Analog Devices Inc. LTC1515CS8#TRPBF

Overview

LTC1515CS8#TRPBF from Analog Devices (formerly Linear Technology) is a micropower switched capacitor DC/DC converter that provides regulated 3.3V or 5V output via logic-selectable voltage mode, operates from 2V–10V input, delivers up to 50mA, features open-drain POR output with 200ms delay, and is used in SIM interface power supplies for GSM handsets.

For engineers reviewing the LTC1515CS8#TRPBF datasheet, LTC1515CS8#TRPBF pinout, LTC1515CS8#TRPBF application, or LTC1515CS8#TRPBF equivalent, key selection criteria include input voltage range compatibility (2V–10V), dual-output voltage selection (3.3V/5V), shutdown current (<1µA), soft-start timing (4ms), and SO-8 package thermal performance (θ_JA = 110°C/W).

Technical Context

The LTC1515CS8#TRPBF implements a step-up/step-down charge pump architecture with automatic mode switching based on VIN–VOUT differential sensing. It uses internal resistor networks and a logic-controlled 5/3 pin to select between 3.3V and 5V outputs, eliminating external feedback components.

Regulation relies on comparator hysteresis (±4% output tolerance) and an internal 1.232V reference; output ripple (100mV_P-P) is inherent to burst-mode operation. The device integrates soft-start, thermal shutdown (~150°C trip), short-circuit protection (12–40mA limit), and open-drain POR with 6.5% trip threshold and 140–280ms delay.

Key Specifications

Pinout & Package

8-lead plastic SO (SO-8, narrow 0.150") package with exposed pad not present; JEDEC MS-012AC compliant; θ_JA = 110°C/W, T_JMAX = 125°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar switched-capacitor DC/DC converter applications.

Compared with LTC1515IS8-3.3/5, the LTC1515CS8#TRPBF offers lower cost and smaller inventory footprint for commercial-grade designs, while LTC1516CS8#TRPBF sacrifices voltage flexibility and system-level reset capability to reduce component count in fixed-5V systems.

Availability

LTC1515CS8#TRPBF is available at Aetrix Electronics and suitable for GSM SIM interfaces, smart card readers, and portable medical sensors requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LTC1515CS8#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 its precision analog and power management portfolio. Linear pioneered high-efficiency switched-capacitor DC/DC converters for battery-constrained applications.

The LTC1515 series was designed specifically for dual-voltage SIM card power delivery in GSM cellular handsets, integrating voltage selection, POR, and wide-input operation into a single SO-8 IC to replace multi-component discrete solutions.

FAQ

What output voltages does the LTC1515CS8#TRPBF support, and how are they selected?

The LTC1515CS8#TRPBF supports 3.3V and 5V regulated outputs. Selection is controlled by the logic level applied to the 5/3 pin: a high signal sets VOUT to 5V, and a low signal sets it to 3.3V. This eliminates external feedback resistors and enables dynamic voltage switching in SIM card protocols. The LTC1515CS8#TRPBF does not support adjustable output voltages - that function is exclusive to the non-suffixed LTC1515 variant with FB pin.

Does the LTC1515CS8#TRPBF require external capacitors, and what values are recommended?

Yes, the LTC1515CS8#TRPBF requires three external capacitors: a 0.22µF ceramic flying capacitor (C1) between C1+ and C1– pins, and ≥10µF low-ESR input (CIN) and output (COUT) capacitors. For VIN > 8V, COUT should be increased to 22µF or more to maintain ≤100mV_P-P ripple. Ceramic or tantalum types are recommended; aluminum electrolytics are not suitable due to high ESR.

How does the power-on reset (POR) function work on the LTC1515CS8#TRPBF?

The POR pin on the LTC1515CS8#TRPBF is an open-drain output that remains low until VOUT reaches and sustains regulation within ±6.5% for 140–280ms (typ 200ms). It asserts low again during shutdown or power loss. An external pull-up resistor to VOUT is required. This timing aligns with GSM baseband processor reset requirements and ensures deterministic microcontroller boot sequencing. The LTC1515CS8#TRPBF POR does not provide programmable delay or voltage threshold adjustment.

What protection features are built into the LTC1515CS8#TRPBF?

The LTC1515CS8#TRPBF includes short-circuit protection (limiting output current to 12–40mA when VOUT < 100mV), overtemperature shutdown (~150°C trip, ~140°C recovery), and soft-start circuitry that limits inrush current during turn-on. It also features internal current limiting during large VIN–VOUT differentials to prevent input supply disruption. These protections allow indefinite short-circuit survival and robust operation in portable equipment with unstable input sources.

Can the LTC1515CS8#TRPBF operate from a single-cell Li-ion battery?

Yes, the LTC1515CS8#TRPBF operates from 2V to 10V, fully covering the discharge range of a single-cell Li-ion battery (2.7V–4.2V). At VIN = 2.7V, it delivers 50mA at 5V output; at VIN = 3.3V, it sustains full 50mA output for both 3.3V and 5V modes. Its 60µA quiescent current and <1µA shutdown current maximize battery life in Li-ion-powered devices such as handheld scanners and medical sensors. The LTC1515CS8#TRPBF requires no additional pre-regulator for this use case.