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Texas Instruments LM5115MTC/NOPB
- Part No.:
- LM5115MTC/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Power Supply Controllers, Monitors
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM5115MTC/NOPB.pdf
- Description:
- IC SECONDARY SIDE CTRLR 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:256
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Product details
Overview
LM5115MTC/NOPB from Texas Instruments is a secondary-side post-regulator and synchronous buck controller for isolated multi-output DC/DC converters. It implements leading-edge PWM control, supports 0.75V–13.5V output regulation, delivers 2.5A peak gate drive, and operates with VBIAS input from 4.5V to 30V in applications such as telecom power supplies and industrial isolated adapters.
For engineers reviewing the LM5115MTC/NOPB datasheet, LM5115MTC/NOPB pinout, LM5115MTC/NOPB application, or LM5115MTC/NOPB equivalent, key selection considerations include its SSPR capability, adaptive dead-time control, voltage-mode control with current injection, wide common-mode current sense range (0V–13.5V), and thermal shutdown at 150°C.
Technical Context
The LM5115MTC/NOPB uses leading-edge pulse width modulation synchronized to an external phase signal, enabling stable auxiliary regulation without destabilizing peak-current-mode main controllers. Its RAMP generator charges with 3× SYNC current and discharges via internal MOSFET, supporting line feed-forward through amplitude-proportional ramp slope adjustment.
Voltage-mode control is enhanced by current injection: the CS–VOUT sense amplifier (gain = 16 V/V, offset = 1.27V) produces a CV reference that modulates the PWM threshold in real time. The error amplifier features 4MHz GBW, 60dB open-loop gain, and 300µA COMP pull-up current - enabling fast transient response without external lead networks.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBIAS Range | 4.5V to 30V - powers internal LDO and current sense amplifier; enables direct bias from wide-input isolated rails. |
| Output Voltage Range | 0.75V to 13.5V - set via FB resistor divider; reference voltage is 0.75V ±13mV over temperature. |
| Gate Drive Capability | 2.5A sink / 2A source per driver - drives high- and low-side NMOS in synchronous buck stage with minimal external components. |
| Current Sense Threshold | 45mV (typical) - triggers current limiting when differential voltage across sense resistor exceeds this value. |
| Error Amplifier GBW | 4MHz - enables high-bandwidth loop compensation without external lead network, improving load transient response. |
| Thermal Shutdown | 150°C ±15°C - protects device during overload or poor heatsinking; hysteresis of 25°C prevents oscillation near trip point. |
| RAMP Amplitude | 1.0V to 1.75V - programmable via external capacitor; sets PWM timing resolution and noise immunity. |
Pinout & Package
TSSOP-16 package (PW0016A) with exposed pad for thermal performance; pin-compatible with WSON-16 (NHQ0016A) variant but requires separate layout verification.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CS | Current sense positive input | Connects to high side of sense resistor; senses inductor current with 16× gain and 1.27V offset. |
| VOUT | Current sense negative input | Connects to output node; defines common-mode range (0V–13.5V) for accurate current measurement. |
| AGND | Analog ground reference | Must be tied directly to PGND to minimize noise coupling into error amplifier and feedback path. |
| CO | Current limit output | Open-drain output; connected to COMP to assert current limit by pulling down PWM threshold. |
| COMP | Error amplifier output | 300µA internal pull-up; interfaces with R-C compensation network and CO for combined voltage/current loop control. |
| FB | Feedback input | Inverting input of error amp; referenced to SS pin (0.75V); sets output voltage via resistor divider. |
| SS | Soft-start control | Charged by internal 60kΩ divider; controls startup slew rate and prevents inrush current in downstream loads. |
| RAMP | PWM ramp generator node | External capacitor sets ramp slope; charge current scales with SYNC input, enabling line feed-forward. |
| SYNC | Synchronization input | Low-impedance (2.5kΩ) current input; accepts square-wave phase signal to lock switching frequency to main converter. |
| PGND | Power ground return | High-current return path for LO, HO, and bootstrap circuitry; must be low-inductance connection to AGND. |
| LO | Low-side gate driver output | Drives gate of low-side NMOS; 2.5A sink capability ensures fast turn-off and reduced conduction loss. |
