Data Sheet

ManualsBrandsUnbranded ManualsActive ComponentsPMIC - DC/DC voltage regulator LMR62421XMFE/NOPB Boost, SEPIC SOT 23 5

LMR62421

www.ti.com

SNVS734B –OCTOBER 2011–REVISED APRIL 2013

LMR62421 SIMPLE SWITCHER

24Vout, 2.1A Step-Up Voltage Regulator in SOT-23

Check for Samples: LMR62421

FEATURES

DESCRIPTION

The LMR62421 is an easy-to-use, space-efficient

• Input Voltage Range of 2.7V to 5.5V

2.1A low-side switch regulator ideal for Boost and

• Output Voltage up to 24V

SEPIC DC-DC regulation. It provides all the active

• Switch Current up to 2.1A

functions to provide local DC/DC conversion with fast-

transient response and accurate regulation in the

• 1.6 MHz Switching Frequency

smallest PCB area. Switching frequency is internally

• Low Shutdown Iq, 80 nA

set to 1.6 MHz, allowing the use of extremely small

• Cycle-by-Cycle Current Limiting

surface mount inductor and chip capacitors while

providing efficiencies near 90%. Current-mode control

• Internally Compensated

and internal compensation provide ease-of-use,

• Internal Soft-Start

minimal component count, and high-performance

• 5-Pin SOT-23 (2.92 x 2.84 x 1mm) and 6-Pin

regulation over a wide range of operating conditions.

WSON (3 x 3 x 0.8 mm) Packaging

External shutdown features an ultra-low standby

current of 80 nA ideal for portable applications. Tiny

• Fully Enabled for WEBENCH® Power Designer

5-pin SOT-23 and 6-pin WSON packages provide

space-savings. Additional features include internal

PERFORMANCE BENEFITS

soft-start, circuitry to reduce inrush current, pulse-by-

• Extremely Easy to Use

pulse current limit, and thermal shutdown.

• Tiny Overall Solution Reduces System Cost

APPLICATIONS

• Boost / SEPIC Conversions from 3.3V, 5V Rails

• Space Constrained Applications

• Embedded Systems

• LCD Displays

• LED Applications

System Performance

Efficiency vs Load Current Efficiency vs Load Current

OUT

= 20V V

OUT

= 12V

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 (32 pages)

