DATA SHEET
LM3670 Miniature Step-Down DC-DC Converter for Ultralow Voltage Circuits
1 Features
- Input Voltage Range: 2.5 V to 5.5 V
- Adjustable Output Voltages (VOUT): 0.7 V to 2.5 V
- Fixed Output Voltages: 1.2 V, 1.5 V, 1.6 V, 1.8 V, 1.875 V, 3.3V
- 15-µA Typical Quiescent Current
- 350-mA Maximum Load Capability
- 1-MHz PWM Fixed Switching Frequency (Typical)
- Automatic PFM and PWM Mode Switching
- Low Dropout Operation – 100% Duty Cycle Mode
- Internal Synchronous Rectification for High Efficiency
- Internal Soft Start
- 0.1-µA Typical Shutdown Current
- Current Overload Protection
- Operates from a Single Li-Ion Cell or Three-Cell NiMH/NiCd Batteries
- Only Three Tiny Surface-Mount External Components Required (One Inductor, Two Ceramic Capacitors)
2 Applications
- Mobile Phones and Handheld Devices
- PDAs
- Palm-Top PCs
- Portable Instruments
- Battery-Powered Devices
3 Description
The LM3670 step-down DC-DC converter is optimized for powering ultralow voltage circuits from a single Li-Ion cell or three-cell NiMH/NiCd batteries. It provides up to 350-mA load current, over an input voltage range from 2.5 V to 5.5 V. There are several different fixed voltage output options available as well as an adjustable output voltage version.
The device offers superior features and performance for mobile phones and similar portable applications with complex power management systems. Automatic intelligent switching between pulse width modulation (PWM) low-noise and pulse frequency modulation (PFM) low-current mode offers improved system control. During full-power operation, a fixed-frequency 1-MHz (typical) PWM mode drives loads from approximately 70 mA to 350 mA maximum, with up to 95% efficiency. Hysteretic PFM mode extends the battery life through reduction of the quiescent current to 15 µA (typical) during light current loads and system standby. Internal synchronous rectification provides high efficiency (90% to 95% typical at loads between 1 mA and 100 mA). In shutdown mode (enable (EN) pin pulled low) the device turns off and reduces battery consumption to 0.1 µA (typical).
The LM3670 is available in a 5-pin SOT-23 package. A high switching frequency (1 MHz typical) allows use of tiny surface-mount components. Only three external surface-mount components, an inductor and two ceramic capacitors, are required.
Device Information(1)
| PART NUMBER | PACKAGE | BODY SIZE (NOM) |
|---|---|---|
| LM3670 | SOT-23 (5) | 2.90 mm × 1.60 mm |
- For all available packages, see the orderable addendum at the end of the data sheet.
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Typical Application: Fixed Output
Typical Application: Adjustable Output Voltage
4 Revision History
Changes from E Revision (February 2013) to F Revision
- Changed "(0.7V min) to "0.7 V to 2.5 V"Go
- Added Device Information and Pin Configuration and Functions sections, ESD Ratings and Thermal Information tables, Feature Description, Device Functional Modes, Application and Implementation, Power Supply Recommendations, Layout, Device and Documentation Support, and Mechanical, Packaging, and Orderable Information sectionsGo
- Deleted phone and fax numbers of manufacturers from suggested inductors table Go
- Deleted phone and fax numbers of manufacturers from suggested capacitors table Go
- Deleted rest of text from paragraph beginning "For any output voltages...."Go
- Deleted row beginning with "1.24... "from Table 3 Go
Changes from D Revision (February 2013) to E Revision
- Changed layout of National Data Sheet to TI formatGo
5 Connection Diagram
DBV Package
5-Pin SOT-23
Top View
Pin Functions
| PIN | TYPE | DESCRIPTION | |
|---|---|---|---|
| NUMBER | NAME | ||
| 1 | VIN | Power | Power supply input. Connect to the input filter capacitor ( Typical Application: Fixed Output). |
| 2 | GND | Ground | Ground pin. |
| 3 | EN | Digital | Enable input. |
| 4 | FB | Analog | Feedback analog input. Connect to the output filter capacitor (Typical Application: Fixed Output). |
| 5 | SW | Analog | Switching node connection to the internal PFET switch and NFET synchronous rectifier. Connect to an inductor with a saturation current rating that exceeds the 750-mA maximum switch peak current limit specification. |
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)(2)| MIN | MAX | UNIT | ||
|---|---|---|---|---|
| VIN pin: voltage to GND | –0.2 | 6 | V | |
| EN pin: voltage to GND | –0.2 | 6 | V | |
| FB, SW pins | (GND −0.2) | VIN + 0.2 | V | |
| Junction temperature, TJ-MAX | –45 | 125 | °C | |
| Maximum lead temperature (soldering, 10 seconds) | 260 | °C | ||
| Storage temperature, Tstg | –45 | 150 | °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, contact the TI Sales Office/Distributors for availability and specifications.
