October 17, 2008
LM22670
3A SIMPLE SWITCHER®, Step-Down Voltage Regulator
with Synchronization or Adjustable Switching Frequency
LM22670 3A SIMPLE SWITCHER®, Step-Down Voltage Regulator with Synchronization or
Adjustable Switching Frequency
General Description
The LM22670 series of regulators are monolithic integrated
circuits which provide all of the active functions for a stepdown (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 N-channel MOSFET. The series consists of a
fixed 5V output and an adjustable version.
The SIMPLE SWITCHER® concept provides for an easy to
use complete design using a minimum number of external
components and National’s WEBENCH® design tool.
National’s WEBENCH® tool includes features such as external component calculation, electrical simulation, thermal simulation, and Build-It boards for easy design-in. The switching
clock frequency is provided by an internal fixed frequency oscillator which operates at 500 kHz. The switching frequency
can also be adjusted with an external resistor or synchronized
to an external clock up to 1MHz. It is also possible to selfsynchronize multiple regulators to share the same switching
frequency. The LM22670 series also has built in thermal shutdown, current limiting and an enable control input that can
power down the regulator to a low 25 µA quiescent current
standby condition.
Features
Wide input voltage range: 4.5V to 42V
■
Internally compensated voltage mode control
■
Stable with low ESR ceramic capacitors
■
120 mΩ N-channel MOSFET TO-263 THIN package
■
100 mΩ N-channel MOSFET PSOP-8 package
■
Output voltage options:
■
-ADJ (outputs as low as 1.285V)
-5.0 (output fixed to 5V)
±1.5% feedback reference accuracy
■
Switching frequency of 500 kHz, adjustable between 200
■
kHz and 1 MHz
-40°C to 125°C operating junction temperature range
■
Precision enable pin
■
Integrated boot diode
■
Integrated soft-start
■
Fully WEBENCH® enabled
■
Step-down and inverting buck-boost applications
■
Package
PSOP-8 (Exposed Pad)
■
TO-263 THIN (Exposed Pad)
■
Applications
Industrial Control
■
Telecom and Datacom Systems
■
Embedded Systems
■
Automotive Telematics and Body Electronics
■
Conversions from Standard 24V, 12V and 5V Input Rails
■
Simplified Application Schematic
30076001
© 2008 National Semiconductor Corporation 300760 www.national.com
Connection Diagrams
LM22670
8-Lead Plastic PSOP-8 Package
NS Package Number MRA08B
7-Lead Plastic TO-263 THIN Package
NS Package Number TJ7A
30076040
30076002
Ordering Information
Output Voltage Order Number Package Type NSC Package
Drawing
ADJ LM22670MR-ADJ PSOP-8 Exposed Pad MRA08B 95 Units in Rails
ADJ LM22670MRE-ADJ 250 Units in Tape and Reel
ADJ LM22670MRX-ADJ 2500 Units in Tape and Reel
ADJ LM22670TJE-ADJ TO-263 THIN Exposed Pad TJ7A 250 Units in Tape and Reel
ADJ LM22670TJ-ADJ 1000 Units in Tape and Reel
5.0 LM22670MR-5.0 PSOP-8 Exposed Pad MRA08B 95 Units in Rails
5.0 LM22670MRE-5.0 250 Units in Tape and Reel
5.0 LM22670MRX-5.0 2500 Units in Tape and Reel
5.0 LM22670TJE-5.0 TO-263 THIN Exposed Pad TJ7A 250 Units in Tape and Reel
5.0 LM22670TJ-5.0 1000 Units in Tape and Reel
Supplied As
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Pin Descriptions
LM22670
Pin Numbers
PSOP-8
Package
1 3 BOOT Bootstrap input Provides the gate voltage for the high side NFET.
2 - NC Not Connected Pin is not electrically connected inside the chip. Pin
3 5 RT/
4 6 FB Feedback pin Inverting input to the internal voltage error amplifier.
5 7 EN Precision enable pin When pulled low regulator turns off.
6 4 GND System ground Provide good capacitive decoupling between VIN and
7 2 VIN Source input voltage Input to the regulator. Operates from 4.5V to 42V.
8 1 SW Switch pin Attaches to the switch node.
Pin Numbers
TO-263 THIN
Package
Name Description Application Information
does function as thermal conductor.
SYNC
Oscillator frequency adjust pin or
frequency synchronization
A resistor connected from this pin to GND adjusts the
oscillator frequency. This pin can also accept an input
for synchronization from an external clock. Pin can be
left floating and internal setting will be default to 500
kHz.
this pin.
