L7987 - 61V 3A Async Step-Down DC/DC Converter | STMicroelectronics
MPN: L7987 ✓ فعالL7987 نمای کلی
A step-down (buck) switching regulator is a DC/DC converter topology that produces a lower output voltage from a higher input voltage by switching an inductor-capacitor filter at high frequency. Asynchronous buck regulators use a Schottky diode for the freewheeling path instead of a second MOSFET, trading a small amount of efficiency for simplicity and lower BOM cost. Buck regulators sit within the broader power-management hierarchy: switching regulator -> DC/DC converter -> voltage regulator -> power management IC. They are preferred over linear regulators (LDOs) whenever the input-to-output voltage differential or load current is large enough that linear efficiency would be unacceptably low.
Key features of the L7987 include a fixed 250 kHz switching frequency (adjustable with an external resistor from 250 kHz to 1500 kHz), external synchronization input (SYNCH pin), embedded switchover on the VBIAS pin that maximizes efficiency at light load, adjustable current limitation, and thermal shutdown. The 16-HTSSOP exposed pad keeps junction-to-ambient thermal resistance low enough to dissipate multi-watt loads without an external heatsink. The architecture uses peak-current-mode control, which simplifies loop compensation and provides inherent input-voltage feed-forward.
Typical applications include industrial 24 V/48 V bus regulation, distributed point-of-load conversion, battery-powered equipment, and any system where a wide input voltage range and high efficiency must coexist in a compact 16-pin surface-mount footprint. When laying out this device, place the input bypass capacitor and the bootstrap capacitor directly at their respective pins, keep the high-current loop area minimal, and stitch thermal vias into the exposed pad to pull heat into the inner copper planes.
جایگزین‌های drop-in برای L7987 — همان پکیج، سازگار پین‌به‌پین. قطعات با پکیج متفاوت که نیاز به تغییر PCB دارند مستثنی هستند.
گونه‌ها در این سری
مدل‌های هم‌سری که جایگزین مستقیم هستند برای L7987 (همان فرم‌فاکتور و فوت‌پرینت) — متفاوت در Efficiency, Output Voltage Range, Package, Switching Frequency, Input Voltage Range.
L7987TR
✅ جایگزین مستقیم📋 جایگزین مرجع (خارج از کاتالوگ)
L7987LTR
✅ جایگزین مستقیمبرای قیمت تماس بگیرید
مشاهده دیتاشیت ←L7987A
✅ جایگزین مستقیم ⚠️ مشخصات تأییدنشده📋 جایگزین مرجع (خارج از کاتالوگ)
L7987 حداکثر مقادیر مجاز و مشخصات الکتریکی
| توپولوژی | Step-down (buck), asynchronous |
| محدوده ولتاژ ورودی | 4.5 V to 61 V |
| محدوده ولتاژ خروجی | 0.8 V to VIN (adjustable) |
| حداکثر جریان خروجی | 3 A |
| فرکانس سوئیچینگ | 250 kHz (typ), adjustable 250 kHz to 1500 kHz |
| Synchronization Range | 250 kHz to 1500 kHz (external clock on SYNCH) |
| Duty Cycle | Up to 100% (fail-safe mode) |
| Control Method | Peak current mode |
| بازدهی | Up to ~90% (application dependent) |
| محدودیت جریان | Adjustable |
| بسته‌بندی | 16-TSSOP (HTSSOP) with exposed pad |
| Package Body Size | 0.173" (4.40 mm) width |
| نوع نصب | Surface Mount |
| وضعیت RoHS | Compliant |
| Embedded Switchover | Yes (VBIAS pin) |
| Synchronization Pin | Yes (SYNCH) |
پیکربندی پین L7987
| پین 1 | BOOT — Bootstrap capacitor for high-side gate drive |
| پین 2 | VIN — Input supply voltage (4.5 V to 61 V) |
| پین 3 | SW — Switch node - connect to inductor and Schottky cathode |
| پین 4 | GND — Ground |
| پین 5 | FB — Feedback (voltage divider to VOUT) |
| پین 6 | COMP — Compensation network for the error amplifier |
| پین 7 | EN — Enable input (active high) |
| پین 8 | VCC — Internal regulator output - decouple with 1 uF |
| پین 9 | VBIAS — Switchover supply input for internal LDO |
| پین 10 | SYNCH — Synchronization input (250 kHz to 1500 kHz) |
| پین 11 | FSW — Frequency select resistor to GND |
| پین 12 | ILIM — Current limit set resistor to GND |
| پین 13 | NC — Not connected (per datasheet) |
| پین 14 | NC — Not connected (per datasheet) |
| پین 15 | GND — Ground |
| پین 16 | PGND — Power ground (return for low-side driver) |
| پین EP | Exposed Pad — Thermal pad - solder to PCB ground plane for heat dissipation |
کاربردهای معمول
L7987 مناسب است برای 7 کاربردs: Industrial 24V/48V Bus Point-of-Load Conversion, Automotive 12V Body and Infotainment Rails, Battery-Powered Portable Equipment, Distributed POL in Industrial PLC and IO Modules, LED Lighting Drivers and Constant-Current Regulation, Telecom and Networking Auxiliary Rails, Test and Measurement Instrumentation.
