LR8N8-G - 450V, 20mA Adjustable Linear Regulator | Microchip
부품 번호: LR8N8-G ✓ 활성LR8N8-G 개요
An adjustable linear regulator is a type of analog voltage regulator whose output is set by an external resistor divider rather than a fixed internal reference. Within the broader power-management hierarchy, the LR8 sits in the linear regulator (LDO-class) family, which itself is a subset of voltage regulators. Linear regulators dissipate the difference between input and output as heat rather than switching it, trading efficiency for very low output noise and minimal EMI. The LR8 specifically targets the niche of high-voltage bias rails where most general-purpose LDOs cannot operate.
Key features include a 5% output voltage tolerance, integrated output current limiting, a typical ADJ pin bias current of 10 µA, and internal junction temperature protection. Because the device is a 3-terminal part (IN, OUT, ADJ) in the same SOT-89 footprint as a conventional low-voltage regulator, it offers a drop-in, compact solution for offline-derived auxiliary rails without the complexity of a switching converter.
Typical applications include biasing of IGBT/SiC gate drivers in motor drives, bias for solid-state relay (SSR) and opto-coupler LED drivers, offline LED string drivers, and as an auxiliary supply for industrial control boards tapped from a 120/230 VAC or 380 VDC bus.
When designing with the LR8N8-G, plan thermal dissipation carefully: at 400 V input and a 1 mA load, the device still dissipates the full VIN minus VOUT drop. The SOT-89 package has limited thermal mass, so always verify worst-case junction temperature using the datasheet's theta_JA value and the actual PCB copper area.
This page synthesizes distributor inventory, parametric cross-references, and engineering design notes - information not assembled in any single manufacturer datasheet - to accelerate sourcing and first-pass design decisions for the LR8N8-G.
드롭인 대체품: LR8N8-G — 동일 패키지, 핀 호환. PCB 재작업이 필요한 다른 패키지 부품은 제외됩니다.
LR8N3-G
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
LR8K4-G
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
LR8N8-G-Q1
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
LR8N8-G-TR
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
LR8N8
✅ 드롭인📋 참조 대체품 (카탈로그에 없음)
LR8N8-G 최대 정격 & 전기적 특성
| Manufacturer | Microchip Technology (formerly Supertex, Inc.) |
| Product Type | High-Voltage Adjustable Linear Regulator |
| 입력 전압 범위 | 13.2 V to 450 V |
| 출력 전압 범위 | 1.20 V to 438 V |
| 최대 출력 전류 | 20 mA |
| Typical Output Current | 10 mA |
| Minimum VIN - VOUT Headroom | 12 V |
| Output Voltage Tolerance | 5 % |
| ADJ Pin Bias Current (typical) | 10 µA |
| Output Current Limiting | Yes (internal) |
| Junction Temperature Protection | Yes (internal thermal limit) |
| 패키지 | TO-243AA (SOT-89), 3 leads |
| 실장 유형 | Surface Mount |
LR8N8-G 핀 구성
| 핀 1 | ADJ — Adjust pin - connect external resistor divider here to set VOUT |
| 핀 2 | OUT — Regulated output voltage (1.20 V to 438 V) |
| 핀 3 | IN — Input voltage (13.2 V to 450 V); also connected to the SOT-89 tab for heatsinking |
일반적인 애플리케이션
LR8N8-G 적합 용도: 6 애플리케이션s: IGBT/SiC Gate Driver Bias Supply, Solid-State Relay (SSR) and Optocoupler LED Driver, Offline LED String Driver (Bias Source), Industrial 24 V/120 V/230 V Auxiliary Supply, High-Voltage Sensor Bias (Piezo, Strain Gauge, HV Probe), TFT/LCD Backlight Driver Bias (Industrial Display).
IGBT/SiC Gate Driver Bias Supply
The LR8N8-G is well matched to IGBT and SiC gate-driver bias rails because it accepts the rectified 300-400 VDC bus directly and outputs the 15-18 V typical gate-drive rail with up to 20 mA, enough for one driver channel plus a small optocoupler LED string. According to Microchip datasheet 20005399B, only 12 V of headroom is needed above the programmed output, leaving plenty of margin on a 390 VDC bus. The SOT-89 footprint drops onto the same land pattern as a low-voltage LDO, simplifying PCB layout versus a discrete Zener-dropper circuit. Designers should still budget thermal dissipation: at 400 V input and 10 mA load, the part dissipates roughly 3.85 W and needs copper-pour heatsinking to keep the junction below 125 °C.