6.2 ESD Ratings
| VALUE | UNIT | |||
|---|---|---|---|---|
| V(ESD) | Electrostatic discharge | Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) | ±2000 | V |
| Charged-device model (CDM), per JEDEC specification JESD22-C101(2) | ±200 | |||
(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)(1)| MIN | NOM | MAX | UNIT | ||
|---|---|---|---|---|---|
| Input voltage | 2.5 | 5.5 | A | ||
| Recommended load current | 0 | 350 | mA | ||
| Junction temperature, TJ | –40 | 125 | °C | ||
| Ambient temperature, TA | –40 | 85 | °C | ||
(1) All voltages are with respect to the potential at the GND pin.
6.4 Thermal Information
| THERMAL METRIC(1) | LM3670 | UNIT | |
|---|---|---|---|
| DBV (SOT-23) | |||
| 5 PINS | |||
| RθJA | Junction-to-ambient thermal resistance | 163.3 | °C/W |
| RθJC(top) | Junction-to-case (top) thermal resistance | 114.3 | °C/W |
| RθJB | Junction-to-board thermal resistance | 26.8 | °C/W |
| ψJT | Junction-to-top characterization parameter | 12.4 | °C/W |
| ψJB | Junction-to-board characterization parameter | 26.3 | °C/W |
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953.
6.5 Electrical Characteristics
Unless otherwise specified, limits for typical values are TJ = 25°C, and minimum and maximum limits apply over the full operating junction temperature range (−40°C ≤ TJ ≤ +125°C); VIN = 3.6 V, VOUT = 1.8 V, IOUT = 150 mA, EN = VIN.| PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | |
|---|---|---|---|---|---|---|
| VIN | Input voltage | See(1) | 2.5 | 5.5 | V | |
| VOUT | Fixed output voltage: 1.2 V | 2.5 V ≤ VIN ≤ 5.5 V IOUT = 10 mA |
–2% | 4% | ||
| 2.5 V ≤ VIN ≤ 5.5 V 0 mA ≤ IOUT ≤ 150 mA |
–4.5% | 4% | ||||
| Fixed output voltage: 1.5 V | 2.5 V ≤ VIN ≤ 5.5 V IOUT = 10 mA |
–2.5% | 4% | |||
| 2.5 V ≤ VIN ≤ 5.5 V 0 mA ≤ IOUT ≤ 350 mA |
–5% | 4% | ||||
| Fixed output voltage: 1.6 V, 1.875 V | 2.5 V ≤ VIN ≤ 5.5 V IOUT = 10 mA |
–2.5% | 4% | |||
| 2.5 V ≤ VIN ≤ 5.5V 0 mA ≤ IOUT ≤ 350 mA |
–5.5% | 4% | ||||
| Fixed output voltage: 1.8 V | 2.5 V ≤ VIN ≤ 5.5 V IOUT = 10 mA |
–1.5% | 3% | |||
| 2.5 V ≤ VIN ≤ 5.5 V 0 mA ≤ IOUT ≤ 350 mA |
–4.5% | 3% | ||||
| Fixed output voltage: 3.3 V | 3.6 V ≤ VIN ≤ 5.5 V IOUT = 10 mA |
–2% | 4% | |||
| 3.6V ≤ VIN ≤ 5.5V 0 mA ≤ IOUT ≤ 350 mA |
