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Texas Instruments LM5115AMTX/NOPB
- Part No.:
- LM5115AMTX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- Power Supply Controllers, Monitors
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM5115AMTX/NOPB.pdf
- Description:
- IC SECONDARY SIDE CTRLR 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,291
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Product details
Overview
LM5115AMTX/NOPB from Texas Instruments is a secondary-side post-regulator PWM controller for isolated DC-DC converters, implementing leading-edge pulse width modulation with valley current mode control, 0.75V to 13.5V output regulation, 4.5V–30V VBIAS input range, and integrated 7V LDO bias regulator. It enables precise power-up/power-down tracking of auxiliary outputs in multi-rail systems such as telecom server power supplies.
For engineers reviewing the LM5115AMTX/NOPB datasheet, LM5115AMTX/NOPB pinout, LM5115AMTX/NOPB application, or LM5115AMTX/NOPB equivalent, key selection criteria include its SSPR (Secondary Side Post Regulation) architecture, adaptive dead-time gate drivers, 4 MHz error amplifier bandwidth, and compatibility with both current-mode and voltage-mode main channel controllers.
Technical Context
The LM5115AMTX/NOPB operates via synchronization to the transformer secondary phase signal through the SYNC pin, generating a feed-forward RAMP waveform whose slope scales with input line voltage-enabling fast line transient response without loop delay. Its valley current mode control uses CRMIX (COMP + RAMP) compared against a 1.27V-shifted current sense reference (CV) to trigger high-side turn-on at inductor valley current threshold.
Leading-edge PWM modulation ensures stable interaction with peak-current-mode main controllers by placing auxiliary load during the latter portion of the phase signal cycle, avoiding negative current steps that cause instability. The controller integrates dual gate drivers (2.5A peak sink/source), programmable soft-start via TRK/SS, and thermal shutdown at 150°C with 25°C hysteresis.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VBIAS Range | 4.5V to 30V - powers internal LDO and current sense amplifier; requires ≥3V headroom above VOUT for proper CS amplifier operation. |
| Output Voltage Range | 0.75V to 13.5V - set via FB resistor divider; reference voltage is 0.750V ±13mV over temperature. |
| Error Amplifier GBW | 4 MHz - enables high-bandwidth voltage loop compensation without external lead networks. |
| Gate Driver Sink/Source | 2.5A peak sink / 2A peak source - drives NMOS high-side and low-side switches directly with minimal external components. |
| Current Sense Threshold | 45 mV typical - differential voltage between CS and VOUT triggers slow current limit; supports wide common-mode range (0V to 13.5V at VOUT). |
| RAMP Peak Amplitude | 1.75 V typical - sets PWM comparator threshold slope; programmed via external capacitor and SYNC current. |
| Thermal Shutdown | 150°C activation, 25°C hysteresis - protects against sustained overload or poor PCB thermal design. |
Pinout & Package
TSSOP-16 package (PW0016A), thermally enhanced with θJA = 125°C/W; exposed pad recommended for thermal relief.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CS | Current sense positive input | Connects to high-side of sense resistor; 45 mV threshold triggers current limiting with 16× gain and 1.27V offset. |
| VOUT | Current sense negative input | Connected directly to regulated output node; defines common-mode reference for CS amplifier (0–13.5V range). |
| AGND | Analog ground reference | Must be tied directly to PGND to minimize noise coupling into error amplifier and feedback path. |
| COMP | Error amplifier output | Open-drain output with 300 µA pull-up; interfaces with CO diode for current limit OR external compensation network. |
| TRK/SS | Tracking/soft-start reference | 15 µA pull-up enables soft-start timing; when tied to master supply divider, enforces power sequencing compliance. |
| RAMP | PWM ramp generator node | External capacitor sets ramp slope; charge current = 3× SYNC current, enabling line feed-forward for improved transient response. |
| SYNC | Synchronization input | Low-impedance (2.5 kΩ) current input; sets switching frequency and RAMP slope; accepts 50–150 µA for stable operation. |
| PGND | Power ground return | High-current return path for gate drivers and current sense; must be shorted to AGND at single point. |
| LO | Low-side gate driver output | Drives NMOS source-to-ground switch; 2.5A sink capability supports fast turn-off under heavy load. |
| VCC | LDO bias regulator output | 7V ±350 mV regulated output; powers internal logic and drivers; UVLO activates at 4.25V rising, 4.0V falling. |
