676T-3.3, LM2676T-12, LM2676SX-5.0, LM2676SX-3.3 Datasheet
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April 2000
LM2676
SIMPLE SWITCHER® High Efficiency 3A Step-Down
Voltage Regulator
General Description
The LM2676 series of regulators are monolithic integrated circuits which provide all of the active functions for a step-down (buck) switching regulator capable of driving up to 3A loads with excellent line and load regulation characteristics. High efficiency (>90%) is obtained through the use of a low ON-resistance DMOS power switch. The series consists of fixed output voltages of 3.3V, 5V and 12V and an adjustable output version.
The SIMPLE SWITCHER concept provides for a complete design using a minimum number of external components. A high fixed frequency oscillator (260KHz) allows the use of physically smaller sized components. A family of standard inductors for use with the LM2676 are available from several manufacturers to greatly simplify the design process.
The LM2676 series also has built in thermal shutdown, current limiting and an ON/OFF control input that can power down the regulator to a low 50µA quiescent current standby condition. The output voltage is guaranteed to a ±2% tolerance. The clock frequency is controlled to within a ±11% tolerance.
Features
nEfficiency up to 94%
nSimple and easy to design with (using off-the-shelf external components)
n150 mΩ DMOS output switch
n3.3V, 5V and 12V fixed output and adjustable (1.2V to 37V ) versions
n50µA standby current when switched OFF
n±2%maximum output tolerance over full line and load conditions
nWide input voltage range: 8V to 40V
n260 KHz fixed frequency internal oscillator
n−40 to +125ÊC operating junction temperature range
Applications
nSimple to design, high efficiency (>90%) step-down switching regulators
nEfficient system pre-regulator for linear voltage regulators
nBattery chargers
Typical Application
DS100914-3
SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation.
Regulator Voltage Down-Step 3A Efficiency High SWITCHER SIMPLE LM2676
© 2000 National Semiconductor Corporation |
DS100914 |
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LM2676
Connection Diagram and Ordering Information
TO-263 Package
Top View
DS100914-1
Order Number
LM2676S-3.3, LM2676S-5.0,
LM2676S-12 or LM2676S-ADJ
See NSC Package Number TS7B
TO-220 Package
Top View
DS100914-2
Order Number
LM2676T-3.3, LM2676T-5.0,
LM2676T-12 or LM2676T-ADJ
See NSC Package Number TA07B
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2 |
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
Input Supply Voltage |
45V |
ON/OFF Pin Voltage |
−0.1V to 6V |
Switch Voltage to Ground |
−1V to V IN |
Boost Pin Voltage |
VSW + 8V |
Feedback Pin Voltage |
−0.3V to 14V |
Power Dissipation |
Internally Limited |
ESD (Note 2) |
2 kV |
Storage Temperature Range |
−65ÊC to 150ÊC |
Soldering Temperature |
|
Wave |
4 sec, 260ÊC |
Infrared |
10 sec, 240ÊC |
Vapor Phase |
75 sec, 219ÊC |
Operating Ratings
Supply Voltage |
8V to 40V |
Junction Temperature Range (TJ) |
−40ÊC to 125ÊC |
Electrical Characteristics Limits appearing in bold type face apply over the entire junction temperature range of operation, −40ÊC to 125ÊC. Specifications appearing in normal type apply for T A = TJ = 25ÊC.
