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

STMicroelectronics L7987LTR

Name: L7987LTR
Brand: STMicroelectronics
SKU: L7987LTR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L7987LTR

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

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

Datasheet:: L7987LTR.pdf

Description:: IC REG BUCK ADJ 2A 16HTSSOP

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Product details

Overview

L7987LTR from STMicroelectronics is a 61 V, 2 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 2 A DC output current, supports 4.5–61 V input range, features 300 mΩ typical high-side R_DS(on), and provides PGOOD open-collector output for power sequencing in PLCs and fail-safe tolerant systems.

For engineers reviewing the L7987LTR datasheet, L7987LTR pinout, L7987LTR application, or L7987LTR equivalent, key selection considerations include its adjustable switching frequency (250 kHz–1.5 MHz), programmable peak current limit (0.68–3.45 A), light-load efficiency via VBIAS switchover, digital frequency foldback under short-circuit, and HTSSOP16 thermal performance (R_thJA = 40 °C/W).

Technical Context

The L7987LTR implements voltage-mode PWM control with a fixed-frequency sawtooth ramp generator whose slope is adjusted via input voltage feed-forward and external FSW resistor programming. Its error amplifier (100 dB gain, 23 MHz GBWP) drives COMP with low output impedance and supports Type II/III compensation networks depending on output capacitor ESR.

It integrates advanced protection: pulse-by-pulse current sensing with digital frequency foldback and peak current foldback during short-circuit, auto-recovery thermal shutdown at 170 °C, UVLO on VCC (4.10 V typ. rising threshold), and synchronized operation across up to five devices via 180° phase-shifted SYNCH signal.

Key Specifications

Parameter	Value and Actual Design Meaning
Input Voltage Range	4.5 V to 61 V - supports wide industrial input rails including 24 V and 48 V buses without derating.
Output Current	2 A DC - enables compact 2 A buck designs with minimal external components and no external MOSFET required.
Switching Frequency	250 kHz to 1.5 MHz - adjustable via FSW pin resistor; higher frequencies reduce inductor size but require careful layout for EMI control.
Quiescent Current	11 µA typ. in shutdown, 1 mA typ. at 24 V_IN/3.3 V_OUT - ensures ultra-low standby power for always-on industrial systems.
Current Limit Range	0.68 A to 3.45 A - set by ILIM pin resistor; allows precise inductor RMS current matching to nominal load requirements.
PGOOD Threshold	0.70 V ±30 mV hysteresis on FB - enables accurate output voltage monitoring and reliable power-up sequencing in multi-rail systems.
VBIAS Switchover	2.90 V (rising), 4.05 V (falling) - automatically switches internal bias supply from VCC to VBIAS above threshold, improving light-load efficiency.
Thermal Shutdown	170 °C with 15 °C hysteresis - protects against thermal runaway while allowing safe recovery after fault clearance.

Pinout & Package

Package: HTSSOP16 (exposed pad), R_thJA = 40 °C/W, suitable for industrial ambient temperatures up to +125 °C junction.

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 if used.
2,3 VIN	Main power input	Dual pins reduce trace resistance and thermal stress; accepts 4.5–61 V DC with integrated UVLO.
4 VCC	Internal circuitry supply	Bypass with 1 µF ceramic capacitor; powers control logic and reference circuits before VBIAS takeover.
5 EN	Enable control	Active-high; internal pull-down ensures safe default-off state; compatible with 3.3 V/5 V logic levels.
6 SS	Soft-start timing node	5 µA constant-current source charges external capacitor; sets monotonic V_OUT ramp time and inrush control.
7 SYNCH	Master/slave synchronization I/O	Accepts external clock (250 kHz–1.5 MHz) or outputs 180° phase-shifted signal for multi-device noise reduction.
8 COMP	Error amplifier output	Connects to Type II/III compensation network; drives feedback loop stability and transient response.
9 FB	Inverting feedback input	Senses output voltage divider; referenced to 0.800 V ±1% internal bandgap; enables 0.8 V to V_IN regulation.
10 FSW	Frequency setting input	Pull-down resistor selects switching frequency: 10 kΩ → 1.5 MHz; floating → 250 kHz typ.
11 ILIM	Peak current limit setting	Pull-down resistor programs current limit: 27 kΩ → 3.05 A typ.; 100 kΩ → 0.85 A typ.
12 PGOOD	Power-good status output	Open-drain output asserts low when FB < 0.67 V; enables sequencing and system-level fault detection.
13,14 LX	Switching node	Connects to external inductor and bootstrap capacitor; dual pins minimize parasitic inductance and ringing.
15 BOOT	Bootstrap capacitor connection	100 nF ceramic capacitor between BOOT–LX supplies gate drive for internal N-channel HS MOSFET.
16 GND	Signal ground / exposed pad	Must connect exposed thermal pad to PCB ground plane for optimal thermal dissipation and noise immunity.