| VCC | LDO bias regulator output | 7V ±350mV regulated supply; powers internal logic and drivers; bypass with 0.1–10µF ceramic capacitor. |
| HS | High-side source reference | Connects to source of high-side NMOS and bootstrap capacitor negative terminal; defines floating ground for HO. |
| HO | High-side gate driver output | Drives gate of high-side NMOS; 2.5A sink ensures robust turn-off under Miller plateau conditions. |
| HB | Bootstrap rail supply | Supplies gate drive voltage above HS; requires 0.047µF ceramic capacitor placed adjacent to HB and HS pins. |
| VBIAS | Bias supply input | Main power input for internal LDO; UVLO activates at 4.5V rising; supports operation up to 30V. |
Key Features
| Feature | Design Value |
|---|---|
| Secondary Side Post Regulation (SSPR) | Enables precise auxiliary output regulation using main converter's phase signal - eliminates need for optocoupler or third winding. |
| Leading Edge PWM Modulation | Prevents instability in peak-current-mode main converters by shifting auxiliary load current to latter portion of phase pulse. |
| Voltage-Mode Control with Current Injection | Eliminates external lead network in feedback loop - simplifies compensation while maintaining >4MHz loop bandwidth. |
| Adaptive Dead-Time Control | Automatically adjusts HO/LO overlap timing to prevent shoot-through, independent of MOSFET gate charge variations. |
| Wide Common-Mode Current Sense | Operates from 0V to 13.5V at VOUT pin - supports buck configurations with ground-referenced outputs or high-side sensing. |
| Programmable Soft-Start | SS pin controlled by external capacitor; start-up time defined by τ = 60kΩ × CSS - ensures monotonic output rise without overshoot. |
Applications
| Telecom Power Supply | Industrial Isolated Adapter |
|---|---|
Use Scenario: Dual-output isolated flyback supplying 3.3V main and 2.5V auxiliary rails for base station control logic and monitoring circuits. IC Role / Device Role / Timing Role: LM5115MTC/NOPB acts as secondary-side synchronous buck controller, regulating 2.5V rail using transformer phase signal as clock and feedback reference. Use Value: Achieves <96% efficiency at full load with no optocoupler, reducing BOM cost and improving long-term reliability versus traditional TL431+opto solutions. | Use Scenario: 24V input industrial power module delivering 5V/3A and 12V/1A outputs, where auxiliary rail powers isolated CAN transceivers and sensor interfaces. IC Role / Device Role / Timing Role: LM5115MTC/NOPB serves as standalone synchronous buck controller for 12V rail, driven by DC input via free-run mode (SYNC current sourced internally). Use Value: Enables single-chip auxiliary regulation with 4.5V–30V VBIAS support, eliminating need for discrete LDO or additional switching controller. |
| Server PSU Auxiliary Rail | Medical Imaging Power System |
Use Scenario: High-efficiency server PSU with primary LLC resonant converter and multiple secondary-side regulated rails including +1.8V DDR memory supply. IC Role / Device Role / Timing Role: LM5115MTC/NOPB implements SSPR on +1.8V rail, synchronizing to main converter phase signal and using current injection for tight transient response. Use Value: Delivers ±1% output regulation across line/load/temperature with 10µs load-step recovery - critical for memory stability during burst access. | Use Scenario: Isolated imaging subsystem requiring tightly regulated ±5V analog supplies and 3.3V digital logic, with strict EMI and safety compliance. IC Role / Device Role / Timing Role: LM5115MTC/NOPB regulates +5V rail in synchronous buck configuration, leveraging its 0.75V precision reference and 4MHz error amplifier for low-noise performance. Use Value: Meets IEC 60601 ripple requirements (<10mVpp) without additional post-filtering due to high PSRR and adaptive dead-time control. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5117MTC/NOPB | Higher VBIAS max (75V vs. 30V); integrated bootstrap diode; no SSPR mode. | Designed for standalone high-input-voltage buck converters, not secondary-side regulation. | Select when input exceeds 30V or bootstrap diode integration reduces board area. |
| UCC28911DR | Primary-side flyback controller with integrated HV start-up; no secondary-side regulation capability. | Replaces entire isolated converter topology - not a drop-in replacement for LM5115MTC/NOPB's SSPR function. | Choose only when redesigning from secondary-side to primary-side regulation architecture. |
Compared with LM5115MTC/NOPB, LM5117MTC/NOPB offers higher input voltage tolerance but lacks SSPR synchronization, while UCC28911DR eliminates the need for secondary regulation entirely but requires full topology re-engineering and forfeits the precision and efficiency benefits of synchronous rectification.
