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Texas Instruments LM2597N-ADJ
- Part No.:
- LM2597N-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
LM2597N-ADJ.pdf
- Description:
- IC REG BUCK ADJ 500MA 8PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,252
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Product details
Overview
LM2597N-ADJ from Texas Instruments is a monolithic nonsynchronous step-down (buck) DC-DC converter IC delivering 0.5-A output current with adjustable output voltage ranging from 1.2 V to 37 V, ±4% tolerance over line and load, operating at a fixed 150-kHz switching frequency, and supporting input voltages up to 40 V - used in industrial power supplies, embedded system point-of-load regulation, and battery-powered equipment requiring wide-input, low-quiescent-current conversion.
For engineers reviewing the LM2597N-ADJ datasheet, LM2597N-ADJ pinout, LM2597N-ADJ application, or LM2597N-ADJ equivalent, key selection considerations include its 8-pin PDIP package, bias supply (VBS) pin for efficiency optimization at high VIN/low VOUT, shutdown/soft-start dual-function pin, error flag with delay timing, and thermal shutdown with current-limit protection.
Technical Context
The LM2597N-ADJ integrates a PWM controller, power switch, oscillator, error amplifier, and protection circuitry into a single 8-pin PDIP package. Its fixed-frequency 150-kHz operation enables compact external filter design using standard off-the-shelf inductors and capacitors, while the internal compensation eliminates need for external loop compensation components.
It implements a two-stage current limit and thermal shutdown for fault protection, and features a dedicated Bias Supply (VBS) pin that powers internal circuitry from VOUT instead of VIN - improving efficiency by up to ~5% under light-load/high-input-voltage conditions. The Error Flag output provides open-collector reset signaling with programmable delay via external capacitor on the Delay pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 0.5 A DC maximum - supports mid-power buck conversion without external current boosting. |
| Input Voltage Range | 4.5 V to 40 V - compatible with 12 V, 24 V, and 36 V industrial bus rails and wide-range battery inputs. |
| Output Voltage Range | 1.2 V to 37 V (adjustable via external resistor divider) - enables flexible system-level voltage scaling. |
| Switching Frequency | 150 kHz ±15% - balances EMI, inductor size, and efficiency; allows use of low-cost, high-saturation-current inductors. |
| Feedback Reference Voltage | 1.23 V ±2% - sets output accuracy; determines resistor ratio for precise VOUT programming. |
| Standby Quiescent Current | 85 μA typical - enables ultra-low-power shutdown mode for battery-backed systems. |
| Efficiency | 80% typical at 12 VIN/3 VOUT/0.5 A - achieved with integrated switch and optimized gate drive; improves with VBS pin connection. |
| Thermal Resistance (θJA) | 150 °C/W (PDIP-8) - requires minimal PCB copper area for heat sinking under full load at 25 °C ambient. |
Pinout & Package
LM2597N-ADJ is supplied in an 8-pin Plastic Dual Inline Package (PDIP) with 9.81 mm × 6.35 mm body size and 0.3 inch lead spacing - suitable for through-hole prototyping and legacy industrial PCB assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - Error Flag | Open-collector output | Asserts low when VOUT drops >5% below nominal; used as microprocessor reset signal with user-defined delay. |
| 2 - Delay | Capacitor-connected timing node | Sets delay time between VOUT reaching 95% and Error Flag going high; enables controlled power-up sequencing. |
| 3 - Bias Supply (VBS) | Internal regulator supply input | Accepts VOUT (≥3.5 V) to power internal circuitry - reduces VIN current draw and improves efficiency at high VIN/low VOUT. |
| 4 - Feedback (FB) | Inverting input of error amplifier | Monitors divided output voltage; regulates VOUT to maintain 1.23 V at this pin - defines output setpoint. |
| 5 - Shutdown/Soft-Start (SD/SS) | Dual-function logic input | Pulled low → shutdown (IQ ≈ 85 μA); capacitor added → soft-start ramp controlling dV/dt of VOUT. |
| 6 - Ground | Power and signal reference | Common return path for internal switch, control circuitry, and feedback network - must be low-impedance. |
