Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - DC/DC voltage regulator Holder LLP 16 EP

LM26420

www.ti.com

SNVS579F –FEBRUARY 2009–REVISED MARCH 2013

LM26420/LM26420Q Dual 2.0A, High Frequency Synchronous Step-Down DC-DC

Regulator

Check for Samples: LM26420

FEATURES

DESCRIPTION

The LM26420 regulator is a monolithic, high

• Input Voltage Range of 3.0V to 5.5V

frequency, dual PWM step-down DC/DC converter in

• Output Voltage Range of 0.8V to 4.5V

a 16 Pin WQFN and a 20 Pin TSSOP package. It

• 2.0A Output Current per Output

provides all the active functions to provide local

DC/DC conversion with fast transient response and

• High Switching Frequencies

accurate regulation in the smallest possible PCB

– 2.2MHz (LM26420X)

area. With a minimum of external components, the

– 0.55MHz (LM26420Y)

LM26420 is easy to use. The ability to drive two 2.0A

loads with an internal 75 mΩ PMOS top switch and

• 75mΩ PMOS Switch

an internal 50 mΩ NMOS bottom switch using state-

• 50mΩ NMOS Switch

of-the-art 0.5 µm BiCMOS technology results in the

• 0.8V, 1.5% Internal Voltage Reference

best power density available. The world-class control

circuitry allows on-times as low as 30ns, thus

• Internal Soft-start

supporting exceptionally high frequency conversion

• Independent Power Good for Each Output

over the entire 3V to 5.5V input operating range down

• Independent Precision Enable for Each Output

to the minimum output voltage of 0.8V. Switching

• Current Mode, PWM Operation

frequency is internally set to 550 kHz or 2.2 MHz,

allowing the use of extremely small surface mount

• Thermal Shutdown

inductors and chip capacitors. Even though the

• Over Voltage Protection

operating frequency is high, efficiencies up to 93%

• Start-up into Pre-biased Output Loads

are easy to achieve. External shutdown is included,

featuring an ultra-low stand-by current. The LM26420

• Outputs are 180° Out of Phase

utilizes current-mode control and internal

• LM26420Q is an Automotive Grade Product

compensation to provide high-performance regulation

that is AEC-Q100 Grade 1 Qualified (-40°C to

over a wide range of operating conditions. Additional

+125°C Operating Junction Temperature)

features include internal soft-start circuitry to reduce

inrush current, pulse-by-pulse current limit, thermal

APPLICATIONS

shutdown, power good indicators, precision enables,

and output over-voltage protection.

• Local 5V to Vcore Step-Down Converters

• Core Power in HDDs

• Set-Top Boxes

• USB Powered Devices

• DSL Modems

• Powering Core and I/O Voltages for FPGAs,

CPLDs, and ASICs

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 (36 pages)

