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STMicroelectronics L5970AD
- Part No.:
- L5970AD
- Manufacturer:
- STMicroelectronics
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
L5970AD.pdf
- Description:
- IC REG BUCK ADJ 1.5A 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,258
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Product details
Overview
L5970AD from STMicroelectronics is a monolithic step-down switching regulator with an internal 1.5A P-channel DMOS switch, 500kHz fixed switching frequency, adjustable output voltage (1.235V–35V), and 4.4V–36V input range-designed for compact DC-DC conversion in 5V bus–powered systems such as printers, LCD monitors, and automotive battery converters.
For engineers reviewing the L5970AD datasheet, L5970AD pinout, L5970AD application, or L5970AD equivalent, key selection criteria include its 200mΩ typical RDS(on), 3.3V ±2% reference, zero-load burst-mode operation, thermal shutdown at 150°C, and SYNC pin support for master/slave multi-phase configurations.
Technical Context
The L5970AD integrates a transconductance error amplifier (2.3mS gm, 57dB open-loop gain), PWM comparator, and sawtooth oscillator to deliver voltage-mode control with feedforward compensation. Its internal P-MOS switch eliminates bootstrap capacitor requirements and enables 100% duty cycle low-dropout operation.
Current protection combines pulse-by-pulse limiting (1.8A max) with frequency foldback during overcurrent, while the INH pin provides logic-level enable/disable with <100µA standby current. Feedback disconnection detection disables the device if FB floats, preventing unregulated high-voltage output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Current Limit | 1.8A peak - ensures robust short-circuit protection without external sensing |
| Input Voltage Range | 4.4V to 36V - supports direct 5V bus, 12V industrial, and 24V automotive rails |
| Output Voltage Range | 1.235V to 35V - set via external resistor divider on FB pin |
| Switching Frequency | 500kHz fixed - minimizes external inductor/capacitor size (e.g., 15µH in typical 3.3V design) |
| RDS(on) | 0.25Ω typical - reduces conduction loss and thermal load at 1A output |
| Reference Voltage | 3.3V ±2% - stable internal VREF for biasing and feedback scaling |
| Quiescent Current | 7mA operating / 100µA standby - enables efficient light-load and sleep-mode operation |
Pinout & Package
Package: SO-8 (Small Outline, 8-pin, surface-mount). Thermal resistance junction-to-ambient is 120°C/W on standard PCB layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 OUT | Regulator output node | Connects directly to power inductor and output capacitor; carries switched high-current path |
| 2 SYNC | Master/slave synchronization interface | Accepts external clock >500kHz or outputs synchronized signal; enables phase alignment of multiple regulators |
| 3 INH | Inhibit control input | Active-high logic: ≥2.2V disables regulator (≤100µA IQ); ≤0.8V enables; floating = disabled via internal pull-up |
| 4 COMP | Error amplifier output | Drives external RC compensation network to stabilize loop response and prevent oscillation |
| 5 FB | Feedback input | Senses output voltage via resistor divider; internal 1.235V reference sets regulation point |
| 6 VREF | 3.3V reference output | Stable, low-noise reference for external circuitry; no bypass capacitor required |
| 7 GND | Power and signal ground | Common return for internal circuits, power switch, and feedback network |
| 8 VCC | Unregulated input supply | Provides power to internal bias circuitry; must be ≥4.4V and ≤40V absolute max |
Key Features
| Feature | Design Value |
|---|---|
| Voltage feedforward | Improves line transient response by modulating PWM ramp with input voltage, reducing output deviation during input rail steps |
| Zero-load burst mode | Enables stable regulation with no output load-critical for always-on subsystems like remote wake-up circuits |
| Internal thermal shutdown | Turns off power stage at 150°C junction temperature with ~20°C hysteresis to prevent cycling during overload |
| Feedback disconnect protection | Automatically disables regulator if FB pin floats, avoiding destructive overvoltage at output |
| SYNC pin dual-role capability | Supports both master (output sync signal) and slave (accept external sync) modes-enables scalable multi-regulator designs |
Applications
| Printer Power Supply | LCD Monitor DC-DC |
|---|---|
Use Scenario: Provides regulated 3.3V/5V rails from 12V or 24V input in inkjet/laser printer mainboards. IC Role / Device Role / Timing Role: Primary buck converter delivering >1A continuous current to logic, motor drivers, and sensor interfaces. Use Value: High efficiency (>90% at 5V/12V) and 500kHz switching reduce heatsink and filter component size in space-constrained chassis. |
Use Scenario: Generates 5V and 12V supplies for TCON, backlight inverters, and USB peripherals in desktop LCD monitors. IC Role / Device Role / Timing Role: Adjustable-output buck regulator supporting multiple voltage domains from single 12V or 19V adapter input. Use Value: 1.235V–35V adjustability and SYNC pin allow coordinated multi-rail sequencing and EMI reduction via phase shifting. |
