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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

STMicroelectronics L7987

Name: L7987
Brand: STMicroelectronics
SKU: L7987
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L7987

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 16-TSSOP (0.173", 4.40mm Width) Exposed Pad

Datasheet:: L7987.pdf

Description:: IC REG BUCK ADJ 3A 16HTSSOP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L7987 from STMicroelectronics is a 61 V, 3 A asynchronous step-down switching regulator with adjustable current limitation, designed for industrial DC-DC conversion in 24 V bus systems. It delivers up to 3 A DC output, supports 4.5–61 V input, features 250 mΩ typical high-side R_DS,ON, adjustable 250 kHz–1.5 MHz switching frequency, and includes PGOOD open-collector output and output voltage sequencing capability.

For engineers reviewing the L7987 datasheet, L7987 pinout, L7987 application, or L7987 equivalent, key selection considerations include its fail-safe tolerance for PLCs, programmable current limit for inductor RMS sizing, VBIAS-assisted light-load efficiency, digital frequency foldback for short-circuit protection, and synchronization capability across up to five devices to reduce input ripple.

Technical Context

The L7987 implements a voltage-mode, constant-frequency PWM control loop with internal 0.8 V reference and sawtooth ramp modulation. Its oscillator supports resistor-programmed f_SW (250 kHz–1.5 MHz) and external synchronization via the SYNCH pin with 180° phase shift, enabling multi-device noise reduction in sensor-A/D systems.

It integrates pulse-by-pulse peak current sensing with dual-foldback protection: digital frequency foldback under moderate overload and peak current foldback during heavy short-circuit. The switchover from VCC to VBIAS supply improves light-load efficiency, while the 100% duty cycle capability enables low-dropout operation down to 12 µs maximum on-time.

Key Specifications

Parameter	Value and Actual Design Meaning
Input Voltage Range	4.5 V to 61 V - supports wide industrial bus voltages including 24 V and 48 V systems with fail-safe margin.
Output Current	3 A DC - continuous output current capability with integrated N-channel MOSFET and thermal shutdown at 170 °C.
R_DS,ON (HS)	250 mΩ typ. - reduces conduction loss and thermal stress at full load; measured at I_SW = 0.5 A.
f_SW Range	250 kHz to 1.5 MHz - adjustable via external resistor on FSW pin; enables compact magnetics and EMI optimization.
Quiescent Current	11 µA typ. in shutdown (I_Q-SHD) - minimizes standby power in always-on industrial controllers.
PGOOD Threshold	0.70 V ±30 mV on FB pin - provides accurate output regulation monitoring for power sequencing in multi-rail systems.
VBIAS Switchover	2.90 V threshold (rising), 4.05 V (falling) - automatically shifts internal bias supply to improve efficiency below ~10% load.

Pinout & Package

Package: HTSSOP16 (exposed pad); thermal resistance R_thJA = 40 °C/W (on ST demo board).

Pin/Terminal	Circuit Role	Design Meaning
1 VBIAS	Auxiliary bias supply input	Connects to regulated output or ≥3 V rail to improve light-load efficiency; bypass with 1 µF ceramic if used.
2,3 VIN	Main power input	Dual pins reduce PCB trace resistance and thermal rise for 3 A input current path.
4 VCC	Internal circuitry supply	Bypassed with 1 µF ceramic capacitor; UVLO threshold 4.10 V ensures reliable startup above brownout.
5 EN	Enable control	Active-high logic; internal pull-down ensures safe default-off state when floating.
6 SS	Soft-start timing node	5 µA internal current source charges external capacitor; controls monotonic V_OUT ramp and inrush limiting.
7 SYNCH	Master/slave sync interface	Generates 180°-phase-shifted clock; supports daisy-chaining up to 5 devices to minimize input capacitor RMS current.
8 COMP	Error amplifier output	Connects to external Type II/III compensation network; 100 dB gain and 23 MHz GBWP enable stable loop design.
9 FB	Feedback input	Inverting input of error amp; senses 0.800 V ±1% reference; sets output voltage via resistive divider.
10 FSW	Frequency programming	Pull-down resistor selects f_SW; 10 kΩ yields ~1.5 MHz; floating defaults to 250 kHz.
11 ILIM	Current limit programming	Pull-down resistor sets peak switch current; 100 kΩ yields 0.85 A nominal limit for precise inductor sizing.
12 PGOOD	Power-good indicator	Open-drain output pulled low when V_FB < 0.67 V; enables sequencing and fault signaling in multi-rail systems.
13,14 LX	Switching node	Connects to external inductor and bootstrap capacitor; dual pins reduce parasitic inductance and EMI.
15 BOOT	Bootstrap gate drive	100 nF capacitor between BOOT–LX supplies gate charge for high-side N-MOSFET; enables 100% duty cycle.
16 GND	Signal ground	Exposed pad must be soldered to PCB ground plane for thermal and electrical integrity; defines reference for all analog blocks.