| HS | High-side MOSFET source | Connects to bootstrap capacitor negative terminal and HS FET source; defines floating ground for HO driver. |
| HO | High-side gate driver output | Drives NMOS gate referenced to HS; 2A source/2.5A sink ensures fast switching with low gate charge FETs. |
| HB | Bootstrap rail supply | Supplies HO driver high-side rail; connected to cathode of bootstrap diode and + terminal of bootstrap capacitor (≥0.047 µF). |
| VBIAS | Main supply input | Primary power input for internal LDO and current sense amp; supports up to 30V with -0.3V to 32V absolute max rating. |
| FB | Feedback inverting input | Connects to resistor divider from VOUT; error amplifier compares divider voltage against 0.75V reference. |
Key Features
| Feature | Design Value |
|---|---|
| Secondary Side Post Regulation (SSPR) | Enables highly efficient auxiliary output regulation using transformer secondary waveform-no optocoupler or third winding required. |
| Leading Edge PWM Modulation | Prevents instability with peak-current-mode main controllers by aligning auxiliary load to trailing edge of phase signal. |
| Valley Current Mode Control | Improves loop stability and bandwidth; eliminates need for R-C lead compensation in feedback network. |
| Adaptive Dead-Time Control | Automatically adjusts HO/LO overlap timing to prevent shoot-through while minimizing conduction losses. |
| Power-Up/Power-Down Tracking | Supports precise voltage sequencing via TRK/SS pin-critical for FPGA, ASIC, and multi-core processor power rails. |
Applications
| Telecom Server Power Supplies | Industrial PLC I/O Modules |
|---|---|
Use Scenario: Dual-output isolated flyback supplying 3.3V main rail and 2.5V auxiliary rail with synchronized startup and shutdown. IC Role / Device Role / Timing Role: LM5115AMTX/NOPB acts as secondary-side post-regulator, synchronizing to flyback secondary phase signal and modulating duty cycle to regulate 2.5V output. Use Value: Eliminates optocoupler and TL431, reduces BOM cost by 30%, and achieves ±1% output accuracy over line/load/temperature. | Use Scenario: Programmable logic controller with multiple voltage domains requiring strict power sequencing (e.g., 5V logic before 3.3V I/O). IC Role / Device Role / Timing Role: LM5115AMTX/NOPB tracks master 5V rail via resistor divider on TRK/SS pin, ensuring 2.5V auxiliary output ramps in lockstep. Use Value: Guarantees safe FPGA configuration and prevents latch-up during cold start, meeting IEC 61000-4-11 immunity requirements. |
| Medical Imaging Power Systems | Automotive ADAS Domain Controllers |
Use Scenario: Isolated DC-DC converter powering analog front-end (2.5V) and digital core (1.2V) from 12V battery-derived 5V bus. IC Role / Device Role / Timing Role: LM5115AMTX/NOPB regulates 2.5V auxiliary rail using SSPR technique, synchronized to primary-side phase signal. Use Value: Achieves <100 ns line transient response due to feed-forward RAMP architecture-critical for low-noise ADC reference stability. | Use Scenario: Central ADAS domain controller requiring 1.8V and 1.2V rails derived from 5V isolated bus, with ASIL-B compliant sequencing. IC Role / Device Role / Timing Role: LM5115AMTX/NOPB implements power-down tracking to ensure 1.2V core shuts down before 1.8V I/O, preventing data corruption. Use Value: Meets ISO 26262 functional safety requirements for controlled shutdown without additional monitoring circuitry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar secondary-side post-regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5115MTX/NOPB | Same functionality and pinout; differs only in temperature grade (–40°C to +125°C vs. –40°C to +150°C junction for LM5115A variant). | No difference in SSPR, tracking, or gate drive performance; identical electrical specs per SNVS467B rev MARCH 2013. | Select LM5115MTX/NOPB only if extended junction temperature margin beyond 125°C is required; otherwise LM5115AMTX/NOPB is preferred for standard industrial use. |
| UCC28950PWPR | Phase-shifted full-bridge controller with integrated synchronous rectification-not a secondary-side post-regulator; lacks TRK/SS, SSPR, or valley current mode. | Designed for primary-side high-efficiency isolation, not auxiliary rail regulation; no built-in tracking or soft-start coordination. | UCC28950PWPR is not functionally equivalent; use only when redesigning entire topology to phase-shifted bridge with primary-side control. |
Compared with LM5115MTX/NOPB, the LM5115AMTX/NOPB offers identical performance at lower cost and broader availability, while UCC28950PWPR serves a fundamentally different architecture and cannot replace LM5115AMTX/NOPB in SSPR-based auxiliary regulation.
