LM3671

Part: LM3671, LM3671Q from Texas Instruments

Type: Synchronous Step-Down DC-DC Converter

Description: The LM3671 is a 2 MHz, 600 mA synchronous step-down DC-DC converter optimized for low voltage circuits, operating from a 2.7–5.5 V input with automatic PFM/PWM mode switching for high efficiency and low quiescent current.

Operating Conditions:

• Supply voltage: 2.7V to 5.5V
• Operating temperature: -40°C to +125°C (Junction Temperature)
• Recommended load current: 0 mA to 600 mA
• Output voltage range: 0.9V to 3.3V (adjustable version)

Absolute Maximum Ratings:

• Max supply voltage: 5.5V (operating max, no higher absolute max explicitly stated)
• Max continuous current: 600 mA
• Max junction temperature: 150°C (thermal shutdown engages)

Key Specs:

• Quiescent Current (IQ): 16 μA (typ.)
• Shutdown Supply Current (ISHND): 0.01 μA (typ.)
• Switch Peak Current Limit (ILIM): 830 mA (min)
• Internal Oscillator Frequency (Fosc): 2 MHz (typ.)
• PFET On-Resistance (RDSON (P)): 380 mΩ (typ.) at VIN = VGS = 3.6V
• NFET On-Resistance (RDSON (N)): 250 mΩ (typ.) at VIN = VGS = 3.6V
• Logic High Input (VIH): 1.0 V (min)
• Logic Low Input (VIL): 0.4 V (max)

Features:

• 16 μA Typical Quiescent Current
• 600 mA Maximum Load Capability
• 2 MHz PWM Fixed Switching Frequency (typ.)
• Automatic PFM/PWM Mode Switching
• Internal Synchronous Rectification for High Efficiency
• Internal Soft start
• 0.01 μA Typical Shutdown Current
• Operates from a Single Li-Ion Cell Battery
• Only Three Tiny Surface-Mount External Components Required (One Inductor, Two Ceramic Capacitors)
• Current Overload and Thermal Shutdown Protection
• Available in Fixed Output Voltages and Adjustable Version
• LM3671Q is an Automotive Grade Product that is AEC-Q100 Grade 1 Qualified

Applications:

• Mobile Phones
• PDAs
• MP3 Players
• W-LAN
• Portable Instruments
• Digital Still Cameras
• Portable Hard Disk Drives
• Automotive

Package:

• SOT-23-6
• 5-Bump DSBGA
• 6-Pin USON

• 16 μA Typical Quiescent Current
• 600 mA Maximum Load Capability
• 2 MHz PWM Fixed Switching Frequency (typ.)
• Automatic PFM/PWM Mode Switching
• Internal Synchronous Rectification for High Efficiency
• Internal Soft start
• 0.01 μA Typical Shutdown Current
• · Operates from a Single Li-Ion Cell Battery
• Only Three Tiny Surface-Mount External Components Required (One Inductor, Two Ceramic Capacitors)
• Current Overload and Thermal Shutdown Protection
• Available in Fixed Output Voltages and Adjustable Version
• LM3671Q is an Automotive Grade Product that is AEC-Q100 Grade 1 Qualified
• SOT-23, 5-Bump DSBGA and 6-Pin USON Packages

• Mobile Phones
• PDAs
• MP3 Players
• W-LAN
• Portable Instruments
• Digital Still Cameras
• Portable Hard Disk Drives
• Automotive

PIN DESCRIPTIONS (5-Bump DSBGA)

PIN DESCRIPTIONS (6-Pin USON)

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.

Limits in standard typeface are for T_J = 25°C. Limits in boldface type apply over the entire junction temperature range for operation, -40^° C to +125^° C. Unless otherwise noted, specifications apply to the LM3671MF/TL/LC with V_IN = EN = 3.6V

• All voltages are with respect to the potential at the GND pin.
• Min and Max limits are specified by design, test or statistical analysis. Typical numbers are not specified, but do represent the most
• (3) The parameters in the electrical characteristic table are tested at V_IN= 3.6V unless otherwise specified. For performance over the input voltage range refer to datasheet curves.
• (4) The input voltage range recommended for ideal applications performance for the specified output voltages are given below: V_IN = 2.7V to 4.5V for 1.1V ≤ V_OUT < 1.5VV_IN = 2.7V to 5.5V for 1.5V ≤ V_OUT < 1.8VV_IN = ( V_OUT + V_DROPOUT ) to 5.5V for 1.8V ≤ V_OUT ≤ 3.3Vwhere V_DROPOUT = I_LOAD * (R_{DSON, PFET} + R_INDUCTOR) (5) Test condition: for V_OUT less than 2.5V, V_IN = 3.6V ; for V_OUT greater than or equal to 2.5V, V_IN = V_OUT + 1V .
• (6) ADJ version is configured to 1.5V output. For ADJ output version: V_IN = 2.7V to 4.5V for 0.90V ≤ V_OUT < 1.1VV_IN = 2.7V to 5.5V for 1.1V ≤ V_OUT < 3.3V
• (7) Refer to datasheet curves for closed loop data and its variation with regards to supply voltage and temperature. Electrical Characteristic table reflects open loop data (FB=0V and current drawn from SW pin ramped up until cycle by cycle current limit is activated). Closed loop current limit is the peak inductor current measured in the application circuit by increasing output current until output voltage drops by 10%.

