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Texas Instruments LM3668SDX-3.3/NOPB
- Part No.:
- LM3668SDX-3.3/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 12-WFDFN Exposed Pad
- Datasheet:
-
LM3668SDX-3.3/NOPB.pdf
- Description:
- IC REG BUCK BOOST 3.3V 1A 12WSON
- Quantity:
- Payment:
- Shipping:
Inventory:2,804
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Product details
Overview
LM3668SDX-3.3/NOPB from Texas Instruments is a synchronous dual-mode buck-boost DC-DC converter delivering 3.3 V output from 2.5–5.5 V input, supporting up to 1-A load at VIN ≥ 2.8 V, with 2.2-MHz fixed-frequency PWM and automatic PFM-PWM mode switching. It regulates continuously across input voltage transitions using internal N- and P-channel MOSFETs in a single-inductor topology, deployed in Li-ion-powered portable electronics requiring stable dual-rail voltage conversion.
For engineers reviewing the LM3668SDX-3.3/NOPB datasheet, LM3668SDX-3.3/NOPB pinout, LM3668SDX-3.3/NOPB application, or LM3668SDX-3.3/NOPB equivalent, key selection considerations include its 45-µA quiescent current in PFM mode, 0.01-µA shutdown current, VSEL-configurable 3.3-V output, SYNC/MODE pin for external clock synchronization (1.6–2.7 MHz), and thermal shutdown protection at 150°C.
Technical Context
The LM3668SDX-3.3/NOPB implements a voltage-mode control architecture with seamless buck-to-boost transition determined by real-time comparison of feedback error (Vc) against a center reference (Vcenter). In buck mode, P2 remains on while P1/N1 switch; in boost mode, P1 stays on while N2/P2 switch - eliminating discontinuous conduction and minimizing output ripple during mode crossing.
It integrates four internal MOSFETs (two N-channel, two P-channel), synchronous rectification, soft-start (600-µs max), undervoltage lockout (~2 V), short-circuit current limiting (reduced to ~0.9 A under fault), and thermal shutdown (trip at 150°C, recovery at 125°C). MODE/SYNC pin supports either automatic PFM-PWM mode or forced PWM operation with external frequency synchronization.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3 V (set by VSEL = high); ±3% feedback accuracy ensures stable regulation under load/temperature variation. |
| Input Voltage Range | 2.5 V to 5.5 V; supports full Li-ion battery discharge curve (3.0–4.2 V) plus USB 5 V and legacy 3.3 V rails. |
| Max Output Current | 1 A at VIN ≥ 2.8 V; enables direct powering of baseband processors, RF transceivers, or memory subsystems. |
| Quiescent Current | 45 µA typical in PFM mode; extends standby time in always-on peripherals like touch controllers or sensors. |
| Switching Frequency | 2.2 MHz typical (PWM mode); allows use of compact 2.2-µH inductor and low-ESR ceramic capacitors (10 µF CIN, 22 µF COUT). |
| Shutdown Current | 0.01 µA typical; minimizes battery drain during system sleep or power-off states. |
| RDS(on) (PFET) | 130–180 mΩ; reduces conduction loss in high-side switches during buck and boost phases. |
| RDS(on) (NFET) | 100–150 mΩ; improves efficiency in synchronous rectification path, especially at light loads. |
Pinout & Package
LM3668SDX-3.3/NOPB uses a 12-pin WSON (DQB) package, 3.00 mm × 3.00 mm, with exposed die attach pad (DAP) connected to SGND for enhanced thermal performance. The package is RoHS-compliant and moisture-sensitive level 2a.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT | Output voltage node | Connects directly to output capacitor; supplies regulated 3.3 V to load with low-impedance path. |
| SW2 | Switching node (P2/N2) | Interface to internal PFET P2 and NFET N2; critical for boost-phase energy transfer and layout EMI control. |
| PGND | Power ground return | High-current return path for inductor and power switches; must be separated from SGND in PCB layout. |
| SW1 | Switching node (P1/N1) | Interface to internal PFET P1 and NFET N1; dominant in buck-phase operation and requires tight loop routing. |
| PVIN | Power input supply | Primary input rail connection; ties to input capacitor and supplies gate drive for power FETs. |
| EN | Enable control input | Active-high digital enable; pulling low disables all switches and reduces current to 0.01 µA. |
| VDD | Signal supply input | Bias supply for control circuitry; recommended 1-µF bypass capacitor near pin for noise immunity. |
