Datasheet

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BOOT

COMP

RAMP

DITH/RES

VCC

VIN

OUT

CSG

VOUT

GND

DITHER/RESTART

VCC

RAMP

COMP

OUT1

OUT2

FB2

FB1

BOOT

UV2

UV1

VIN (4.5V-42V)

RT/SYNC

LM25088

LM25088-Q1

www.ti.com

SNVS609H –DECEMBER 2008–REVISED MARCH 2013

LM25088/LM25088-Q1 Wide Input Range Non-Synchronous Buck Controller

Check for Samples: LM25088, LM25088-Q1

FEATURES

DESCRIPTION

The LM25088 high voltage non-synchronous buck

• LM25088Q is an Automotive Grade Product

controller features all the necessary functions to

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

implement an efficient high voltage buck converter

+125°C Operating Junction Temperature)

using a minimum number of external components.

• Emulated Current Mode Control

The LM25088 can be configured to operate over an

ultra-wide input voltage range of 4.5V to 42V. This

• Drives External High-Side N-Channel MOSFET

easy to use controller includes a level shifted gate

• Ultra-Wide Input Voltage Range from 4.5V to

driver capable of controlling an external N-channel

42V

buck switch. The control method is based upon peak

• Low I

Shutdown and Standby Modes

current mode control utilizing an emulated current

ramp. The use of an emulated control ramp reduces

• High Duty Cycle Ratio Feature for Reduced

noise sensitivity of the pulse-width modulation circuit,

Dropout Voltage

allowing reliable control of very small duty cycles

• Spread Spectrum EMI Reduction (LM25088-1)

necessary in high input voltage/low output voltage

• Hiccup Timer for Overload Protection

applications. The LM25088 switching frequency is

(LM25088-2)

programmable from 50 kHz to 1 MHz.

• Adjustable Output Voltage from 1.205V with

The LM25088 is available in two versions: The

1.5% Feedback Reference Accuracy

LM25088-1 provides a +/-5% frequency dithering

function to reduce the conducted and radiated EMI,

• Wide Bandwidth Error Amplifier

while the LM25088-2 provides a versatile restart timer

• Single Resistor Oscillator Frequency Setting

for overload protection. Additional features include a

• Oscillator Synchronization Capability

low dropout bias regulator, tri-level enable input to

• Programmable Soft-Start

control shutdown and standby modes, soft-start and

oscillator synchronization capability. The device is

• High Voltage, Low Dropout Bias Regulator

available in a thermally enhanced HTSSOP-16 pin

• Thermal Shutdown Protection

package.

PACKAGE

• HTSSOP-16

Simplified Application Schematic

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 (33 pages)

