LM285D-1.2RG - 1.235V Micropower Shunt Voltage Ref | onsemi
Артикул: LM285D-1.2RG ✓ Активен| Кол-во | Цена за ед. | Итого |
|---|---|---|
| 1 | $0.49 | $0,49 |
| 10 | $0.4 | $4,00 |
| 100 | $0.28 | $28,00 |
| 500 | $0.21 | $105,00 |
| 1.000 | $0.16 | $160,00 |
| 3.000 | $0.13 | $390,00 |
LM285D-1.2RG Обзор
A shunt voltage reference is a two-terminal analog component that maintains a constant voltage across its terminals when biased with a regulated current, similar in behavior to a precision zener diode but with much lower minimum bias, lower noise, and better long-term drift. The LM285 family occupies the lowest tier of the voltage-reference hierarchy (shunt reference -> reference diode -> power management IC) and is intended for portable, battery-powered, or remote-sensor designs that cannot tolerate the quiescent draw of a series-mode reference IC.
Key features include a typical dynamic impedance of 0.6 ohm at 1 mA cathode current, 60 uVrms broadband output noise, an initial accuracy of ±1% (the tighter ±0.3% option marks the LM285B variant), and exceptionally stable operation over time and temperature thanks to on-chip trimming of the bandgap core. The 8-SOIC footprint enables automated SMT assembly while exposing a thermal pad-less body that dissipates heat through the SO-8 leads.
The device uses a bipolar bandgap reference architecture with on-chip thin-film resistors trimmed at wafer probe to set the 1.235 V output. Because the part is a true two-terminal shunt, the surrounding circuit fixes the cathode current via an external bias resistor or active current source, which makes the LM285D-1.2RG behave more like a precision zener than a three-terminal regulator. The wide 10 uA to 20 mA operating window allows designers to trade quiescent current against reference accuracy at the application level.
Typical applications include ADC and DAC reference inputs, portable meter calibration, threshold detectors in battery monitoring circuits, and as a precision reference in 4-20 mA loop transmitters. The 1.235 V output pairs naturally with low-voltage ADCs that expect a sub-2.5 V full-scale reference.
Designers should bias the LM285D-1.2RG with at least 10 uA of cathode current to ensure proper bandgap startup; below this current the output becomes undefined. For best temperature stability, operate near the 1 mA to 10 mA region where dynamic impedance and noise are simultaneously minimized.
Аналоги без доработки для LM285D-1.2RG — тот же корпус, pin-to-pin совместимость. Компоненты в других корпусах, требующие переработки PCB, исключены.
Инструмент быстрого сравнения — выберите альтернативные компоненты для сравнения бок о бок:
LM285BD-1.2RG
✅ Прямая замена ⚠️ Характеристики не проверены📋 Справочный аналог (нет в каталоге)
LM285D-1.2RG
✅ Прямая замена✓ В наличии
$0.13 / шт.
Открыть даташит →LM385BD-1.2G
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
LM285D-1.2RG
✅ Прямая замена✓ В наличии
$0.13 / шт.
Открыть даташит →LM385D-1.2G
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
LM285D-1.2RG Характеристики
| Reference Type | Shunt Voltage Reference (2-terminal bandgap) |
| Nominal Output Voltage | 1.235 V |
| Initial Accuracy | +/-1% (LM285D-1.2) |
| Cathode Current Range | 10 uA to 20 mA |
| Temperature Coefficient | 30 ppm/°C (typical) |
| Output Noise (broadband) | 60 uVrms |
| Диапазон рабочих температур | -40°C to +85°C |
| Quiescent Current (min) | 8 uA (typical) |
| Корпус | SOIC-8 (D, body 3.9 mm) |
| Тип монтажа | Surface Mount |
| Architecture | Bipolar bandgap with on-chip trim |
| Топология | Shunt (cathode to V+, anode to GND) |
| Статус RoHS | Compliant |
| Уровень MSL | 1 |
Конфигурация выводов LM285D-1.2RG
| Контакт 1 | K (Cathode) — Cathode - positive reference terminal; biased via external resistor |
| Контакт 2 | NC — Not internally connected - tie to anode on PCB |
| Контакт 3 | NC — Not internally connected - tie to anode on PCB |
| Контакт 4 | NC — Not internally connected - tie to anode on PCB |
| Контакт 5 | NC — Not internally connected - tie to anode on PCB |
| Контакт 6 | NC — Not internally connected - tie to anode on PCB |
| Контакт 7 | NC — Not internally connected - tie to anode on PCB |
| Контакт 8 | A (Anode) — Anode - typically tied to ground |
Типичное применение
LM285D-1.2RG подходит для 6 применениеs: ADC and DAC Reference Input, Portable Battery-Powered Calibration Source, Threshold Detector in Battery Management, 4-20 mA Loop Transmitter Reference, Comparator Trip-Point Reference, Precision Current Source Calibration.
