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Texas Instruments LM3668SD-3.3/NOPB
- Part No.:
- LM3668SD-3.3/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 12-WFDFN Exposed Pad
- Datasheet:
-
LM3668SD-3.3/NOPB.pdf
- Description:
- IC REG BUCK BOOST 3.3V 1A 12WSON
- Quantity:
- Payment:
- Shipping:
Inventory:1,743
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Product details
Overview
LM3668SD-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 operation and automatic PFM-PWM mode transition. It serves as a single-inductor pre-regulator for Li-ion-powered portable electronics requiring seamless voltage regulation across battery discharge.
For engineers reviewing the LM3668SD-3.3/NOPB datasheet, LM3668SD-3.3/NOPB pinout, LM3668SD-3.3/NOPB application, or LM3668SD-3.3/NOPB equivalent, key selection considerations include its 45-µA quiescent current in PFM mode, internal synchronous rectification, VSEL-configurable 3.3-V output, MODE/SYNC pin for forced PWM or external clock synchronization (1.6–2.7 MHz), and thermal shutdown protection at 150°C.
Technical Context
The LM3668SD-3.3/NOPB implements a four-switch buck-boost topology with two integrated N-channel and two P-channel MOSFETs, enabling continuous conduction through buck, boost, and direct-conduction modes without discontinuity. Its voltage-mode control loop uses an internal error amplifier comparing FB voltage against a 0.6-V reference, with automatic mode switching determined by the relationship between error signal Vc and center voltage Vcenter.
In buck mode (VIN > VOUT), P2 remains on while P1/N1 switch; in boost mode (VIN < VOUT), P1 remains on while N2/P2 switch. The device supports both forced PWM (via MODE/SYNC = high) and auto PFM-PWM mode (MODE/SYNC = low), with hysteretic PFM operation reducing IQ to 45 µA typical at light loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3 V (set by VSEL = high); regulated ±3% over line/load/temperature |
| Input Voltage Range | 2.5 V to 5.5 V - supports full Li-ion (2.7–4.2 V) and multi-cell NiMH discharge profiles |
| Max Output Current | 1 A at VIN ≥ 2.8 V - enables direct powering of baseband processors or RF modules |
| Switching Frequency | 2.2 MHz typical (PWM mode); allows use of 2.2-µH inductor and compact 10-µF/22-µF ceramic caps |
| Quiescent Current | 45 µA typical (PFM mode) - extends standby time in always-on peripherals |
| Shutdown Current | 0.01 µA typical - minimizes battery drain during system sleep |
| RDS(on) (PFET) | 130–180 mΩ - limits conduction loss in high-side switches during buck/boost transitions |
| Thermal Shutdown | 150°C trip point - protects die under sustained overload or poor PCB thermal design |
Pinout & Package
LM3668SD-3.3/NOPB is housed in a 12-pin WSON (DQB) package measuring 3.00 mm × 3.00 mm with exposed thermal pad (DAP). The DAP must be soldered to SGND for optimal thermal performance; NC pin (Pin 8) is internally unconnected and requires connection to SGND on PCB.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT (Pin 1) | Regulated output node | Connects directly to output capacitor; supplies power to downstream 3.3-V circuitry |
| SW2 (Pin 2) | Switching node (P2/N2) | Internal connection to PFET P2 and NFET N2; critical for boost-mode energy transfer |
| PGND (Pin 3) | Power ground return | Low-impedance path for high-current switch return; separate from analog ground |
| SW1 (Pin 4) | Switching node (P1/N1) | Internal connection to PFET P1 and NFET N1; critical for buck-mode energy transfer |
| PVIN (Pin 5) | Main power input | Supplies gate drive and power switches; connect to 10-µF input capacitor near pin |
| EN (Pin 6) | Digital enable input | Logic-high (>1.1 V) enables regulation; logic-low (<0.4 V) enters 0.01-µA shutdown |
| VDD (Pin 7) | Signal supply rail | Bias for control circuitry; recommended 1-µF ceramic cap placed adjacent to pin |
| NC (Pin 8) | No-connect terminal | Internally open; must be tied to SGND on PCB for mechanical stability and thermal relief |
| SGND (Pin 9) | Analog/control ground | Reference for FB, MODE/SYNC, VSEL; must be star-connected to PGND at single point |