Availability
LM5115MTC/NOPB is available at Aetrix Electronics and suitable for telecom power supplies, industrial isolated adapters, server PSU auxiliary rails, and medical imaging power systems requiring stable component supply and long-lifecycle support.
Supply support for LM5115MTC/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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and communications markets.
The LM5115MTC/NOPB belongs to TI's high-performance power controller product line, designed specifically for efficient, isolated multi-output DC/DC conversion with emphasis on secondary-side regulation accuracy and system-level reliability.
FAQ
What is the primary function of the LM5115MTC/NOPB in a power supply design?
The LM5115MTC/NOPB functions as a secondary-side post-regulator and synchronous buck controller. It enables precise regulation of auxiliary output rails using the phase signal from an isolated main converter - eliminating optocouplers and third windings. In standalone mode, it operates as a voltage-mode synchronous buck controller with current injection, supporting inputs from 4.5V to 30V and outputs from 0.75V to 13.5V. Its design centers on stability, efficiency, and integration for multi-rail isolated systems.
How does the LM5115MTC/NOPB achieve line feed-forward without external components?
The LM5115MTC/NOPB achieves line feed-forward through its SYNC and RAMP pins: the SYNC pin accepts a square-wave phase signal whose amplitude varies with main converter input voltage, and the internal current mirror generates a RAMP charge current proportional to SYNC current. This causes the RAMP slope to scale with input line changes, automatically adjusting PWM duty cycle to maintain auxiliary output regulation - all without external op-amps or feed-forward networks.
Can the LM5115MTC/NOPB be used without an external phase signal?
Yes, the LM5115MTC/NOPB supports free-run mode when no external phase signal is present. In this configuration, a DC current applied to the SYNC pin sets the internal oscillator frequency, allowing the device to operate as a standalone synchronous buck controller. The RAMP capacitor still determines timing, and the controller maintains full functionality including soft-start, current limiting, and adaptive dead-time control - making LM5115MTC/NOPB viable for non-isolated or DC-input applications.
What is the role of the CO pin in the LM5115MTC/NOPB current protection scheme?
The CO pin in the LM5115MTC/NOPB is the open-drain output of the current limit amplifier. During overcurrent events, when the CS–VOUT differential exceeds 45mV, the current limit amplifier pulls the CO pin low. Since CO is typically connected to COMP, this action forces the COMP voltage downward, reducing the CRMIX signal below the CV threshold and inhibiting PWM pulses until fault clearance. This provides cycle-by-cycle current limiting with foldback behavior at low VOUT, protecting both the LM5115MTC/NOPB and external power stages.
Why does the LM5115MTC/NOPB use leading-edge PWM instead of trailing-edge modulation?
The LM5115MTC/NOPB uses leading-edge PWM to avoid instability when regulating auxiliary outputs in systems with peak-current-mode main controllers. Trailing-edge modulation would draw auxiliary load current early in the main converter's phase pulse, causing a non-monotonic negative step in transformer current that disrupts current-sense slope compensation. Leading-edge modulation shifts the auxiliary load to the latter portion of the pulse, producing a benign positive current step that the main controller can accommodate - ensuring stable, jitter-free operation across all line/load conditions.
LM5115MTC/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Programmable:
- Not Verified
- Applications:
- Secondary-Side Controller
- Voltage - Input:
- 5V ~ 30V
- Voltage - Supply:
- 5V ~ 7.5V
- Current - Supply:
- 4 mA
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
LM5115MTC/NOPB FAQ
1.How can I place an order for LM5115MTC/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM5115MTC/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 LM5115MTC/NOPB reliable?
The price and inventory of LM5115MTC/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM5115MTC/NOPB is usually 5 days.
3.What payment methods are accepted for LM5115MTC/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM5115MTC/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM5115MTC/NOPB?
LM5115MTC/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM5115MTC/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 LM5115MTC/NOPB?
For technical support, including LM5115MTC/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM5115MTC/NOPB requirements.
6.How does Aetrix verify that LM5115MTC/NOPB is sourced from the original manufacturer or authorized distributors?
All LM5115MTC/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 LM5115MTC/NOPB meets industry standards.
7.What is the process for return or replacement of LM5115MTC/NOPB?
All LM5115MTC/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM5115MTC/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 LM5115MTC/NOPB part is unused and in its original packaging.
Return procedure for LM5115MTC/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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