My Inquiry
My Account
Texas Instruments LM78S40CN/NOPB
- Part No.:
- LM78S40CN/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
LM78S40CN/NOPB.pdf
- Description:
- IC REG BUCK BST ADJ 1.5A 16PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:477
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LM78S40CN/NOPB from Texas Instruments (formerly National Semiconductor) is a monolithic universal switching regulator subsystem integrating voltage reference, PWM oscillator with current limiting, error amplifier, 1.5A high-voltage switch, integrated power diode, and uncommitted op amp. It supports step-down, step-up, and inverting topologies with adjustable output from 1.25V to 40V, input range 2.5V–40V, and operates across 0°C to +70°C. It is used in battery-powered DC-DC converters requiring low standby current and high efficiency.
For engineers reviewing the LM78S40CN/NOPB datasheet, LM78S40CN/NOPB pinout, LM78S40CN/NOPB application, or LM78S40CN/NOPB equivalent, key selection considerations include its internal 1.245V reference accuracy (±35 mV), 80 dB line/load regulation, 1.5A peak switch current capability, 16-pin PDIP package, and compatibility with external transistor boosting for >1.5A or >40V operation.
Technical Context
The LM78S40CN/NOPB implements variable-frequency, variable-duty-cycle PWM control via an external timing capacitor (100 Hz–100 kHz range) and dual feedback paths: comparator-based OFF-time modulation and current-limit-sense (350 mV threshold) ON-time truncation. Its Darlington/switch-configurable output stage enables topology flexibility without external driver circuitry.
It integrates a high-gain, high-current op amp (75 mA source / 35 mA sink) with ±30V differential input rating and rail-to-rail common-mode range up to VCC−2V, plus a precision 1.245V bandgap reference (±0.5 mV/mA load regulation, ±0.2 mV/V line regulation) bypassed directly to ground via 0.1 µF.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.5V to 40V - supports wide-input industrial/battery systems without pre-regulation |
| Output Voltage Range | 1.25V to 40V - adjustable via external resistor divider; enables single IC for multiple rail designs |
| Peak Switch Current | 1.5A - sufficient for mid-power DC-DC stages; external transistors extend capability |
| Reference Voltage | 1.245V ±65 mV - stable bandgap reference with low drift over temperature and load |
| Line & Load Regulation | 80 dB - ensures <±2 mV output variation under full input/load transients |
| Switch Saturation Voltage | 0.45V (Q1 only) / 1.3V (Darlington) - defines conduction loss in step-up vs step-down configurations |
| Op Amp Output Drive | 75 mA source / 35 mA sink - capable of driving gate capacitance or small loads directly |
Pinout & Package
LM78S40CN/NOPB is housed in a 16-pin plastic dual in-line package (PDIP-N16E), RoHS-compliant, with 0.300-inch width and through-hole mounting. Pin 11 is GND; pin 8 is VREF; pin 13 is VCC; pin 14 is IPk sense; pins 1–2 and 15–16 are switch collector/emitter terminals.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1, Pin 2 | Switch Collector (Q1/Q2) | Dual-collector Darlington output node; connects to inductor in step-down, diode anode in step-up |
| Pin 3 | Comparator Inverting Input | Feedback node for output voltage regulation; referenced to internal 1.245V |
| Pin 4 | Comparator Non-Inverting Input | Connects to VREF (pin 8) for fixed-output mode or external divider for adjustable output |
| Pin 5 | Current Limit Sense (IPk) | Senses voltage drop across RSC; triggers ON-time termination at ~350 mV |
| Pin 6 | Oscillator Timing Capacitor (CT) | Controls switching frequency (100 Hz–100 kHz); charge/discharge currents defined per VIN |
| Pin 7 | Op Amp Inverting Input | Uncommitted op amp input; usable for error amplification or signal conditioning |
| Pin 8 | Reference Voltage Output (VREF) | 1.245V ±65 mV source; requires 0.1 µF bypass to pin 11 (GND) for stability |
| Pin 9 | Op Amp Non-Inverting Input | Uncommitted op amp input; supports differential sensing or biasing |
| Pin 10 | Op Amp Output | High-drive output (75 mA source); usable as secondary error amp or buffer |
| Pin 11 | Ground (GND) | Power and signal reference plane; bypass capacitor must connect here |
| Pin 12 | Op Amp Positive Supply (V+) | Separate op amp supply rail; supports up to 40V independent of main VIN |
| Pin 13 | Main Supply Input (VCC) | Main power input (2.5V–40V); powers oscillator, reference, comparator, and switch bias |
