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STMicroelectronics LD2985AM28R
- Part No.:
- LD2985AM28R
- Manufacturer:
- STMicroelectronics
- Package:
- SC-74A, SOT-753
- Datasheet:
-
LD2985AM28R.pdf
- Description:
- IC REG LINEAR 2.8V 150MA SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:4,913
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Product details
Overview
LD2985AM28R from STMicroelectronics is a 150 mA fixed-output low-dropout linear voltage regulator with 2.8 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 targets battery-powered portable electronics requiring ultra-low quiescent current and clean power delivery.
For engineers reviewing the LD2985AM28R datasheet, LD2985AM28R pinout, LD2985AM28R application, or LD2985AM28R equivalent, this page delivers verified electrical parameters, validated SOT23-5L pin mapping, real-world use cases in portable devices, and confirmed alternative regulators with documented functional differences.
Technical Context
The LD2985AM28R uses a PNP pass transistor architecture enabling ultra-low dropout (7 mV at 1 mA, 280 mV at 150 mA) and sub-1 µA shutdown current when INHIBIT is pulled low. Its internal feedback network sets a precise 2.8 V output with ±2.4% tolerance over temperature and load.
It integrates thermal and current limiting, supports external bypass capacitor (10 nF to GND on Pin 4) for noise reduction to 30 µVrms, and accepts input voltages from 2.5 V to 16 V. The inhibit function is not internally pulled up and requires explicit logic-level drive.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 2.8 V ±2.4% (1.728–1.872 V for 1.8 V variant; for 2.8 V: 2.688–2.912 V over −40 to 125 °C) |
| Dropout Voltage | 280 mV at 150 mA load - enables regulation with only 3.08 V input for 2.8 V output |
| Quiescent Current | 80 µA at no load; drops to <1 µA in inhibit-off state - extends battery life in standby |
| Output Noise | 30 µVrms (300 Hz–50 kHz) with 10 nF bypass capacitor - suitable for RF/analog supply domains |
| Supply Rejection | 45 dB at 1 kHz - suppresses ripple from noisy DC-DC stages feeding the LDO |
| Operating Temp | −40 °C to +125 °C junction - qualified for automotive cabin and industrial edge applications |
| Inhibit Threshold | VIL = 0.15 V max; VIH = 2 V min - compatible with 3.3 V and 5 V logic without level shift |
Pinout & Package
SOT23-5L package: 5-pin surface-mount, 1.3 mm height, 2.95 mm × 1.60 mm footprint, ECOPACK® compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (IN) | Input voltage supply | Accepts 2.5–16 V DC; requires ≥1 µF ceramic capacitor within 12.7 mm of pin |
| 2 (GND) | Power ground reference | Low-impedance analog return path for regulator core and bypass capacitor |
| 3 (INHIBIT) | Logic-controlled enable/disable | TTL-compatible input; pulls regulator into <1 µA shutdown when ≤0.15 V |
| 4 (BYPASS) | Noise reduction node | Connects 10 nF capacitor to GND to reduce output noise to 30 µVrms |
| 5 (OUT) | Regulated 2.8 V output | Delivers up to 150 mA; requires 2.2 µF ceramic capacitor (low ESR) for stability |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low dropout | 7 mV at 1 mA load enables operation from single-cell Li-ion (3.0 V min) down to end-of-discharge |
| Sub-µA shutdown | <1 µA quiescent current in inhibit-off mode extends shelf life and sleep-mode runtime |
| Bypass-enabled low noise | 30 µVrms noise with 10 nF CBYP meets ADC reference and RF bias supply requirements |
| Integrated protection | Thermal foldback and current limit prevent damage during overload or ambient overheating |
| Wide input range | 2.5–16 V input supports direct connection to unregulated wall adapters or intermediate DC rails |
Applications
| Portable Audio Power | Camera Sensor Bias |
|---|---|
|
Use Scenario: Powering MEMS microphones and Class-D audio amplifiers in Bluetooth earbuds. IC Role / Device Role / Timing Role: Local low-noise 2.8 V supply decoupled from noisy system rail. Use Value: 30 µVrms noise prevents audible hiss; 280 mV dropout preserves headroom during battery sag. |
Use Scenario: Providing stable bias to CMOS image sensor analog front-end in compact action cameras. IC Role / Device Role / Timing Role: Precision voltage source for pixel readout circuitry and ADC reference. Use Value: ±2.4% output tolerance ensures consistent exposure calibration; −40 to 125 °C rating supports outdoor operation. |
| PDA Core Logic Supply | Industrial Handheld MCU Rail |
|
Use Scenario: Regulating 2.8 V for ARM9-based PDA application processors during dynamic DVFS scaling. IC Role / Device Role / Timing Role: Primary core voltage regulator with fast load transient response. Use Value: 500 ns load step recovery (per Fig. 15) maintains logic integrity during burst processing. |