–6% | 4% | ||||
| Adjustable output voltage(2) | 2.5 V ≤ VIN ≤ 5.5 V IOUT = 10 mA |
–2.5% | 4.5% | |||
| 2.5 V ≤ VIN ≤ 5.5 V 0 mA ≤ IOUT ≤ 150 mA |
–4% | 4.5% | ||||
| Line_reg | Line regulation | 2.5 V ≤ VIN ≤ 5.5 V IOUT = 10 mA |
0.26 | %/V | ||
| Load_reg | Load regulation | 150 mA ≤ IOUT ≤ 350 mA | 0.0014 | %/mA | ||
| VREF | Internal reference voltage | 0.5 | V | |||
| IQ_SHDN | Shutdown supply current | TA = 85ºC | 0.1 | 1 | µA | |
| IQ | DC bias current into VIN | No load, device is not switching (VOUT forced higher than programmed output voltage) | 15 | 30 | µA | |
| VUVLO | Minimum VIN below which VOUT is disabled | TA = −40°C ≤ TJ ≤ 125°C | 2.4 | V | ||
| RDSON (P) | Pin-pin resistance for PFET | VIN = VGS= 3.6V | 360 | 690 | mΩ | |
| RDSON (N) | Pin-pin resistance for NFET | VIN = VGS= 3.6 V | 250 | 660 | mΩ | |
| ILKG (P) | P channel leakage current | VDS = 5.5 V, TA = 25°C | 0.1 | 1 | µA | |
| ILKG (N) | N channel leakage current | VDS = 5.5 V, TA = 25°C | 0.1 | 1.5 | µA | |
| ILIM | Switch peak current limit | 400 | 620 | 750 | mA | |
| η | Efficiency | VIN = 3.6 V, VOUT = 1.8 V ILOAD = 1 mA |
91% | |||
| VIN = 3.6 V, VOUT = 1.8 V ILOAD = 10 mA |
94% | |||||
| VIN = 3.6 V, VOUT = 1.8 V ILOAD = 100 mA |
94% | |||||
| VIN = 3.6 V, VOUT = 1.8 V ILOAD = 200 mA |
94% | |||||
| VIN = 3.6 V, VOUT = 1.8 V ILOAD = 300 mA |
92% | |||||
| VIN = 3.6 V, VOUT = 1.8 V ILOAD = 350 mA |
90% | |||||
| VIH | Logic high input | 1.3 | V | |||
| VIL | Logic low input | 0.4 | V | |||
| IEN | Enable (EN) input current | 0.01 | 1 | µA | ||
| ƒOSC | Internal oscillator frequency | PWM mode | 550 | 1000 | 1300 | kHz |
(1) The input voltage range recommended for the specified output voltages are given below: VIN = 2.5 V to 5.5 V for 0. 7 V ≤ VOUT < 1.875 V, VIN = ( VOUT + VDROPOUT) to 5.5 for 1.875 ≤ VOUT ≤ 3.3 V, where VDROPOUT = ILOAD × (RDSON (P) + RINDUCTOR).
(2) Output voltage specification for the adjustable version includes tolerance of the external resistor divider.
6.6 Typical Characteristics
Unless otherwise stated, VIN = 3.6 V and VOUT= 1.8 V.
| VIN = 2.6 V to 3.6 V | ILOAD = 100 mA |
| ILOAD = 3 mA to 280 mA | ||
| ILOAD = 350 mA |
| VIN = 3.6 V to 4.6 V | ILOAD = 100 mA |
| ILOAD = 0 mA to 70 mA | ||
