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LM26400Y

www.ti.com

SNVS457C –FEBRUARY 2007–REVISED APRIL 2013

LM26400Y Dual 2A, 500kHz Wide Input Range Buck Regulator

Check for Samples: LM26400Y

FEATURES

DESCRIPTION

The LM26400Y is a monolithic, two-output fixed

• Input Voltage Range of 3-20V

frequency PWM step-down DC/DC regulator in a 16-

• Dual 2A Output

pin WSON or thermally enhanced HTSSOP package.

• Output Voltage Down to 0.6V

With a minimum number of external components and

internal loop compensation, the LM26400Y is easy to

• Internal Compensation

use. The ability to drive 2A loads with an internal

• 500kHz PWM Frequency

175mΩ NMOS switch using state-of-the-art 0.5µm

• Separate Enable Pins

BiCMOS technology results in a high-power density

design. The world class control circuitry allows for an

• Separate Soft Start Pins

ON-time as low as 40 ns, thus supporting high-

• Frequency Foldback Protection

frequency conversion over the entire input range of

• 175mΩ NMOS Switch

3V to 20V and down to an output voltage of only

0.6V. The LM26400Y utilizes peak current-mode

• Integrated Bootstrap Diodes

control and internal compensation to provide high-

• Over-Current Protection

performance regulation over a wide range of line and

• HTSSOP and WSON Packages

load conditions. Switching frequency is internally set

• Thermal Shutdown

to 500kHz, optimal for a broad range of applications

in terms of size versus thermal tradeoffs. Given a

non-synchronous architecture, efficiencies above

APPLICATIONS

90% are easy to achieve. External shutdown is

• DTV-LCD

included, enabling separate turn-on and turn-off of

• Set-Top Box

the two channels. Additional features include

programmable soft-start circuitry to reduce inrush

• XDSL

current, pulse-by-pulse current limit and frequency

• Automotive

foldback, integrated bootstrap structure and thermal

• Computing Peripherals

shutdown.

• Industrial Controls

• Point of Load

Typical Application

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 (31 pages)

