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Texas Instruments LM2651MTCX-ADJ/NOPB
- Part No.:
- LM2651MTCX-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM2651MTCX-ADJ/NOPB.pdf
- Description:
- IC REG BUCK ADJ 1.5A 16TSSOP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LM2651MTCX-ADJ/NOPB from Texas Instruments is a 1.5-A synchronous step-down DC-DC switching regulator in a 16-pin TSSOP package, featuring adjustable output voltage (via external resistor divider), 300-kHz fixed-frequency current-mode PWM control, and automatic hysteretic mode transition at light loads to maintain ≥80% efficiency down to 15 mA. It integrates high- and low-side MOSFETs with 75-mΩ typical RDS(on), patented internal current sensing (no external sense resistor), and 7-µA shutdown current - designed for battery-powered portable electronics requiring long runtime in both active and standby states.
For engineers reviewing the LM2651MTCX-ADJ/NOPB datasheet, LM2651MTCX-ADJ/NOPB pinout, LM2651MTCX-ADJ/NOPB application, or LM2651MTCX-ADJ/NOPB equivalent, key selection considerations include its ADJ-output configuration (VFB = 1.238 V), 4–14-V input range, thermal shutdown at 165°C, soft-start programmability via capacitor on SD(SS), and compatibility with Schottky diode-assisted layout for improved noise immunity and efficiency above 5 V input.
Technical Context
The LM2651MTCX-ADJ/NOPB operates in constant-frequency (300 kHz) current-mode PWM under moderate-to-heavy loads (>100 mA), using internal MOSFET current sensing to eliminate external sense resistors and improve noise immunity. Its error amplifier transconductance is 1250 µmho, and it features feed-forward input voltage compensation to stabilize current limit across the 4–14-V input range.
Under light loads (<100 mA), it automatically transitions to low-power hysteretic mode, reducing switching frequency to sustain >80% efficiency at 15 mA. The device includes integrated bootstrap regulation (6.7 V typical), undervoltage lockout (3.85 V rising threshold with 210-mV hysteresis), and cycle-by-cycle current limiting (2 A typical).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Adjustable via external resistor divider; feedback reference = 1.238 V ±2.5% - enables precise custom output setting (e.g., 1.8 V to 5 V) without changing IC. |
| Input Voltage Range | 4 V to 14 V - supports single-cell Li-ion (4.2 V max) up to 12-V industrial rails, with UVLO activation at 3.85 V to prevent unstable operation. |
| Switching Frequency | 300 kHz ±10% - enables use of compact, low-profile inductors (e.g., 4.7–10 µH) and reduces EMI compared to lower-frequency alternatives. |
| Max Output Current | 1.5 A continuous - sufficient for powering core logic, memory, or I/O subsystems in PDAs, scanners, and peripherals. |
| Efficiency | Up to 97% at mid-load; ≥80% at 15 mA - achieved via synchronous rectification and automatic hysteretic mode, extending battery life in sleep/standby modes. |
| Shutdown Current | 7 µA typical - reduces system quiescent power during off-state, critical for always-on or low-power wake-up applications. |
| Thermal Shutdown | 165°C with 25°C hysteresis - protects against sustained overload or poor PCB thermal design without requiring external thermal monitoring. |
Pinout & Package
LM2651MTCX-ADJ/NOPB is housed in a 16-pin TSSOP package (5.00 mm × 4.40 mm body size, 0.65-mm pitch), optimized for compact portable designs and compatible with standard surface-mount assembly processes.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2 - SW | Switched-node output | Connection to source of internal high-side MOSFET and drain of low-side MOSFET; carries high dv/dt switching waveform - requires tight layout with PGND and minimal trace inductance. |
| 3–5 - VIN | Main power input | Distributes 4–14-V input to internal power stages; must be decoupled with low-ESR ceramic + bulk capacitor near pins to suppress RMS current spikes. |
| 6 - VCB | Bootstrap capacitor node | Supplies gate drive voltage for high-side MOSFET; requires 0.1-µF ceramic capacitor between VCB and SW to sustain 6.7-V bootstrap rail during high-duty-cycle operation. |
| 7 - SD(SS) | Shutdown / soft-start control | Pulling below 0.3 V disables regulator (7-µA IQ); capacitor to GND sets soft-start ramp - prevents inrush current and enables power sequencing. |
| 9 - FB | Voltage feedback input | Senses output via resistor divider; 1.238-V reference enables precise ADJ-output configuration - trace must be short, noise-shielded, and routed away from SW/PGND. |
| 10 - COMP | Error amplifier compensation | Connects external RC/C network to stabilize loop response; typical values: 15 kΩ + 2.2 nF for COUT > 68 µF - critical for transient stability and phase margin >45°. |