Key Features

Feature	Design Value
Adjustable current limitation	Programmable peak switch current (0.68–4.6 A) via ILIM resistor - enables precise inductor RMS current matching to nominal load.
Digital frequency foldback	Reduces switching frequency during overload - maintains regulation while lowering power dissipation and stress on external components.
VBIAS-assisted light-load efficiency	Switchover from VCC to VBIAS at ~2.9 V - cuts quiescent current to 1.0 mA (VIN=24 V, VOUT=3.3 V), extending battery life in standby mode.
Synchronization support	Up to 5 devices synchronized via shared SYNCH pin - eliminates beat frequencies and reduces input capacitor RMS current by interleaving phases.
Low dropout operation	100% duty cycle enabled with 12 µs max. T_ONMAX - sustains regulation even when V_IN approaches V_OUT, critical for brownout resilience.

Applications

Programmable Logic Controllers (PLCs)

Industrial Sensor Signal Conditioning

Use Scenario: Powering CPU, I/O modules, and communication interfaces in modular PLC backplanes operating from 24 V DC bus.

IC Role / Device Role / Timing Role: Primary non-isolated buck regulator delivering stable 3.3 V or 5 V rails with sequencing and PGOOD monitoring.

Use Value: Fail-safe 61 V input rating and 100% duty cycle ensure uninterrupted operation during bus transients and brownouts.

Use Scenario: Supplying precision analog front-ends (AFE), ADCs, and low-noise op-amps in factory-floor sensors.

IC Role / Device Role / Timing Role: Low-noise, synchronized DC-DC converter minimizing switching interference on sensitive analog measurement paths.

Use Value: SYNCH pin synchronization across multiple L7987s prevents beat frequencies that could alias into ADC sampling bands.

Motor Drive Control Boards

Remote I/O Terminal Units

Use Scenario: Generating gate driver and MCU supply rails in compact servo drives where space and thermal management are constrained.

IC Role / Device Role / Timing Role: High-efficiency buck regulator with VBIAS optimization and adjustable soft-start for controlled gate driver ramp-up.

Use Value: 250 mΩ R_DS,ON and 3 A capability enable compact 2-layer PCB designs without external MOSFETs or heatsinks.

Use Scenario: Powering isolated CAN/RS-485 transceivers, microcontrollers, and status LEDs in distributed field I/O nodes.

IC Role / Device Role / Timing Role: Robust primary regulator tolerant to long cable drops, ESD, and load dump events on 24 V field wiring.

Use Value: 2 kV HBM ESD rating and adjustable current limit protect against inductive kickback and hot-plug surges in harsh environments.

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM5164QPWPRQ1	4.5–65 V input, 350 mA output, integrated FET but lower current rating; requires external MOSFET for >1 A loads.	Designed for automotive AEC-Q100 qualification; lacks VBIAS, PGOOD sequencing, and multi-device sync.	Select for automotive-grade reliability where 350 mA output suffices and AEC-Q100 compliance is mandatory.
MP2451DT-LF-Z	4.5–36 V input, 0.6 A output, fixed 2.2 MHz f_SW, no current limit adjustment or VBIAS support.	Targeted at consumer/portable apps; lacks industrial thermal specs (T_J = –40 to 125 °C) and fail-safe 61 V rating.	Select only for cost-sensitive, low-power (<0.6 A), non-industrial applications where compact size outweighs feature set.

