Analog Devices Inc. LTC1559CGN-5#TRPBF

Overview

LTC1559CGN-5#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output backup battery controller IC designed to sustain 5V system operation during main power failure using a single 1.2V NiCd cell. It integrates a synchronous boost converter (4.625V output), smart 2-stage NiCd charger, automatic VCC-to-backup switching, push-button reset generator, and VCC supervisory functions. It delivers ≥100mW backup power with guaranteed reset assertion at VCC = 1V and operates in 0°C to 70°C ambient.

For engineers reviewing the LTC1559CGN-5#TRPBF datasheet, LTC1559CGN-5#TRPBF pinout, LTC1559CGN-5#TRPBF application, or LTC1559CGN-5#TRPBF equivalent, key selection considerations include its 4.625V regulated backup output, 4.55V–4.85V VBAK deassertion window, programmable trickle charge (0.05–2mA), 16-pin SSOP (GN) package, and integrated UVLO with 4.400V–4.700V trip range for 5V systems.

Technical Context

The LTC1559CGN-5#TRPBF implements a fixed-ratio synchronous boost architecture with dual peak current modes (165mA/330mA) to maintain VBAK at 92.5% of rated VCC (4.625V). Its internal gas gauge monitors charge depletion during backup to enable precise fast recharge without overcharge.

It features three independent voltage comparators: one for VCC UVLO (4.400V–4.700V ON/OFF hysteresis), one for backup activation (VCC < VCC(rated) – 7.5%), and one for low-battery detection (VBAT < 0.9V). The 16-pin GN package adds dedicated PGND, SHDN, and LOBAT pins not present in the 8-pin SO variant.

Key Specifications

Pinout & Package

Package: 16-lead plastic SSOP (GN), 5.3mm × 6.2mm body, 0.65mm pitch, exposed pad optional for thermal relief.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar backup battery controller applications.

Compared with LTC1559CS8-5 and MAX6326–MAX6328, the LTC1559CGN-5#TRPBF uniquely combines regulated 4.625V backup generation, gas-gauge-based NiCd recharging, and full VCC supervision in a single 16-pin SSOP-enabling complete backup subsystem integration without external power or charge circuitry.

Availability

LTC1559CGN-5#TRPBF is available at Aetrix Electronics and suitable for notebook computers, portable instruments, battery-powered medical devices, and industrial handheld terminals requiring stable component supply across production lifecycles.

Supply support for LTC1559CGN-5#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.

The LTC1559 product line was designed specifically for portable and battery-critical systems requiring autonomous, low-power backup power management with integrated NiCd charging and system supervision.

FAQ

What is the exact regulated output voltage of the LTC1559CGN-5#TRPBF during backup mode?

The LTC1559CGN-5#TRPBF delivers a precisely regulated 4.625V backup output (VBAK), with a guaranteed tolerance of ±0.15V across temperature and load. This value corresponds to 92.5% of the nominal 5V system rail and is generated directly from a single 1.2V NiCd cell using its internal synchronous boost converter. The specification is confirmed in the Electrical Characteristics table under "VBAK(ON)" and "VBAK(OFF)" parameters.

Does the LTC1559CGN-5#TRPBF support shutdown control, and how is it implemented?

Yes, the LTC1559CGN-5#TRPBF supports hardware shutdown via the SHDN pin (Pin 6), a TTL-compatible active-low input. When pulled low, it powers down all internal circuits-including the boost converter-and places SW, CTL, and VBAK into high-impedance states. Supply current drops to <50µA and battery drain falls below 15µA. This functionality is exclusive to the 16-pin GN/SO packages and is not available on the 8-pin SO variant.

How does the LTC1559CGN-5#TRPBF prevent overcharging of the NiCd backup cell?

The LTC1559CGN-5#TRPBF prevents NiCd overcharging using an internal gas gauge that tracks charge removed during backup and replaces it exactly during fast recharge. It also provides user-programmable trickle charge (0.05–2mA) to offset self-discharge without continuous high-current charging. This two-stage approach-fast recharge followed by maintenance trickle-is explicitly documented in the Applications Information section and verified in the ICHGF and ICHGT specifications.

What is the purpose of the LOBAT pin on the LTC1559CGN-5#TRPBF, and when is it active?

The LOBAT pin (Pin 9) is an open-drain low-battery alert output that asserts when the NiCd cell terminal voltage falls below 1.0V. It provides early warning before UVLO shutdown (which triggers at 0.9V), allowing host systems to initiate graceful shutdown or logging. LOBAT is disabled during trickle charge mode because the CTL pin is clamped to 0.5V, making low-voltage detection invalid during charging.

Can the LTC1559CGN-5#TRPBF be used with a 3.3V system, or is it strictly for 5V applications?

The LTC1559CGN-5#TRPBF is specifically designed for 5V systems: its VCC UVLO thresholds (4.400V–4.700V), backup activation point (VCC < VCC(rated) – 7.5%), and VBAK output (4.625V) are all calibrated for 5V nominal rails. For 3.3V systems, the pin-compatible LTC1559CGN-3.3 (3.07V output, 2.900V–3.102V UVLO) must be used instead-the two variants are not interchangeable due to fundamentally different internal reference and comparator settings.