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Texas Instruments LM3351MM/NOPB
- Part No.:
- LM3351MM/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LM3351MM/NOPB.pdf
- Description:
- IC REG CHRG PUMP INV 50MA 8VSSOP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LM3351MM/NOPB from Texas Instruments (formerly National Semiconductor) is a CMOS switched-capacitor voltage converter IC designed for bidirectional DC-DC conversion between 3.3V and 5V rails in portable systems. It delivers 3/2 step-up (3.3V→5V) or 2/3 step-down (5V→3.3V) conversion with 95% typical efficiency at 50 mA, 200 kHz switching frequency, and 250 nA shutdown current in Mini SO-8 package. It enables compact, inductorless power rail translation in battery-powered handheld instrumentation.
For engineers reviewing the LM3351MM/NOPB datasheet, LM3351MM/NOPB pinout, LM3351MM/NOPB application, or LM3351MM/NOPB equivalent, key selection considerations include its fixed-ratio charge-pump architecture, dual-mode operation without external inductors, low-quiescent-current shutdown, and compatibility with standard 1 µF ceramic capacitors for minimal BOM cost and EMI footprint.
Technical Context
The LM3351MM/NOPB implements a fixed-ratio charge-pump topology using an internal 1.6 MHz oscillator divided to 200 kHz for switch control. Its CMOS switch array operates in synchronized sequences to transfer energy via four external capacitors-two sampling (Cap1+, Cap1−, Cap2+, Cap2−) and two bulk (Cin, Cout)-enabling either step-up or step-down mode depending on Vlow/Vhigh terminal assignment.
It requires no inductor and avoids linear regulator losses, achieving >90% power conversion efficiency across load currents up to 50 mA. The device lacks short-circuit protection and relies on external Schottky diode D1 during step-up startup to bias Vhigh, while step-down operation needs no diode. Shutdown is controlled by active-high ENABLE pin with 1.7 V threshold.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Conversion Ratio | Fixed 3/2 (step-up) or 2/3 (step-down); enables precise 3.3V↔5V rail translation without feedback loop complexity. |
| Switching Frequency | 200 kHz (typical); allows use of small, low-cost 1 µF ceramic capacitors with minimal size and EMI impact. |
| Output Impedance | 4.2 Ω (step-up), 1.8 Ω (step-down); determines load regulation capability and voltage droop under 50 mA load. |
| Power Efficiency | 95% (typical at 50 mA); maximizes battery runtime in portable systems by minimizing conversion loss. |
| Shutdown Current | 250 nA (typical); extends system standby time significantly in low-power sleep modes. |
| Input Voltage Range | 2.5–3.65 V (step-up), 2.2–5.5 V (step-down); defines safe operating window for each mode without damage. |
| Enable Threshold | 1.7 V (typical); ensures reliable logic-level activation with standard 3.3V or 5V GPIO signals. |
Pinout & Package
LM3351MM/NOPB is housed in an 8-pin Mini SO (SOIC-8) package (NSC drawing MUA08A, package marking S05A), with exposed pad not electrically connected. Pin spacing is 0.050″ (1.27 mm), body width 3.9 mm, and total length 4.9 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - Cap1+ | Sampling capacitor positive terminal | Connects to + side of first flying capacitor; critical path for charge transfer timing and ripple control. |
| 2 - Cap1− | Sampling capacitor negative terminal | Connects to − side of first flying capacitor; forms half of charge-pump switching node pair. |
| 3 - Cap2+ | Sampling capacitor positive terminal | Connects to + side of second flying capacitor; completes dual-capacitor charge-reversal sequence. |
| 4 - Cap2− | Sampling capacitor negative terminal | Connects to − side of second flying capacitor; enables 3/2 or 2/3 voltage ratio synthesis. |
| 5 - Vlow | Mode-dependent rail terminal | In step-up: input (3.3V); in step-down: output (3.3V); must be decoupled with Cin/Cout per mode. |
| 6 - Gnd | Power and signal reference | Common ground return for all capacitors and enable logic; requires low-inductance layout connection. |