PAGE 1
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 LM25088/LM25088-Q1 Wide Input Range Non-Synchronous Buck Controller Check for Samples: LM25088, LM25088-Q1 FEATURES DESCRIPTION • The LM25088 high voltage non-synchronous buck controller features all the necessary functions to implement an efficient high voltage buck converter using a minimum number of external components. The LM25088 can be configured to operate over an ultra-wide input voltage range of 4.5V to 42V.
PAGE 2
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com Connection Diagram VIN VCC VIN VCC EN BOOT EN BOOT SS HG SS HG RAMP RAMP SW SW HTSSOP-16 HTSSOP-16 CS RT GND CS RT GND CSG CSG EP EP COMP DITH COMP RES FB OUT FB OUT Figure 1. Top View (Dither version) LM25088-1 Figure 2.
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LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 PIN DESCRIPTIONS (continued) Pin(S) Name Description 10 RES Hiccup Mode Restart ( LM25088-2 Only) Application Information The RES pin is normally connected to an external capacitor that sets the timing for hiccup mode current limiting. In normal operation, a 25 µA current source discharges the RES pin capacitor to ground.
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LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com Electrical Characteristics 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 specified through test, design, or statistical correlation. Typical values represent at TJ = 25°C, and are provided for reference purposes only.
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LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 Electrical Characteristics (continued) 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 specified through test, design, or statistical correlation. Typical values represent at TJ = 25°C, and are provided for reference purposes only.
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LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics 6 Typical Application Circuit Efficiency VCC vs VIN Figure 3. Figure 4. VVCC vs IVCC Shutdown Current Figure 5. Figure 6. Frequency vs RRT Frequency vs VVCC Figure 7. Figure 8.
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LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 Typical Performance Characteristics (continued) VFB vs Temperature Forced-Off Time vs Temperature Figure 9. Figure 10. Soft-Start vs Temperature Current-Limit vs Temperature Figure 11. Figure 12. Frequency vs Temperature 150 40 120 30 90 20 60 10 30 0 0 -10 1E+04 1E+05 1E+06 PHASE (°) GAIN (dB) Error Amplifier Gain/Phase 50 -30 1E+07 FREQUENCY (Hz) Figure 13. Figure 14.
PAGE 8
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com Block Diagram LM25088 VIN VIN (4.5V-42V) VIN VCC 7.7V Regulator C VCC 5V 1.2V RUV2 CIN 5 uA STANDBY THERMAL SHUTDOWN UVLO EN CFT RUV1 BOOT SHUTDOWN UVLO DIS CBOOT 0.4V 11 uA SS 5V CSS 0.9V DRIVER CLK STANDBY S Q R Q HG C COMP FB MINIMUM OFF- TIME LOGIC ERROR AMP I- LIMIT VIN + COMP DITHER LM5088 -1 ONLY DITHER CLK 1.2 R COMP FREQUENCY DITHERING L VOUT SW PWM 1.
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LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 An auxiliary supply voltage can be applied to the VCC pin to reduce the IC power dissipation. If the auxiliary voltage is greater than 8.2V, the internal regulator will be disabled. The VCC regulator series pass transistor includes a diode between VCC and VIN that should not be forward biased in normal operation.
PAGE 10
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com Error Amplifier and PWM Comparator The internal high gain error amplifier generates an error signal proportional to the difference between the regulated output voltage and an internal precision voltage reference (1.205V). The output of the error amplifier is connected to the COMP pin allowing the user to connect loop compensation components. Generally a type II network, as illustrated in Figure 15, is sufficient.
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LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 The sample & hold DC level illustrated in Figure 17 is derived from a measurement of the re-circulating (or freewheeling) diode current. The diode current flows through the current sense resistor connected between the CS and CSG pins. The voltage across the sense resistor is sampled and held just prior to the onset of the next conduction interval of the buck switch.
PAGE 12
LM25088 LM25088-Q1 www.ti.com VIN SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 VOUT Dropout CLK Regulation Point Forced off-time ON-TIME Forced off-time TON(max) Extended TON(max) TON(maxDFC) increased to reduce dropout fSW(minDFC) Normal Operation Transition Region Low Dropout Mode Figure 18.
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LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 +5V LM25088 25 PA 1.14V 1.26V + - 1.20V 1.14V R Q S Q DITHER C dither 50 PA 1. 26V + - Oscillator Tosc - 't Tosc Tosc +'t Figure 19. Frequency Dithering Scheme Figure 20. Conducted Emissions Measured at the Input of a LM25088 Based Buck Converter Figure 20 shows the conducted emissions on the LM25088 evaluation board input power line.
PAGE 14
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 1.2V - 25 PA x IPEAK = www.ti.com VOUT VIN x fSW x CRAMP A x RS or IPEAK # 0.12V RS where • • • A = 10V/V is the current sense amplifier gain CRAMP is the Ramp capacitor RS is the sense resistor 25 PA x • • VOUT VIN x fSW x CRAMP is the voltage ramp added for slope compensation 1.
