STMicroelectronics L4964HT

Overview

L4964HT from STMicroelectronics is a monolithic stepdown switching regulator delivering 4 A continuous output current with adjustable output voltage from 5.1 V to 28 V, ±3 % on-chip reference, 0–100 % duty cycle control, and up to 120 kHz switching frequency in a Multiwatt15 horizontal plastic power package. It integrates soft start, open-collector reset output, remote inhibit, synchronization input, thermal shutdown, and current limiting - used in industrial power supplies requiring stable high-current DC-DC conversion.

For engineers reviewing the L4964HT datasheet, L4964HT pinout, L4964HT application, or L4964HT equivalent, this page provides verified functional identity, validated terminal roles, confirmed thermal and efficiency specs (up to 90 %), exact package mapping (Multiwatt15 Horizontal), and real-world design constraints including N.C. pins (1, 4, 15), soft-start capacitor dependency, and reset delay timing via external C.

Technical Context

The L4964HT implements a fixed-frequency PWM stepdown regulator using an internal 5.1 V zener-zap-trimmed reference and sawtooth oscillator. Regulation is achieved by comparing feedback voltage against the reference in an error amplifier, then modulating the output stage via PWM comparator.

It supports multichip synchronization via Pin 7 (Sync Input), enables system-level reset sequencing via Pin 14 (open-collector) with programmable delay (Pin 13), and provides overload protection through internal metal-resistor current sensing and flip-flop-based latch-off with automatic recovery.

Key Specifications

Pinout & Package

Package: Multiwatt15 Horizontal (MW15H), 15-lead plastic power package with integrated heatsink tab (Pin 8 = Ground). Pins 1, 4, and 15 are No-Connect and must remain unconnected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar stepdown switching regulator applications.

Compared with LM2678-ADJ and TPS544B20, the L4964HT uniquely combines 4 A capability, analog-programmable soft start/reset timing, open-collector reset, and multichip sync in a thermally robust power package - making it optimal for industrial analog-digital hybrid systems requiring deterministic power sequencing and ruggedness.

Availability

L4964HT is available at Aetrix Electronics and suitable for industrial PLC power rails, telecom line card supplies, test equipment power modules, and motor drive auxiliary supplies requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L4964HT 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, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The L4964HT belongs to ST's legacy high-current linear-compatible switching regulator product line, engineered for rugged industrial power conversion where reliability, thermal resilience, and analog control flexibility outweigh digital feature density.

FAQ

What is the maximum input voltage rating for the L4964HT?

The absolute maximum input voltage (Pin 3) is 36 V. Exceeding this risks permanent damage to internal circuitry. The recommended operating range is 9 V to 36 V, with optimal efficiency observed between 12 V and 28 V input for typical 5.1–24 V output configurations. Derating is required above 30 V due to increased power dissipation in the internal regulator.

Can the L4964HT be used without the soft-start capacitor?

No - the soft-start capacitor on Pin 5 is mandatory. It controls both startup slew rate and average short-circuit current limit. Omitting it causes uncontrolled inrush, potential output overshoot, and unreliable current limiting. The datasheet specifies minimum capacitance values (e.g., 100 nF for ~10 ms ramp) based on desired startup behavior and fault current targets.

How does the reset function behave during input voltage transients?

The reset output (Pin 14) goes low immediately when input voltage falls below the falling threshold (≈4.75 V), regardless of delay capacitor state. Upon rising edge, it asserts only after the input exceeds the rising threshold (≈4.85–4.95 V) AND the delay capacitor on Pin 13 charges to 4.5 V. This ensures clean, glitch-free reset signaling during brownouts and line sags.

Is thermal derating required for continuous 4 A operation?

Yes - continuous 4 A output requires proper heatsinking. With R_{th j-case} = 3 °C/W, maintaining T_j ≤ 125 °C demands case temperature ≤ 90 °C. At 24 V_in/12 V_out/4 A, power dissipation is ~4.8 W; a 10 °C/W heatsink keeps case at ~75 °C. Above 90 °C case temperature, output current must be reduced per the derating curve in Figure 12 of the datasheet.