Industrial 24V/48V Bus Point-of-Load Conversion
The L7987 is purpose-built for industrial 24 V and 48 V distributed bus systems that step down to 5 V, 3.3 V, or 1.8 V logic rails at the point of load. Its 4.5 V to 61 V input range covers the full envelope of nominal, transient, and load-dump conditions found on a factory DC bus, while the 100% duty-cycle capability holds VOUT stable during input brown-out events. The 3 A output handles multi-rail processors, FPGAs, and motor-driver housekeeping without forcing designers to stack parallel stages. Typical BOM uses a 22-47 uH inductor, a low-ESR ceramic output capacitor bank, and a small Schottky on the SW node, achieving 90%+ efficiency at 24 V to 5 V / 2 A.
پیشنهادی
Automotive 12V Body and Infotainment Rails
The L7987's 61 V input rating gives it strong margin against 12 V automotive load-dump transients (commonly up to 35 V) and jump-start events, making it a robust choice for body controllers, infotainment head units, and gateway ECUs. Its adjustable current limit, 250 kHz to 1500 kHz switching range, and external synchronization pin let designers tune the EMI signature to clear CISPR 25 automotive EMC limits by spreading switching harmonics. Note: the standard L7987 is not AEC-Q100 qualified; confirm the qualification status of the specific ordering code with STMicroelectronics before deploying in a production automotive module.
پیشنهادی
Battery-Powered Portable Equipment
Portable and battery-powered equipment running from a 2S to 4S lithium pack (8 V to 17 V nominal) uses the L7987 to step the pack down to logic rails efficiently. The peak-current-mode control simplifies the compensation network, while the VBIAS switchover feature lets the internal LDO draw from the output rail at light load, slashing quiescent current and extending battery life. The 3 A peak capability delivers ample headroom for short radio transmit bursts in Wi-Fi, BLE, or sub-GHz transceivers without a separate boost stage. A typical 2-cell-to-3.3 V design uses a 10 uH inductor and 2 x 22 uF output ceramic for sub-50 mV ripple.
پیشنهادی
Distributed POL in Industrial PLC and IO Modules
Programmable logic controllers, distributed IO modules, and industrial Ethernet gateways need isolated or non-isolated 24 V-to-3.3 V/5 V conversion at each module. The L7987's compact 16-HTSSOP exposed-pad footprint and high switching range simplify placement next to each load zone, minimizing trace-induced losses and ground-bounce noise. The SYNCH input permits synchronizing multiple L7987s across a backplane to a single master clock, eliminating beat-frequency interference. External compensation on the COMP pin gives designers the freedom to optimize transient response for tight digital load steps from microcontrollers and FPGAs.
پیشنهادی
LED Lighting Drivers and Constant-Current Regulation
Although the L7987 is a voltage-mode buck, designers commonly reconfigure it as a constant-current LED driver by replacing the VFB divider with a current-sense resistor. The 61 V input comfortably drives strings of high-brightness LEDs from 24 V or 48 V supplies, and the 3 A peak supports multi-watt architectural and industrial lighting fixtures. The adjustable switching frequency allows pushing the frequency above the AM band to avoid audiblenoise interference, while the VBIAS switchover keeps standby efficiency high in dimming modes. Thermal performance is straightforward: stitch vias under the exposed pad keep Tj1 well below 125 C at full load.
پیشنهادی
Telecom and Networking Auxiliary Rails
Telecom base stations, network switches, and small-cell radios generate a variety of intermediate bus voltages (typically 12 V, 24 V, or 48 V) that must be stepped down to 5 V, 3.3 V, or 1.8 V for digital logic. The L7987's wide input range, 3 A output, and external synchronization make it well suited to these distributed POL architectures. Its peak-current-mode control provides clean transient response to load steps from switch ASICs and PHYs. Synchronizing the L7987 to the system clock or to a master regulator prevents beat-frequency interference in dense multi-rail designs.
