SNVS896B August   2013  – November 2014 LM27403

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (Continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Input Range: VIN
      2. 8.3.2  Output Voltage: FB Voltage and Accuracy
      3. 8.3.3  Input and Bias Rail Voltages: VIN and VDD
      4. 8.3.4  Precision Enable: UVLO/EN
      5. 8.3.5  Switching Frequency
        1. 8.3.5.1 Frequency Adjust: FADJ
        2. 8.3.5.2 Clock Synchronization: SYNC
      6. 8.3.6  Temperature Sensing: D+ and D-
      7. 8.3.7  Thermal Shutdown: OTP
      8. 8.3.8  Inductor-DCR-Based Overcurrent Protection
      9. 8.3.9  Current Sensing: CS+ and CS-
      10. 8.3.10 Current Limit Handling
      11. 8.3.11 Soft-Start: SS/TRACK
        1. 8.3.11.1 Tracking
      12. 8.3.12 Monotonic Startup
      13. 8.3.13 Prebias Startup
      14. 8.3.14 Voltage-Mode Control
      15. 8.3.15 Output Voltage Remote Sense: RS
      16. 8.3.16 Power Good: PGOOD
      17. 8.3.17 Gate Drivers: LG and HG
      18. 8.3.18 Sink and Source Capability
    4. 8.4 Device Functional Modes
      1. 8.4.1 Fault Conditions
        1. 8.4.1.1 Thermal Shutdown
        2. 8.4.1.2 Current Limit and Short Circuit Operation (Positive Overcurrent)
        3. 8.4.1.3 Negative Current Limit
        4. 8.4.1.4 Undervoltage Threshold (UVT)
        5. 8.4.1.5 Overvoltage Threshold (OVT)
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Design and Implementation
      2. 9.1.2 Power Train Components
        1. 9.1.2.1 Filter Inductor
        2. 9.1.2.2 Output Capacitors
        3. 9.1.2.3 Input Capacitors
        4. 9.1.2.4 Power MOSFETs
      3. 9.1.3 Control Loop Compensation
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1 - High-Efficiency Synchronous Buck Regulator for Telecom Power
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Design 2 - Powering FPGAs Using Flexible 30A Regulator With Small Footprint
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Design 3 - Powering Multicore DSPs
      4. 9.2.4 Design 4 - Regulated 12-V Rail with LDO Low-Noise Auxiliary Output for RF Power
      5. 9.2.5 Design 5 - High Power Density Implementation From 3.3-V or 5-V Supply Rail
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Power Stage Layout
      2. 11.1.2 Gate Drive Layout
      3. 11.1.3 Controller Layout
      4. 11.1.4 Thermal Design and Layout
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
      2. 12.1.2 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

7 Specifications

7.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1).
MIN MAX UNIT
Voltage(2) VIN, CS+, CS–, SW(3)(5) –0.3 22 V
VDD, PGOOD –0.3 6 V
SS/TRACK, SYNC, FADJ, COMP, FB, RS –0.3 VVDD + 0.3 V
UVLO/EN –0.3 min (VVIN + 0.3, 6) V
CBOOT(4) –0.3 24 V
CBOOT to SW –0.3 6 V
CS+ to CS– –1 1 V
OTP, D+, D– –0.3 VVDD V
Thermal Operating junction temperature, TJ –40 150 °C
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other condition beyond those included under Recommended Operating Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods of time may affect device reliability.
(2) All voltages are with respect to the network ground pin unless otherwise noted.
(3) The SW pin can tolerate negative voltage spikes as low as –10 V and as high as 30 V for a duration up to 10 ns.
(4) The CBOOT pin can tolerate positive voltage spikes as high as 35 V for a duration up to 10 ns.
(5) Body diode of the low-side MOSFET notwithstanding, parasitic inductance in a real application may result in the SW voltage ringing negative.

7.2 Handling Ratings

MIN MAX UNIT
Tstg Storage temperature range –65 150 °C
V(ESD) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins(1) –2 2 kV
Charged device model (CDM), per JEDEC specification JESD22-C101, all pins(2) –500 500 V
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

7.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)(1).
MIN NOM MAX UNIT
VIN Input voltage(2) VIN tied to VDD 3.0 5.5 V
VIN 3.0 20 V
SW SW pin voltage –0.3 20 V
VDD VDD pin voltage 2.6 4.7 5.5 V
PGOOD PGOOD pin voltage 0 5.5 V
UVLO/EN UVLO/EN pin voltage 0 min (VVIN, 5.5) V
SS/TRACK SS/TRACK pin voltage 0 VVDD V
SYNC SYNC pin voltage 0 5.5 V
RS RS pin voltage –0.1 0.1 V
TJ Operating junction temperature –40 +125 °C
TA Operating free-air temperature –40 +125 °C
(1) Recommended Operating Conditions are conditions under which operation of the device is intended to be functional but does not guarantee performance limits.
(2) VDD is the output of the internal linear regulator bias supply. Under normal operating conditions, where VIN is greater than 5.5 V, VDD must not be tied to any external voltage source. In an application where VIN is between 3.0 V and 5.5 V, connecting VIN to VDD maximizes the bias supply rail voltage.