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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 LM26400Y Dual 2A, 500kHz Wide Input Range Buck Regulator Check for Samples: LM26400Y FEATURES DESCRIPTION • • • • • • • • • • • • • The LM26400Y is a monolithic, two-output fixed frequency PWM step-down DC/DC regulator in a 16pin WSON or thermally enhanced HTSSOP package. With a minimum number of external components and internal loop compensation, the LM26400Y is easy to use.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com Connection Diagram Figure 1. 16-Lead HTSSOP (top view) Package Drawing PWP0016A Figure 2. 16-Lead WSON (top view) Package Drawing NHQ0016A PIN DESCRIPTIONS Pin Name Description 1 FB1 Feedback pin of Channel 1. Connect FB1 to an external voltage divider to set the output voltage of Channel 1. 2 SS1 Soft start pin of Channel 1. Connect a capacitor between this pin and ground to program the start up speed.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 Absolute Maximum Ratings (1) (2) AVIN, PVIN −0.5V to 22V SWx Voltage −0.5V to 22V BSTx Voltage −0.5V to 26V −0.5V to 6V BSTx to SW Voltage −0.5V to 3V FBx Voltage ENx Voltage (3) −0.5V to 22V −0.5V to 3V SSx Voltage Junction Temperature ESD Susceptibility +150°C Human Body Model (4) Storage Temperature Range (1) (2) (3) (4) 2kV -65°C to 150°C Absolute maximum ratings indicate limits beyond which damage to the device may occur.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com Electrical Characteristics Unless otherwise stated, the following conditions apply: AVIN = PVIN = VIN = 5V. Limits in standard type are for TJ = 25°C only; limits in boldfacetype 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.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 Typical Performance Characteristics Unless otherwise specified or thermal-shutdown related, TA = 25°C for efficiency curves, loop gain plots and waveforms, and TJ = 25°C for all others. Efficiency, VOUT = 5V Efficiency, VOUT = 3.3V Figure 3. Figure 4. Efficiency, VOUT = 2.5V Efficiency, VOUT = 1.2V Figure 5. Figure 6. AVIN Shutdown Current vs. Temperature VIN Shutdown Current vs. VIN Figure 7. Figure 8.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified or thermal-shutdown related, TA = 25°C for efficiency curves, loop gain plots and waveforms, and TJ = 25°C for all others. 6 Switching Frequency vs. Temperature Feedback Voltage vs. Temperature Figure 9. Figure 10. Feedback Voltage vs. VIN Frequency Foldback Figure 11. Figure 12. SS-Pin Current vs. Temperature FET RDS_ON vs. Temperature Figure 13.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Unless otherwise specified or thermal-shutdown related, TA = 25°C for efficiency curves, loop gain plots and waveforms, and TJ = 25°C for all others. Switch Current Limit vs. Temperature Loop Gain, CCM Figure 15. Figure 16. Loop Gain, DCM Loop Gain, CCM Figure 17. Figure 18. Loop Gain, DCM Load Step Response Figure 19. Figure 20.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified or thermal-shutdown related, TA = 25°C for efficiency curves, loop gain plots and waveforms, and TJ = 25°C for all others. 8 Load Step Response Line Transient Response Figure 21. Figure 22. Start-Up (No Load) Start-Up (No Load) Figure 23. Figure 24. Shutdown Thermal Shutdown Figure 25. Figure 26.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 Typical Performance Characteristics (continued) Unless otherwise specified or thermal-shutdown related, TA = 25°C for efficiency curves, loop gain plots and waveforms, and TJ = 25°C for all others. Recovery from Thermal Shutdown Short-circuit Triggering Figure 27. Figure 28. Short-circuit Release Figure 29.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com Block Diagram SHARED CONTROL EN1 AVIN EN1_buf EN2 UVLO Comparator uvlo Thermal Shutdown TSD Vref_LDO Reference Internal Regulator Vref EN2_buf CLK1 Main OSC Internal Regulator Vbst Vddi CLK2 Vbst Switching Regulator 1 PVIN + I-sense amp TSD Iref - Bootstrap Diode EN_buf BST Current Limit Driver Logic SW CLK Slave OSC 0.32V OV Comparator Reset Pulse Isense Freq.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 APPLICATION HINTS GENERAL The LM26400Y is a dual PWM peak-current mode buck regulator with two integrated power MOSFET switches. The part is designed to be easy to use. The two regulators are mostly identical and share the same input voltage and the same reference voltage (0.6V). The two PWM clocks are of the same frequency but 180° out of phase.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com It is generally okay to connect the EN pin to VIN to simplify the system design. However, if the VIN ramp is slow and the load current is relatively high during soft-start, the VOUT ramp may have a notch in it and a slight overshoot at the end of startup. This is due to the reduced load current handling capability of the LM26400Y for VIN lower than 5V. If this kind of behavior is a problem for the system designer, there are two solutions.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 An easy strategy to build a stable loop with reasonable phase margin is to try to cross over between 20kHz and 100kHz, assuming the output capacitor is ceramic. When using pure ceramic capacitors at the output, simply use the following equation to find out the crossover frequency. (3) where 22S (22 Siemens) is the equivelant of the 27dBS transfer admittance mentioned above and r is the ratio of 0.6V to the output voltage.