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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 LMR62421 SIMPLE SWITCHER® 24Vout, 2.1A Step-Up Voltage Regulator in SOT-23 Check for Samples: LMR62421 FEATURES DESCRIPTION • • • • • • • • • The LMR62421 is an easy-to-use, space-efficient 2.1A low-side switch regulator ideal for Boost and SEPIC DC-DC regulation. It provides all the active functions to provide local DC/DC conversion with fasttransient response and accurate regulation in the smallest PCB area.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com Typical Application VOUT VIN L1 D1 R2 R3 4 C3 3 C2 2 5 R1 1 C1 GND Connection Diagrams SW 1 5 VIN 4 EN PGND 1 6 SW VIN 2 5 AGND EN 3 4 FB GND 2 FB 3 Figure 1. 5-Pin SOT-23 (Top View) See DBV Package 2 Figure 2.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 PIN DESCRIPTIONS - 5-Pin SOT-23 Pin Name Function 1 SW 2 GND Switch node. Connect to the inductor, output diode. 3 FB Feedback pin. Connect FB to external resistor divider to set output voltage. 4 EN Shutdown control input. Logic high enables operation. Do not allow this pin to float or be greater than VIN + 0.3V. 5 VIN Supply voltage for power stage, and input supply voltage. Signal and power ground pin.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) VIN -0.5V to 7V SW Voltage -0.5V to 26.5V FB Voltage -0.5V to 3.0V EN Voltage -0.5V to VIN + 0.3V ESD Susceptibility (3) 2kV Junction Temperature (4) 150°C Storage Temp.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 Electrical Characteristics (1) (2) Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature range of (TJ = -40°C to 125°C). Minimum and Maximum limits are ensured through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. VIN = 5V unless otherwise indicated under the Conditions column.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics 6 Current Limit vs Temperature FB Pin Voltage vs Temperature Figure 3. Figure 4. Oscillator Frequency vs Temperature Typical Maximum Output Current vs VIN Figure 5. Figure 6. RDSON vs Temperature Efficiency vs Load Current, Vo = 20V Figure 7. Figure 8.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Efficiency vs Load Current, Vo = 12V Output Voltage Load Regulation Figure 9. Figure 10. Output Voltage Line Regulation Figure 11.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com Simplified Internal Block Diagram EN VIN ThermalSHDN Control Logic + UVLO = 2.3V Oscillator Corrective - Ramp SW cv S R R Q 1.6 MHz + + - FB VREF = 1.255V NMOS Internal Compensation ILIMIT ISENSE-AMP Soft-Start + - GND Figure 12.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 APPLICATION INFORMATION THEORY OF OPERATION The following operating description of the LMR62421 will refer to the Simplified Block Diagram (Figure 12) the simplified schematic (Figure 13), and its associated waveforms (Figure 14). The LMR62421 supplies a regulated output voltage by switching the internal NMOS control switch at constant frequency and variable duty cycle.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com VO + VD Vsw (t) t VIN VL(t) t VIN - VOUT - VD I L (t) iL t I DIODE (t) t ( iL - - i OUT ) I Capacitor (t) t - i OUT 'v VOUT (t) DTS TS Figure 14. Typical Waveforms CURRENT LIMIT The LMR62421 uses cycle-by-cycle current limiting to protect the internal NMOS switch. It is important to note that this current limit will not protect the output from excessive current during an output short circuit.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 SOFT-START This function forces VOUT to increase at a controlled rate during start up. During soft-start, the error amplifier’s reference voltage ramps to its nominal value of 1.255V in approximately 4.0ms. This forces the regulator output to ramp up in a more linear and controlled fashion, which helps reduce inrush current.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com 2'iL § VIN · =¨ ¸ DTS © L ¹ § VIN · ¸¸ x DTS ÂiL = ¨¨ © 2L ¹ (4) A good design practice is to design the inductor to produce 10% to 30% ripple of maximum load. From the previous equations, the inductor value is then obtained. § VIN · ¸ x DTS L =¨ ©2 x 'iL¹ where • 1/TS = FSW = switching frequency (5) One must also ensure that the minimum current limit (2.1A) is not exceeded, so the peak current in the inductor must be calculated.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 OUTPUT CAPACITOR The LMR62421 operates at frequencies allowing the use of ceramic output capacitors without compromising transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing output ripple. The output capacitor is selected based upon the desired output ripple and transient response. The initial current of a load transient is provided mainly by the output capacitor.