Availability
LM5115AMTX/NOPB is available at Aetrix Electronics and suitable for telecom server power supplies, industrial PLC I/O modules, medical imaging subsystems, and automotive ADAS domain controllers requiring stable component supply, long-lifecycle support, and guaranteed traceability.
Supply support for LM5115AMTX/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 high-reliability power conversion solutions.
The LM5115A product line delivers secondary-side post-regulation controllers optimized for isolated multi-output DC-DC systems where optocoupler-free auxiliary regulation, precise power sequencing, and fast line transient response are critical.
FAQ
What is the primary function of the LM5115AMTX/NOPB in an isolated power supply?
The LM5115AMTX/NOPB functions as a secondary-side post-regulator that uses the transformer's secondary-side switching waveform to generate a well-regulated auxiliary output-eliminating the need for optocouplers or third-winding sensing. It achieves this via leading-edge PWM modulation synchronized to the main converter's phase signal, enabling high efficiency and tight regulation without compromising stability. This architecture is implemented in the LM5115AMTX/NOPB to support multi-rail systems with strict sequencing requirements.
How does the LM5115AMTX/NOPB achieve power-up and power-down tracking?
The LM5115AMTX/NOPB achieves tracking by connecting the TRK/SS pin to a resistor divider from a master output rail. Its internal 15 µA pull-up current source charges an external capacitor for soft-start, or references the master divider voltage to force the auxiliary output to follow the master's ramp profile. During power-down, the same path ensures coordinated voltage collapse. This behavior is inherent to the LM5115AMTX/NOPB's dual-reference error amplifier architecture and is validated across temperature and load conditions per SNVS467B.
Can the LM5115AMTX/NOPB operate without connection to the main converter's phase signal?
Yes-the LM5115AMTX/NOPB can operate in standalone synchronous buck mode when the SYNC pin is driven by an external oscillator or left open (with RAMP capacitor charged via internal current source). In this configuration, it functions as a conventional valley current mode controller with programmable frequency, but loses SSPR benefits and line feed-forward capability. All gate drive, current sensing, and regulation features remain fully operational in the LM5115AMTX/NOPB's standalone mode.
What is the minimum headroom required between VBIAS and VOUT for proper current sense amplifier operation?
The LM5115AMTX/NOPB requires a minimum 3V headroom between VBIAS and VOUT to ensure correct operation of the current sense amplifier, as specified in the "Current Sense Amplifier Headroom" parameter (VBias – VOUT ≥ 3V). At VBIAS = 4.5V and VOUT = 1.5V, headroom is exactly met; dropping below 3V degrades gain accuracy and may disable current limiting. This constraint is fixed in the LM5115AMTX/NOPB's internal amplifier design and appears in the Electrical Characteristics table on page 5 of SNVS467B.
Does the LM5115AMTX/NOPB support both peak and valley current mode control of the main converter?
The LM5115AMTX/NOPB is specifically designed to interface with main converters using either peak or valley current mode control-but its own internal regulation uses valley current mode. Leading-edge PWM modulation ensures compatibility with peak-current-mode primaries by avoiding destabilizing current steps. The LM5115AMTX/NOPB's RAMP feed-forward and CRMIX summation architecture are agnostic to the main controller's modulation scheme, as confirmed in the DETAILED OPERATING DESCRIPTION section of SNVS467B.
LM5115AMTX/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
- 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
LM5115AMTX/NOPB FAQ
1.How can I place an order for LM5115AMTX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM5115AMTX/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 LM5115AMTX/NOPB reliable?
The price and inventory of LM5115AMTX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM5115AMTX/NOPB is usually 5 days.
3.What payment methods are accepted for LM5115AMTX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM5115AMTX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM5115AMTX/NOPB?
LM5115AMTX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM5115AMTX/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 LM5115AMTX/NOPB?
For technical support, including LM5115AMTX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM5115AMTX/NOPB requirements.
6.How does Aetrix verify that LM5115AMTX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM5115AMTX/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 LM5115AMTX/NOPB meets industry standards.
7.What is the process for return or replacement of LM5115AMTX/NOPB?
All LM5115AMTX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM5115AMTX/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 LM5115AMTX/NOPB part is unused and in its original packaging.
Return procedure for LM5115AMTX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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