| NC | No-connect terminal | Internally unconnected; must be tied to SGND on PCB per TI layout guidelines. |
| SGND | Analog/control ground | Reference for FB, MODE/SYNC, VSEL, and error amplifier; kept separate from PGND to avoid noise coupling. |
| MODE/SYNC | Mode select / sync input | Logic-low = auto PFM-PWM; logic-high = forced PWM; accepts 1.6–2.7 MHz external clock for EMI reduction. |
| VSEL | Output voltage select | Logic-high (≥1.1 V) sets 3.3 V output; logic-low (≤0.4 V) selects 2.8 V - defines exact operating point for this variant. |
| FB | Feedback input | Monitors output via resistive divider; internal 0.6 V reference enables precise regulation without external components. |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost topology | Eliminates need for dual inductors or transformer; reduces BOM count, board area, and cost in space-constrained portable designs. |
| Automatic PFM-PWM mode transition | Switches seamlessly at ~80 mA load threshold; maintains >85% efficiency from 1 mA to 1 A without manual mode control. |
| Internal synchronous rectification | Replaces external Schottky diodes; achieves >90% peak efficiency at 500 mA with 3.6 V input → 3.3 V output. |
| Integrated soft-start (600 µs) | Prevents inrush current and output overshoot during power-up; eliminates need for external timing components. |
| Thermal and overload protection | Shuts down at 150°C junction temperature and limits peak switch current to 1.85 A; recovers automatically after cooling. |
| VIN undervoltage lockout (~2 V) | Disables operation before battery depletion; prevents erratic behavior and protects downstream circuits from brownout. |
Applications
| Handset Power Management | MP3 Player Core Supply |
|---|---|
Use Scenario: Powers baseband processor and display driver from single Li-ion cell with varying voltage (3.0–4.2 V). IC Role / Device Role / Timing Role: Dual-mode buck-boost regulator maintaining constant 3.3 V despite input sag during transmit bursts. Use Value: Enables uninterrupted operation across full battery discharge cycle without requiring intermediate LDOs or multiple converters. |
Use Scenario: Supplies audio DAC, flash memory, and microcontroller in ultra-portable MP3 player. IC Role / Device Role / Timing Role: Primary DC-DC converter delivering low-noise 3.3 V rail with <45 µA quiescent current in standby. Use Value: Extends playback time by >20% versus traditional boost-only solutions due to high light-load efficiency. |
| PDA Application Processor Rail | WiMAX Modem Pre-regulation |
Use Scenario: Generates clean 3.3 V core voltage for ARM-based application processor in PDA with dynamic DVFS scaling. IC Role / Device Role / Timing Role: High-efficiency pre-regulator feeding low-dropout linear regulators for noise-sensitive analog blocks. Use Value: Reduces thermal load on main SoC by delivering 1-A peak current with <150 mV output ripple in PWM mode. |
Use Scenario: Provides stable 3.3 V supply to WiMAX RF front-end ICs operating from noisy shared battery rail. IC Role / Device Role / Timing Role: Isolates sensitive RF circuitry from input voltage fluctuations and transient noise via fast line/load transient response. Use Value: Achieves <200 µs recovery from 50% load step (0→500 mA) in forced PWM mode, preserving signal integrity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost DC-DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS63020DSJR | Higher 2.5-A output capability; 3.2-MHz switching frequency; requires external compensation network. | Better suited for higher-current applications like tablets; less optimal for ultra-low-IQ portable devices. | Select when >1-A load or tighter output tolerance (<±1%) is required; verify layout compatibility with higher fSW. |
| MAX8815AETE+T | Lower 0.8-A max output; 1.5-MHz fixed frequency; no SYNC pin; 25-µA IQ in PFM mode. | Targeted at cost-sensitive, lower-power handhelds; lacks frequency synchronization for EMI-critical designs. | Choose where minimal quiescent current and smaller solution size outweigh need for 1-A capability or EMI control. |
Compared with TPS63020DSJR and MAX8815AETE+T, the LM3668SDX-3.3/NOPB offers the best balance of 1-A output, 45-µA PFM quiescent current, and 2.2-MHz SYNC-capable operation in a 3-mm² WSON package - making it ideal for mid-tier portable devices needing robust battery life and EMI compliance without overengineering.
