STMicroelectronics B5973D

Overview

B5973D from STMicroelectronics is an AEC-Q100 Grade 1 qualified monolithic step-down switching regulator for automotive power systems, featuring a 2.25 A minimum switch current limit, 4 V to 36 V input range, and adjustable output from 1.235 V to 35 V. It integrates a P-channel DMOS switch (R_DS(on) = 250 mΩ typ), operates at 250 kHz fixed frequency, and supports zero-load operation with inhibit control.

For engineers reviewing the B5973D datasheet, B5973D pinout, B5973D application, or B5973D equivalent, key selection criteria include thermal performance (R_th(JA) = 40 °C/W in HSOP8), ±2% reference accuracy, synchronization capability, feedback disconnection protection, and AEC-Q100 compliance for under-hood automotive use.

Technical Context

The B5973D employs voltage-mode control with feedforward compensation and an internal error amplifier (50–65 dB open-loop gain, 2.3 mS transconductance) to stabilize output across line and load variations. Its pulse-by-pulse current limiting-combined with internal frequency modulation-delivers constant-current short-circuit protection without external sensing.

Thermal management is enabled by the HSOP8 package's exposed frame, achieving R_th(JA) ≈ 40 °C/W when mounted per JEDEC standards. The device supports 100% duty cycle low-dropout operation and maintains regulation down to 4 V input, making it suitable for 5 V bus systems and cold-crank automotive conditions.

Key Specifications

Pinout & Package

Package: HSOP8 with exposed thermal pad (JEDEC MO-220 variant), lead-free ECOPACK® compliant, R_th(JA) = 40 °C/W on standard PCB layout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2678SD-ADJ/NOPB and TPS54202DDCR, the B5973D uniquely combines AEC-Q100 Grade 1 compliance, integrated 3.3 V reference, SYNC I/O, and HSOP8 thermal performance-making it the only option validated for under-hood automotive deployment with tight thermal constraints and functional safety awareness.

Availability

B5973D is available at Aetrix Electronics and suitable for engine control units, ADAS camera modules, infotainment systems, and body control modules requiring stable component supply across extended temperature ranges and automotive lifecycle demands.

Supply support for B5973D 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, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The B5973D belongs to ST's automotive-grade power management portfolio, engineered specifically for robust DC-DC conversion in harsh vehicle environments-including under-hood, chassis, and lighting subsystems-where reliability, thermal resilience, and AEC-Q100 compliance are mandatory.

FAQ

What is the maximum allowable junction temperature for continuous operation?

The B5973D has a specified operating junction temperature range of –40 °C to +150 °C. Thermal shutdown activates above +150 °C to prevent permanent damage. Sustained operation near this limit requires careful PCB layout with the exposed pad fully soldered to a thermal plane and ambient temperature below +85 °C to maintain safe derating margins.

Can the B5973D operate with an input voltage lower than 4 V?

No-the absolute minimum operating input voltage is 4 V, as confirmed in Table 4 of the datasheet. Below this threshold, internal biasing fails and regulation ceases. This limit ensures reliable startup during automotive cold-crank conditions but excludes sub-4 V battery chemistries or supercapacitor backup scenarios.

Is external compensation required, and what topology is supported?

Yes-external compensation is mandatory via the COMP pin using a Type II or Type III network. The error amplifier's 50–65 dB open-loop gain and 2.3 mS transconductance require proper pole-zero placement; typical configurations use a series RC from COMP to FB and a capacitor from COMP to GND, as shown in Figure 1 of the datasheet.

Does the VREF pin support loading beyond 5 mA?

No-the VREF pin is specified for 0–5 mA output current (Table 4). Exceeding 5 mA risks reference voltage droop and instability. For higher current needs, buffer the VREF with an op-amp or use the FB divider's top node as a scaled reference instead of drawing directly from VREF.