Key Features

Feature	Design Value
Adjustable current limitation	Programmable 0.68–3.45 A peak limit via ILIM pin resistor - matches inductor RMS rating to application load profile.
Digital frequency foldback	Reduces switching frequency during short-circuit - maintains regulation while lowering power dissipation and stress on LX node.
VBIAS switchover	Switches internal bias supply from VCC to VBIAS at 2.90 V rising threshold - cuts quiescent current by ~50% at light loads.
Advanced bootstrap management	Integrated low-side MOSFET discharges LX during off-time - ensures reliable C_BOOT recharge even at ultra-light loads (<10 mA).
Output voltage sequencing	PGOOD open-collector output tied to FB monitoring - enables controlled power-up of downstream ICs in multi-rail systems.
Synchronization capability	Supports up to five devices on shared SYNCH line with automatic master/slave arbitration - eliminates beat frequencies in sensor/A-D systems.

Applications

Industrial PLC Power Supply

24 V Bus DC-DC Conversion

Use Scenario: Primary 24 V-to-5 V/3.3 V conversion in programmable logic controller backplanes with strict EMI and thermal constraints.

IC Role / Device Role / Timing Role: Asynchronous buck regulator providing isolated, sequenced, and monitored DC output for CPU, I/O, and communication modules.

Use Value: Adjustable current limit and soft-start prevent inrush into large capacitive loads; PGOOD enables safe firmware boot sequence.

Use Scenario: Point-of-load regulation in factory automation equipment powered from centralized 24 V distribution rails.

IC Role / Device Role / Timing Role: High-efficiency step-down converter delivering stable 3.3 V/5 V/12 V outputs with tight tolerance and fast transient response.

Use Value: VBIAS switchover maintains >85% efficiency down to 10 mA load; HTSSOP16 package fits dense industrial PCB layouts.

Fail-Safe Sensor Interface

Multi-Channel Synchronized Power

Use Scenario: Powering analog front-ends and ADCs in safety-critical sensors where undervoltage lockout and fault signaling are mandatory.

IC Role / Device Role / Timing Role: Regulator with UVLO, PGOOD, and thermal shutdown ensuring continuous compliance with IEC 61508 functional safety requirements.

Use Value: Digital frequency foldback prevents thermal runaway during sensor short-circuit; 170 °C shutdown with 15 °C hysteresis enables safe recovery.

Use Scenario: Simultaneous power delivery to multiple isolated subsystems (e.g., motor drivers, encoders, comms) requiring synchronized switching to suppress input ripple.

IC Role / Device Role / Timing Role: Master-slave synchronized buck controller sharing SYNCH net to align switching edges and minimize RMS input current.

Use Value: Up to five L7987LTRs synchronized with 180° phase shift - reduces input capacitor RMS current by up to 40% versus unsynchronized operation.

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, 1 A output, integrated high-side FET, no VBIAS pin, lower IQ (26 µA shutdown)	Lacks adjustable current limit and PGOOD sequencing; optimized for automotive AEC-Q100, not industrial temperature range	Select when automotive qualification is required and 1 A output suffices; avoid for 2 A industrial PLC use cases.
MP2451DT-LF-Z	4.5–36 V input, 0.6 A output, fixed 2.2 MHz f_SW, no synchronization, no VBIAS, no PGOOD	Lower voltage/current rating; lacks critical industrial features (sequencing, sync, current programming)	Only suitable for low-power, cost-sensitive non-industrial applications; cannot replace L7987LTR in 24 V PLC or fail-safe systems.