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com In an extreme case where the load goes to less than 100mA during a large load step, output voltage may exhibit extra undershoot. This usually happens when the load toggles high at the time VOUT just ramps down to its regulation level from an overshoot. Figure 33 shows such a case where the load toggles between 1.7A and only 50mA. Figure 33. Extreme Load Step In the example, the load first goes down to 50mA quickly (0.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 POWER LOSS ESTIMATION The total power loss in the LM26400Y comprises of three parts - the power FET conduction loss, the power FET switching loss and the IC's housekeeping power loss. Use the following equation to estimate the conduction loss. (6) where TJ is the junction temperature or the target junction temperature if the former is unknown. RDS is the ON resistance of the internal FET at room temperature.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com Figure 35. Programming Output Voltage It is recommended that the lower feedback resistor R2 always be 5.9kΩ. This simplifies the selection of the CFF value (For an explanation of CFF, please refer to the section LOAD STEP RESPONSE). The 5.9kΩ is also a suitable R2 value in applications that need to increase the output voltage on the fly by paralleling another resistor with R2. Since the FB pin is 0.
PAGE 17
LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 Ferrite core inductors are recommended for less AC loss and less fringing magnetic flux. The drawback of ferrite core inductors is their quick saturation characteristic. Once the inductor gets saturated, its current can spike up very quickly if the switch is not turned off immediately. The current limit circuit has a propagation delay and so is oftentimes not fast enough to stop the saturated inductor from going above the current limit.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com Figure 36. Capacitance vs. Applied DC Voltage The amount of output capacitance directly contributes to the output voltage ripple magnitude. A quick way to estimate the output voltage ripple is to multiply the inductor peak-to-peak ripple current by the impedance of the output capacitors. For example, if the inductor ripple current is 0.6A peak-to-peak, and the output capacitance is 44µF, then the output voltage ripple should be close to 0.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 Example: VIN = 5V, VOUT1 = 3.3V, IOUT1 = 2A, VOUT2 = 1.2V, IOUT2 = 1.5A, RDS = 170mΩ, RDC = 30mΩ. (IOUT1 is the same as I1 in the input ripple RMS current equation, IOUT2 is the same as I2). First, find out the duty cycles. Plug the numbers into the duty cycle equation and we get D1 = 0.75, and D2 = 0.33. Next, follow the decision tree in Figure 37 to find out the values of d1, d2 and d3. In this case, d1 = 0.5, d2 = D2 + 0.5 - D1 = 0.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com When prototyping the design, it is necessary to know the junction temperature of the LM26400Y to assess the thermal margin. The best way to measure the LM26400Y's junction temperature when the board is working in its usual mode is to measure the package-top temperature using an infrared thermal imaging camera. Look for the highest temperature reading across the case-top.
PAGE 21
LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 LM26400Y Design Examples Figure 39. Example Circuit 1 Table 2. Bill of Materials (Circuit 1, VIN = 12V±10%, Output1 = 1.2V/2A, Output2 = 2.5V/2A) Part Description Part Values Physical Size Part Number Manufacturer C1 Capacitor, Ceramic 10µF, 16V, X5R 1210 GRM32DR61C106KA01 Murata C2 Capacitor, Ceramic 0.22µF, 16V, X5R 0603 EMK107BJ224KA-T Taiyo Yuden C3 Capacitor, Ceramic 0.1µF, 6.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com LM26400Y Design Examples Table 3. Bill of Materials (Circuit 1, VIN = 7V to 20V, Output1 = 3.3V/2A, Output2 = 5V/2A) Part Description Part Values Physical Size Part Number Manufacturer C1 Capacitor, Ceramic 10µF, 25V, X5R 1812 GRM43DR61E106KA12 Murata C2 Capacitor, Ceramic 0.22µF, 25V, X5R 0603 TMK107BJ224KA-T Taiyo Yuden C3 Capacitor, Ceramic 0.1µF, 6.3V, X5R 0402 C1005X5R0J104K TDK C4 Capacitor, Ceramic 0.1µF, 6.
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LM26400Y www.ti.com SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 Table 4. Bill of Materials (Circuit 2, VIN = 3V to 5V, Output1 = 1.2V/2A, Output2 = 1.8V/2A) Part Description Part Values Physical Size Part Number Manufacturer C1 Capacitor, Ceramic 10µF, 6.3V, X5R 1206 GRM319R60J106KE19 Murata C2 Capacitor, Ceramic 0.22µF, 6.3V, X5R 0402 JMK105BJ224KV-F Taiyo Yuden C3 Capacitor, Ceramic 0.1µF, 6.3V, X5R 0402 C1005X5R0J104K TDK C4 Capacitor, Ceramic 0.1µF, 6.
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LM26400Y SNVS457C – FEBRUARY 2007 – REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Revision B (April 2013) to Revision C • 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 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-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) LM26400YMHX/NOPB HTSSOP PWP 16 2500 330.0 12.4 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 6.95 8.3 1.6 8.0 12.0 Q1 LM26400YSD/NOPB WSON NHQ 16 1000 178.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1 LM26400YSDE/NOPB WSON NHQ 16 250 178.0 12.4 5.3 5.3 1.3 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM26400YMHX/NOPB HTSSOP PWP 16 2500 367.0 367.0 35.0 LM26400YSD/NOPB WSON NHQ 16 1000 210.0 185.0 35.0 LM26400YSDE/NOPB WSON NHQ 16 250 210.0 185.0 35.0 LM26400YSDX/NOPB WSON NHQ 16 4500 367.0 367.0 35.
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MECHANICAL DATA PWP0016A MXA16A (Rev A) www.ti.
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MECHANICAL DATA NHQ0016A SDA16A (Rev A) www.ti.
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