7.4 Thermal Information

THERMAL METRIC(1) LM27403 UNIT
RTW
24 PINS
θJA Junction-to-ambient thermal resistance 32.7 °C/W
θJCtop Junction-to-case (top) thermal resistance 31.2
θJB Junction-to-board thermal resistance 11.2
ψJT Junction-to-top characterization parameter 0.2
ψJB Junction-to-board characterization parameter 11.2
θJCbot Junction-to-case (bottom) thermal resistance 1.4
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

7.5 Electrical Characteristics

Typical values correspond to TJ = 25°C. Minimum and maximum limits apply over –40°C to +125°C junction temperature range unless otherwise stated(1),(2). VVIN = 12 V and all parameters at zero power dissipation (unless otherwise noted).
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
OPERATIONAL SPECIFICATIONS
IQ Quiescent current VFB = 0.6 V (not switching) 3.5 5.0 mA
IQ-SD Shutdown quiescent current VUVLO/EN = 0 V 25 45 µA
REFERENCE
VFB FB pin voltage accuracy 594 600 606 mV
IFB FB pin bias current VFB = 0.65 V –165 0 165 nA
INTERNAL UVLO
UVLO Input undervoltage lockout VVIN rising, VVDD rising 2.6 2.7 2.8 V
UVLO_hys UVLO hysteresis VVIN falling, VVDD falling 250 mV
SWITCHING
FSW Switching frequency RFADJ = 4.12 kΩ 925 1050 1150 kHz
RFADJ = 20 kΩ 435 500 555 kHz
RFADJ = 95.3 kΩ 185 215 250 kHz
DMAX Maximum duty cycle FSW = 500 kHz 90% 93%
TOFF-MIN Minimum off-time VFB = 0.5 V, FSW = 500 kHz 110 150 190 ns
TON-MIN Minimum controllable on-time VFB = 0.7 V, FSW = 500 kHz 30 ns
VDD SUBREGULATOR AND BOOT
VDD Subregulator output voltage IVDD = 25 mA 4.2 4.7 5.3 V
VDDVDO Dropout voltage IVDD = 15 mA, VVIN = 3.0 V 150 mV
VDDCL VDD current limit VVDD = 4.0 V 106 mA
IQBOOT CBOOT pin leakage current VCBOOT – VSW = 4.5 V 0.5 nA
ERROR AMPLIFIER
BW-3dB Error amplifier open-loop bandwidth 6 MHz
AVOL Error amplifier dc gain 70 dB
ISOURCE COMP source current VFB = 0.5 V 1 mA
ISINK COMP sink current VFB = 0.7 V 100 µA
VCOMP-MAX Maximum COMP voltage VFB = 0.5 V 3.9 V
VCOMP-MIN Minimum COMP voltage VFB = 0.7 V 0.5 V
OVERCURRENT PROTECTION
VCS_OFFSET Current limit comparator offset voltage –3.5 0 3.5 mV
ICS Current limit offset current VCS– = 3 V, ΔVBE = 59.4 mV(3), TJ = 25°C 9.3 9.9 10.5 µA
VCS– = 3 V, D+ shorted to D– 3.4 5.0 6.6 µA
ICS-CV1 ICS compliance voltage VVIN – VCS–, ΔICS < 5% VVIN = 12 V 800 mV
ICS-CV2 VVIN = 3 V 800 mV
ICS-TC ICS temperature coefficient Referenced to ΔVBE(5) 160 187 212 nA/mV
TCL-DELAY Current limit hiccup delay 5 ms
GATE DRIVERS
RDS(ON)1 High-side MOSFET driver on-state resistance VCBOOT – VSW = 4.5 V IHG = 0.1 A (pullup) 1.5 Ω
RDS(ON)2 IHG = –0.1 A (pulldown) 1.0 Ω
IDRV-HG-SRC High-side MOSFET driver peak current CLOAD = 3 nF Source current (pullup) 1.5 A
IDRV-HG-SINK Sink current (pulldown) 2.0 A
RDS(ON)3 Low-side MOSFET driver on-state resistance VDD = 4.5 V ILG = 0.1 A (pullup) 1.5 Ω
RDS(ON)4 ILG = –0.1 A (pulldown) 0.9 Ω
IDRV-LG-SRC Low-side MOSFET driver peak current CLOAD = 3 nF Source current (pullup) 1.5 A
IDRV-LG-SINK Sink current (pulldown) 2.0 A
TDEAD Adaptive dead-time 15 ns
SOFT-START
ISS Soft-start source current VSS/TRACK = 0 V 1.0 3.0 5.0 µA
ISS-PD Soft-start pulldown resistance VSS/TRACK = 0.6 V 330 Ω
TSS-INT Internal soft-start timeout 1.28 ms
POWER GOOD
IPGS PGOOD low sink current VPGOOD = 0.2 V, VFB = 0.75 V 70 100 µA
IPGL PGOOD leakage current VPGOOD = 5 V 1 10 µA
OVT Overvoltage threshold VFB rising, RS tied to GND 111% 116.5% 123%
OVTHYS OVT hysteresis VFB falling, RS tied to GND 3.5%
UVT Undervoltage threshold VFB rising, RS tied to GND 86% 91% 97%
UVTHYS UVT hysteresis VFB falling, RS tied to GND 4%
tdeglitch Deglitch time VPGOOD rising and falling 20 µs
UVLO/ENABLE
VUVLO1 Logic low threshold VUVLO/EN falling 0.94 0.985 1.03 V
VUVLO2 Logic high threshold VUVLO/EN rising 1.11 1.15 1.18 V
VUVLO-HYS UVLO/EN voltage hysteresis VUVLO/EN falling 139 165 190 mV
IUVLO1 UVLO/EN pullup current, disabled VUVLO/EN = 0 V 0.8 1.8 2.7 µA
IUVLO2 UVLO/EN pullup current, enabled VUVLO/EN = 1.25 V 5.5 10.5 15.5 µA
CLOCK SYNCHRONIZATION
VIH-SYNC SYNC pin VIH 2 V
VIL-SYNC SYNC pin VIL 0.8 V
SYNCFSW-L Minimum clock sync frequency 200 kHz
SYNCFSW-H Maximum clock sync frequency 1.2 MHz
SYNCI SYNC pin input current 1 µA
EXTERNAL TEMPERATURE SENSE AND THERMAL SHUTDOWN
ID+1 D+ pin state 1 current 10 µA
ID+2 D+ pin state 2 current 100 µA
IOTP Remote thermal current ΔVBE = 79.3 mV(4) 13.5 14.6 15.5 µA
IOTP-TC IOTP temperature coefficient Referenced to ΔVBE(5) 158 187 213 nA/mV
VTRIP Remote thermal trip point 1.15 V
VTRIP-HYS Remote thermal trip point hysteresis 80 mV
ROTP OTP resistance, thermal shutdown ROTP(nom) = 80.7 kΩ, ΔVBE = 79.3 mV(4), TJ = 125°C –5% 5%
TSHD Internal thermal shutdown threshold Rising 150 °C
TSHD-HYS Internal thermal shutdown threshold hysteresis 20 °C
(1) All hot and cold limits are specified by correlating the electrical characteristic to process and temperature variations and applying statistical process control.
(2) The junction temperature (TJ in °C) is calculated from the ambient temperature (TA in °C) and power dissipation (PD in Watts) as follows: TJ = TA + (PD × θJA) where (°C/W) is the package thermal impedance provided in the Thermal Information section.
(3) The specified parameter is calculated based on a 2N3904 transistor at 25°C.
(4) The specified parameter is calculated based on a 2N3904 transistor at 125°C.
(5) Multiply by 19.9 to scale from nA/mV to ppm/°C (assumes 2N3904 BJT temperature sensor with ideality factor η =1.004).