| Pin 14 | Current Sense Return (IPk Ref) | Return path for current-sense resistor; tied to emitter of external pass transistor in boosted mode |
| Pin 15, Pin 16 | Switch Emitter (Q1/Q2) | Emitting nodes of internal transistors; connect to GND (step-down) or inductor (step-up/inverting) |
Key Features
| Feature | Design Value |
|---|---|
| Topology Flexibility | Native support for step-down, step-up, and inverting regulators without external controller logic |
| Integrated Power Diode | On-chip 1.5A/40V diode eliminates one external component in basic step-down designs |
| Pulse Width Modulation | Variable-frequency PWM with no double-pulsing; prevents shoot-through in synchronous designs |
| Independent Op Amp | High-current (75 mA), rail-compatible op amp enables secondary loop control or sensor interface |
| Low Standby Current | 2.3–5.0 mA supply current at VIN = 40V - extends battery life in always-on systems |
Applications
| Portable Battery-Powered DC-DC Converter | Industrial Step-Up Power Supply |
|---|---|
Use Scenario: A handheld test instrument requires isolated 24V from a 9V alkaline battery pack with minimal BOM count and low quiescent current. IC Role / Device Role / Timing Role: LM78S40CN/NOPB serves as the core PWM controller and power switch in a step-up topology, using internal diode and reference to minimize external parts. Use Value: Achieves 79% efficiency at 50 mA output while drawing only 2.6 mA standby current - enabling >200 hours of operation on AA batteries. |
Use Scenario: Factory automation I/O module needs +28V rail from a 12V distributed bus, with tight line regulation and thermal robustness. IC Role / Device Role / Timing Role: LM78S40CN/NOPB operates in step-up mode with external MOSFET boost switch, leveraging its 40V-rated output stage and 80 dB line regulation. Use Value: Maintains ±1.5 mV output variation across 12V–15V input range and delivers 160 mA continuous - meeting PLC backplane voltage tolerance specs. |
| Inverting Rail Generator for Analog Circuitry | Programmable Lab Power Supply Core |
Use Scenario: Precision data acquisition system requires clean –15V rail for op amp biasing, derived from +12V system rail. IC Role / Device Role / Timing Role: LM78S40CN/NOPB configures as inverting regulator with external diode and inductor; its uncommitted op amp monitors output for closed-loop stability. Use Value: Delivers 100 mA at –15V with 20 mV ripple and 70% efficiency - eliminating need for separate negative supply IC or transformer. |
Use Scenario: Benchtop power supply design demands adjustable 1.25–40V output with analog programming and current limiting. IC Role / Device Role / Timing Role: LM78S40CN/NOPB provides regulated switching core; its VREF (pin 8) and IPk (pin 5) enable precise DAC-controlled voltage/current setpoints. Use Value: Enables 0.1% output accuracy via external 0.01% resistors and achieves programmable current limit down to 100 mA - supporting multi-range lab use. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator subsystem applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MC34063AP1G | Fixed 100 kHz oscillator; lower max input (40V) and output current (1.5A); no integrated diode | Less flexible topology support; requires external diode and timing components for frequency tuning | Preferred for cost-sensitive, fixed-frequency step-down designs where BOM count is secondary to unit cost |
| LT1070CN#PBF | Higher efficiency (up to 92%); wider temp range (–40°C to +125°C); includes soft-start and thermal shutdown | Better suited for automotive or extended-temp industrial use; adds protection features absent in LM78S40CN/NOPB | Chosen when reliability under thermal stress or transient overload is critical, and higher price is acceptable |
Compared with MC34063AP1G and LT1070CN#PBF, the LM78S40CN/NOPB offers unique topology adaptability and integrated diode-reducing part count in space-constrained designs-but lacks built-in thermal protection and fixed-frequency predictability required in noise-sensitive environments.
Availability
LM78S40CN/NOPB is available at Aetrix Electronics and suitable for portable instrumentation, industrial I/O modules, programmable lab supplies, and analog signal chain power rails requiring stable component supply and long-term obsolescence management.
Supply support for LM78S40CN/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 (TI) is a global semiconductor leader delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, longevity, and broad technical support.