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com COMPENSATION The LMR62421 uses constant frequency peak current mode control. This mode of control allows for a simple external compensation scheme that can be optimized for each application. A complicated mathematical analysis can be completed to fully explain the LMR62421’s internal & external compensation, but for simplicity, a graphical approach with simple equations will be used.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 The simplest method to determine the compensation component value is as follows. Set the output voltage with the following equation. § VOUT · - 1¸¸ x R1 R 2 = ¨¨ © VREF ¹ where • R1 is the bottom resistor • R2 is the resistor tied to the output voltage. and (10) The next step is to calculate the value of C3.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 FZERO - CF = www.ti.com 1 2S(R2 x C3) (14) There is an associated pole with the zero that was created in the above equation. FPOLE - CF = 1 2S((R1 R2) x C3) (15) It is always higher in frequency than the zero. A right-half plane zero (RHPZ) is inherent to all boost converters. One must remember that the gain associated with a right-half plane zero increases at 20dB per decade, but the phase decreases by 45° per decade.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 Small ripple approximation: In a well-designed SEPIC converter, the output voltage, and input voltage ripple, the inductor ripple and is small in comparison to the DC magnitude. Therefore it is a safe approximation to assume a DC value for these components. The main objective of the Steady State Analysis is to determine the steady state duty-cycle, voltage and current stresses on all components, and proper values for all components.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com VIN VO L1 D1 C6 LMR62421 C1 1 6 2 5 3 4 L2 R2 R3 C2 C5 C4 C3 R1 Figure 21.
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LMR62421 www.ti.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com SEPIC Converter PCB Layout The layout guidelines described for the LMR62421 Boost-Converter are applicable to the SEPIC Converter. Below is a proper PCB layout for a SEPIC Converter. CIN PCB VIN PGND L1 FB EN 4 3 AGND VIN 5 2 PGND SW 6 1 CIN COUT D1 VO C6 L2 Figure 22. SEPIC PCB Layout WSON Package The LMR62421 packaged in the 6–pin WSON: Figure 23.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 For certain high power applications, the PCB land may be modified to a "dog bone" shape (see Figure 24). Increasing the size of ground plane, and adding thermal vias can reduce the RθJA for the application. COPPER PGND 1 6 SW Vin 2 5 AGND EN 3 4 FB COPPER Figure 24. PCB Dog Bone Layout LMR62421 Design Example 1 L1 4 VIN R3 1 M: EN 6.8 PH 2.9A 3 FB 2 2A 20V GND 5 Vin C1 10 PF 10V 12V 1 SW D1 C2 10 PF 25V R2 86.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com LMR62421 Design Example 2 L1 10 PH 1.2A 1 M: 3 4 FB SHDN R3 2 1A 20V GND VIN 5V 1 5 SW Vin D1 C1 10 PF 6.3V R2 30.1k C2 10 PF 10V C3 1 nF R LOAD R1 10k Figure 26. Vin = 3V, Vout = 5V @ 500 mA LMR62421 Design Example 3 L1 10 PH 1.2A 1 M: 4 R3 SHDN 3 FB 2 GND VIN 5 Vin C1 22 PF 6.3V 500 mA 30V 20V 1 SW D1 R2 150k C2 4.7 PF 50V C3 470 pF 50V R LOAD R1 10k Figure 27. Vin = 3.
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LMR62421 www.ti.com SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 LMR62421 SEPIC Design Example 4 VIN L1 6.8 PH 1.2A 2.2 PF 16V 1A 20V D1 VO C6 LMR62421 1 6 2 5 L2 6.8 PH 1.2A R2 16.5k 3 C1 22 PF 10V C2 4 R3 100k C5 2.2 nF C3 10 PF 10V C4 (opt) R1 10.2k (opt) Figure 28. Vin = 2.7V - 5V, Vout = 3.
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LMR62421 SNVS734B – OCTOBER 2011 – REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Revision A (April 2013) to Revision B • 24 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 11-Apr-2013 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties.
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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) LMR62421XMF/NOPB SOT-23 DBV 5 1000 178.0 8.4 LMR62421XMFE/NOPB SOT-23 DBV 5 250 178.0 LMR62421XMFX/NOPB SOT-23 DBV 5 3000 178.0 LMR62421XSD/NOPB WSON NGG 6 1000 LMR62421XSDE/NOPB WSON NGG 6 LMR62421XSDX/NOPB WSON NGG 6 3.2 3.2 1.4 4.0 8.
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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) LMR62421XMF/NOPB SOT-23 DBV 5 1000 210.0 185.0 35.0 LMR62421XMFE/NOPB SOT-23 DBV 5 250 210.0 185.0 35.0 LMR62421XMFX/NOPB SOT-23 DBV 5 3000 210.0 185.0 35.0 LMR62421XSD/NOPB WSON NGG 6 1000 210.0 185.0 35.0 LMR62421XSDE/NOPB WSON NGG 6 250 210.0 185.0 35.0 LMR62421XSDX/NOPB WSON NGG 6 4500 367.
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MECHANICAL DATA NGG0006A SDE06A (Rev A) www.ti.
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