ADC and DAC Reference Input
The LM285D-1.2RG provides a stable 1.235 V low-impedance reference rail for low-voltage ADCs and DACs in precision measurement equipment. Its +/-1% initial accuracy and 30 ppm/°C temperature coefficient hold the LSB weighting of a 12-bit ADC stable across the industrial -40°C to +85°C window. Designers place the LM285D-1.2RG between the supply rail and the ADC REF pin, biased via a single 3.76 kohm resistor from 5 V to deliver 1 mA of cathode current. Unlike a series LDO reference, the shunt topology allows the reference to share the same ground-return path as the analog front-end, minimizing ground-loop errors in mixed-signal PCBs.
Рекомендуется
Portable Battery-Powered Calibration Source
Battery-powered handheld instruments rely on the LM285D-1.2RG to deliver a stable calibration point from a single Li-ion cell or 9 V battery. Drawing only 10 uA minimum bias, the LM285D-1.2RG does not measurably tax the battery during sleep or measurement idle states, extending runtime in dataloggers and field meters. The 1.235 V output can be divided externally to provide ratiometric calibration points for pressure transducers, thermocouple cold-junction compensators, and pH probes. Its SOIC-8 SO package withstands reflow profiles up to 260°C with an MSL-1 floor life, simplifying high-volume production.
Рекомендуется
Threshold Detector in Battery Management
The LM285D-1.2RG functions as a precision voltage threshold in battery management circuits for Li-ion, lead-acid, and NiMH packs. Wired as a comparator reference against a divider tap from the battery stack, the LM285D-1.2RG triggers a low-battery alert when the pack voltage crosses the 1.235 V trip point - this can be scaled for 3 V, 12 V, or 24 V packs by selecting the appropriate divider ratio. The 30 ppm/°C temperature coefficient keeps the trip threshold stable across automotive under-hood (-40°C cold crank) and consumer storage conditions. Compared to a TL431 the LM285D-1.2RG offers lower minimum bias and a smaller SOIC-8 PCB footprint.
Рекомендуется
4-20 mA Loop Transmitter Reference
Industrial 4-20 mA current-loop transmitters use the LM285D-1.2RG as a fixed 1.235 V excitation reference for the input-side sensor bridge or RTD conditioning circuit. The shunt topology is ideal because the loop itself already provides a regulated current source to the transmitter card, and the LM285D-1.2RG simply clamps a voltage across its terminals. Operating at 0.5 mA to 5 mA cathode current, the device adds less than 50 uA to the total loop budget while delivering low 60 uVrms noise that preserves the 16-bit effective resolution typical in HART-enabled smart transmitters. The -40°C to +85°C industrial temperature rating matches the harsh-environment needs of process-control loops.
Рекомендуется
Comparator Trip-Point Reference
Window comparators and precision over/under-voltage detectors use the LM285D-1.2RG to set a stable 1.235 V trip threshold. Tie the reference cathode to the comparator reference pin and the anode to GND; the 30 ppm/°C temperature coefficient keeps the trip point stable across the operating temperature range without digital compensation. The 10 uA minimum cathode current lets the reference operate in micropower supervisory circuits where the comparator draws negligible bias from the supply rail - a popular topology for power-good signals in MCU-based designs.
