Analog Devices Inc. LT3970HMS#PBF

Overview

LT3970HMS#PBF from Analog Devices is a 40V, 350mA monolithic step-down switching regulator with integrated boost and catch diodes, 2.5µA quiescent current, adjustable 200kHz–2.2MHz switching frequency, and power good flag - designed for automotive battery regulation and industrial supplies requiring high input voltage tolerance and ultra-low standby power.

For engineers reviewing the LT3970HMS#PBF datasheet, LT3970HMS#PBF pinout, LT3970HMS#PBF application, or LT3970HMS#PBF equivalent, key selection criteria include its H-grade (–40°C to 150°C) junction temperature rating, 10-lead MSOP package, integrated diode architecture, low ripple Burst Mode operation (<5mV_P-P), and accurate 1V enable threshold with 0.7µA shutdown current.

Technical Context

The LT3970HMS#PBF implements constant-frequency current-mode control with internal slope compensation, enabling fast transient response and stable loop behavior across wide input (4.2V–40V) and output (1.21V–25V) ranges. Its bipolar NPN switch is driven via an external BOOST capacitor to ensure full saturation, while internal sense circuitry limits catch diode valley current to 350mA (typical) for short-circuit protection.

Burst Mode operation reduces quiescent current to 1.7µA at light loads while maintaining output ripple below 5mV_P-P; the power good flag asserts when FB reaches 90% of regulation voltage, with 120mV hysteresis offset and open-drain output capable of sinking 80µA. The device features internal compensation and fixed 1.21V feedback reference with ±10mV accuracy over –40°C to 150°C.

Key Specifications

Pinout & Package

LT3970HMS#PBF is housed in a 10-lead plastic MSOP package (θ_JA = 100°C/W), with exposed pad not present (unlike DFN variant). Pin 1 is FB (feedback input for adjustable versions), Pin 2 is EN (enable with 1V rising threshold), Pin 3 is VIN (main power input), Pins 4 & 5 are GND (dual ground connections), Pin 6 is SW (switch node), Pin 7 is BOOST (external bootstrap capacitor connection), Pin 8 is BD (bias diode anode), Pin 9 is PG (open-drain power good), and Pin 10 is RT (frequency-setting resistor).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3639EMSE#PBF and TPS54331DR, LT3970HMS#PBF uniquely combines AEC-Q100 H-grade qualification, integrated diodes, sub-3µA quiescent current, and power good signaling - making it optimal for space-constrained, thermally demanding automotive and industrial buck applications where reliability and low standby power are mandatory.

Availability

LT3970HMS#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial power supplies, and portable medical devices requiring stable component supply with guaranteed long-term availability and AEC-Q100 compliance.

Supply support for LT3970HMS#PBF 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LT3970 series was developed to address demand for highly integrated, ultra-low-IQ buck regulators capable of operating across extreme automotive and industrial temperature ranges while maintaining low noise and high reliability.

FAQ

What is the maximum junction temperature specification for LT3970HMS#PBF?

The LT3970HMS#PBF is an H-grade device with a guaranteed operating junction temperature range of –40°C to 150°C, fully qualified per AEC-Q100 for automotive under-hood applications. This rating is verified through characterization and statistical process controls, and derating applies above 125°C to ensure long-term reliability. Thermal design must account for θ_JA = 100°C/W in the MSOP package.

Does LT3970HMS#PBF require external diodes for operation?

No, LT3970HMS#PBF integrates both the boost diode and catch diode on-die, eliminating the need for external diodes. This integration reduces component count, PCB area, and thermal complexity. The internal catch diode supports up to 350mA valley current, and the boost diode enables efficient bipolar NPN switch drive via the BOOST pin capacitor.

How does the power good (PG) function work on LT3970HMS#PBF?

The PG pin on LT3970HMS#PBF is an open-drain output that remains low until the FB pin reaches 90% of its regulated voltage (e.g., 1.089V for a 1.21V reference), with 120mV hysteresis. It is valid only when VIN >4.2V and EN is high. An external pull-up resistor is required; the pin can sink up to 80µA. This enables reliable power sequencing and fault monitoring in safety-critical systems.

What is the minimum input voltage required for LT3970HMS#PBF to regulate properly?

The LT3970HMS#PBF has a minimum operating input voltage of 4.2V, defined by internal circuitry requirements. Below this, regulation cannot be maintained. In practice, minimum VIN also depends on duty cycle constraints: for example, at 2.2MHz switching frequency and 5V output, the calculated minimum VIN rises to ~5.0V due to t_OFF(MIN) = 160ns. Always verify against the specific V_OUT and f_SW used.

Can LT3970HMS#PBF be used in Burst Mode for ultra-low-power applications?

Yes, LT3970HMS#PBF automatically enters low-ripple Burst Mode at light loads, reducing quiescent current to 1.7µA while keeping output ripple below 5mV_P-P. This mode disables non-essential circuitry between bursts, making it ideal for battery-powered systems requiring multi-year standby life. No external enable/disable control is needed - Burst Mode is inherent and seamless.