| 7 - Vhigh | Mode-dependent rail terminal | In step-down: input (5V); in step-up: output (5V); requires Schottky diode D1 for startup bias in step-up only. |
| 8 - Enable | Active-high logic control | CMOS-compatible input; tie to Vlow (step-up) or Vhigh (step-down) to enable; tie to GND to enter 250 nA shutdown. |
Key Features
| Feature | Design Value |
|---|---|
| Inductorless architecture | Eliminates magnetic components, reducing PCB area, cost, and radiated EMI in space-constrained portable designs. |
| Dual-mode fixed-ratio conversion | Supports both 3.3V-to-5V and 5V-to-3.3V translation using same IC and capacitor set-no redesign needed for rail direction change. |
| Low quiescent current | 1.1 mA (step-up) / 0.8 mA (step-down) operating IQ extends battery life in always-on subsystems. |
| High-efficiency charge pump | 95% typical efficiency at 50 mA load minimizes thermal rise and power waste compared to LDO-based solutions. |
| Mini SO-8 footprint | Standard 8-pin SOIC package enables drop-in replacement in existing layouts and compatibility with automated assembly. |
Applications
| Laptop Power Rail Translation | PCMCIA Card Voltage Adaptation |
|---|---|
Use Scenario: Dual-voltage logic interface between 3.3V host controller and 5V legacy peripherals in notebook expansion slots. IC Role / Device Role / Timing Role: Bidirectional DC-DC converter providing regulated 5V supply from 3.3V main rail or stepping down 5V bus to 3.3V I/O domain. Use Value: Enables interoperability without discrete regulators or level shifters, reducing component count and board area in tight clamshell form factors. |
Use Scenario: Voltage translation for PCMCIA Type II cards requiring simultaneous 3.3V and 5V operation within a single slot. IC Role / Device Role / Timing Role: On-card charge-pump converter generating local 3.3V or 5V rail from host-supplied voltage, eliminating need for dual-voltage connectors. Use Value: Simplifies card design and improves reliability by removing dependency on host-side dual-rail delivery and associated connector wear. |
| Handheld Instrumentation Power Management | Mixed-Voltage Embedded Controller Interface |
Use Scenario: Portable multimeter or data logger with mixed-signal ASIC (3.3V core) and analog front-end (5V ADC reference). IC Role / Device Role / Timing Role: Efficient, low-noise local voltage translator powering precision analog circuitry from battery-derived 3.3V domain. Use Value: Maintains high ADC accuracy by delivering clean, stable 5V reference without inductor-induced noise or LDO dropout limitations. |
Use Scenario: Microcontroller-based sensor node interfacing 3.3V MCU with 5V industrial sensors or actuators over UART/SPI. IC Role / Device Role / Timing Role: Rail translator supplying isolated 5V power to external peripherals while sharing ground with 3.3V logic domain. Use Value: Avoids level-shifter ICs and their propagation delay; provides full-rail power with minimal voltage drop and no timing skew. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switched-capacitor voltage converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX680ESA+ | Single-mode 5V-to-±10V dual-output charge pump; no step-down capability; higher 100 kHz fSW; ±10V outputs require different capacitor routing. | Designed for op-amp dual-supply generation-not for 3.3V/5V bidirectional rail translation. | Select when needing split supplies rather than unidirectional/bidirectional DC-DC conversion between 3.3V and 5V. |
| TPS60403DBVR | 3.3V-to-5V-only step-up charge pump; 2.5V–5.5V input range; 90% efficiency at 60 mA; 1.2 MHz fSW enables smaller 0.47 µF caps. | Unidirectional only; lacks 5V-to-3.3V step-down functionality; optimized for ultra-low-IQ portable apps. | Select when only step-up is required and minimum quiescent current (<1 µA shutdown) is critical over dual-mode flexibility. |
Compared with MAX680ESA+ and TPS60403DBVR, the LM3351MM/NOPB uniquely supports reversible 3.3V/5V conversion in one device with balanced step-up/step-down output impedances (4.2 Ω / 1.8 Ω), making it optimal for systems where rail direction may vary or coexist-without redesigning power architecture.