Рекомендуется
Precision Current Source Calibration
Test and measurement equipment uses the LM285D-1.2RG as a calibration anchor for active current sources up to 20 mA. The shunt topology makes the LM285D-1.2RG naturally suited for constant-current sinks/mirrors that need a low-noise reference to set their compliance voltage. In a Howland current source, the LM285D-1.2RG provides the 1.235 V set-point that drives the op-amp servo loop, ensuring source accuracy is dominated by the LM285D-1.2RG's +/-1% initial tolerance rather than the resistor drift. This application favors the tighter +/-0.3% LM285BD-1.2RG variant when source accuracy targets tighter than 0.5% are required.
Рекомендуется
Сводка рекомендуемых товаров
Справочные инженерные данные для LM285D-1.2RG — сравнение, рекомендации по проектированию и информация о соответствии.
Руководство по выбору
Сравнение с аналогами
| Параметр | Этот товар | LM285BD-1.2RG | LM285D-1.2RG (TI) | LM385BD-1.2G | LM385D-1.2G | LM285D-1.2RG (HANSCHIP) |
|---|---|---|---|---|---|---|
| Brand | onsemi | onsemi | Texas Instruments | onsemi | onsemi | HANSCHIP semiconductor |
| Package | SOIC-8 (D) | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same | SOIC-8 (D) - same |
| Output Voltage | 1.235 V | 1.235 V | 1.235 V | 1.235 V | 1.235 V | 1.235 V |
| Initial Accuracy | +/-1% | +/-0.3% | +/-1% | +/-0.5% | +/-2% | +/-0.3% |
| Cathode Current Range | 10 uA to 20 mA | 10 uA to 20 mA | 10 uA to 20 mA | 10 uA to 20 mA | 10 uA to 20 mA | 10 uA to 20 mA |
| Temperature Coefficient | 30 ppm/°C | 30 ppm/°C | 30 ppm/°C | 30 ppm/°C | 30 ppm/°C | 30 ppm/°C |
| Operating Temperature | -40°C to +85°C | -40°C to +85°C | -40°C to +85°C | 0°C to +70°C | 0°C to +70°C | -40°C to +85°C |
| Output Noise | 60 uVrms | 60 uVrms | 60 uVrms | 60 uVrms | 60 uVrms | 60 uVrms |
| RoHS Status | Compliant | Compliant | Compliant | Compliant | Compliant | Compliant |
Ключевые отличия
- Multi-source second-sourceable across onsemi, Texas Instruments, and HANSCHIP (против TI LM285D-1.2)
- Tighter +/-0.3% initial accuracy option in same package (LM285BD-1.2RG) (против LM385D-1.2G)
- Industrial -40°C to +85°C temperature grade (против LM385BD-1.2G)
Заметки по проектированию
Estimated: at IK = 1 mA with VSUP = 5 V and the SOIC-8 footprint (theta_JA approx 170 C/W), power dissipation is approximately 3.8 mW, well within the SOIC-8 thermal envelope. Even at IK = 20 mA the dissipation stays below 80 mW, so thermal concerns are negligible for this part - focus instead on bias-resistor sizing. The most common design error is biasing below 10 uA: below this knee the bandgap becomes unstable and the output voltage sags. Always select R = (VSUP - 1.235) / IK with IK equal to at least 100 uA to leave margin at cold temperatures.
Place the LM285D-1.2RG SOIC-8 close to the ADC/DAC reference pin with a 0.1 uF X7R bypass capacitor directly across cathode (pin 1) and anode (pin 8). The six internal NC pins (2-7) should be tied to the anode (ground) on the PCB land pattern to prevent stray capacitive coupling into the reference node. Keep digital traces and switching regulator inductors away from the reference pin by at least 5 mm to preserve the 60 uVrms noise floor.
The cathode (pin 1) carries the bias current and is therefore a high-impedance node sensitive to leakage; route it on a keepout away from any high-voltage switching planes. The anode (pin 8) should tie directly to the analog ground plane via a short, low-inductance trace. If the LM285D-1.2RG sits at the end of a long cable or sensor harness, add a 1 uF capacitor in parallel with the bias resistor at the reference end to absorb cable-induced transients.
Информация о соответствии
RoHS and REACH compliant per onsemi LM285 product family. Lead-free SOIC-8 termination finish. Not AEC-Q100 qualified; for automotive AEC-Q100 equivalents, consider the LM285-Q1 family from TI. Conflict-minerals compliant to onsemi standard policy.