| MODE/SYNC (Pin 10) | Mode control / clock sync | Low = auto PFM-PWM; high = forced PWM; external 1.6–2.7 MHz clock accepted when high |
| VSEL (Pin 11) | Output voltage select | High = 3.3 V (for LM3668SD-3.3/NOPB); low = 2.8 V (not applicable to this variant) |
| FB (Pin 12) | Feedback input | Monitors output via resistor divider; internal 0.6-V reference sets regulation accuracy |
Key Features
| Feature | Design Value |
|---|---|
| Single-inductor buck-boost architecture | Eliminates need for separate buck + boost stages; reduces BOM count and board area by ~40% vs dual-converter solutions |
| Automatic PFM-PWM mode transition | Maintains >85% efficiency from 1 mA to 1 A load - critical for mixed-use portable devices with burst traffic |
| Internal synchronous rectification | Replaces external Schottky diodes; achieves >90% peak efficiency at 500 mA with 2.2-µH inductor |
| Integrated soft-start (600 µs max) | Prevents inrush current into output capacitors; avoids undershoot on VOUT during power-up sequences |
| Current limit & thermal shutdown | 1.85-A typical peak switch current limit plus 150°C thermal cutoff - protects IC and PCB under fault conditions |
| VIN undervoltage lockout (~2 V) | Disables switching before battery reaches deep discharge - preserves Li-ion cell health and system reliability |
Applications
| Handset Baseband Power | MP3 Player Audio Codec Supply |
|---|---|
Use Scenario: Powers 3.3-V baseband processor and memory in GSM/WCDMA smartphones operating from single Li-ion cell (2.7–4.2 V). IC Role / Device Role / Timing Role: Primary buck-boost regulator providing stable 3.3-V rail independent of battery voltage sag during transmit bursts. Use Value: Seamless buck-to-boost transition prevents brownout during RF transmission; 45-µA PFM IQ extends standby time beyond 7 days. |
Use Scenario: Supplies clean 3.3-V bias to stereo audio DAC and headphone amplifier in flash-based MP3 players. IC Role / Device Role / Timing Role: Pre-regulator feeding low-noise LDOs; operates in forced PWM mode to suppress switching noise near sensitive analog circuits. Use Value: 2.2-MHz switching frequency places harmonics beyond audio band (≥22 kHz); reduces need for additional EMI filtering. |
| PDA Application Processor Core | WiMAX Modem RF Front-End |
Use Scenario: Delivers 3.3-V core voltage to ARM9/ARM11 application processors in handheld PDAs with variable workload. IC Role / Device Role / Timing Role: Main system power rail with dynamic load response; leverages auto PFM-PWM to adapt to CPU sleep/active cycles. Use Value: Load transient recovery <10 µs (50–150 mA step) ensures stable core voltage during instruction fetch bursts. |
Use Scenario: Powers 3.3-V RF transceiver and PA bias circuitry in mobile WiMAX CPE units powered by 3.7-V Li-ion packs. IC Role / Device Role / Timing Role: High-efficiency intermediate rail generator; synchronized to system clock via MODE/SYNC pin to reduce spectral interference. Use Value: 1.6–2.7 MHz SYNC range enables deterministic switching alignment with baseband timing, lowering conducted EMI by 8–12 dB. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck-boost regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS63020DSJR | Higher 2.5-A output capability; 3.2-MHz switching; no VSEL pin - fixed 3.3-V option requires external feedback resistors | Preferred for higher-current applications like tablets; lacks pin-strapped voltage selection simplicity | Select TPS63020DSJR when >1-A load or tighter output tolerance (<±1.5%) is required; rework needed for VOUT adjustment |
| MAX8646ETA+ | Lower 600-mA max output; 1.5-MHz switching; integrated I²C interface for dynamic voltage scaling | Suitable for systems requiring programmable output (e.g., adaptive core voltage scaling); not pin-compatible | Choose MAX8646ETA+ only if I²C-controlled VOUT adjustment is mandatory; incompatible footprint and control logic |
Compared with LM3668SD-3.3/NOPB, TPS63020DSJR offers greater current headroom but requires external feedback tuning, while MAX8646ETA+ adds digital control at the cost of reduced output capability and non-interchangeable packaging - neither provides identical pin-strapped 3.3-V simplicity and 12-pin WSON footprint.
