Analog Devices Inc. LTC3642IMS8E-3.3#PBF

Overview

LTC3642IMS8E-3.3#PBF from Analog Devices (formerly Linear Technology) is a high-voltage, synchronous step-down DC/DC converter with integrated high-side and low-side MOSFETs, delivering up to 50mA output current at a fixed 3.3V output, operating from 4.5V to 45V input, and drawing only 12µA quiescent current in Burst Mode® operation. It is used in industrial control supplies and battery-operated devices requiring robust input surge tolerance and ultra-low standby power.

For engineers reviewing the LTC3642IMS8E-3.3#PBF datasheet, LTC3642IMS8E-3.3#PBF pinout, LTC3642IMS8E-3.3#PBF application, or LTC3642IMS8E-3.3#PBF equivalent, key selection criteria include its 60V transient tolerance, programmable peak current limit (25–115mA), precise RUN pin threshold (1.21V rising), internal soft-start (0.75ms), and thermally enhanced MS8E package for high ambient temperature operation up to 125°C.

Technical Context

The LTC3642IMS8E-3.3#PBF implements a hysteretic Burst Mode® control architecture with an internal 0.800V feedback reference and 5mV comparator hysteresis, enabling high efficiency across load currents from 100µA to 50mA. Its peak current limit is set via external resistor on ISET (or floating/grounded), directly determining maximum average output current (up to 55mA).

Start-up is controlled by a precision RUN comparator with 110mV hysteresis and adjustable threshold via HYST pin; shutdown reduces supply current to 3µA. The device features no-compensation design, 100% duty-cycle low-dropout operation, and internal overvoltage lockout (47–52V) and undervoltage lockout (3.75–4.50V).

Key Specifications

Pinout & Package

The LTC3642IMS8E-3.3#PBF is housed in an 8-lead plastic MSOP (MS8E) package with exposed pad (Pin 9), requiring soldering to PCB ground for optimal thermal performance (θ_JA = 40°C/W). Pin count and layout are identical to standard MSOP-8 but with enhanced thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage, low-I_Q step-down converter applications.

Compared with LTC3642EMS8E-3.3#PBF, the LTC3642IMS8E-3.3#PBF offers guaranteed operation down to –40°C and up to 125°C, making it suitable for harsh environments; versus LT3643EMS8E-3.3#PBF, it provides lower quiescent current and pin-compatible layout but sacrifices output current headroom.

Availability

LTC3642IMS8E-3.3#PBF is available at Aetrix Electronics and suitable for industrial control supplies, portable instruments, and automotive power systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LTC3642IMS8E-3.3#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC3642 product line was designed specifically for high-input-voltage, ultra-low-quiescent-current DC/DC conversion in space- and power-constrained systems where reliability across wide temperature and transient conditions is mandatory.

FAQ

What is the guaranteed operating temperature range for the LTC3642IMS8E-3.3#PBF?

The LTC3642IMS8E-3.3#PBF is guaranteed to operate over a junction temperature range of –40°C to 125°C. This I-grade rating is confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables, distinguishing it from the E-grade (0°C to 85°C) variant LTC3642EMS8E-3.3#PBF. Thermal design must ensure PCB layout and airflow maintain this range under full 50mA load.

Does the LTC3642IMS8E-3.3#PBF require external compensation components?

No, the LTC3642IMS8E-3.3#PBF uses a proprietary hysteretic Burst Mode® control architecture that requires no external compensation network. Its internal loop is stabilized by fixed internal gain and comparator hysteresis, allowing full functionality with only three external components (inductor, input capacitor, output capacitor) for fixed-output operation.

How is the peak inductor current programmed on the LTC3642IMS8E-3.3#PBF?

The peak inductor current on the LTC3642IMS8E-3.3#PBF is set via the ISET pin (Pin 3), which sources a precise 1µA current. Connecting a resistor R_ISET from ISET to GND generates a voltage offset that adjusts the peak current comparator threshold between 25mA (R_ISET = 0Ω) and 115mA (ISET floating). The relationship is linear: R_ISET (kΩ) ≈ 9.09 × I_PEAK (mA).

What is the function of the HYST pin on the LTC3642IMS8E-3.3#PBF?

The HYST pin (Pin 7) is an open-drain logic output that pulls low when the RUN pin voltage falls below 1.2V, indicating shutdown state. It can be used with an external resistor divider to increase the effective hysteresis of the RUN comparator, improving noise immunity in high-EMI environments-especially when RUN monitors VIN through a resistive divider.

Can the LTC3642IMS8E-3.3#PBF operate with input voltage equal to its 3.3V output?

Yes, the LTC3642IMS8E-3.3#PBF supports 100% duty-cycle operation, enabling regulation down to VIN = VOUT (3.3V). This low-dropout capability is confirmed in the Features list and allows continued operation during brownout conditions such as cold-crank (down to 4.5V min) or battery depletion, maintaining system uptime where other converters would dropout.