Availability
LM3668SDX-3.3/NOPB is available at Aetrix Electronics and suitable for handset peripherals, MP3 players, and portable hard disk drives requiring stable component supply with guaranteed long-term manufacturability and consistent parametric performance.
Supply support for LM3668SDX-3.3/NOPB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in power management IC design and high-volume manufacturing reliability.
The LM3668 product line targets portable battery-powered systems requiring efficient, compact, and flexible voltage conversion - specifically engineered to replace discrete buck + boost solutions with a single-inductor architecture that simplifies layout and improves system-level efficiency.
FAQ
What output voltage does LM3668SDX-3.3/NOPB deliver, and how is it selected?
The LM3668SDX-3.3/NOPB delivers a fixed 3.3 V output. This is set by the VSEL pin: when pulled high (≥1.1 V), the device configures for 3.3 V; when low (≤0.4 V), it defaults to 2.8 V. The "-3.3" suffix in the part number confirms factory-trimmed 3.3 V operation, eliminating need for external feedback resistors. The internal 0.6-V reference and precision feedback amplifier ensure ±3% regulation across temperature and load.
Does LM3668SDX-3.3/NOPB support external frequency synchronization, and what range is supported?
Yes, LM3668SDX-3.3/NOPB supports external frequency synchronization via the MODE/SYNC pin. When driven with a clean square wave, it locks to an input frequency between 1.6 MHz and 2.7 MHz - enabling EMI reduction through spread-spectrum-like placement or alignment with system clocks. In SYNC mode, the device operates exclusively in forced PWM, overriding automatic PFM-PWM transition.
What is the maximum continuous output current for LM3668SDX-3.3/NOPB at 3.6 V input?
At 3.6 V input, LM3668SDX-3.3/NOPB supports up to 1 A continuous output current in PWM mode. This is confirmed in the datasheet's "For 2.8-V–3.3-V Versions" table. Performance depends on thermal design: with proper DAP-to-SGND connection and 2-oz copper layers, it sustains 1 A at ambient ≤85°C. Derating applies below 2.8 V input or above 85°C ambient.
How does LM3668SDX-3.3/NOPB handle transitions between buck and boost modes?
LM3668SDX-3.3/NOPB uses a voltage-mode control architecture with a dedicated Vcenter reference to manage buck-boost transitions. The internal error amplifier compares FB voltage to 0.6 V, generating error signal Vc. When Vc < Vcenter, it operates in buck mode; when Vc > Vcenter, in boost mode. This ensures seamless, ripple-minimized crossover - verified in Figure 20 of the datasheet - without output glitches or mode-hunting behavior.
What protection features are integrated into LM3668SDX-3.3/NOPB?
LM3668SDX-3.3/NOPB integrates five key protections: (1) current limit (1.85-A typical peak switch current), (2) thermal shutdown (150°C trip, 125°C recovery), (3) undervoltage lockout (~2 V), (4) short-circuit foldback (current halved during output short), and (5) shutdown mode (0.01-µA IQ). All are fully internal - no external components required - and operate autonomously without host intervention.
LM3668SDX-3.3/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 12-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck-Boost
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.5V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 1A
- Frequency - Switching:
- 2.2MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 12-WSON (3x3)
LM3668SDX-3.3/NOPB FAQ
1.How can I place an order for LM3668SDX-3.3/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3668SDX-3.3/NOPB on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LM3668SDX-3.3/NOPB reliable?
The price and inventory of LM3668SDX-3.3/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3668SDX-3.3/NOPB is usually 5 days.
3.What payment methods are accepted for LM3668SDX-3.3/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3668SDX-3.3/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3668SDX-3.3/NOPB?
LM3668SDX-3.3/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3668SDX-3.3/NOPB order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LM3668SDX-3.3/NOPB?
For technical support, including LM3668SDX-3.3/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3668SDX-3.3/NOPB requirements.
6.How does Aetrix verify that LM3668SDX-3.3/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3668SDX-3.3/NOPB products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LM3668SDX-3.3/NOPB meets industry standards.
7.What is the process for return or replacement of LM3668SDX-3.3/NOPB?
All LM3668SDX-3.3/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3668SDX-3.3/NOPB, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LM3668SDX-3.3/NOPB part is unused and in its original packaging.
Return procedure for LM3668SDX-3.3/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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