| 7 - +VIN | Main power input | Supplies switching transistor and internal bias; requires local 100 nF ceramic bypass capacitor to minimize transients. |
| 8 - Output | Switching node (drain of internal NPN) | Connects to external catch diode and inductor; swings between (VIN − VSAT) and ≈−0.5 V - demands minimal PCB trace area. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 0.5-A NPN power switch | Eliminates need for external MOSFET or transistor - reduces BOM count and layout complexity. |
| Fixed 150-kHz oscillator | Enables predictable EMI profile and consistent inductor sizing - avoids variable-frequency jitter and filter tuning. |
| VBS bias supply pin | Improves efficiency by 3–5% at high input voltages (e.g., 36 VIN/5 VOUT) by powering control circuitry from regulated output. |
| Shutdown/Soft-Start dual-function pin | Reduces peak inrush current from 700 mA to 160 mA - prevents input rail collapse during cold start. |
| Out-of-regulation error flag with delay | Provides reliable power-good signaling with user-adjustable hold-off time - supports safe microcontroller boot sequencing. |
| Thermal shutdown + current limiting | Two-stage current limit and junction temperature cutoff at 150 °C - ensures robust operation under overload or poor heatsinking. |
Applications
| Industrial Power Supply | Embedded System PoL Regulator |
|---|---|
|
Use Scenario: Converting 24 V DC industrial bus to 5 V or 3.3 V for PLC I/O modules and sensor interfaces. IC Role / Device Role / Timing Role: Primary step-down regulator providing stable, efficient, and fault-protected local power. Use Value: Delivers 0.5 A at >82% efficiency with built-in thermal/current protection - eliminates need for discrete supervision circuitry. |
Use Scenario: Generating configurable rail voltages (e.g., 1.8 V, 2.5 V, 3.3 V) from a 12 V motherboard supply in edge computing gateways. IC Role / Device Role / Timing Role: Adjustable-output buck converter enabling flexible voltage domain partitioning across SoC peripherals. Use Value: 1.23 V reference and ±4% output tolerance ensure accurate voltage setting; soft-start prevents brownout during FPGA configuration. |
| Battery-Powered Instrumentation | Positive-to-Negative Converter |
|
Use Scenario: Powering handheld test equipment (e.g., multimeters, data loggers) from 9 V or 12 V alkaline or Li-ion packs. IC Role / Device Role / Timing Role: High-efficiency preregulator stepping down variable battery voltage to fixed intermediate rail. Use Value: 85 μA standby current extends battery life in sleep mode; wide VIN range accommodates discharge curve from 12 V to 6 V. |
Use Scenario: Generating −5 V or −12 V from +12 V or +24 V supply for op-amp biasing or analog front-end circuits. IC Role / Device Role / Timing Role: Inverting buck-derived topology using internal switch and external diode/inductor/capacitor. Use Value: Enables bipolar supply generation without dedicated inverting IC; uses same LM2597N-ADJ die - simplifies inventory and design reuse. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596-ADJ | Higher 3-A output current rating; 150-kHz frequency; wider 3.5–40 V input range; requires larger external components. | Preferred for higher-current loads (>0.5 A); less suitable for space-constrained layouts due to larger inductor requirements. | Select LM2596-ADJ only if ≥1.5 A output is required; LM2597N-ADJ offers better fit for 0.5-A applications with smaller footprint. |
| TPS54302DDCR | Synchronous buck controller; 3-A output; 2.5–28 V input; 500-kHz switching; integrated high-side/low-side FETs; no external diode needed. | Delivers higher efficiency at light loads and smaller solution size; lacks error flag and delay functions - requires external monitoring. | Choose TPS54302DDCR for new designs prioritizing efficiency and board area; retain LM2597N-ADJ where error flag, soft-start, and proven reliability are critical. |
Compared with LM2596-ADJ and TPS54302DDCR, LM2597N-ADJ provides unique integration of error flag with programmable delay, VBS efficiency enhancement, and ruggedized 40-V input handling - making it optimal for cost-sensitive, medium-power industrial and instrumentation applications where supervisory features and long-term availability matter.