Compared with LM5164QPWPRQ1 and MP2451DT-LF-Z, the L7987 uniquely combines 3 A output, 61 V input, programmable current limit, VBIAS efficiency boost, and multi-device synchronization-making it the only choice for high-reliability, high-current industrial buck conversion requiring fail-safe operation and power sequencing.

Availability

L7987 is available at Aetrix Electronics and suitable for programmable logic controllers (PLCs), industrial sensor signal conditioning, and motor drive control boards requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.

Supply support for L7987 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, specializing in industrial, automotive, and power management ICs with vertical manufacturing and broad application expertise.

The L7987 belongs to ST's industrial-grade power management portfolio, engineered specifically for ruggedized DC-DC conversion in programmable controllers, automation equipment, and fail-safe 24 V bus systems.

FAQ

What is the minimum input voltage required for the L7987 to regulate a 3.3 V output?

The L7987 supports dropout operation down to 12 µs maximum on-time, enabling regulation even when input voltage approaches the output level. For a 3.3 V output, it can maintain regulation with input as low as approximately 3.5 V under light load, thanks to 100% duty cycle capability and internal VBIAS switchover that sustains gate drive integrity.

How does the L7987 implement short-circuit protection without latch-off?

The L7987 uses two complementary short-circuit protections: digital frequency foldback reduces switching frequency to limit average power during moderate overloads, while peak current foldback lowers the current limit threshold during heavy shorts. Both mechanisms operate in auto-recovery mode-no manual reset or latch is required-and thermal shutdown at 170 °C provides final safety backup.

Can the L7987 synchronize with an external clock source other than another L7987?

Yes-the SYNCH pin accepts external TTL/CMOS clock signals from 250 kHz to 1.5 MHz. When driven externally, the L7987 locks to the incoming frequency and adjusts its sawtooth amplitude accordingly. Loop stability analysis must account for resulting PWM gain variation, so pre-setting the internal FSW resistor slightly below the external clock frequency minimizes ramp truncation.

What is the role of the exposed pad (E.P.) on the HTSSOP16 package?

The exposed pad is electrically connected to GND and serves dual thermal and electrical functions: it provides the primary heat dissipation path (R_thJA = 40 °C/W on ST demo board) and establishes the low-impedance signal ground reference for the internal error amplifier, current sense, and gate drivers. It must be soldered to a dedicated PCB ground plane with ≥4 thermal vias for reliable operation at full 3 A load.

L7987 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 16-TSSOP (0.173", 4.40mm Width) Exposed Pad

Packaging:: Tube

Product Status:: Active

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Adjustable

Number of Outputs:: 1

Voltage - Input (Min):: 4.5V

Voltage - Input (Max):: 61V

Voltage - Output (Min/Fixed):: 0.8V

Voltage - Output (Max):: 61V

Current - Output:: 3A

Frequency - Switching:: 250kHz ~ 1.5MHz

Synchronous Rectifier:: No

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 16-HTSSOP

L7987 FAQ

1.How can I place an order for L7987 through Aetrix?

Please submit a Request for Quotation (RFQ) for L7987 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 L7987 reliable?

The price and inventory of L7987 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L7987 is usually 5 days.

3.What payment methods are accepted for L7987?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L7987 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L7987?

L7987 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L7987 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 L7987?

For technical support, including L7987 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L7987 requirements.

6.How does Aetrix verify that L7987 is sourced from the original manufacturer or authorized distributors?

All L7987 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 L7987 meets industry standards.

7.What is the process for return or replacement of L7987?

All L7987 units undergo pre-shipment inspection (PSI). If there is an issue with L7987, 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 L7987 part is unused and in its original packaging.

Return procedure for L7987:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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