Analog Devices Inc. LT1614CMS8#PBF

Overview

LT1614CMS8#PBF from Analog Devices (formerly Linear Technology) is a fixed-frequency, current-mode inverting switching regulator IC that generates negative output voltages down to –24V from input voltages as low as 1V. It integrates an NPN power switch with 295mV V_CE(SAT) at 500mA, operates at 600kHz, and features a low-battery detector with 200mV reference - enabling compact, low-noise bias supplies for LCD, MR head, and GaAs FET applications.

For engineers reviewing the LT1614CMS8#PBF datasheet, LT1614CMS8#PBF pinout, LT1614CMS8#PBF application, or LT1614CMS8#PBF equivalent, this page delivers verified technical context, exact pin functions, real-world efficiency curves (e.g., 5V→–5V/200mA at >80%), confirmed package dimensions (MSOP-8), and two validated alternative parts with documented functional and thermal differences.

Technical Context

The LT1614CMS8#PBF implements a current-mode PWM architecture with a –1.24V internal feedback reference and 600kHz oscillator, enabling stable regulation of negative outputs without external compensation complexity. Its error amplifier (100V/V gain, 16µmhos transconductance) drives a ramp-comparator-controlled flip-flop to regulate switch on-time cycle-by-cycle.

It supports two topologies: charge-pump–enhanced boost (single inductor) and Cuk-derived inverting (dual inductor), the latter delivering <5mV_P–P ripple using ceramic output capacitors. The low-battery detector (200mV threshold, ±15mV tolerance) disables LBO when SHDN is low and exhibits 1000V/V gain into a 1MΩ load.

Key Specifications

Pinout & Package

LT1614CMS8#PBF is housed in an 8-lead MSOP package (3.0mm × 3.0mm × 0.86mm body, 0.65mm pitch), rated for 0°C to 70°C operation with θ_JA = 120°C/W. Lead finish is lead-free (Pb-free) and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar inverting DC/DC converter applications.

Compared with LT1614CMS8#PBF, LT1611IS5#TRMPBF trades monitoring functionality and thermal margin (θ_JA = 250°C/W) for minimal footprint, while LT1931ES5#TRMPBF prioritizes ripple performance and current capability over integrated power-good signaling - making LT1614CMS8#PBF optimal for cost-sensitive, battery-aware industrial bias supplies.

Availability

LT1614CMS8#PBF is available at Aetrix Electronics and suitable for MR head bias, LCD panel drivers, GaAs FET RF stages, and positive-to-negative conversion requiring stable component supply, long-lifecycle assurance, and consistent parametric performance across production batches.

Supply support for LT1614CMS8#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 acquired Linear Technology in 2017 and maintains full product support, datasheet archives, and application engineering for legacy Linear parts including the LT1614 series.

The LT1614 belongs to Linear's micropower inverting regulator family, designed specifically for space-constrained, battery-operated systems needing clean, efficient negative voltage generation from low-input sources - not general-purpose switching or buck-boost applications.

FAQ

What is the minimum input voltage required for LT1614CMS8#PBF to start switching?

The LT1614CMS8#PBF starts switching at a minimum input voltage of 0.92V (typical) and is fully specified down to 1.0V across temperature. At –40°C, the minimum operating input rises to 1.1V, while at 85°C it drops to 0.8V - enabling reliable startup from nearly depleted single-cell batteries. This behavior is confirmed in the Absolute Maximum and Electrical Characteristics tables of the official datasheet.

Can LT1614CMS8#PBF be used with all-ceramic capacitors, and what are the layout requirements?

Yes, LT1614CMS8#PBF supports full-ceramic designs: 1µF X5R/X7R ceramic for the flying cap (C2), 22–33µF X5R/X7R for output (C3), and ≥1µF ceramic for input bypass (C1). Critical layout requirements include placing C1 adjacent to VIN/GND pins, cutting ground copper under D1's cathode to isolate high-di/dt return paths, and minimizing SW and VC trace areas to prevent EMI coupling - all validated in Figures 10–12 of the datasheet.

What is the function of the LBI and LBO pins on LT1614CMS8#PBF, and how are they configured?

The LBI (Pin 7) is the low-battery detector input, referenced internally to 200mV; applying a divided battery voltage here triggers LBO (Pin 8) - an open-collector output that sinks 10µA when the LBI voltage falls below threshold. LBO is disabled during shutdown (SHDN = low). A typical configuration uses a 100kΩ resistor from LBI to GND and a 1MΩ pull-up on LBO, as shown in Figure 14 of the datasheet - enabling system-level brownout detection without external components.

Does LT1614CMS8#PBF require external compensation, and what are the recommended values?

Yes, LT1614CMS8#PBF requires external compensation via the VC pin (Pin 2). A series RC network (e.g., 100kΩ resistor + 1nF capacitor) connected from VC to GND sets loop stability and transient response. These values are validated in Figure 1 and Table 1 of the datasheet for standard 5V→–5V/200mA designs. Adjusting R or C tailors bandwidth and phase margin - larger C increases stability margin but slows load-step response.

What is the maximum continuous output current achievable with LT1614CMS8#PBF in a Cuk topology?

In Cuk topology with 22µH coupled inductors (e.g., Coiltronics CTX20-1), LT1614CMS8#PBF delivers up to 290mA at –5V from a 5V input, as documented in the Component Selection section (page 8). This assumes proper thermal design (θ_JA = 120°C/W), 295mV V_CE(SAT) at 500mA, and derating for ambient temperature - exceeding the 200mA capability of the basic boost-charge-pump configuration shown in Figure 1.