Availability
LM2597N-ADJ is available at Aetrix Electronics and suitable for industrial power supplies, embedded system point-of-load regulation, and battery-powered instrumentation requiring stable component supply, long-lifecycle support, and proven field reliability.
Supply support for LM2597N-ADJ 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 experience in high-reliability power conversion ICs.
The LM2597 series belongs to TI's SIMPLE SWITCHER® portfolio, designed specifically for ease-of-use, minimal external component count, and robust performance in industrial, automotive, and telecom power applications - targeting engineers needing fast, reliable buck conversion without complex design iterations.
FAQ
What is the maximum input voltage supported by the LM2597N-ADJ?
The LM2597N-ADJ supports a maximum input voltage of 40 V under recommended operating conditions. Absolute maximum rating is 45 V, but continuous operation above 40 V risks degradation or failure. For applications requiring up to 60 V input, the LM2597HV-ADJ variant must be used instead - the LM2597N-ADJ is not rated for 60 V operation.
How does the Bias Supply (VBS) pin improve efficiency in the LM2597N-ADJ?
The VBS pin on the LM2597N-ADJ allows internal circuitry to be powered from the regulated output voltage instead of VIN. When VOUT is ≥3.5 V, connecting VBS to VOUT reduces VIN current draw by ~4 mA and improves full-load efficiency by 3–5%, especially at high input voltages (e.g., 36 VIN/5 VOUT). This feature is inactive if VBS is left open or connected to <3.5 V - the LM2597N-ADJ defaults to VIN-powered operation.
Can the LM2597N-ADJ be used in an inverting (positive-to-negative) configuration?
Yes, the LM2597N-ADJ can be configured as a positive-to-negative inverting regulator by floating the GND pin to the negative output rail and grounding the FB pin - as documented in TI's SNVS119D datasheet Figure 24. This topology supports outputs such as −5 V or −12 V from +12 V or +24 V inputs. However, maximum output current depends on |VIN| + |VOUT| ≤ 40 V, and startup inrush current may reach 0.8 A - soft-start is strongly recommended for stability.
What is the purpose of the Delay pin on the LM2597N-ADJ?
On the LM2597N-ADJ, the Delay pin (Pin 2) sets the time interval between when VOUT reaches 95% of its target value and when the open-collector Error Flag (Pin 1) transitions high. A capacitor connected from Delay to GND determines this delay - typically 10–100 nF yields 1–10 ms delays. This ensures clean power-good assertion after output stabilization, preventing premature microcontroller release from reset during transient settling.
Does the LM2597N-ADJ require external compensation components?
No, the LM2597N-ADJ includes fully internal frequency compensation - no external RC networks or compensation capacitors are needed. Its fixed 150-kHz oscillator and optimized error amplifier design allow stable operation with only four external components: input capacitor, output capacitor, power inductor, and feedback divider resistors. This simplifies design, reduces BOM cost, and improves layout repeatability compared to externally compensated controllers.
LM2597N-ADJ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.5V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.2V
- Voltage - Output (Max):
- 37V
- Current - Output:
- 500mA
- Frequency - Switching:
- 150kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
LM2597N-ADJ FAQ
1.How can I place an order for LM2597N-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2597N-ADJ 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 LM2597N-ADJ reliable?
The price and inventory of LM2597N-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2597N-ADJ is usually 5 days.
3.What payment methods are accepted for LM2597N-ADJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2597N-ADJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2597N-ADJ?
LM2597N-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2597N-ADJ 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 LM2597N-ADJ?
For technical support, including LM2597N-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2597N-ADJ requirements.
6.How does Aetrix verify that LM2597N-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2597N-ADJ 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 LM2597N-ADJ meets industry standards.
7.What is the process for return or replacement of LM2597N-ADJ?
All LM2597N-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2597N-ADJ, 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 LM2597N-ADJ part is unused and in its original packaging.
Return procedure for LM2597N-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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