추천
Solid-State Relay (SSR) and Optocoupler LED Driver
The LR8N8-G can supply the input-side LED current of solid-state relays and optocouplers directly from a high-voltage AC or DC bus, replacing bulky resistor-capacitor dropper circuits. With 20 mA of output and a programmable 1.20-438 V rail, it can bias multiple optocoupler LEDs in series at low current while keeping the input-side isolated from the high-voltage rail. Compared with a discrete Zener + resistor dropper, the LR8N8-G gives a regulated LED current independent of mains fluctuations, improving SSR turn-on threshold stability across the 85-264 VAC universal input range. The internal current limit also protects the optocoupler LED from inrush surges during SSR activation.
추천
Offline LED String Driver (Bias Source)
In offline LED lighting, the LR8N8-G serves as the constant-current reference bias rail that sets the operating point of a high-voltage BJT or depletion-mode FET driving an LED string. The 450 V input rating means it can sit on the rectified mains side without a preregulator, and the 1.20-438 V adjustable output can be dialed to the precise LED string forward voltage. Output current up to 20 mA is sufficient to drive a sense-FET gate plus housekeeping circuitry. Designers should note that 12 V minimum headroom means the part cannot be used as the LED current regulator directly for high-current strings; it is best used as a low-current bias reference in a two-stage topology.
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Industrial 24 V/120 V/230 V Auxiliary Supply
Industrial PLCs and motor controllers often need a small auxiliary 12 V or 15 V rail derived directly from the bus voltage without an isolating switching converter. The LR8N8-G fills this niche with its 13.2-450 V input range and 1.20-438 V programmable output, perfect for tapping 24 V from a 48 V bus, 15 V from a 24 V bus, or any low-voltage rail from a 380 V industrial DC link. Its 20 mA output can power housekeeping ICs, sensors, and indicator LEDs. The SOT-89 package fits into the same PCB real estate as a conventional LDO, enabling a unified footprint for low- and high-voltage boards.
추천
High-Voltage Sensor Bias (Piezo, Strain Gauge, HV Probe)
Piezoelectric sensors, strain-gauge bridges in high-voltage test equipment, and HV oscilloscope probes often require a small excitation voltage that floats at hundreds of volts above ground. The LR8N8-G can provide a clean, low-noise regulated bias up to 438 V at up to 20 mA directly from a high-voltage rail, eliminating the need for a separate isolated DC-DC converter. Its 5% output tolerance is sufficient for sensor excitation when paired with precision external resistors. Designers using the part as a probe bias should add an external output capacitor to reduce output impedance at AC and ensure the LR8N8-G tab (IN pin) is on a thermally adequate copper pour.
추천
TFT/LCD Backlight Driver Bias (Industrial Display)
Industrial TFT panels and CCFL-replacement LED-backlit LCDs sometimes require a small high-voltage bias rail for the gate-on voltage of the source drivers or the charge-pump stages. The LR8N8-G can derive such a rail from the existing 12-24 V display supply, stepping up to the 25-35 V needed for VGH. While its 20 mA output is too small to drive the backlight directly, it is ideal as a low-power bias source feeding a charge pump or as a VGL/VGH reference. Compared with discrete Zener solutions, the LR8N8-G keeps the bias voltage stable over temperature and input variation, improving display contrast uniformity.
추천
추천 제품 요약
엔지니어링 참조 데이터: LR8N8-G — 비교, 설계 지침 및 규정 준수 정보.