پیشنهادی
Test and Measurement Instrumentation
Bench power supplies, data acquisition systems, and laboratory instruments often stack multiple isolated rails (e.g. +/-15 V, 5 V, 3.3 V) from a single 24 V or 48 V input. The L7987 provides a high-efficiency positive rail, leaving a companion inverting topology (or a charge-pump) for the negative rail. Its adjustable current limit doubles as a board-level fault-protection threshold during prototype bring-up. The exposed pad and 16-HTSSOP footprint sit comfortably next to SOIC op-amps and DACs on the same PCB, simplifying the layout of mixed-signal instrumentation boards.
پیشنهادی
خلاصه محصولات پیشنهادی
داده‌های مرجع مهندسی برای L7987 — مقایسه، راهنمای طراحی و اطلاعات انطباق.
راهنمای انتخاب
مقایسه با جایگزین‌ها
| پارامتر | این محصول | L7987TR | L7987L | L7987A |
|---|---|---|---|---|
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics |
| Package | 16-TSSOP (HTSSOP) with exposed pad | 16-TSSOP (HTSSOP) with exposed pad - same | 16-TSSOP (HTSSOP) with exposed pad - same | 16-TSSOP (HTSSOP) with exposed pad - same |
| Input Voltage Range | 4.5 V to 61 V | 4.5 V to 61 V | 4.5 V to 61 V | 4.5 V to 61 V |
| Output Current | 3 A | 3 A | Lower current variant | 3 A |
| Switching Frequency | 250 kHz (adj. to 1500 kHz) | 250 kHz (adj. to 1500 kHz) | 250 kHz (adj. to 1500 kHz) | 250 kHz (adj. to 1500 kHz) |
| Output Voltage Range | 0.8 V to VIN | 0.8 V to VIN | 0.8 V to VIN | 0.8 V to VIN |
| Synchronization Pin | Yes (SYNCH, 250 kHz to 1500 kHz) | Yes | Yes | Yes |
| VBIAS Switchover | Yes (light-load efficiency) | Yes | Yes | Yes |
تفاوت‌های کلیدی
- Wide 61 V input range with 100% duty cycle for fail-safe operation (در مقابلL7987L)
- Synchronization input (SYNCH) eliminates beat frequencies in multi-rail designs (در مقابلL7987A (assumed))
- Embedded VBIAS switchover minimizes quiescent current at light load (در مقابلGeneric 3 A asynchronous buck)
یادداشت‌های طراحی
Estimated: at VIN = 24 V, VOUT = 5 V, and IOUT = 2 A the L7987 dissipates roughly (24-5)*0.03 + (5*2/0.9 - 5*2) approx 2 W assuming 90% efficiency. The 16-HTSSOP exposed pad has a typical theta_JA around 40 C/W when soldered to a 1-square-inch copper pour, yielding a junction temperature rise near 80 C. For higher output currents, expand the copper area or add airflow. Always solder the exposed pad with a full array of thermal vias to the inner ground plane.
Place the input ceramic bypass capacitor (typically 4.7 uF to 10 uF X7R) as close as possible to the VIN and GND pins, and place the bootstrap capacitor (typically 100 nF) directly between BOOT and SW. Keep the high-current loop formed by VIN, the high-side MOSFET, the SW node, the inductor, the output capacitor, and the return path as small as possible to minimize EMI and ringing. Use a wide SW node pour to reduce trace resistance.
Route the FB trace away from the SW node to avoid capacitive coupling that distorts the feedback signal. Place the compensation network (RC on COMP pin) close to the IC to keep the high-impedance loop small. Stitch the ground plane under the exposed pad with a 3x3 or 4x4 via array to pull heat into inner copper layers. Connect PGND and signal GND at a single point under the exposed pad.
Do not omit the bootstrap capacitor - the high-side gate driver will fail without it. Ensure the chosen inductor has a saturation current comfortably above the L7987's adjusted current limit (typically 30-50% margin). When using the VBIAS switchover, tie VBIAS to VOUT above 5V to maximize efficiency; below 5V, leave VBIAS tied to VIN. Never exceed 61 V on VIN, even transiently, or the internal MOSFET will avalanche.
To pass CISPR 22 / CISPR 25 EMC limits, place a small RC snubber (typically 2-5 ohm + 1 nF) across the low-side Schottky diode or SW-to-PGND. Shielding the input filter network with a pi-filter (LC) attenuates differential-mode EMI. Synchronizing the L7987 to a system clock outside the AM broadcast band (typically above 1.5 MHz) avoids audible rectification in audio circuits.
اطلاعات انطباق
RoHS compliance inferred from STMicroelectronics product page. AEC-Q100 qualification status not stated in available data - confirm with ST for automotive deployments. Halogen-free status not found in verified data.