| 11 - NC | No internal connection | Unbonded pad; must remain unconnected and unpopulated on PCB - no routing or copper fill allowed. |
| 12, 13 - AGND | Analog ground reference | Low-noise return for FB, COMP, and internal control circuitry - must be isolated from PGND and connected at single point near IC to avoid noise coupling. |
| 14–16 - PGND | Power ground return | High-current return path for VIN, SW, and internal MOSFETs - requires wide copper pour and direct connection to input/output capacitors' ground pads. |
Key Features
| Feature | Design Value |
|---|---|
| Patented internal current sensing | Eliminates external sense resistor - reduces BOM cost, PCB area, and noise susceptibility while enabling accurate cycle-by-cycle current limiting (2 A typical). |
| Automatic PWM-to-hysteretic mode transition | Maintains ≥80% efficiency at 15 mA load without manual mode control - extends battery life in intermittent-use devices like handheld scanners and PDAs. |
| Integrated high- and low-side MOSFETs | 75-mΩ typical RDS(on) (high-side) enables high efficiency without external switches - simplifies design and improves thermal performance over discrete solutions. |
| Adjustable soft-start | Programmable via capacitor on SD(SS) pin - controls inrush current and enables reliable power-up sequencing in multi-rail systems. |
| Input undervoltage lockout with hysteresis | 3.85-V turn-on threshold + 210-mV hysteresis prevents brownout oscillation during weak battery or supply sag - ensures clean start/stop behavior. |
Applications
| Personal Digital Assistants (PDAs) | Computer Peripherals |
|---|---|
|
Use Scenario: Powering ARM-based application processors and LPDDR memory in handheld PDA platforms with single-cell Li-ion battery (3.0–4.2 V). IC Role / Device Role / Timing Role: Primary synchronous buck regulator delivering stable 1.2-V core and 3.3-V I/O rails; manages dynamic load steps during UI rendering and wireless communication bursts. Use Value: 97% peak efficiency and 7-µA shutdown current extend usable battery life by >30% versus non-synchronous alternatives; ADJ output allows precise voltage tuning per SoC requirements. |
Use Scenario: Supplying 5-V USB-powered peripherals (keyboards, mice, card readers) from variable wall-adapter inputs (5–12 V). IC Role / Device Role / Timing Role: High-efficiency 5-V conversion stage replacing linear regulators; handles 10-mA standby to 1.5-A active load transitions without thermal derating. Use Value: 300-kHz fixed frequency enables small 4.7-µH inductor and 22-µF ceramic output cap - reduces solution size by 40% vs 500-kHz+ competitors while maintaining <20-mV ripple. |
| Battery-Powered Devices | Handheld Scanners |
|
Use Scenario: Providing regulated 3.3-V rail for microcontroller, display, and sensor interface in portable medical monitors and asset trackers. IC Role / Device Role / Timing Role: Main power converter operating across full battery discharge curve (4.2 V → 3.0 V), maintaining regulation until UVLO triggers. Use Value: Hysteretic light-load mode sustains >85% efficiency at 20 mA - doubles operational time in low-duty-cycle logging modes versus fixed-frequency-only regulators. |
Use Scenario: Powering CMOS image sensor, laser driver, and Bluetooth radio in barcode scanners powered by rechargeable NiMH packs (4.8–6.0 V). IC Role / Device Role / Timing Role: Single-chip 3.3-V supply supporting rapid on/off cycling during scan events; soft-start prevents voltage droop during cold startup. Use Value: Integrated MOSFETs and internal current sensing reduce component count to just 5 passives - accelerates design validation and lowers assembly cost by $0.18/unit. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS5430DDAR | 3-A rating, 500-kHz switching, external compensation; no integrated bootstrap diode - requires external FET gate drive support. | Higher current capability suits motor drivers or FPGA cores; less suitable for ultra-low-IQ battery standby due to 17-µA shutdown current. | Select when >1.5-A output or higher-frequency operation is required; verify layout supports faster edge rates and added compensation complexity. |
| LM2678SD-ADJ/NOPB | 2.5-A rating, 260-kHz frequency, similar ADJ topology but larger SO-8 package; lacks automatic hysteretic mode - fixed PWM only. | Better thermal margin for continuous 2-A loads; efficiency drops to ~72% at 15 mA, limiting battery life in intermittent-use devices. | Prefer for thermally constrained 24/7 industrial applications where light-load efficiency is secondary to peak current delivery. |
Compared with TPS5430DDAR and LM2678SD-ADJ/NOPB, the LM2651MTCX-ADJ/NOPB delivers superior light-load efficiency and smaller footprint for portable applications, while trading off peak current and maximum switching frequency - making it optimal for cost-sensitive, battery-life-critical designs below 1.5 A.