LM2676-3.3
Symbol |
Parameter |
Conditions |
Typical |
Min |
Max |
Units |
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(Note 3) |
(Note 4) |
(Note 4) |
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VOUT |
Output Voltage |
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A |
3.3 |
3.234/3.201 |
3.366/3.399 |
V |
η |
Efficiency |
VIN = 12V, ILOAD = 3A |
86 |
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% |
LM2676-5.0
Symbol |
Parameter |
Conditions |
Typical |
Min |
Max |
Units |
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(Note 3) |
(Note 4) |
(Note 4) |
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VOUT |
Output Voltage |
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A |
5.0 |
4.900/4.850 |
5.100/5.150 |
V |
η |
Efficiency |
VIN = 12V, ILOAD = 3A |
88 |
|
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% |
LM2676-12
Symbol |
Parameter |
Conditions |
Typical |
Min |
Max |
Units |
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(Note 3) |
(Note 4) |
(Note 4) |
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VOUT |
Output Voltage |
VIN = 15V to 40V, 100mA ≤ IOUT ≤ 3A |
12 |
11.76/11.64 |
12.24/12.36 |
V |
η |
Efficiency |
VIN = 24V, ILOAD = 3A |
94 |
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% |
LM2676-ADJ
Symbol |
Parameter |
Conditions |
Typ |
Min |
Max |
Units |
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(Note 3) |
(Note 4) |
(Note 4) |
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VFB |
Feedback |
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A |
1.21 |
1.186/1.174 |
1.234/1.246 |
V |
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Voltage |
VOUT Programmed for 5V |
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η |
Efficiency |
VIN = 12V, ILOAD = 3A |
88 |
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% |
LM2676
3 |
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LM2676
All Output Voltage Versions
Electrical Characteristics
Limits appearing in bold type face apply over the entire junction temperature range of operation, −40ÊC to 125ÊC. Specifications appearing in normal type apply for TA = TJ = 25ÊC. Unless otherwise specified VIN=12V for the 3.3V, 5V and Adjustable versions and VIN=24V for the 12V version.
Symbol |
Parameter |
Conditions |
Typ |
Min |
Max |
Units |
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DEVICE PARAMETERS |
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IQ |
Quiescent |
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Current |
VFEEDBACK = 8V |
4.2 |
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6 |
mA |
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For 3.3V, 5.0V, and ADJ Versions |
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VFEEDBACK = 15V |
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For 12V Versions |
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ISTBY |
Standby |
ON/OFF Pin = 0V |
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Quiescent |
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50 |
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100/150 |
µA |
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Current |
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ICL |
Current Limit |
|
4.5 |
3.8/3.6 |
5.25/5.4 |
A |
IL |
Output |
VIN = 40V, ON/OFF Pin = 0V |
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µA |
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Leakage |
VSWITCH = 0V |
1 |
|
200 |
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mA |
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Current |
VSWITCH = −1V |
6 |
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15 |
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RDS(ON) |
Switch |
ISWITCH = 3A |
0.15 |
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0.17/0.29 |
Ω |
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On-Resistance |
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fO |
Oscillator |
Measured at Switch Pin |
260 |
225 |
280 |
kHz |
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Frequency |
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D |
Duty Cycle |
Maximum Duty Cycle |
91 |
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% |
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Minimum Duty Cycle |
0 |
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% |
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IBIAS |
Feedback Bias |
VFEEDBACK = 1.3V |
85 |
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nA |
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Current |
ADJ Version Only |
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VON/OFF |
ON/OFF |
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Threshold |
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1.4 |
0.8 |
2.0 |
V |
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Voltage |
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ION/OFF |
ON/OFF Input |
ON/OFF Input = 0V |
20 |
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45 |
µA |
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Current |
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θJA |
Thermal |
T Package, Junction to Ambient |
65 |
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Resistance |
(Note 5) |
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θJA |
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T Package, Junction to Ambient |
45 |
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(Note 6) |
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θJC |
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T Package, Junction to Case |
2 |
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θJA |
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S Package, Junction to Ambient |
56 |
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ÊC/W |
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(Note 7) |
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θJA |
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S Package, Junction to Ambient |
35 |
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(Note 8) |
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θJA |
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S Package, Junction to Ambient |
26 |
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(Note 9) |
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θJC |
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S Package, Junction to Case |
2 |
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++ |
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 TA = TJ = 25ÊC 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 TA = TJ = 25ÊC. 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: 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 6: 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.
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4 |
(Continued)
Note 7: 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 8: 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 9: 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.
LM2676
5 |
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LM2676
Typical Performance Characteristics
Normalized |
Line Regulation |
Efficiency vs Input Voltage |
Output Voltage |
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|
DS100914-10 |
DS100914-11 |
|
DS100914-9 |
|
Efficiency vs ILOAD |
Switch Current Limit |
Operating Quiescent Current |
DS100914-12 DS100914-4 DS100914-5
Standby Quiescent Current ON/OFF Threshold Voltage ON/OFF Pin Current (Sourcing)
DS100914-40 |
DS100914-14 |
DS100914-13 |
Switching Frequency Feedback Pin Bias Current
DS100914-15 |
DS100914-16 |
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6 |
Block Diagram
*Active Inductor Patent Number 5,514,947
²Active Capacitor Patent Number 5,382,918
LM2676
DS100914-6
7 |
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