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Texas Instruments LM2578AM
- Part No.:
- LM2578AM
- Manufacturer:
- Texas Instruments
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM2578AM.pdf
- Description:
- IC REG BUCK BOOST 750MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,386
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Product details
Overview
LM2578AM from Texas Instruments is a monolithic switching regulator controller IC designed for buck, boost, and inverting DC-DC conversion topologies. It integrates a 1.0V reference comparator with separate inverting/non-inverting inputs, a programmable oscillator (up to 100 kHz), and a 750 mA NPN output transistor with <0.9V collector saturation voltage. It operates from 2V to 40V input and supports duty cycles up to 90%, enabling compact, efficient power supplies in industrial and embedded systems.
For engineers reviewing the LM2578AM datasheet, LM2578AM pinout, LM2578AM application, or LM2578AM equivalent, key selection considerations include its dual-reference comparator architecture, ground- or VIN-referenced current limit sensing, thermal shutdown, and compatibility with external PNP/NPN boost transistors for higher output current - all critical for robust, layout-efficient switching regulator design.
Technical Context
The LM2578AM implements a pulse-width modulation (PWM) control architecture where an internal 1.0V reference is applied to both comparator inputs, enabling flexible feedback polarity without external op-amps. Its oscillator frequency is set by a single external capacitor (fOSC = 8×10−5/CT) and includes blanking to enforce ≤90% max duty cycle.
Current limiting operates cycle-by-cycle via a 110 mV sense threshold referenced either to ground or VIN, while the output stage uses an NPN transistor with separate collector and emitter terminals - requiring careful attention to emitter swing limits (≤−1V at TJ < 100°C) to avoid unintended turn-on.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2V to 40V - supports wide-input industrial and automotive battery-supplied systems without pre-regulation. |
| Output Current Capability | 750 mA pulsed - sufficient for medium-power converters; external transistor support enables >1 A designs. |
| Reference Voltage | 1.0 V ±1% - stable internal reference eliminates need for external voltage reference in feedback networks. |
| Oscillator Frequency Range | Up to 100 kHz - adjustable via single timing capacitor; enables optimization of size (inductor/capacitor) vs EMI performance. |
| Current Limit Threshold | 110 mV - precise, temperature-stable sense voltage allows accurate overcurrent protection with minimal sense resistor power loss. |
| Max Duty Cycle | 90% - enables high step-down ratios in buck configurations and supports wide VIN-to-VOUT ranges. |
| Operating Temperature | −40°C to +85°C ambient - qualified for industrial-grade operation without derating below 95°C/W junction-to-ambient. |
Pinout & Package
LM2578AM is available in 8-pin PDIP (package number P0008E) and SOIC (D0008A) packages. Both variants share identical pinout and thermal characteristics.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - Feedback (Inverting Input) | Comparator inverting input with internal 1.0V reference | Accepts regulated output voltage feedback; enables direct connection to resistive divider without level-shifting circuitry. |
| 2 - Ground | Circuit common reference | Return path for internal logic, reference, and current limit circuits; must be low-impedance for stability. |
| 3 - Current Limit | Current sense input referenced to ground or VIN | Detects overcurrent via external sense resistor; 110 mV threshold enables low-loss, high-accuracy protection. |
| 4 - Non-Inverting Input | Comparator non-inverting input with internal 1.0V reference | Supports alternative feedback configurations (e.g., inverting regulators) without external op-amp inversion. |
| 5 - Timing Capacitor | Oscillator timing node | Connects external capacitor to set switching frequency; value directly determines fOSC per f = 8×10−5/CT. |
| 6 - Emitter | NPN transistor emitter terminal | Provides low-side switch node; emitter voltage must not exceed −1V below ground (−0.6V above 100°C junction). |
| 7 - Collector | NPN transistor collector terminal | High-current switching node; supports up to 750 mA pulsed load with <0.9V saturation drop at full current. |
| 8 - VIN | Power supply input | Supplies internal circuitry and drives collector output; accepts 2V–40V, with absolute max 50V. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-reference comparator inputs | Separate inverting and non-inverting pins each with internal 1.0V reference - eliminates external op-amp in inverting regulator designs. |
| Configurable current limit reference | 110 mV sense threshold selectable to ground or VIN - simplifies overcurrent protection in buck, boost, and inverting topologies. |
| Thermal shutdown & current limit | Integrated protection activates at 150°C junction temp and on cycle-by-cycle overcurrent - prevents device destruction under fault conditions. |
| External duty cycle adjustment | Resistor network on pin 1/4 enables manual or remote duty cycle tuning from 0% to 90% - supports analog dimming or variable-speed control. |
| Under-voltage lockout (UVLO) | Automatic disable below ~2V input - prevents erratic operation during brownout or startup, improving system reliability. |
Applications
| Industrial Power Supply | Automotive Lighting Control |
|---|---|
Use Scenario: 24V truck battery powering isolated 5V logic rails for CAN nodes and sensors. IC Role / Device Role / Timing Role: Buck regulator controller driving external MOSFET/PNP to deliver 1.5A at 5V with tight line/load regulation. Use Value: Dual-reference comparator simplifies feedback loop design across wide input range; UVLO ensures clean startup during cranking. | Use Scenario: PWM-controlled LED headlamp driver with adjustable brightness and short-circuit protection. IC Role / Device Role / Timing Role: Boost controller regulating 12V–16V automotive supply to constant-current LED string at 36V. Use Value: Ground-referenced current limit enables accurate LED current sensing; 90% max duty cycle supports high step-up ratios. |
| Portable Instrumentation Power | Inverting Polarity Converter |
Use Scenario: Battery-powered oscilloscope requiring clean ±12V analog rails from single 9V alkaline pack. IC Role / Device Role / Timing Role: Inverting regulator controller generating −15V at 300mA with low ripple and high efficiency. Use Value: Separate inverting/non-inverting inputs eliminate need for external inverter op-amp; 1.0V reference ensures stable negative output regulation. | Use Scenario: RS-232 line driver needing isolated −12V supply from +5V microcontroller rail. IC Role / Device Role / Timing Role: Inverting topology controller delivering −12V at 100mA with minimal external components. Use Value: Internal 1.0V reference and dual comparator inputs enable direct feedback from negative output without level-shifting resistors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2578A | Same die, standard grade (−40°C to +85°C); LM2578AM is military-qualified variant with extended screening and traceability. | LM2578A lacks MIL-PRF-38535 compliance and enhanced burn-in; suitable for commercial/industrial use only. | Select LM2578AM when DO-254/DO-178 or defense/aerospace qualification is required; otherwise LM2578A offers cost advantage. |
| MC34063AP | Higher quiescent current (2.5 mA vs 2.0 mA), lower max output current (1.5A vs 750 mA pulsed), fixed 100 kHz oscillator. | MC34063AP integrates current-sense amplifier and requires fewer external components but lacks dual-reference comparator flexibility. | Choose MC34063AP for simpler, lower-cost buck/boost designs where 100 kHz fixed frequency is acceptable and dual feedback polarity is unnecessary. |
Compared with LM2578A, the LM2578AM provides assured reliability for mission-critical environments, while MC34063AP trades comparator flexibility for integration and cost - making LM2578AM optimal for ruggedized, high-precision DC-DC control where feedback architecture and qualification matter.