Availability
LM2651MTCX-ADJ/NOPB is available at Aetrix Electronics and suitable for personal digital assistants (PDAs), computer peripherals, and battery-powered handheld scanners requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for LM2651MTCX-ADJ/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 technologies, with decades of expertise in high-efficiency DC-DC conversion for portable and industrial applications.
The LM2651 product line was engineered specifically for battery-powered portable electronics demanding ultrahigh efficiency across wide load ranges - emphasizing integration, low quiescent current, and robust protection features without external complexity.
FAQ
What is the feedback reference voltage for LM2651MTCX-ADJ/NOPB?
The LM2651MTCX-ADJ/NOPB has a precision feedback reference voltage of 1.238 V ±2.5%, measured at the FB pin under nominal conditions. This value is used in the resistor-divider equation VOUT = 1.238 × (1 + R1/R2) to set the output voltage. The LM2651MTCX-ADJ/NOPB maintains this reference across temperature and load, enabling stable ADJ-output regulation from 1.8 V to 5 V with appropriate resistor selection.
Does LM2651MTCX-ADJ/NOPB require an external Schottky diode?
Yes - TI recommends an external Schottky diode (D1) connected from SW to PGND to prevent conduction through the intrinsic body diode of the low-side MOSFET during dead time. Without D1, reverse-recovery current and higher forward voltage degrade efficiency by 1–2%, especially at higher input voltages and loads. The LM2651MTCX-ADJ/NOPB's layout guidelines specify placing D1 close to SW and PGND pins to minimize parasitic inductance.
What is the maximum duty cycle of LM2651MTCX-ADJ/NOPB?
The LM2651MTCX-ADJ/NOPB supports a maximum duty cycle of 92% at VIN = 4 V, enabling operation down to output voltages as low as ~0.37 V (4 V × 0.092). This high duty cycle allows the LM2651MTCX-ADJ/NOPB to regulate efficiently even with small input-to-output differentials, such as generating 3.3 V from a 4-V minimum battery voltage - critical for maintaining functionality late in battery discharge.
How does the soft-start function work on LM2651MTCX-ADJ/NOPB?
The LM2651MTCX-ADJ/NOPB implements soft-start via an internal current source charging an external capacitor on the SD(SS) pin. At power-up, a 11-µA current charges the capacitor until the pin reaches 0.6 V (shutdown threshold), then increases to ~10 µA to ramp the current limit and duty cycle gradually. This controlled ramp prevents inrush current and output overshoot. The LM2651MTCX-ADJ/NOPB enters full regulation only after the SD(SS) voltage exceeds ~1.3 V.
What thermal protection features does LM2651MTCX-ADJ/NOPB include?
The LM2651MTCX-ADJ/NOPB incorporates thermal shutdown at 165°C with 25°C hysteresis, plus cycle-by-cycle current limiting (2 A typical) and input undervoltage lockout (3.85 V rising threshold). These protections operate independently and do not require external components. When thermal shutdown activates, the LM2651MTCX-ADJ/NOPB halts switching and resumes only after junction temperature falls below 140°C - preventing permanent damage during sustained overload or inadequate heatsinking.
LM2651MTCX-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4V
- Voltage - Input (Max):
- 14V
- Voltage - Output (Min/Fixed):
- 1.238V
- Voltage - Output (Max):
- 13V
- Current - Output:
- 1.5A
- Frequency - Switching:
- 300kHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
LM2651MTCX-ADJ/NOPB FAQ
1.How can I place an order for LM2651MTCX-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2651MTCX-ADJ/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 LM2651MTCX-ADJ/NOPB reliable?
The price and inventory of LM2651MTCX-ADJ/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2651MTCX-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LM2651MTCX-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2651MTCX-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2651MTCX-ADJ/NOPB?
LM2651MTCX-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2651MTCX-ADJ/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 LM2651MTCX-ADJ/NOPB?
For technical support, including LM2651MTCX-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2651MTCX-ADJ/NOPB requirements.
6.How does Aetrix verify that LM2651MTCX-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LM2651MTCX-ADJ/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 LM2651MTCX-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LM2651MTCX-ADJ/NOPB?
All LM2651MTCX-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM2651MTCX-ADJ/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 LM2651MTCX-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LM2651MTCX-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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