PAGE 1
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 LM26420/LM26420Q Dual 2.0A, High Frequency Synchronous Step-Down DC-DC Regulator Check for Samples: LM26420 FEATURES DESCRIPTION • • • • The LM26420 regulator is a monolithic, high frequency, dual PWM step-down DC/DC converter in a 16 Pin WQFN and a 20 Pin TSSOP package. It provides all the active functions to provide local DC/DC conversion with fast transient response and accurate regulation in the smallest possible PCB area.
PAGE 2
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com Typical Application Circuit Vin 3V to 5.5V VIN PG2 VOUT1 EN1 2.5V/2A SW1 LM26420 PG1 Buck 1 Buck 2 VOUT2 EN2 1.2V/2A SW2 FB2 FB1 GND Connection Diagram 4 3 2 1 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 16 5 15 6 DAP 7 14 8 13 9 10 11 12 Figure 1. 16-Pin WQFN (TOP VIEW) Figure 2.
PAGE 3
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 PIN DESCRIPTIONS 20-PIN TSSOP (continued) Pin Name 19 EN2 Function Enable control input. Logic high enable operation for Buck 2. Do not allow this pin to float or be greater than VIN + 0.3V. 10, 11, DAP Die Attach Pad Connect to system ground for low thermal impedance, but it cannot be used as a primary GND connection. Pin Name Function 1,2 VIND1 Power Input supply for Buck 1. 11, 12 VIND2 Power Input supply for Buck 2.
PAGE 4
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com Electrical Characteristics Per Buck VIN = 5V unless otherwise indicated under the Conditions column. Limits in standard type are for TJ = 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 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.
PAGE 5
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 Typical Performance Characteristics All curves taken at VIN = 5.0V with configuration in typical application circuit shown in Application Information section of this datasheet. TJ = 25°C, unless otherwise specified. η vs Load "X" VIN = 5V, VOUT = 3.3V η vs Load "Y" VIN = 5V, VOUT = 3.3V Figure 3. Figure 4. η vs Load - "X" VIN = 5V & 3V, VOUT = 2.5V η vs Load "Y" VIN = 5V & 3V, VOUT = 2.5V Figure 5. Figure 6.
PAGE 6
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) η vs Load "X" VIN= 5V & 3V, VOUT = 1.2V η vs Load "Y" VIN = 5V & 3V, VOUT = 1.2V Figure 9. Figure 10. η vs Load "X" VIN = 5V & 3V, VOUT = 0.8V η vs Load "Y" VIN = 5V & 3V, VOUT = 0.8V Figure 11. Figure 12. Load Regulation VIN = 5V, VOUT = 1.8V (All Options) Load Regulation VIN = 3V, VOUT = 1.8V (All Options) 1.808 1.808 1.807 1.807 1.806 1.
PAGE 7
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 Typical Performance Characteristics (continued) All curves taken at VIN = 5.0V with configuration in typical application circuit shown in Application Information section of this datasheet. TJ = 25°C, unless otherwise specified. Line Regulation - "X" VOUT = 1.8V, IOUT = 1,000mA 1.808 1.797 1.807 1.796 1.806 OUTPUT (V) OUTPUT (V) 1.798 Line Regulation - "Y" VOUT = 1.8V, IOUT = 1,000mA 1.795 1.794 1.804 1.793 1.792 1.805 1.803 3.
PAGE 8
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) All curves taken at VIN = 5.0V with configuration in typical application circuit shown in Application Information section of this datasheet. TJ = 25°C, unless otherwise specified.
PAGE 9
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 Typical Performance Characteristics (continued) All curves taken at VIN = 5.0V with configuration in typical application circuit shown in Application Information section of this datasheet. TJ = 25°C, unless otherwise specified. Start-Up (Soft-Start) (VOUT = 1.8V @ 1A, VIN = 5V) Enable - Disable (VOUT = 1.8V @ 1A, VIN = 5V) Figure 27. Figure 28. VFB vs Temperature Current Limit vs Temperature (VIN = 5V and 3.3V) 3.
PAGE 10
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com Simplified Block Diagram Per Buck VIN EN ThermalSHDN + + - ILIMIT ENABLE and UVLO + OVPSHDN VREF x 1.15 + ISENSE Control Logic RAMPArtificial Clock 2.2 MHz/550 kHz ISENSE S FB + - + R R Q P-FET DeadTimeControl Logic SW DRIVERS N-FET InternalComp Q VREF=0.
PAGE 11
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 APPLICATIONS INFORMATION THEORY OF OPERATION The LM26420 is a constant frequency dual PWM buck synchronous regulator IC that delivers two 2.0A load currents. The regulator has a preset switching frequency of 2.2MHz or 550kHz. This high frequency allows the LM26420 to operate with small surface mount capacitors and inductors, resulting in a DC/DC converter that requires a minimum amount of board space.
