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LM26484

www.ti.com

SNVS573F –SEPTEMBER 2008–REVISED MARCH 2013

LM26484 Power Management Unit

Check for Samples: LM26484

FEATURES

APPLICATIONS

• Step-Down DC/DC Converter (Buck)

• Digital Cores and I/Os (FPGAs, ASICs, DSPs)

– 3.0–5.5V Input Range • Automotive Infotainment

– Externally Adjustable V

OUT

: • Set-Top-Box

– Bucks 1 & 2: 0.8V–3.5V @ 2A • Cordless Phone Base Station

– 180° Phase Shift Between Bucks Clocks • Networking Router

– 2 MHz PWM Switching Frequency • Printers

– ±1% feedback Voltage Accuracy

DESCRIPTION

– Automatic Soft Start

The LM26484 is a multi-function, configurable Power

– Current Overload Protection

Management Unit. This device integrates two highly

– PWM/PFM efficiency Modes Available

efficient 2.0A Step-Down DC/DC converters, one

LDO Controller, a POR (Power On Reset) circuit, and

• Linear Regulator (LDO) Controller

thermal overload protection circuitry. All regulator

– 3.0V–5.5V Input Range

output voltages are externally adjustable. The LDO

– Externally Adjustable V

OUT

controller is a low-voltage NMOS voltage regulator.

The LM26484 is offered in a 5 x 4 x 0.8 mm WQFN-

– ±1.5% Feedback Voltage Accuracy

24 pin package.

– Regulated to Low V

- Low V

OUT

LI-LO (Low

Input Low Output) NFET Operation

– Input to the LI-LO Configuration, Can Be

Post Regulated When Supply is Regulated

by Buck2

– Up to 1000 mA Output Current by Selection

of External FET

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 (25 pages)