선택 가이드
대체품과의 비교
| 파라미터 | 이 제품 | LR8N3-G | LR8K4-G | LR8N8-G-Q1 | LR8N8-G-TR | LR8N8 |
|---|---|---|---|---|---|---|
| Package | TO-243AA (SOT-89) | TO-92 | TO-252 (DPAK) | TO-243AA (SOT-89) - same | TO-243AA (SOT-89) - same | TO-243AA (SOT-89) - same |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Input Voltage Range | 13.2 V to 450 V | 13.2 V to 450 V | 13.2 V to 450 V | 13.2 V to 450 V | 13.2 V to 450 V | 13.2 V to 450 V |
| Output Voltage Range | 1.20 V to 438 V | 1.20 V to 438 V | 1.20 V to 438 V | 1.20 V to 438 V | 1.20 V to 438 V | 1.20 V to 438 V |
| Maximum Output Current | 20 mA | 20 mA | 20 mA | 20 mA | 20 mA | 20 mA |
| Output Voltage Tolerance | 5 % | 5 % | 5 % | 5 % | 5 % | 5 % |
| Thermal Performance (theta_JA) | ~100 C/W (SOT-89, 1 oz copper, JEDEC EIA/JESD51) | ~160 C/W (TO-92, free air) | ~50 C/W (DPAK, 1 oz copper) | ~100 C/W (SOT-89) | ~100 C/W (SOT-89) | ~100 C/W (SOT-89) |
| Automotive Grade (AEC-Q100) | No | No | No | Yes | No | No |
주요 차별점
- Only Microchip regulator with 450 V input in a SOT-89 surface-mount package (vs LM317 (TO-220/TO-92, 40 V max))
- Better thermal dissipation in SOT-89 than TO-92 LR8N3-G (vs LR8N3-G (TO-92))
- Pin-compatible with LR8N8-G-Q1 for AEC-Q100 automotive designs (vs LR8N8-G-Q1 (AEC-Q100))
- Higher power dissipation than SOT-89 in DPAK LR8K4-G (vs LR8K4-G (DPAK))
설계 노트
Estimated: at VIN = 400 V, VOUT = 15 V and IOUT = 10 mA, the LR8N8-G dissipates approximately (400-15) × 0.010 = 3.85 W. With the SOT-89 thermal resistance of ~100 C/W on a JEDEC 1-oz copper test board, the junction would rise 385 °C above ambient, far exceeding the 125 °C limit. In practice, designers must attach the SOT-89 tab to at least 100-200 mm² of 2-oz copper, add thermal vias to inner planes, and reduce either the input voltage (use a preregulator) or the load current. A DPAK-packaged LR8K4-G variant exists for designs that cannot achieve adequate SOT-89 heatsinking.
Place the output capacitor (>= 1 µF ceramic, X7R, rated >= VOUT + 10%) as close as possible to the OUT and GND/ADJ return path. The Microchip datasheet specifies a minimum output capacitance for loop stability; values below 1 µF or with excessive ESR may cause oscillation. Use wide copper traces on IN and OUT, and treat the SOT-89 tab as both an electrical (IN) and thermal connection - a star-grounded pour around the tab keeps both the heatsink and the input return low-impedance.
Three pitfalls to avoid: (1) Do not assume the ADJ pin has negligible current - the 10 µA typical bias current introduces an output error of IADJ × R1; either use small-value divider resistors (kΩ not MΩ) or compensate with a parallel resistor. (2) Do not operate without the minimum 12 V headroom or VOUT will drop out of regulation. (3) Do not exceed 450 V on IN even transiently - add a TVS such as SMBJ440A across the input for inductive load transients when the LR8N8-G is fed from a long wiring harness.
Route the high-voltage IN trace on an inner or bottom layer with adequate clearance (>1 mm per 100 V) from low-voltage traces and from any user-accessible circuitry, per IEC 60950 / IEC 62368 reinforced-insulation rules. Keep the OUT and ADJ traces short and physically separated from IN traces to minimize capacitive coupling of input ripple into the output. Use a guard ring around the ADJ pin trace tied to ADJ itself to reduce leakage and noise pickup on the high-impedance feedback node.
Do not parallel multiple LR8N8-G outputs to increase current - the parts lack active current sharing and one will hog the load. If >20 mA is needed, use a single LR8N8-G as a reference driving a discrete high-voltage pass transistor (e.g. MPSA42 or MJE13003), or step down to a switching converter such as LM2591HVS-ADJ for higher currents at the cost of switching noise.
규정 준수 정보
RoHS/REACH compliance inferred from the '-G' Microchip suffix indicating Green/Pb-free packaging. AEC-Q100 qualification requires the LR8N8-G-Q1 variant; the standard LR8N8-G is not AEC-Q100 qualified. Conflict-minerals compliance per Microchip's standard CMRT filings.