PAGE 12
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com RATIOMETRIC START UP VOUT1 VOLTAGE VOUT2 VEN1,2 TIME Figure 34. OUTPUT OVER-VOLTAGE PROTECTION The over-voltage comparator compares the FB pin voltage to a voltage that is approximately 15% higher than the internal reference VREF. Once the FB pin voltage goes 15% above the internal reference, the internal PMOS control switch is turned off, which allows the output voltage to decrease toward regulation.
PAGE 13
LM26420 www.ti.com D= SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 VOUT VIN (1) The voltage drop across the internal NMOS (SW_BOT) and PMOS (SW_TOP) must be included to calculate a more accurate duty cycle. Calculate D by using the following formulas: D= VOUT + VSW_BOT VIN + VSW_BOT ± VSW_TOP (2) VSW_TOP and VSW_BOT can be approximated by: VSW_TOP = IOUT x RDSON_TOP VSW_BOT = IOUT x RDSON_BOT (3) (4) The inductor value determines the output ripple current.
PAGE 14
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com with a saturation current limit of > 2.3A. There is no need to specify the saturation or peak current of the inductor at the 3.25A typical switch current limit. The difference in inductor size is a factor of 5. Ferrite based inductors are preferred to minimize core losses when opperating with the frequencies used by the LM26420. This presents little restriction since the variety of ferrite-based inductors is huge.
PAGE 15
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 Figure 36. Determining d1, d2 and d3 OUTPUT CAPACITOR 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. The output ripple of the converter is: 'VOUT = 'IL RESR + 1 8 x FSW x COUT (12) When using MLCCs, the ESR is typically so low that the capacitive ripple may dominate.
PAGE 16
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com LOUT LM26420 VOUT SW VIND VINC COUT R1 EN FB R2 AGND PGND Figure 37. Programming VOUT To determine the maximum allowed resistor tolerance , use the following equation: 1 V= VFB 1 1 + 2x VOUT TOL I (15) where TOL is the set point accuracy of the regulator, Φ is the tolerance of VFB. Example: VOUT = 2.5V, with a set point accuracy of +/- 3.5%. 1 V= 0.8V 2.5V 1 + 2x 3.5% 1.5% 1 = 1.4% (16) Choose 1% resistors.
PAGE 17
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 USING PRECISION ENABLE AND POWER GOOD The LM26420's precision enable and power good pins address many of the sequencing requirements required in today's challenging applications. Each output can be controlled independently and have independent power goods. This allows for a multitude of ways to control each output.
PAGE 18
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com VOUT +14% +10% -10% -14% ~7.5 Ps t VPG t Figure 42. Power Good Hysterysis Operation OVER-CURRENT PROTECTION When the switch current reaches the current limit value, it immediately is turned off. This effectively reduces the duty cycle and therefore the output voltage dips and continues to droop until the output load matches the peak current limit inductor current.
PAGE 19
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 Or K= POUT POUT + PLOSS (18) Calculations for determining the most significant power losses are shown below. Other losses totaling less than 2% are not discussed. Power loss (PLOSS) is the sum of two basic types of losses in the converter: switching and conduction. Conduction losses usually dominate at higher output loads, whereas switching losses remain relatively fixed and dominate at lower output loads.
PAGE 20
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com Due to Dead-Time-Control Logic in the converter, there is a small delay (~4nS) between the turn ON and OFF of the TOP and BOTTOM FET. During this time, the body diode of the BOTTOM FET is conducting with a voltage drop of VBDIODE (~.65V). This allows the inductor current to circulate to the output, until the BOTTOM FET is turned ON and the inductor current passes through the FET.
PAGE 21
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 The PCB size, weight of copper used to route traces and ground plane, and number of layers within the PCB can greatly effect RθJA. The type and number of thermal vias can also make a large difference in the thermal impedance. Thermal vias are necessary in most applications. They conduct heat from the surface of the PCB to the ground plane.
PAGE 22
