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LM2650

www.ti.com

SNVS133C –JUNE 1999–REVISED APRIL 2013

LM2650 Synchronous Step-Down DC/DC Converter

Check for Samples: LM2650

FEATURES

DESCRIPTION

The LM2650 is a step-down DC/DC converter

• Ultra High Efficiencies (95% possible)

featuring high efficiency over a 3A to milliamperes

• High Efficiency Over a 3A to Milliamperes

load range. This feature makes the LM2650 an ideal

Load Range

fit in battery-powered applications that demand long

• Synchronous Switching of Internal NMOS

battery life in both run and standby modes.

Power FETs

The LM2650 also features a logic-controlled

• Wide Input Voltage Range (4.5V to 18V)

shutdown mode in which it draws at most 25μA from

the input power supply.

• Output Voltage Adjustable from 1.5V to 16V

• Automatic Low-Power Sleep Mode

The LM2650 employs a fixed-frequency pulse-width

modulation (PWM) and synchronous rectification to

• Logic-Controlled Micropower Shutdown (I

QSD

≤

achieve very high efficiencies. In many applications,

25 µA)

efficiencies reach 95%+ for loads around 1A and

• Frequency Adjustable up to 300 kHz

exceed 90% for moderate to heavy loads from 0.2A

• Frequency Synchronization with External

to 2A.

Signal

A low-power hysteretic or "sleep" mode keeps

• Programmable Soft-Start

efficiencies high at light loads. The LM2650 enters

and exits sleep mode automatically as the load

• Short-Circuit Current Limiting

crosses "sleep in" and "sleep out" thresholds. The

• Thermal Shutdown

LM2650 provides nodes for programming both

• Available in 24-lead Small-Outline Package

thresholds via external resistors. A logic input allows

the user to override the automatic sleep feature and

APPLICATIONS

keep the LM2650 in PWM mode regardless of the

load level.

• Notebook and Palmtop Personal Computers

An optional soft-start feature limits current surges

• Portable Data Terminals

from the input power supply at start up and provides

• Modems

a simple means of sequencing multiple power

• Portable Instruments

supplies.

• Global Positioning Devices (GPSs)

• Battery-Powered Digital Devices

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (19 pages)

PAGE 1
LM2650 www.ti.com SNVS133C – JUNE 1999 – REVISED APRIL 2013 LM2650 Synchronous Step-Down DC/DC Converter Check for Samples: LM2650 FEATURES DESCRIPTION • • The LM2650 is a step-down DC/DC converter featuring high efficiency over a 3A to milliamperes load range. This feature makes the LM2650 an ideal fit in battery-powered applications that demand long battery life in both run and standby modes.
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LM2650 SNVS133C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Typical Application Figure 1. Converting a Four-Cell Li Ion Battery to 5V LM2650-ADJ Efficiency Figure 2. Connection Diagram Figure 3.
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LM2650 www.ti.com SNVS133C – JUNE 1999 – REVISED APRIL 2013 PIN DESCRIPTIONS (1) Pins Description 1, 12 SUB: These pins make electrical contact with the substrate of the die. Ground them. For best thermal performance, ground them to the same large, uninterrupted copper plane as the PGND pins.
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LM2650 SNVS133C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Absolute Maximum Ratings (1) (2) (All voltages are referenced to the PGND and GND pins.) DC Voltage at PVIN and VIN 20V DC Voltage at SD, SLEEP LOGIC and SYNC 15V DC current into SW ±7.5A Junction Temperature Limited by the IC DC Power Dissipation (3) 1.
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LM2650 www.ti.com SNVS133C – JUNE 1999 – REVISED APRIL 2013 Electrical Characteristics (continued) VPVIN = 15V, VSLEEP LOGIC = 0V and VSD = 0V unless superseded under Conditions. Typicals and limits appearing in plain type apply for TA = TJ = +25°C. Limits appearing in boldface type apply over the full junction temperature range shown under Operating Ratings.
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LM2650 SNVS133C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics 6 IQSD vs Input Voltage IQS vs Input Voltage Figure 4. Figure 5. IQ vs Input Voltage IQ vs Oscillator Frequency Figure 6. Figure 7. RDS(on) Low-Side vs Input Voltage RDS(on) High-Side vs Input Voltage Figure 8. Figure 9.
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LM2650 www.ti.com SNVS133C – JUNE 1999 – REVISED APRIL 2013 Typical Performance Characteristics (continued) RDS(on) Low-Side vs Junction Temperature RDS(on) High-Side vs Junction Temperature Figure 10. Figure 11. Oscillator Frequency vs Junction Temperature Oscillator Frequency vs Adjusting Resistor Figure 12. Figure 13. Current Limit vs Junction Temperature Figure 14.
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LM2650 SNVS133C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Block Diagrams Figure 15. The PWM Circuit with External Components in a Closed Control Loop Figure 16. The Hysteretic or "Sleep" Circuit with External Components in a Closed Control Loop Figure 17.
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LM2650 www.ti.com SNVS133C – JUNE 1999 – REVISED APRIL 2013 OPERATION OVERVIEW The LM2650 uses two step-down conversion modes: fixed-frquency pulse-width modulation (PWM) and hysteretic. It moves freely and automatically between them, using PWM for moderate to heavy loads and hysteretic for light loads. For clarity, separate block diagrams for each conversion mode have been included. See Figure 15 and Figure 16. Blocks used in both modes appear in both diagrams with the same label.
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LM2650 SNVS133C – JUNE 1999 – REVISED APRIL 2013 www.ti.com – The PWM circuit drives the pulse stream into the low-pass filter made up of L1 and COUT. The filter passed the DC component of the stream and attenuates the AC components. The output of the filter is the DC voltage VOUT superimposed with a small ripple voltage. Since the DC component of any periodic waveforms the average value of the waveform, VOUT can be found using: (1) – Here T is the switching period in seconds V(t) is the pulse stream.
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LM2650 www.ti.com SNVS133C – JUNE 1999 – REVISED APRIL 2013 Note that as the load current decreases, it takes increasingly longer periods for the load current to discharge COUT through the hysteretic window, and as the load current increases, the periods become even shorter. It can be seen from the above observation that the switching frequency of the hysteretic loop varies as the load varies.
PAGE 12
LM2650 SNVS133C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Table 2. Toroidal Inductors Using Cores from MICROMETALS, INC. Core Number Core Material Wire Gauge Number of Strands Number of Turns 15μH T38 −52 AWG # 23 1 21 20μH T38 −52 AWG # 23 1 25 33μH T50 −52 AWG # 21 1 41 40μH T50 (B) −18 AWG # 21 1 41 Table 3.
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LM2650 www.ti.com SNVS133C – JUNE 1999 – REVISED APRIL 2013 REVISION HISTORY Changes from Revision B (April 2013) to Revision C • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
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PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM2650MX-ADJ SOIC DW 24 1000 330.0 24.4 10.8 15.9 3.2 12.0 24.0 Q1 LM2650MX-ADJ/NOPB SOIC DW 24 1000 330.0 24.4 10.8 15.9 3.2 12.0 24.
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PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2650MX-ADJ SOIC DW 24 1000 367.0 367.0 45.0 LM2650MX-ADJ/NOPB SOIC DW 24 1000 367.0 367.0 45.
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