| Automotive Infotainment | XDSL Power Module |
Use Scenario: Converts car battery voltage (9V–16V) to stable 3.3V for DSP, display, and CAN interface ICs in head units. IC Role / Device Role / Timing Role: Input-tolerant buck regulator with UVLO hysteresis and thermal protection for harsh automotive environments. Use Value: 4.4V min input enables operation during cold-crank (≥6V), and 36V max rating covers load-dump transients up to 35V. |
Use Scenario: Supplies isolated 3.3V/5V rails in DSL modem power modules where board area and thermal management are critical. IC Role / Device Role / Timing Role: Compact, self-contained buck controller eliminating external MOSFET and gate driver components. Use Value: Integrated 1.5A P-MOS switch and 200mΩ RDS(on) reduce BOM count and improve reliability versus discrete solutions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| L5973AD | 2A switch current, same 500kHz frequency, HSOP8 package (exposed pad) | Higher output current capability; better thermal performance due to exposed thermal pad | Select when >1.5A continuous load or improved thermal margin is required |
| L5970D | 1.5A switch current, 250kHz switching frequency, SO-8 package | Lower switching frequency increases inductor size but reduces EMI and gate drive losses | Select when lower EMI or compatibility with legacy 250kHz designs is prioritized |
Compared with L5970D and L5973AD, the L5970AD offers optimal balance of current capability, switching speed, and thermal footprint in standard SO-8-making it ideal for cost-sensitive, space-constrained 1A-class applications where 500kHz operation is acceptable.
Availability
L5970AD is available at Aetrix Electronics and suitable for printers, LCD monitors, automotive infotainment systems, and XDSL modems requiring stable component supply across extended production lifecycles.
Supply support for L5970AD 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.
The L597x series was designed specifically for compact, high-efficiency non-isolated DC-DC conversion in cost-sensitive applications-emphasizing integration, thermal robustness, and ease of use in SO-8 footprint.
FAQ
What is the minimum input voltage required for L5970AD to regulate a 3.3V output?
The L5970AD requires a minimum input voltage of 4.4V to maintain regulation, even at 100% duty cycle. For a 3.3V output, this provides only 1.1V headroom-so input ripple must stay below 1.1V peak-to-peak to avoid dropout. A 5V nominal input rail is recommended for reliable operation.
Can L5970AD operate without an output load?
Yes-the L5970AD supports zero-load operation using burst-mode control. With no load, the device enters intermittent switching to maintain output regulation while drawing only ~2.7mA quiescent current, making it suitable for always-on standby circuits.
How does the SYNC pin function when two L5970AD devices are connected?
When SYNC pins of two L5970ADs are tied together, the device with the higher internal switching frequency (500kHz nominal) becomes the master and drives the shared SYNC line; the other operates as slave, synchronizing its switching edges to that signal-enabling interleaved operation and reduced input ripple.
What happens if the FB pin is left unconnected?
If the FB pin is left floating, the internal protection circuit detects feedback disconnection and forces the device into shutdown mode-preventing uncontrolled output voltage rise toward the input rail, which could damage downstream components.
L5970AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.4V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 1.235V
- Voltage - Output (Max):
- 35V
- Current - Output:
- 1.5A
- Frequency - Switching:
- 500kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
L5970AD FAQ
1.How can I place an order for L5970AD through Aetrix?
Please submit a Request for Quotation (RFQ) for L5970AD 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 L5970AD reliable?
The price and inventory of L5970AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L5970AD is usually 5 days.
3.What payment methods are accepted for L5970AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L5970AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L5970AD?
L5970AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L5970AD 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 L5970AD?
For technical support, including L5970AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L5970AD requirements.
6.How does Aetrix verify that L5970AD is sourced from the original manufacturer or authorized distributors?
All L5970AD 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 L5970AD meets industry standards.
7.What is the process for return or replacement of L5970AD?
All L5970AD units undergo pre-shipment inspection (PSI). If there is an issue with L5970AD, 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 L5970AD part is unused and in its original packaging.
Return procedure for L5970AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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