PAGE 15
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 LM25088 5.0V Current limit cycle I- Limit 50 PA Hiccup current source logic RES C RES Post-fault Discharge current 27 PA 1.2 PA Non - current limit cycle Q S SS begins Restart Q R 1.2V + - HG OFF SS = 0 + CLK 0.2V Figure 21. Current Limit Restart Circuit Current Limit Persistent Charge Restart cap with 50 PA current 1.2V Discharge Restart cap with 1.2 PA Current Limit Detected at CS 0.
PAGE 16
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com HG Output The LM25088 provides a high current, high-side driver and associated level shift circuit to drive an external NChannel MOSFET. The gate driver works in conjunction with an internal diode and external bootstrap capacitor. A ceramic bootstrap capacitor is recommended, and should be connected directly between the BOOT and SW pins.
PAGE 17
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 I PP IO 0 T = 1/FSW Figure 23. Inductor Current The maximum ripple current occurs at the maximum input voltage. Typically, IPP is selected between 20% and 40% of the full load current. Higher ripple current will result in a smaller inductor. However, it places more burden on the output capacitor to smooth out the ripple current to achieve low output ripple voltage.
PAGE 18
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 CRAMP = www.ti.com gm x L A x RS where • • • L is the value of the output inductor gm is the ramp generator transconductance (5 µA/V) A is the current sense amplifier gain (10V/V) (12) For the current design example, the ramp capacitor is calculated as: 5 PA/V x 6.8 PH = 340 pF CRAMP = 10V/V x 10 m: (13) The next lowest standard value 270 pF was selected for CRAMP. An NPO capacitor with 5% or better tolerance is recommended.
PAGE 19
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 Evaluating, the above equation with a ΔVout of 100 mV results in an output capacitance of 475 µF. As stated earlier, the maximum peak to peak ripple primarily depends on the ESR of the output capacitor and the inductor ripple current. To satisfy the ΔVPK-PK of 50 mV with 40% inductor current ripple, the ESR should be less than 15 mΩ.
PAGE 20
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com OUTPUT VOLTAGE DIVIDER RFB1 and RFB2 set the output voltage level, the ratio of these resistors can be calculated from: RFB2 VOUT -1 = RFB1 1.205V (20) 1.62 kΩ was chosen for RFB1 in this design which results in a RFB2 value of 5.11 kΩ. A reasonable guide is to select the value of RFB1 value such that the current through the resistor (1.2V/ RFB1) is in between 1 mA and 100 µA.
PAGE 21
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 For this example with the maximum input voltage of 36V, the Vds breakdown rating of the selected MOSFET must be greater than 36V plus any ringing across drain to source due to parasitics. In order to minimize switching time and gate drive losses, the selected MOSFET must also have low gate charge (Qg).
PAGE 22
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com 60 200 160 40 120 GAIN (dB) PHASE (°) 80 20 40 0 0 -40 -20 -80 -120 -40 -160 -60 1.E+01 -200 1.E+02 1.E+03 1.E+04 1.E+05 FREQUENCY (Hz) Figure 25. Modular Gain Phase Components RCOMP and CCOMP configure the error amplifier as a type II compensation configuration. The DC gain of the amplifier is 80dB which has a pole at low frequency and a zero at FZero = 1/(2π x RCOMP x CCOMP).
PAGE 23
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 60 200 160 40 120 GAIN (dB) 40 0 0 -40 -20 PHASE (°) 80 20 -80 -120 -40 -160 -60 1.E+02 1.E+03 1.E+04 -200 1.E+05 FREQUENCY (Hz) Figure 27. Overall Loop Gain and Phase PCB BOARD LAYOUT AND THERMAL CONSIDERATIONS In a buck regulator there are two loops where currents are switched very fast. The first loop starts from the input capacitors, through the buck MOSFET, to the inductor then out to the load.
PAGE 24
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com Figure 28.
PAGE 25
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 Figure 29.
PAGE 26
LM25088 LM25088-Q1 SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 www.ti.com Table 1. Bill of Materials for LM25088-1 and LM25088-2 Evaluation Boards Part Value Package Manufacturer Manufacturer Part Number C1,C2,C3,C4 ,C5 2.2µF C1210 Murata GRM32ER72A225KA35L Description CAP CER 2.2µF 100V X7R 1210 C6,C19 0.1µF C0805 TDK Corporation C2012X7R2A104K CAP CER .
PAGE 27
LM25088 LM25088-Q1 www.ti.com SNVS609H – DECEMBER 2008 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision G (March 2013) to Revision H • 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 (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. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided.
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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) LM25088MHX-1/NOPB HTSSOP PWP 16 2500 330.0 12.4 LM25088MHX-2/NOPB B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 6.95 8.3 1.6 8.0 12.0 Q1 HTSSOP PWP 16 2500 330.0 12.4 6.95 8.3 1.6 8.0 12.0 Q1 LM25088QMHX-1/NOPB HTSSOP PWP 16 2500 330.0 12.4 6.95 8.3 1.6 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) LM25088MHX-1/NOPB HTSSOP PWP 16 2500 367.0 367.0 35.0 LM25088MHX-2/NOPB HTSSOP PWP 16 2500 367.0 367.0 35.0 LM25088QMHX-1/NOPB HTSSOP PWP 16 2500 367.0 367.0 35.0 LM25088QMHX-2/NOPB HTSSOP PWP 16 2500 367.0 367.0 35.
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MECHANICAL DATA PWP0016A MXA16A (Rev A) www.ti.
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