Compared with LM5164QPWPRQ1 and MP2451DT-LF-Z, the L7987LTR uniquely combines 2 A output, 61 V input, programmable current limit, VBIAS efficiency boost, PGOOD sequencing, and multi-device synchronization - making it the only option qualified for demanding industrial 24 V bus power systems.

Availability

L7987LTR is available at Aetrix Electronics and suitable for industrial PLC power supplies, 24 V bus DC-DC conversion, fail-safe sensor interfaces, and multi-channel synchronized power systems requiring stable component supply across extended temperature and long product lifecycles.

Supply support for L7987LTR 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, specializing in power management, microcontrollers, and industrial-grade analog ICs with ISO 9001 and IATF 16949 certified manufacturing.

The L7987LTR belongs to ST's high-voltage industrial buck regulator product line, engineered specifically for robust, efficient, and feature-rich DC-DC conversion in programmable logic controllers, factory automation, and safety-critical power systems.

FAQ

What is the minimum recommended input voltage for reliable startup?

The L7987LTR requires a minimum input voltage of 4.5 V to ensure proper UVLO release and internal circuitry initialization. Below this threshold, the device remains in shutdown with <11 µA quiescent current. Startup is guaranteed once VIN exceeds 4.10 V (typical VCC UVLO rising threshold), and full regulation begins after soft-start completion.

How does the VBIAS pin improve efficiency at light load?

VBIAS reduces quiescent current from 1 mA (VIN-only) to 1.6–2.4 mA (VBIAS-supplied) by switching internal bias generation from the high-dropout VCC path to a lower-loss auxiliary rail. When VBIAS ≥2.90 V, the switchover occurs, cutting power dissipation in analog blocks and enabling >85% efficiency at 10 mA output - critical for always-on industrial nodes.

Can the L7987LTR be used in negative buck-boost configurations?

Yes - the datasheet explicitly documents negative buck-boost topology in Section 7.2, using the L7987LTR's ability to regulate VOUT from 0.8 V to VIN and its robust LX node handling. In this configuration, VIN connects to GND, GND connects to negative rail, and VOUT is referenced to the negative rail, enabling regulated negative outputs without external level-shifting circuitry.

What is the maximum allowable thermal resistance for continuous 2 A operation at 60 °C ambient?

At 60 °C ambient and 2 A load, junction temperature must stay ≤125 °C. With max power dissipation ≈1.2 W (based on 300 mΩ R_DS(on) and typical duty cycle), allowable R_thJA = (125−60)/1.2 ≈ 54 °C/W. Since the HTSSOP16 package has R_thJA = 40 °C/W on ST's demo board, it meets this requirement with 14 °C margin - provided the exposed pad is soldered to ≥2 cm² copper area.

L7987LTR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tape & Reel (TR)

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:: 2A

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

L7987LTR FAQ

1.How can I place an order for L7987LTR through Aetrix?

Please submit a Request for Quotation (RFQ) for L7987LTR 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 L7987LTR reliable?

The price and inventory of L7987LTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L7987LTR is usually 5 days.

3.What payment methods are accepted for L7987LTR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L7987LTR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L7987LTR?

L7987LTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L7987LTR 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 L7987LTR?

For technical support, including L7987LTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L7987LTR requirements.

6.How does Aetrix verify that L7987LTR is sourced from the original manufacturer or authorized distributors?

All L7987LTR 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 L7987LTR meets industry standards.

7.What is the process for return or replacement of L7987LTR?

All L7987LTR units undergo pre-shipment inspection (PSI). If there is an issue with L7987LTR, 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 L7987LTR part is unused and in its original packaging.

Return procedure for L7987LTR:

1.Submit a request within 90 days.

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

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