Availability
LM3351MM/NOPB is available at Aetrix Electronics and suitable for laptop computers, PCMCIA cards, and handheld instrumentation requiring stable component supply despite its obsolete status-supported via verified legacy inventory and traceable sourcing.
Supply support for LM3351MM/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 (TI) acquired National Semiconductor in 2011 and maintains legacy product support, quality assurance, and documentation for discontinued parts like the LM3351MM/NOPB.
The LM3351MM/NOPB belongs to TI's legacy switched-capacitor DC-DC converter family, engineered specifically for inductorless, low-EMI voltage translation in space- and power-constrained portable electronics.
FAQ
Is LM3351MM/NOPB still in production?
No, LM3351MM/NOPB was declared obsolete by National Semiconductor on September 22, 2011. However, Aetrix Electronics maintains verified legacy stock with full traceability and offers lifecycle coordination support-including cross-reference guidance and long-term supply planning-for ongoing production use.
What is the correct capacitor configuration for LM3351MM/NOPB step-up mode?
In step-up mode (3.3V → 5V), LM3351MM/NOPB requires four 1.0 µF ±20% X7R ceramic capacitors: two flying caps (C1, C2) connected to pins Cap1+/Cap1− and Cap2+/Cap2−, plus input bypass (Cin) between Vlow and GND, and output hold (Cout) between Vhigh and GND. An external Schottky diode (D1) must also connect Vin to Vhigh for startup bias.
Can LM3351MM/NOPB operate outside the 3.3V/5V conversion range?
Yes-LM3351MM/NOPB supports other ratios based on its fixed 3/2 or 2/3 architecture. For example, a 2.7V input yields ~4.05V output in step-up mode, and a 4.5V input yields ~3.0V in step-down mode-provided input stays within absolute max ratings (≤3.65V step-up, ≤5.5V step-down) and load current remains within capability.
Does LM3351MM/NOPB require special PCB layout considerations?
Yes-due to its 200 kHz switching frequency and high di/dt paths, LM3351MM/NOPB demands short, wide traces between pins Cap1+/Cap1−/Cap2+/Cap2− and their respective capacitors. Cin and Cout must be placed closest to Vlow/GND and Vhigh/GND, with a shared low-inductance ground plane. Layout Figure 3 in SNIS104B shows the recommended copper routing and component placement.
Is LM3351MM/NOPB protected against short circuits?
No-LM3351MM/NOPB has no internal short-circuit protection. If output is shorted, excessive current flows through external capacitors and internal switches, risking thermal damage. System-level protection (e.g., current-limiting resistor or fuse) must be added externally, especially in step-down mode where Vhigh is the input rail.
LM3351MM/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Ratiometric
- Output Configuration:
- Positive
- Topology:
- Charge Pump
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.5V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 3/2Vin, 2/3Vin
- Voltage - Output (Max):
- -
- Current - Output:
- 50mA
- Frequency - Switching:
- 200kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-VSSOP
LM3351MM/NOPB FAQ
1.How can I place an order for LM3351MM/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3351MM/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 LM3351MM/NOPB reliable?
The price and inventory of LM3351MM/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3351MM/NOPB is usually 5 days.
3.What payment methods are accepted for LM3351MM/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3351MM/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3351MM/NOPB?
LM3351MM/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3351MM/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 LM3351MM/NOPB?
For technical support, including LM3351MM/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3351MM/NOPB requirements.
6.How does Aetrix verify that LM3351MM/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3351MM/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 LM3351MM/NOPB meets industry standards.
7.What is the process for return or replacement of LM3351MM/NOPB?
All LM3351MM/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3351MM/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 LM3351MM/NOPB part is unused and in its original packaging.
Return procedure for LM3351MM/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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