DISSIPATION RATING TABLE

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BLOCK DIAGRAM

Figure 6. Simplified Functional Diagram

TYPICAL PERFORMANCE CHARACTERISTICS

Figure 13. Figure 14.

LM3671MF/TL/LC, Circuit of Figure 1, V_IN = 3.6V, V_OUT = 1.5V, T_A = 25°C, unless otherwise noted.

Figure 24.

OPERATION DESCRIPTION

DEVICE INFORMATION

The LM3671, a high-efficiency step-down DC-DC switching buck converter, delivers a constant voltage from a single Li-Ion battery and input voltage rails from 2.7V to 5.5V to portable devices such as cell phones and PDAs. Using a voltage mode architecture with synchronous rectification, the LM3671 has the ability to deliver up to 600 mA depending on the input voltage, output voltage, ambient temperature and the inductor chosen.

There are three modes of operation depending on the current required - PWM (Pulse Width Modulation), PFM (Pulse Frequency Modulation), and shutdown. The device operates in PWM mode at load current of approximately 80 mA or higher. Lighter load current cause the device to automatically switch into PFM for reduced current consumption (I^Q = 16 μA typ) and a longer battery life. Shutdown mode turns off the device, offering the lowest current consumption (ISHUTDOWN = 0.01 μA typ).

Additional features include soft-start, under-voltage protection, current overload protection, and thermal shutdown protection. As shown in Figure 1, only three external power components are required for implementation.

The part uses an internal reference voltage of 0.5V. It is recommended to keep the part in shutdown until the input voltage is 2.7V or higher.

• (1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is specified. Operating Ratings do not imply specified performance limits. For specified performance limits and associated test conditions, see the Electrical Characteristics tables.
• (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. Thermal shutdown engages at T_J= 150°C (typ.) and disengages at T_J= 130°C (typ.).
• (4) The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. MIL-STD-883 3015.7

OPERATING RATINGS(1) (2)

• (1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is specified. Operating Ratings do not imply specified performance limits. For specified performance limits and associated test conditions, see the Electrical Characteristics tables.
• (2) All voltages are with respect to the potential at the GND pin.
• (3) The input voltage range recommended for ideal applications performance for the specified output voltages are given below: V_IN = 2.7V to 4.5V for 1.1V ≤ V_OUT < 1.5VV_IN = 2.7V to 5.5V for 1.5V ≤ V_OUT < 1.8VV_IN = (V_OUT + V_DROPOUT) to 5.5V for 1.8V ≤ V_OUT ≤ 3.3Vwhere V_DROPOUT = I_LOAD *(R_{DSON, PFET} + R_INDUCTOR) (4) In Applications where high power dissipation and/or poor package resistance is present, the maximum ambient temperature may have
• (4) In Applications where high power dissipation and/or poor package resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (T_A-MAX) is dependent on the maximum operating junction temperature (T_J-MAX), the maximum power dissipation of the device in the application (P_D-MAX) and the junction to ambient thermal resistance of the package (θ_JA) in the application, as given by the following equation: T_A-MAX = T_J-MAX (θ_JAX P_D-MAX). Refer to Dissipation rating table for P_D-MAX values at different ambient temperatures.

THERMAL PROPERTIES

(1) Junction to ambient thermal resistance is highly application and board layout dependent. In applications where high power dissipation exists, special care must be given to thermal dissipation issues in board design. Specified value of 130 °C/W for SOT-23 is based on a 4 layer, 4" x 3", 2/1/1/2 oz. Cu board as per JEDEC standards is used.

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(1) Junction to ambient thermal resistance is highly application and board layout dependent. In applications where high power dissipation exists, special care must be given to thermal dissipation issues in board design. Specified value of 130 °C/W for SOT-23 is based on a 4 layer, 4" x 3", 2/1/1/2 oz. Cu board as per JEDEC standards is used.

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Figure 1. Typical Application Circuit

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