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com PINTERNAL = 304mW RTJA = (42) 165oC - 152oC = 42.8o C/W 304 mW (43) If the junction temperature was to be kept below 125°C, then the ambient temperature could not go above 112°C. Tj - (RθJA x PINTERNAL) = TA 125°C - (42.8°C/W x 304mW) = 112.0°C (44) (45) Layout Considerations Figure 43. Internal Connection For certain high power applications, the PCB land may be modified to a dog bone shape (see Figure 44).
PAGE 23
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 LM26420X Design Example 1 Vin 3V to 5.5V C3 R7 C4 C5 R5 R6 VIN1 VINc VIN2 PG1 PG2 LM26420 VOUT1 1.2V/2A EN1 EN2 VOUT2 L1 L2 SW1 SW2 FB1 FB2 R1 2.5V/2A R2 C1 C2 PGND1, PGND2, AGND, DAP R3 R4 Figure 45. LM26420X (2.2MHz): VIN = 5V, VOUT1 = 1.2V @ 2.0A and VOUT2 = 2.5V @ 2.0A Table 2. Bill of Materials Part ID Part Value Manufacturer U1 2A Buck Regulator TI Part Number LM26420X C3, C4 15µF, 6.
PAGE 24
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com LM26420X Design Example 2 Vin 3V to 5.5V R7 C3 C5 C4 R5 R6 VIN1 VINc VIN2 PG1 PG2 LM26420 EN1 VOUT1 EN2 VOUT2 L1 1.8V/2A 0.8V/2A L2 SW1 SW2 FB1 FB2 R2 R1 C1 PGND1, PGND2, AGND, DAP R3 C1 C6 R4 Figure 46. LM26420X (2.2MHz): VIN = 5V, VOUT1 = 1.8V @ 2.0A and VOUT2 = 0.8V @ 2.0A Table 3. Bill of Materials 24 Part ID Part Value Manufacturer U1 2A Buck Regulator TI Part Number LM26420X C3, C4 15µF, 6.
PAGE 25
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 LM26420X Design Example 3 Vin 4.5V to 5.5V C3 R7 C4 C5 R5 R6 VIN1 VINc VIN2 PG1 PG2 LM26420 EN1 VOUT1 3.3V/2A EN2 VOUT2 L1 L2 SW1 SW2 FB1 FB2 R1 1.8V/2A R2 C1 C2 PGND1, PGND2, AGND, DAP R3 R4 Figure 47. LM26420X (2.2MHz): VIN = 5V, VOUT1 = 3.3V @ 2.0A and VOUT2 = 1.8V @ 2.0A Table 4. Bill of Materials Part ID Part Value Manufacturer U1 2A Buck Regulator TI Part Number LM26420X C3, C4 15µF, 6.
PAGE 26
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com LM26420Y Design Example 4 Vin 3V to 5.5V C3 R7 C4 C5 R5 R6 VIN1 VINc VIN2 PG1 PG2 LM26420 EN1 VOUT1 EN2 VOUT2 L1 1.2V/2A L2 SW1 SW2 FB1 FB2 R1 2.5V/2A R2 C1 C2 PGND1, PGND2, AGND, DAP R3 R4 Figure 48. LM26420Y (550kHz): VIN = 5V, VOUT1 = 1.2V @ 2.0A and VOUT2 = 2.5V @ 2.0A Table 5. Bill of Materials 26 Part ID Part Value Manufacturer U1 2A Buck Regulator TI LM26420Y C3, C4 22µF, 6.
PAGE 27
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 LM26420Y Design Example 5 Vin 3V to 5.5V R7 C3 C5 C4 R5 R6 VIN1 VINc VIN2 PG1 PG2 LM26420 EN1 VOUT1 1.8V/2A EN2 VOUT2 L1 0.8V/2A L2 SW1 SW2 FB1 FB2 R2 R1 C1 PGND1, PGND2, AGND, DAP R3 C1 C6 R4 Figure 49. LM26420Y (550kHz): VIN = 5V, VOUT1 = 1.8V @ 2.0A and VOUT2 = 0.8V @ 2.0A Table 6. Bill of Materials Part ID Part Value Manufacturer U1 2A Buck Regulator TI Part Number LM26420Y C3, C4 22µF, 6.
PAGE 28
LM26420 SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 www.ti.com LM26420Y Design Example 6 Vin 4.5V to 5.5V C3 R7 C4 C5 R5 R6 VIN1 VINc VIN2 PG1 PG2 LM26420 EN1 VOUT1 EN2 VOUT2 L1 3.3V/2A L2 SW1 SW2 FB1 FB2 R1 1.8V/2A R2 C1 C2 PGND1, PGND2, AGND, DAP R3 R4 Figure 50. LM26420Y (550kHz): VIN = 5V, VOUT1 = 3.3V @ 2.0A and VOUT2 = 1.8V @ 2.0A Table 7. Bill of Materials 28 Part ID Part Value Manufacturer U1 2A Buck Regulator TI Part Number LM26420Y C3, C4 22µF, 6.
PAGE 29
LM26420 www.ti.com SNVS579F – FEBRUARY 2009 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision E (March 2013) to Revision F • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
PAGE 30
PACKAGE OPTION ADDENDUM www.ti.
PAGE 31
PACKAGE OPTION ADDENDUM www.ti.com (3) 11-Apr-2013 MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Top-Side Marking for that device.
PAGE 32
PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device LM26420Q1XSQ/NOPB Package Package Pins Type Drawing WQFN SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) RUM 16 1000 178.0 12.4 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 4.3 4.3 1.3 8.0 12.0 Q1 LM26420Q1XSQX/NOPB WQFN RUM 16 4500 330.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1 LM26420XMHX/NOPB HTSSOP PWP 20 2500 330.0 16.4 6.95 7.1 1.6 8.0 16.
PAGE 33
PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM26420Q1XSQ/NOPB WQFN RUM 16 1000 213.0 191.0 55.0 LM26420Q1XSQX/NOPB WQFN RUM 16 4500 367.0 367.0 35.0 LM26420XMHX/NOPB HTSSOP PWP 20 2500 367.0 367.0 35.0 LM26420XSQ/NOPB WQFN RUM 16 1000 213.0 191.0 55.0 LM26420XSQX/NOPB WQFN RUM 16 4500 367.0 367.0 35.
PAGE 34
MECHANICAL DATA PWP0020A MXA20A (Rev C) www.ti.
PAGE 35
MECHANICAL DATA RUM0016A SQB16A (Rev A) www.ti.
PAGE 36
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.