SNVSA38 November   2014 LM3281

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 System Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Small Solution Size
      2. 7.3.2  Automatic Analog Bypass with Low Dropout
      3. 7.3.3  Low IQ
      4. 7.3.4  Forced PWM Operation
      5. 7.3.5  High Maximum Current
      6. 7.3.6  High-Capacitance Load and Line Transient Performance
      7. 7.3.7  Soft Start
      8. 7.3.8  Thermal Overload Protection
      9. 7.3.9  Current Limit
      10. 7.3.10 Power-On Reset
    4. 7.4 Device Functional Modes
      1. 7.4.1 PWM Mode
      2. 7.4.2 Forced PWM (FPWM) Mode
      3. 7.4.3 Analog Bypass Mode
      4. 7.4.4 ECO (Economy) Mode
      5. 7.4.5 Shutdown Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
        1. 8.2.1.1 Suggested Passive Components
          1. 8.2.1.1.1 LM3281 Inductor Selection
          2. 8.2.1.1.2 Total Effective Output Capacitance (COUT + CLOAD1 + CLOAD2)
          3. 8.2.1.1.3 LM3281 Capacitor (CIN and COUT) Selection
          4. 8.2.1.1.4 Recommended Load Bypass Capacitors (CLOAD1 and CLOAD2)
          5. 8.2.1.1.5 Alternate Output Capacitor Configuration
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 COUT-to-CLOAD Inductance
      2. 10.1.2 LM3281-to-CIN Inductance
    2. 10.2 Layout Example
    3. 10.3 DSBGA Package Assembly And Use
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted) (1)(2)
MIN MAX UNIT
VIN pin to GND pin voltage –0.2 6 V
EN, FB, MODE, SW pins to GND pin voltage –0.2 VIN + 0.2 or 6
(whichever is smaller)
Junction temperature (TJ) 150 °C
Continuous power dissipation(3) Internally limited
Maximum lead temperature (soldering) 260 °C
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications.
(3) Internal thermal shutdown circuitry protects the device from permanent damage. It engages at TJ = 150°C (typ.) and disengages at TJ = 125°C (typ.).

6.2 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) –1000 1000 V
Charged device model (CDM), per JEDEC specification JESD22-C101, all pins(2) –250 250
(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.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
MIN MAX UNIT
VIN Input voltage (with respect to GND pin) 3 5.5 V
ILOAD(1) Output current 0 1200 mA
ILOAD_BURST(1) Output current, short bursts (< 100 µS burst at < 10% duty cycle) 0 1400
EN EN pin voltage (with respect to GND pin) 0 VIN V
MODE Mode select pin voltage (with respect to GND pin) 0 VIN
TJ Junction temperature –30 125 °C
TA Ambient temperature –30 90
TB PC board temperature –30 105
(1) Refer to section High Maximum Current in this data sheet for load current use case profile.

6.4 Thermal Information

THERMAL METRIC(1) DSBGA UNIT
YFQ
6 PINS
RθJA(2) Junction-to-ambient thermal resistance 131.2 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 1.7
RθJB Junction-to-board thermal resistance 25.6
ψJT Junction-to-top characterization parameter 4.7
ψJB Junction-to-board characterization parameter 25.6
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
(2) RθJA is not useful for CSP packages because the dominant heat loss mechanism is through the PCB. Instead, RθJB is more useful and is used.

6.5 Electrical Characteristics

over operating free-air temperature range (unless otherwise noted) (1)(2)(3)
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
VIN Input voltage range(4) 3 5.5 V
VOUT Output voltage measured at FB pin 3.2 3.3 3.4
ISHDN_IN Total supply current in shutdown EN = SW = FB = MODE = 0 V, Steady State 0.1 1 µA
IQ_OL Quiescent current No switching 15 25
FOSC Internal oscillator frequency 5.4 6 6.6 MHz
VIH EN, MODE pins high level input voltage 1.2 V
VIL EN, MODE pins low level input voltage 0.4
IIH EN, MODE high level input current 1 µA
IIL EN, MODE low level input current EN = MODE = 0 V –1
(1) All voltages are with respect to the GND pin.
(2) All characteristics apply to the Simplified Schematic with VIN = 3.8 V, EN = MODE = VIN, at TA = 25°C, device in PWM operation unless otherwise noted.
(3) Minimum (MIN) and Maximum (MAX) limits are specified by design, test, or statistical analysis over the ambient temperature operating range –30°C to 90°C. Limits are not specified by production testing.
(4) Device is functional at a minimum VIN = 2.6 V but is specified for operation over the range VIN = 3 V to 5.5 V.