Availability
LM3668SD-3.3/NOPB is available at Aetrix Electronics and suitable for handset peripherals, portable hard disk drives, and WiMAX modems requiring stable component supply across extended production lifecycles.
Supply support for LM3668SD-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, embedded processing, and power management ICs, with decades of expertise in battery-powered portable power conversion.
The LM3668 product line targets ultra-compact, high-efficiency DC-DC regulation for space-constrained Li-ion devices, emphasizing seamless mode transition, low IQ, and minimal external component count.
FAQ
What output voltage does the LM3668SD-3.3/NOPB deliver, and how is it set?
The LM3668SD-3.3/NOPB delivers a fixed 3.3-V output. This is configured by tying the VSEL pin (Pin 11) high - either to VIN or a logic-high signal - which selects the 3.3-V internal feedback divider ratio. The device does not support dynamic voltage change; VSEL must remain static during operation. The output is regulated to ±3% over temperature, line, and load per the datasheet's electrical characteristics table.
Can the LM3668SD-3.3/NOPB operate from a 2.5-V input, and what is the maximum load at that voltage?
Yes, the LM3668SD-3.3/NOPB supports inputs as low as 2.5 V. At VIN = 2.5 V, the maximum guaranteed output current is 600 mA - sufficient for low-power peripherals such as sensors or Bluetooth radios. This limitation arises from reduced headroom for boost-mode operation and increased conduction losses; efficiency drops below 75% at full 600 mA under these conditions.
How does the MODE/SYNC pin affect LM3668SD-3.3/NOPB operation?
When MODE/SYNC (Pin 10) is pulled low, the LM3668SD-3.3/NOPB operates in automatic PFM-PWM mode, optimizing efficiency across load range. When pulled high, it forces fixed-frequency PWM mode - essential for noise-sensitive applications - and accepts an external 1.6–2.7 MHz clock signal for EMI reduction. The pin cannot be left floating; a defined logic level is required for stable operation.
What thermal considerations apply to the LM3668SD-3.3/NOPB in a 1-A application?
At 1-A load and 3.6-V input, the LM3668SD-3.3/NOPB dissipates ~350 mW. With RθJA = 47.3°C/W, junction temperature rise exceeds 16°C above ambient - well within the 125°C max rating. However, thermal performance depends critically on DAP soldering to SGND and adequate copper area; insufficient thermal relief may trigger 150°C thermal shutdown under sustained load.
Does the LM3668SD-3.3/NOPB require external compensation components?
No, the LM3668SD-3.3/NOPB uses internal compensation and requires no external RC networks. Its voltage-mode control loop is factory-tuned for stability with standard 2.2-µH inductors and 22-µF ceramic output capacitors. Adding external compensation risks instability; TI specifies only the mandatory input/output capacitors and inductor DCR limits in the datasheet's layout guidelines.
LM3668SD-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)
LM3668SD-3.3/NOPB FAQ
1.How can I place an order for LM3668SD-3.3/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3668SD-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 LM3668SD-3.3/NOPB reliable?
The price and inventory of LM3668SD-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 LM3668SD-3.3/NOPB is usually 5 days.
3.What payment methods are accepted for LM3668SD-3.3/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3668SD-3.3/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3668SD-3.3/NOPB?
LM3668SD-3.3/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3668SD-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 LM3668SD-3.3/NOPB?
For technical support, including LM3668SD-3.3/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3668SD-3.3/NOPB requirements.
6.How does Aetrix verify that LM3668SD-3.3/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3668SD-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 LM3668SD-3.3/NOPB meets industry standards.
7.What is the process for return or replacement of LM3668SD-3.3/NOPB?
All LM3668SD-3.3/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3668SD-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 LM3668SD-3.3/NOPB part is unused and in its original packaging.
Return procedure for LM3668SD-3.3/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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