7.6 Typical Characteristics

Unless otherwise stated, all datasheet curves were recorded using the circuit and powertrain designated in Figure 41 with input and output voltages of 12 V and 1.2 V, respectively, and switching frequency of 250 kHz.
C001_snvs896.pngFigure 1. Efficiency Plot, VOUT = 1.2 V
C003_snvs896.pngFigure 3. Load Regulation
C005_snvs896.pngFigure 5. Temperature Regulation
C007_snvs896.pngFigure 7. Shutdown Quiescent Current vs. Temperature
C009_snvs896.pngFigure 9. Deadtime vs. Temperature
C011_snvs896.pngFigure 11. OTP Current vs. Temperature
C013_snvs896.pngFigure 13. CS– Current Source Compliance Voltage
C015_snvs896.pngFigure 15. Switching Frequency vs. Frequency Adjust Resistance
Startup_nvs896.gifFigure 17. Start-up Characteristic
Shutdown_nvs896.gifFigure 19. Shutdown Characteristic
500kHz_SYNC_nvs896.gifFigure 21. SYNC Waveform
C002_snvs896.pngFigure 2. Efficiency Plot, VIN = 12 V
C004_snvs896.pngFigure 4. Line Regulation
C006_snvs896.pngFigure 6. Quiescent Current vs. Temperature, Nonswitching
C008_snvs896.pngFigure 8. Switching Frequency vs. Temperature
C010_snvs896.pngFigure 10. VDD Voltage vs. Temperature
C012_snvs896.pngFigure 12. CS– Current vs. Temperature
C014_snvs896.pngFigure 14. Current Limit Inception vs. Temperature
loadtransient_nvs896.gifFigure 16. 10-A Step Load Transient Response, 2.5-A/µs Slew Rate
Prebias_startup_nvs896.gifFigure 18. Prebias Start-up Characteristic
hiccup_nvs896.gifFigure 20. Current Limit Hiccup Mode
SW_waveform_nvs896.gifFigure 22. Switch Node Waveform