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STMicroelectronics LD2985AM35R
- Part No.:
- LD2985AM35R
- Manufacturer:
- STMicroelectronics
- Package:
- SC-74A, SOT-753
- Datasheet:
-
LD2985AM35R.pdf
- Description:
- IC REG LINEAR 3.5V 150MA SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:3,899
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Product details
Overview
LD2985AM35R from STMicroelectronics is a 150 mA fixed-output low-dropout linear voltage regulator with 3.3 V output, 280 mV dropout at 150 mA, 30 µVrms output noise, and TTL-compatible inhibit control on Pin 3. It operates from −40 °C to 125 °C and is designed for local regulation in battery-powered portable electronics requiring ultra-low quiescent current and low-noise power.
For engineers reviewing the LD2985AM35R datasheet, LD2985AM35R pinout, LD2985AM35R application, or LD2985AM35R equivalent, key selection criteria include dropout performance at light load, inhibit logic thresholds (VIL ≤ 0.15 V), bypass capacitor dependency for noise reduction, and SOT23-5L thermal resistance (RthJA = 255 °C/W).
Technical Context
The LD2985AM35R uses a PNP pass transistor architecture enabling ultra-low dropout-7 mV at 1 mA and 280 mV at 150 mA-while maintaining stability with ceramic output capacitors as low as 2.2 µF. Its internal feedback resistors (42.6 kΩ / 51.15 kΩ) set the 3.3 V output and enable reverse-current blocking when VOUT > VIN.
Shutdown is implemented via a dedicated INHIBIT pin (Pin 3) with TTL-compatible thresholds (VIL ≤ 0.15 V, VIH ≥ 2 V); pulling INHIBIT low reduces quiescent current to <1 µA. The Bypass pin (Pin 4) requires a 10 nF capacitor to ground to achieve the specified 30 µVrms noise performance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output voltage | 3.3 V ±1.2% over −40 °C to 125 °C; ensures stable core logic supply for 3.3 V microcontrollers and sensors |
| Dropout voltage | 280 mV at 150 mA; enables operation down to 3.58 V input while sustaining full rated output |
| Quiescent current | 80 µA at no load; supports multi-day battery life in always-on sensor nodes |
| Output noise | 30 µVrms (300 Hz–50 kHz) with 10 nF bypass cap; meets analog front-end and RF LDO requirements |
| Inhibit logic low | VIL ≤ 0.15 V; compatible with open-drain GPIOs and low-voltage logic without level shifting |
| Thermal resistance | RthJA = 255 °C/W in SOT23-5L; limits max junction temperature to 125 °C at 150 mA with minimal PCB copper |
Pinout & Package
SOT23-5L package: 5-pin surface-mount plastic package with exposed pad for thermal enhancement; footprint compliant with JEDEC MO-178AB, body dimensions 2.95 × 1.60 mm, height 1.30 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (IN) | Input voltage supply | Accepts 2.5–16 V DC; requires ≥1 µF ceramic capacitor placed within 12.7 mm of pin |
| 2 (GND) | Ground reference | Common return path for input, output, inhibit, and bypass; must connect to clean analog ground plane |
| 3 (INHIBIT) | Logic-controlled shutdown | TTL-compatible enable input; <0.15 V disables regulator, <1 µA shutdown current; must not float |
| 4 (BYPASS) | Noise reduction node | Connects 10 nF ceramic capacitor to GND to reduce output noise from 120 µVrms to 30 µVrms |
| 5 (OUT) | Regulated output | Delivers 3.3 V ±1.2% at up to 150 mA; requires 2.2 µF ceramic capacitor with ESR <100 mΩ |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low dropout | 7 mV at 1 mA load enables operation from near-dead batteries in wearables and IoT edge nodes |
| Sub-µA shutdown | <1 µA quiescent current in inhibit mode extends shelf life and enables long-term storage without battery drain |
| Bypass-enabled low noise | 30 µVrms noise with 10 nF bypass cap supports precision ADCs, audio codecs, and RF synthesizers |
| Reverse-current blocking | No intrinsic body diode; prevents backfeed from output to input during hot-swap or multi-rail sequencing |
| Wide temperature range | −40 °C to 125 °C operation supports under-hood automotive modules and industrial motor controllers |
Applications
| Portable Medical Sensors | Industrial PLC I/O Modules |
|---|---|
|
Use Scenario: Continuous glucose monitor with Bluetooth LE radio and low-power MCU. IC Role / Device Role / Timing Role: Local 3.3 V LDO supplying analog front-end and BLE SoC, enabled/disabled via host MCU GPIO. Use Value: 80 µA quiescent current and <1 µA shutdown extend single-CR2032 battery life beyond 12 months in sleep mode. |
Use Scenario: DIN-rail mounted programmable logic controller with isolated digital inputs. IC Role / Device Role / Timing Role: Point-of-load regulator for isolated field-side sensor interface ICs requiring clean 3.3 V bias. Use Value: 30 µVrms noise and reverse-current blocking prevent measurement corruption from shared ground transients. |
| Automotive Cabin Camera | Wireless Sensor Node |
|
Use Scenario: AEC-Q100 grade rear-view camera module operating in vehicle cabin ambient. IC Role / Device Role / Timing Role: Primary 3.3 V supply for image sensor and ISP, thermally managed via SOT23-5L exposed pad. Use Value: −40 °C to 125 °C rating and 255 °C/W RthJA ensure stable output across engine-off cold soak and summer cabin heat. |
