Analog Devices Inc. LT1512IGN#TRPBF

Overview

LT1512IGN#TRPBF from Analog Devices (formerly Linear Technology) is a 500kHz current-mode switching regulator IC optimized for constant-current/constant-voltage battery charging in SEPIC topology. It delivers up to 1A charging current for single Li-ion cells, features 1.245V ±1% voltage reference accuracy, 100mV ground-referenced current sense threshold, and integrated 40V switch with 1.5A current limit. It enables charging when input voltage is below, equal to, or above battery voltage - ideal for wall adapter–based portable Li-ion chargers.

For engineers reviewing the LT1512IGN#TRPBF datasheet, LT1512IGN#TRPBF pinout, LT1512IGN#TRPBF application, or LT1512IGN#TRPBF equivalent, key selection considerations include its industrial-grade –40°C to +85°C ambient operation, dual feedback architecture (FB for voltage, IFB for current), 8-lead SO package thermal resistance (130°C/W), and synchronization capability via S/S pin at 600–800kHz.

Technical Context

The LT1512IGN#TRPBF implements current-mode control with dual inverting error amplifier inputs: one referenced to a 1.245V internal bandgap (FB pin) for voltage regulation, and another driven by an external current-sense amplifier (IFB pin) servoed to –100mV for precise constant-current control. Its 500kHz oscillator drives an NPN output switch with 40V breakdown rating and 0.5Ω typical ON resistance.

Thermal design centers on the S8 package's 130°C/W junction-to-ambient thermal resistance; maximum switch duty cycle is 95%, and VC pin voltage (1.0–1.9V) directly modulates peak switch current from 0A to 1.8A. Shutdown reduces supply current to 12µA, and the S/S pin supports both logic-level shutdown and external frequency synchronization without disabling regulation.

Key Specifications

Pinout & Package

LT1512IGN#TRPBF is housed in an 8-lead plastic SO (S8) package with exposed pad thermal enhancement (not electrically connected). Pin spacing is 1.27mm, body dimensions 5.0 × 6.2 mm, and maximum height 1.75mm. The package uses lead-free (Pb-free) finish and is tape-and-reel packaged (#TRPBF).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar constant-current/constant-voltage battery charger applications.

Compared with LTC4002-1 and TPS65023B, the LT1512IGN#TRPBF offers unique SEPIC compatibility, true wide-input operation (2.7–30V), and ground-referenced current sensing - making it the only option among the three that supports charging from sub-battery-voltage sources without additional level-shifting circuitry.

Availability

LT1512IGN#TRPBF is available at Aetrix Electronics and suitable for industrial battery management systems, portable medical device chargers, and telecom backup power supplies requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LT1512IGN#TRPBF 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, documentation, and manufacturing continuity for legacy Linear parts including the LT1512 series.

The LT1512IGN#TRPBF belongs to Linear's dedicated battery charger IC product line, designed specifically for high-accuracy, topology-flexible charging of rechargeable chemistries (Li-ion, NiMH, Pb-acid) in space- and cost-constrained industrial applications.

FAQ

What is the maximum battery voltage supported by the LT1512IGN#TRPBF in SEPIC configuration?

The LT1512IGN#TRPBF itself does not impose a direct battery voltage limit. However, its absolute maximum switch voltage is 40V, and maximum input voltage is 30V. In a SEPIC topology, V_SW = V_IN + V_BAT, so maximum allowable V_BAT = 40V – V_IN. For example, with V_IN = 12V, V_BAT may reach up to 28V - sufficient for up to 7-series NiMH or 8-series Li-ion packs. Always verify thermal limits under worst-case V_IN/V_BAT combinations.

Can the LT1512IGN#TRPBF be used with a flyback topology instead of SEPIC?

Yes, the LT1512IGN#TRPBF supports flyback topology per its datasheet, but with critical caveats: the current sense point must remain ground-referenced, requiring either a secondary-side sense resistor with optocoupler feedback (adding complexity) or primary-side sensing with careful transformer design. Unlike SEPIC, flyback introduces snubber losses and lacks inherent battery-discharge isolation. The LT1512IGN#TRPBF's IFB architecture is optimized for ground-referenced sensing, making SEPIC the preferred and simpler implementation.

How does the LT1512IGN#TRPBF achieve 1% voltage regulation accuracy?

The LT1512IGN#TRPBF achieves 1% voltage regulation accuracy via a trimmed 1.245V ±1% internal bandgap reference applied to the non-inverting input of its voltage error amplifier. This reference is stable over –40°C to +85°C and exhibits <0.03%/V line regulation. When combined with a precision resistor divider (e.g., 1% metal-film R1/R2), the overall output voltage accuracy remains within ±1% across line, load, and temperature - essential for safe Li-ion charging where ±41mV error at 4.2V is the maximum acceptable tolerance.

Is the LT1512IGN#TRPBF pin-compatible with other members of the LT1512 family?

Yes, the LT1512IGN#TRPBF shares identical pinout and electrical characteristics with all LT1512 variants (e.g., LT1512CS8#TRPBF, LT1512IN8#TRPBF), differing only in temperature grade and package type. The "I" suffix denotes industrial –40°C to +85°C operation, and "S8" specifies the 8-lead plastic SO package. All share the same N8/S8 footprint, pin functions, and absolute maximum ratings - enabling drop-in replacement across temperature grades when thermal design margins permit.

What is the purpose of separate GND and GND_S pins on the LT1512IGN#TRPBF?

The LT1512IGN#TRPBF uses separate GND (power ground) and GND_S (signal ground) pins to isolate high-di/dt switch return currents from sensitive analog circuitry. GND carries pulsed switch current (up to 1.5A), while GND_S serves as the quiet reference for FB, IFB, VC, and internal amplifiers. Both pins must connect to the same low-impedance ground plane, but external components (R1/R2 divider, C4 filter, compensation network) must tie exclusively to GND_S - preventing noise coupling that would degrade voltage/current regulation accuracy in the LT1512IGN#TRPBF.