National Semiconductor LM22670 Technical data

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

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

www.national.com 2

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

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

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

Feedback Voltage VIN = 8V to 42V 4.925/4.9 5.0 5.075/5.1 V

LM22670-ADJ

Feedback Voltage VIN = 4.7V to 42V 1.266/1.259 1.285 1.304/1.311 V

All Output Voltage Versions

STDBY

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

DS(ON)

Switch On-Resistance TO-263 THIN Package 0.12 0.16/0.22

PSOP-8 Package 0.10 0.16/0.20

OFFMIN

ONMIN

BIAS

SYNC

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

Thermal Shutdown

150 °C

Threshold

Thermal Resistance TJ Package, Junction to ambient

22 °C/W

temperature resistance (Note 6)

Thermal Resistance MR Package, Junction to ambient

60 °C/W

temperature resistance (Note 7)

Units

Ω

www.national.com 4

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

OUT

= 3.3V

and V

Current Limit vs Temperature

30076027

Normalized Switching Frequency vs Temperature

30076004

Normalized R

vs Temperature

DS(ON)

30076003

30076008

5 www.national.com

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

www.national.com 6

30076013

+ 12 hidden pages