6.6 System Characteristics(1)(2)(3)(4)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
ILOAD_MAX(5) Maximum load current 1200 mA
VO_RIPPLE_PWM PWM mode VOUT ripple ILOAD = 600 mA 1 mV
VO_RIPPLE_ECO ECO mode VOUT ripple ILOAD = 30 mA 60
VO_PWM_ACC PWM mode VOUT VIN = 3.8 V 3.2 3.3 3.4 V
VO_ECO_ACC ECO mode VOUT 3.2 3.3 3.4
ITRIG_PWM_TO_ECO PWM to ECO mode ILOAD threshold ILOAD falling 50 mA
ITRIG_ECO_TO_PWM ECO to PWM mode ILOAD threshold ILOAD rising 70
VDROPOUT_BYPASS Bypass mode total dropout voltage with LSW inductor DCR = 40 mΩ ILOAD = 600 mA, VIN = 3.2V 60 80 mV
ILOAD = 1200 mA, VIN = 3.2V 120 160
ION_SOFT_START Soft-start supply current during turnon averaged in any 10-µs window EN = low-to-high,
ILOAD ≤ 1 mA		 500 1000 mA
TON Turnon transient time from EN = high until VOUT is settled to within ±50 mV of settled value, and full 1200-mA load may be applied EN = low-to-high,
ILOAD ≤ 1 mA		 150 µs
η PWM mode efficiency ILOAD = 1200 mA 89%
ILOAD = 600 mA 93%
ILOAD = 300 mA 94%
ECO mode efficiency ILOAD = 30 mA 91%
IQ_CL Closed loop quiescent current ILOAD = 0 mA 16 25 µA
VLINE_TR_PWM_PWM(6) PWM-to-PWM line transient response ILOAD = 600 mA
VIN = 4.2 V to 3.8 V
VIN = 3.8 V to 4.2 V with 7-µs edge rate		 20 mVpk
TLINE_TR_PWM_PWM(7) 0(8) µS
VLOAD_TR_PWM_PWM(6) PWM-to-PWM load transient response ILOAD = 150 mA to 600 mA or
ILOAD = 600 mA to 150 mA with 1-µs edge rate, VIN = 3.8 V		 80 mVpk
TLOAD_TR_PWM_PWM(7) 3 µS
VLOAD_TR_ECO_TO_PWM(6) ECO-to-PWM load transient response ILOAD = 30 mA to 600 mA with 1-µs edge rate, VIN = 3.8 V 200 mVpk
TLOAD_TR_ECO_TO_PWM(7) 6 µS
VIN_RAMP(9) Input voltage ramp time ILOAD = 0 mA
Input power supply rising from 1.2 V to 2.6 V		 20 µs
(1) All voltages are with respect to the GND pin.
(2) All TYP characteristics apply to the Simplified Schematic with VIN = 3.8 V, EN = MODE = VIN, at TA = 25°C, device in PWM operation, unless otherwise noted and assume the following passive components:
  1. CIN = COUT = Samsung 2.2 µF 0201 case size (PN: CL03A225MQ3CRNC)
  2. LSW = Murata 0.47 µH 2012 case size (PN: LQM21PNR47MGH)
  3. CLOAD1 = Samsung 10 µF 0402 case size (PN: CL05A106MP5NUNC)
  4. CLOAD2 = Samsung 4.7 µF 0402 case size (PN: CL05A475MP5NRNC)
(3) All system characteristics are specified by design, test or statistical analysis and are not specified by production testing.
(4) Minimum (MIN) and Maximum (MAX) limits apply over the ambient temperature operating range –30°C to 90°C and over the VIN range 3 V to 5.5 V, unless otherwise noted.
(5) Refer to section High Maximum Current in this data sheet for load current use case profile.
(6) Transient magnitude is defined as maximum deviation from final settled value during transient time.
(7) Transient time is defined as time elapsed from the start of the event to when VOUT is finally within ±50 mV of settled value.
(8) Transient magnitude does not exceed ± 50 mV of settled value, so transient time is 0 µS.
(9) This parameter is only applicable when EN is tied to VIN. See Power-On Reset section for further details.

6.7 Typical Characteristics

All curves are at TA = 25°C and VIN = 3.8 V, unless otherwise specified. CIN, COUT = 2.2 µF, CLOAD2 = 4.7 µF, CLOAD1 = 10 µF, LSW = 0.47 µH.
tc01_ECO_eff_vs_out_cur_snvsa38.gif
Figure 2. ECO Efficiency vs Output Current
tc03_forced_PWM_eff_vs_out_cur_snvsa38.gif
Figure 4. Forced PWM Efficiency vs Output Current
tc19_no_load_FPWM_in_cur_vs_vin_snvsa38.gif
Figure 6. No Load Forced PWM Input Current vs VIN
tc05_PWM_out_ripple_snvsa38.gif
IOUT = 100 mA
Figure 8. Output Voltage Ripple in PWM Mode
tc07_ECO_burst_freq_vs_out_cur_snvsa38.gif
Figure 10. ECO Burst Frequency vs Output Current
tc09_01_PWM_bypass_drop_volt_vs_fall_vin_snvsa38.gif
Figure 12. PWM-to-Analog Bypass Transition, Falling VIN
tc09b_ECO_bypass_drop_volt_vs_vin_30mA_snvsa38.gif
IOUT = 30 mA
Figure 14. Analog Bypass Transition at Light Load vs VIN
tc11_load_reg_vs_out_cur_snvsa38.gif
Figure 16. Load Regulation vs Output Current
tc02_PWM_eff_vs_out_cur_snvsa38.gif
Figure 3. PWM Efficiency vs Output Current
tc20_no_load_ECO_in_cur_vs_vin_snvsa38.gif
Figure 5. No Load ECO Input Current vs VIN
tc04_ECO_out_ripple_snvsa38.gif
IOUT = 10 mA
Figure 7. Output Voltage Ripple in ECO Mode
tc06_forced_PWM_out_ripple_snvsa38.gif
IOUT = 10 mA
Figure 9. Output Voltage Ripple in Forced PWM Mode
tc08_PWM_switch_freq_vs_vin_snvsa38.gif
Figure 11. PWM Switching Frequency vs VIN
tc09_02_PWM_bypass_drop_volt_vs_rise_vin_snvsa38.gif
Figure 13. Analog Bypass-to-PWM Transition, Rising VIN
tc10_line_reg_vs_out_cur_snvsa38.gif
Figure 15. Line Regulation vs Output Current