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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 LM26484 Power Management Unit Check for Samples: LM26484 FEATURES APPLICATIONS • • • • • • • 1 2 • Step-Down DC/DC Converter (Buck) – 3.0–5.5V Input Range – Externally Adjustable VOUT: – Bucks 1 & 2: 0.8V–3.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com Typical Application Circuit Comm DC Input voltage 19 C9 4 24 L1 2 6 13 ENSW1 ENSW2 Power On-Off Logic ENLDO RESET 23 C4 R2 C2 20 PGND_SW1 21 BG_vref Central Bias Thermal SD and Supervisory C4 and C8 usually not needed depending on the application layout and amount of parasitic on board.
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LM26484 www.ti.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com Absolute Maximum Ratings (1) (2) (3) −0.3V to +6V VIN1, VIN2, AVDD, AVIN nPOR, ENSW1, FB1, ENSW2, FB2, ENLDO, LDO_FB −0.3 to VIN + 0.3V GND to GND SLUG ±0.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 General Electrical Characteristics (1) Typical values and limits appearing in normal type apply for TJ = 25°C. Limits appearing in boldface type apply over the entire junction temperature range for operation, −40°C to +125°C. (2) (3) Symbol VIN Parameter Operational Voltage Range Conditions AVDD, AVIN Typ Max Units 3.0 3.3 5.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com Buck Converters SW1, SW2 (continued) Unless otherwise noted, AVDD=AVIN=VIN1=VIN2 = 3.3V, CIN = 10 µF, COUT = 22 µF, LOUT = 0.5 µH. Buck1 is configured to 1.8V. Buck2 is configured to 1.0V. Typical values and limits appearing in normal type apply for TA = 25°C. Limits appearing in boldface type apply over the entire junction temperature range for operation, −40°C to +125°C.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 Typical Performance Characteristics — LDO TA = 25°C unless otherwise noted. Load Transient VOUT — 1.0V, IOUT = 200 mA-1A Load Transient VOUT — 1.0V, IOUT = 50 mA- 500 mA 100 mV/ DIV VOUT 500 mA/ DIV IL 200 µs/DIV Figure 2. Figure 3.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics — Buck TA = 25°C unless otherwise noted. 8 Startup of Buck1: VOUT = 1.8V; IOUT = 100 mA Startup of Buck1: VOUT = 1.8V; IOUT = 2A Figure 4. Figure 5. Startup of Buck2: VOUT = 1.0V; IOUT = 100 mA Startup of Buck2: VOUT = 1.0V; IOUT = 2A Figure 6. Figure 7. Line Transient: VIN = 3.0V - 3.6V; IOUT = 250 mA; VOUT = 1.8V Line Transient: VIN = 3.3V - 4.2V IOUT = 250 mA; VOUT = 1.0V Figure 8.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 Typical Performance Characteristics — Buck (continued) TA = 25°C unless otherwise noted. Buck1 Load Transient: VIN = 3.3V; VOUT = 1.8V; IOUT = 250 mA - 1.5A Buck1 Load Transient: VIN = 3.3V; VOUT = 1.8V; IOUT = 500 mA - 2A Figure 10. Figure 11. Buck2 Load Transient: VIN = 3.3V; VOUT = 1.0V; IOUT = 250 mA - 1.5A Buck2 Load Transient: VIN = 3.3V; VOUT = 1.0V; IOUT = 500 mA - 2A Figure 12. Figure 13. Efficiency of Buck1, VOUT = 1.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics — Buck (continued) TA = 25°C unless otherwise noted. Efficiency of Buck1, VOUT = 3.5V at Room Temp Figure 16.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 FLEXIBLE POWER SEQUENCING OF MULTIPLE POWER SUPPLIES The two bucks and the LDO in the LM26484 can be individually controlled with ENSW1, ENSW2, and ENLDO, respectively. All the enable inputs need to be either grounded or tied to VIH. Power-On Reset The LM26484 provides an active low reset output nPOR. Typical waveform is as shown in Figure 17 below: AVIN nPOR 170 ms Figure 17.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com NFET SELECTION There are a few major concerns when selecting an NFET for the LM26484 controller. The most important factor to consider is the maximum power rating. It is important for the NFET to have a maximum power rating larger than the application will need. The LM26484 has the ability to drive the gate voltage very close to VIN and down to approximately 1.5V. Selecting an NFET where the ensured operation of the VGS is ≥1.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 There are three modes of operation depending on the current required - PWM, PFM, and shutdown. PWM mode handles current loads of approximately 70 mA or higher, delivering voltage precision with high efficiency. Lighter output current loads cause the device to automatically switch into PFM for reduced current consumption (Iq = 15 µA typ.) and a longer battery life.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com Once the PMOS power switch is turned off, the NMOS power switch is turned on until the inductor current ramps to zero. When the NMOS zero-current condition is detected, the NMOS power switch is turned off. If the output voltage is below the ‘high’ PFM comparator threshold (see Figure 18), the PMOS switch is again turned on and the cycle is repeated until the output reaches the desired level.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 LOW DROPOUT OPERATION The LM26484 can operate at 100% duty cycle (no switching; PMOS switch completely on) for low dropout support of the output voltage. In this way the output voltage will be controlled down to the lowest possible input voltage. When the device operates near 100% duty cycle, output voltage ripple is approximately 25 mV.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com The Buck control loop will force the voltage on VFB to be 0.50V. Table 4 shows ideal resistor values to establish buck voltages from 0.8V to 3.5V along with common resistor values to establish these voltages. Common resistors do not always produce the target value, error is given in the delta column. CAP VALUE (% of NOMINAL 1 PF) In addition to the resistor feedback, feedback capacitors are also required.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 INDUCTOR SELECTION FOR SW1 AND SW2 A nominal inductor value of 0.5 µH is recommended. It is important to ensure the inductor core does not saturate during any foreseeable operational situation. Care should be taken when reviewing the different saturation current ratings that are specified by different manufacturers.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com IRIPPLE 8 x F x COUT VCOUT = VROUT = IRIPPLE x ESRCOUT VPPOUT = VCOUT2 + VROUT2 where • • • VCOUT: Estimated reactive output ripple VROUT: Estimated real output ripple VPPOUT: Estimated peak-to-peak output ripple (5) The output capacitor needs to be mounted as close as possible to the output pin of the device.
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LM26484 www.ti.com SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 Model Type Vendor Voltage Rating Case Size Inch (mm) 22 µF for COUT; C10, C2, C7 GRM31CR70J226KE23L Ceramic, X7R Murata 6.3V 1206, (3216) JMK316B7226ML-T Ceramic, X7R Taiyo-Yuden 6.3V 1206, (3216) Capacitor Min Value Unit Description Recommended Type C10, Table 4 10.0 µF LDO1 output capacitor Ceramic, 6.3V, X5R C2, Table 4 10.0 µF SW1 output capacitor Ceramic, 6.3V, X5R C7, Table 4 10.
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LM26484 SNVS573F – SEPTEMBER 2008 – REVISED MARCH 2013 www.ti.com REVISION HISTORY Changes from Revision E (March 2013) to Revision F • 20 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE MATERIALS INFORMATION www.ti.com 21-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing LM26484SQ/NOPB WQFN NHZ 24 LM26484SQE/NOPB WQFN NHZ LM26484SQX/NOPB WQFN NHZ SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1000 178.0 12.4 4.3 5.3 1.3 8.0 12.0 Q1 24 250 178.0 12.4 4.3 5.3 1.3 8.0 12.0 Q1 24 4500 330.0 12.4 4.3 5.3 1.3 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 21-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM26484SQ/NOPB WQFN NHZ 24 1000 210.0 185.0 35.0 LM26484SQE/NOPB WQFN NHZ 24 250 210.0 185.0 35.0 LM26484SQX/NOPB WQFN NHZ 24 4500 367.0 367.0 35.
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MECHANICAL DATA NHZ0024B SQA24B (Rev A) www.ti.
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