3 www.national.com
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
LM22670
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
VIN to GND 43V
EN Pin Voltage -0.5V to 6V
RT/SYNC Pin Voltage -0.5V to 7V
SW to GND (Note 2) -5V to V
BOOT Pin Voltage VSW + 7V
FB Pin Voltage -0.5V to 7V
Power Dissipation Internally Limited
Junction Temperature 150°C
Soldering Information
Vapor Phase (75 sec.) 219°C
Infrared (10 sec.) 240°C
Wave (4 sec.) 260°C
ESD Rating (Note 3)
Human Body Model ±2 kV
Storage Temperature Range -65°C to +150°C
IN
Operating Ratings (Note 1)
Supply Voltage (VIN)
4.5V to 42V
Junction Temperature Range -40°C to +125°C
Electrical Characteristics Limits in standard type are for T
= 25°C only; limits in boldface type apply over the
J
junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical
correlation. Typical values represent the most likely parametric norm at TA = TJ = 25°C, and are provided for reference purposes
only. Unless otherwise specified: VIN = 12V.
Symbol Parameter Conditions Min
(Note 5)
Typ
(Note 4)
Max
(Note 5)
LM22670-5.0
V
FB
Feedback Voltage VIN = 8V to 42V 4.925/4.9 5.0 5.075/5.1 V
LM22670-ADJ
V
FB
Feedback Voltage VIN = 4.7V to 42V 1.266/1.259 1.285 1.304/1.311 V
All Output Voltage Versions
I
I
STDBY
I
CL
I
Q
L
Quiescent Current VFB = 5V 3.4 6 mA
Standby Quiescent Current EN Pin = 0V 25 40 µA
Current Limit 3.4/3.35 4.2 5.3/5.5 A
Output Leakage Current VIN = 42V, EN Pin = 0V, VSW = 0V 0.2 2 µA
VSW = -1V 0.1 3 µA
R
DS(ON)
Switch On-Resistance TO-263 THIN Package 0.12 0.16/0.22
PSOP-8 Package 0.10 0.16/0.20
f
T
OFFMIN
T
ONMIN
I
BIAS
V
I
EN
F
SYNC
V
SYNC
O
EN
Oscillator Frequency 400 500 600 kHz
Minimum Off-time 300 ns
Minimum On-time 100 ns
Feedback Bias Current VFB = 1.3V (ADJ Version Only) 230 nA
Enable Threshold Voltage 1.3 1.6 1.9 V
Enable Input Current EN Input = 0V 6 µA
Synchronization Frequency V
Synchronization Threshold
= 3.5V, 50% duty-cycle 1 MHz
SYNC
1.75 V
Voltage
T
SD
Thermal Shutdown
150 °C
Threshold
θ
JA
Thermal Resistance TJ Package, Junction to ambient
22 °C/W
temperature resistance (Note 6)
θ
JA
Thermal Resistance MR Package, Junction to ambient
60 °C/W
temperature resistance (Note 7)
Units
Ω
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Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability
and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or other conditions beyond those indicated in
the recommended Operating Ratings is not implied. The recommended Operating Ratings indicate conditions at which the device is functional and should not be
operated beyond such conditions.
Note 2: The absolute maximum specification of the ‘SW to GND’ applies to DC voltage. An extended negative voltage limit of -10V applies to a pulse of up to 50
ns.
Note 3: ESD was applied using the human body model, a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 4: Typical values represent most likely parametric norms at the conditions specified and are not guaranteed.
Note 5: Min and Max limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical
Quality Control (SQC) methods. Limits are used to calculate National’s Average Outgoing Quality Level (AOQL).
Note 6: The value of θJA for the TO-263 THIN (TJ) package of 22°C/W is valid if package is mounted to 1 square inch of copper. The θJA value can range from
20 to 30°C/W depending on the amount of PCB copper dedicated to heat transfer. See application note AN-1797 for more information.
Note 7: The value of θJA for the PSOP-8 exposed pad (MR) package of 60°C/W is valid if package is mounted to 1 square inch of copper. The θJA value can
range from 42 to 115°C/W depending on the amount of PCB copper dedicated to heat transfer.
Typical Performance Characteristics Unless otherwise specified the following conditions apply: Vin =
12V, TJ = 25°C.
LM22670
Efficiency vs I
V
OUT
OUT
= 3.3V
and V
IN
Current Limit vs Temperature
30076027
Normalized Switching Frequency vs Temperature
30076004
Normalized R
vs Temperature
DS(ON)
30076003
30076008
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LM22670
Feedback Bias Current vs Temperature
Normalized Enable Threshold Voltage vs Temperature
30076005
Standby Quiescent Current vs Input Voltage
30076006
Normalized Feedback Voltage vs Input Voltage
30076010
Normalized Feedback Voltage vs Temperature
30076007
Switching Frequency vs RT/SYNC Resistor
30076009
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30076013