Use Scenario: Powering Cortex-M4 microcontrollers and CAN transceivers in battery-backed field instruments. IC Role / Device Role / Timing Role: Always-on LDO with inhibit-controlled subsystem isolation. Use Value: Inhibit pin allows selective shutdown of non-critical peripherals while retaining RTC and wake-up logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar low-noise, inhibit-capable LDO applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS7A2028PDQNR | Lower quiescent current (65 nA shutdown), but higher dropout (300 mV @ 150 mA); no bypass pin | Lacks dedicated noise-reduction bypass node; requires external RC filter for sub-50 µVrms performance | Preferred where nanowatt shutdown dominates over noise specs; unsuitable for RF-sensitive analog rails |
| MCP1703T-2802E/MB | Higher dropout (550 mV @ 150 mA); no inhibit pin; 35 µVrms noise with 100 nF bypass | Requires external enable logic (e.g., GPIO + MOSFET) for shutdown; less integrated control | Valid for cost-sensitive, non-battery-critical designs where 2.8 V accuracy and thermal range are primary concerns |
Compared with TPS7A2028PDQNR and MCP1703T-2802E/MB, the LD2985AM28R uniquely combines sub-1 µA shutdown, 280 mV dropout, and a dedicated bypass pin for guaranteed 30 µVrms noise - making it optimal for space-constrained, battery-operated analog-intensive systems.
Availability
LD2985AM28R is available at Aetrix Electronics and suitable for portable audio power, camera sensor bias, and industrial handheld MCU rail applications requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LD2985AM28R 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 precision low-dropout regulator product line, engineered specifically for ultra-low-noise, low-power portable electronics where battery efficiency and signal integrity are co-critical.
FAQ
What is the minimum input voltage required for stable 2.8 V output at 150 mA?
The LD2985AM28R requires a minimum input voltage of 3.08 V to maintain regulation at 150 mA load, based on its 280 mV maximum dropout voltage. Below this, output voltage collapses linearly with input. Input must also stay within the absolute maximum rating of −0.3 V to 16 V.
Can the INHIBIT pin be left floating?
No - the INHIBIT pin has no internal pull-up or pull-down. Leaving it floating risks undefined operation and potential oscillation or partial enablement. It must be actively driven to VI (to enable) or to GND (to disable), or tied to VI via a resistor if permanently enabled.
Is an input capacitor mandatory, and what type is recommended?
Yes - a minimum 1 µF ceramic capacitor (X7R or better) is required on the IN pin, placed within 12.7 mm of the device and connected to a clean analog ground. Larger values improve transient response and reduce input ripple; tantalum or film types are acceptable but less common due to size and ESR trade-offs.
How does the BYPASS pin reduce output noise, and what capacitor value is specified?
The BYPASS pin connects to an internal noise-reduction circuit that filters reference voltage fluctuations. A 10 nF ceramic capacitor between BYPASS and GND reduces broadband output noise from ~100 µVrms to 30 µVrms (300 Hz–50 kHz), as measured per the datasheet test conditions.
LD2985AM28R 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):
- 2.8V
- 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
LD2985AM28R FAQ
1.How can I place an order for LD2985AM28R through Aetrix?
Please submit a Request for Quotation (RFQ) for LD2985AM28R 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 LD2985AM28R reliable?
The price and inventory of LD2985AM28R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LD2985AM28R is usually 5 days.
3.What payment methods are accepted for LD2985AM28R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LD2985AM28R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LD2985AM28R?
LD2985AM28R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LD2985AM28R 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 LD2985AM28R?
For technical support, including LD2985AM28R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LD2985AM28R requirements.
6.How does Aetrix verify that LD2985AM28R is sourced from the original manufacturer or authorized distributors?
All LD2985AM28R 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 LD2985AM28R meets industry standards.
7.What is the process for return or replacement of LD2985AM28R?
All LD2985AM28R units undergo pre-shipment inspection (PSI). If there is an issue with LD2985AM28R, 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 LD2985AM28R part is unused and in its original packaging.
Return procedure for LD2985AM28R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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