Availability
LM2578AM is available at Aetrix Electronics and suitable for industrial power supplies, automotive lighting controllers, portable instrumentation, and inverting polarity converters requiring stable component supply, long-term lifecycle support, and MIL-qualified traceability.
Supply support for LM2578AM 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-reliability analog ICs.
The LM2578AM belongs to TI's legacy switching regulator controller family, engineered for robust, flexible DC-DC conversion in harsh environments - emphasizing configurability, protection features, and wide operating ranges over digital complexity.
FAQ
What is the maximum allowable emitter voltage swing below ground for LM2578AM?
The LM2578AM emitter output must not be driven more than −1V below ground for junction temperatures below 100°C; above 100°C, this limit tightens to −0.6V. Exceeding these thresholds risks unintended turn-on of the internal NPN transistor due to base-emitter clamping. This constraint is critical in inverting and high-voltage buck designs - external fast-recovery diodes or PNP boost transistors are recommended to enforce compliance. The LM2578AM datasheet explicitly defines this in Absolute Maximum Ratings and Applications Information sections.
Does LM2578AM support synchronization of multiple devices?
Yes, the LM2578AM supports external synchronization: applying a 1.5V–2.0V pulse waveform (≥2 μs width) to the timing capacitor pin (pin 5) synchronizes its oscillator to an external clock. Each LM2578AM requires up to 500 μA drive capability from the source, and timing capacitors should be selected for ~20% lower free-running frequency than the sync signal. This feature enables noise reduction in multi-rail systems and is documented in the Synchronizing Devices section of the LM2578AM datasheet.
Can LM2578AM be used in a buck-boost configuration?
No - the LM2578AM is not designed for true buck-boost (four-switch or SEPIC) topologies. Its internal NPN transistor and dual-comparator architecture support only buck, boost, and inverting configurations. While the inverting regulator produces negative output from positive input, it does not regulate bidirectionally or maintain output during input dropout like a buck-boost. For buck-boost requirements, TI recommends alternatives such as the LM2596 or TPS5430, which offer integrated synchronous rectification and wider topology support.
What is the purpose of the 1.0V reference on both comparator inputs of LM2578AM?
The 1.0V reference on both the inverting and non-inverting inputs of the LM2578AM enables direct feedback connection without external level-shifting components. In buck regulators, the inverting input connects to a resistive divider from VOUT; in inverting regulators, the non-inverting input serves the same role - eliminating the need for an op-amp to invert polarity. This architecture reduces part count, improves accuracy (no op-amp offset), and enhances stability across temperature, as confirmed in the Functional Description and Typical Applications sections of the LM2578AM datasheet.
How does the current limit function differ when referenced to VIN versus ground on LM2578AM?
When the LM2578AM current limit pin (pin 3) is referenced to ground, the sense resistor connects between the current path and ground; when referenced to VIN, it connects between the current path and VIN. The 110 mV threshold remains identical, but the bias current differs: 4.0 μA when referred to VIN, 0.4 μA when referred to ground. This impacts minimum sense resistor value and noise immunity - ground-referenced designs allow higher resistance (lower power loss) but require tighter layout to avoid ground bounce. These distinctions are specified in the Electrical Characteristics table and Applications Information of the LM2578AM datasheet.
LM2578AM Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Function:
- Step-Up, Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost
- Output Type:
- -
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- 750mA (Switch)
- Frequency - Switching:
- 20kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
LM2578AM FAQ
1.How can I place an order for LM2578AM through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2578AM 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 LM2578AM reliable?
The price and inventory of LM2578AM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2578AM is usually 5 days.
3.What payment methods are accepted for LM2578AM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2578AM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2578AM?
LM2578AM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2578AM 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 LM2578AM?
For technical support, including LM2578AM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2578AM requirements.
6.How does Aetrix verify that LM2578AM is sourced from the original manufacturer or authorized distributors?
All LM2578AM 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 LM2578AM meets industry standards.
7.What is the process for return or replacement of LM2578AM?
All LM2578AM units undergo pre-shipment inspection (PSI). If there is an issue with LM2578AM, 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 LM2578AM part is unused and in its original packaging.
Return procedure for LM2578AM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM2578AM Tags
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