Use Scenario: Battery-powered environmental sensor transmitting data every 5 minutes via LoRaWAN. IC Role / Device Role / Timing Role: Always-on LDO powering real-time clock and wake-up circuitry; inhibited during active transmission. Use Value: Inhibit pin allows precise duty-cycling of entire sensor subsystem, reducing average system current by >90%. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| Torex XC6219B332MR-G | 300 mA output, 150 mV dropout at 300 mA, no inhibit pin, 40 µVrms noise | Lacks shutdown control; requires external MOSFET for system-level power gating | Choose when higher output current is needed and inhibit functionality is handled externally |
| Analog Devices ADP160AUJZ-3.3-R7 | 150 mA output, 195 mV dropout at 150 mA, 22 µVrms noise, no bypass pin | Lower noise but no dedicated bypass node; relies on output capacitor alone for noise filtering | Choose when lowest possible noise is critical and board space prohibits adding bypass cap |
Compared with XC6219B332MR-G and ADP160AUJZ-3.3-R7, the LD2985AM35R uniquely combines sub-µA inhibit shutdown, a dedicated bypass pin for deterministic noise reduction, and automotive-grade temperature capability-making it optimal for space-constrained, battery-sensitive designs requiring precise power-state control.
Availability
LD2985AM35R is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, automotive cabin cameras, and wireless sensor nodes requiring stable component supply across extended temperature ranges and low-power operation.
Supply support for LD2985AM35R 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, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.
The LD2985 series belongs to ST's high-performance analog LDO portfolio, engineered specifically for ultra-low-noise, ultra-low-quiescent-current regulation in portable and battery-critical systems.
FAQ
What is the minimum input voltage required for 3.3 V output at 150 mA?
The LD2985AM35R requires a minimum input voltage of 3.58 V to maintain regulated 3.3 V output at 150 mA load, based on its 280 mV maximum dropout voltage specification at that current. Below this threshold, output voltage drops linearly with input.
Can the INHIBIT pin be left unconnected?
No-the INHIBIT pin must never be left floating. It has no internal pull-up or pull-down. To ensure normal operation, tie it directly to the input voltage (VI); to disable the regulator, drive it to ≤0.15 V using an active-low GPIO or open-drain driver.
Is a bypass capacitor mandatory for stable operation?
A 10 nF ceramic capacitor between BYPASS (Pin 4) and GND is mandatory to achieve the specified 30 µVrms output noise. Without it, noise rises to ~120 µVrms. The regulator remains stable without it, but noise performance degrades significantly.
Does the LD2985AM35R support reverse-current protection?
Yes-the internal PNP pass transistor lacks a parasitic body diode, preventing reverse current flow from OUT to IN when VOUT > VIN. Reverse current is limited to ~160 µA through internal feedback resistors, protecting upstream sources during hot-swap or rail sequencing.
LD2985AM35R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- SC-74A, SOT-753
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Output Configuration:
- Positive
- Output Type:
- Fixed
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 16V
- Voltage - Output (Min/Fixed):
- 3.5V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- 0.575V @ 150mA
- Current - Output:
- 150mA
- Current - Quiescent (Iq):
- 150 µA
- Current - Supply (Max):
- 4 mA
- PSRR:
- 45dB (1kHz)
- Control Features:
- Enable
- Protection Features:
- Over Current, Over Temperature
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-5
LD2985AM35R FAQ
1.How can I place an order for LD2985AM35R through Aetrix?
Please submit a Request for Quotation (RFQ) for LD2985AM35R 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 LD2985AM35R reliable?
The price and inventory of LD2985AM35R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD2985AM35R is usually 5 days.
3.What payment methods are accepted for LD2985AM35R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD2985AM35R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LD2985AM35R?
LD2985AM35R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LD2985AM35R 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 LD2985AM35R?
For technical support, including LD2985AM35R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD2985AM35R requirements.
6.How does Aetrix verify that LD2985AM35R is sourced from the original manufacturer or authorized distributors?
All LD2985AM35R 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 LD2985AM35R meets industry standards.
7.What is the process for return or replacement of LD2985AM35R?
All LD2985AM35R units undergo pre-shipment inspection (PSI). If there is an issue with LD2985AM35R, 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 LD2985AM35R part is unused and in its original packaging.
Return procedure for LD2985AM35R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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