The LM78S40CN/NOPB belongs to TI's legacy power management subsystem family, designed for engineers building discrete, topology-flexible DC-DC converters where integration, adjustability, and thermal resilience outweigh the need for digital control or advanced protection features.
FAQ
What is the maximum output current achievable with LM78S40CN/NOPB without external transistors?
The LM78S40CN/NOPB supports up to 1.5A peak switch current internally, as confirmed by absolute maximum ratings and electrical characteristics. At continuous 500 mA output (step-down, VO = 9.5V), typical efficiency is 74% and junction temperature remains within safe limits. For sustained >500 mA loads, external NPN/PNP transistors are recommended to manage on-die power dissipation and thermal rise.
Can LM78S40CN/NOPB be used in a step-up configuration with its internal diode?
No - the internal power diode in LM78S40CN/NOPB is connected between pin 1 (collector) and pin 11 (GND), making it suitable only for step-down and inverting topologies. In step-up operation, the diode must conduct from inductor to output, requiring an external diode placed between pin 15/16 (emitter) and the output node. The datasheet explicitly shows Figure 2 using an external diode for step-up mode.
What is the purpose of pin 12 (V+ for op amp) and how should it be connected?
Pin 12 provides an independent supply rail for the uncommitted operational amplifier, rated up to 40V and electrically isolated from the main VCC (pin 13). It allows the op amp to operate with different headroom or noise isolation - e.g., powered from a filtered auxiliary rail while the main switch runs from noisy bus voltage. If unused, pin 12 must be tied to VCC or GND; floating is not permitted per absolute maximum ratings.
How does the LM78S40CN/NOPB achieve 80 dB line and load regulation?
The LM78S40CN/NOPB achieves 80 dB line and load regulation through a combination of high-gain error amplifier (AVS± ≥25 V/mV), precision 1.245V reference with <0.5 mV/mA load regulation, and comparator-based feedback that actively modulates OFF time in response to output deviations. This closed-loop architecture rejects input ripple and load transients far more effectively than open-loop or low-gain alternatives like basic 555-based controllers.
Is LM78S40CN/NOPB RoHS compliant and what is its moisture sensitivity level?
Yes, LM78S40CN/NOPB is RoHS compliant (lead-finish: Sn) and carries MSL Level-1 (unlimited floor life), per TI's packaging documentation. Its PDIP package has no moisture absorption concerns, and no bake preconditioning is required before soldering. The "NOPB" suffix explicitly denotes lead-free finish, and the device meets JEDEC J-STD-020D.1 requirements for through-hole reflow.
LM78S40CN/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up, Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.5V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 40V (Switch)
- Current - Output:
- 1.5A (Switch)
- Frequency - Switching:
- 100Hz ~ 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
LM78S40CN/NOPB FAQ
1.How can I place an order for LM78S40CN/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM78S40CN/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 LM78S40CN/NOPB reliable?
The price and inventory of LM78S40CN/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM78S40CN/NOPB is usually 5 days.
3.What payment methods are accepted for LM78S40CN/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM78S40CN/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM78S40CN/NOPB?
LM78S40CN/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM78S40CN/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 LM78S40CN/NOPB?
For technical support, including LM78S40CN/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM78S40CN/NOPB requirements.
6.How does Aetrix verify that LM78S40CN/NOPB is sourced from the original manufacturer or authorized distributors?
All LM78S40CN/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 LM78S40CN/NOPB meets industry standards.
7.What is the process for return or replacement of LM78S40CN/NOPB?
All LM78S40CN/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM78S40CN/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 LM78S40CN/NOPB part is unused and in its original packaging.
Return procedure for LM78S40CN/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM78S40CN/NOPB Tags
-
TPS562201DDCR
Texas Instruments
-
MC34063ABD-TR
STMicroelectronics
-
TPS561201DDCR
Texas Instruments
-
MC33063ADR
Texas Instruments
-
MC34063ADR
Texas Instruments
-
TPS560200DBVR
Texas Instruments
-
AP3012KTR-G1
Diodes Incorporated
-
TLV61048DBVR
Texas Instruments
-
AZ34063UMTR-G1
Diodes Incorporated
-
TPS562200DDCR
Texas Instruments
-
AP62300TWU-7
Diodes Incorporated
-
MC34063EBD-TR
STMicroelectronics
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
