Analog Devices Inc. LT1533CS#TRPBF

Overview

LT1533CS#TRPBF from Analog Devices (formerly Linear Technology) is a dual-output, current-mode switching regulator IC designed for ultralow-noise power conversion in precision analog systems. It integrates two 1A current-limited NPN power switches, independent voltage/current slew rate control (VSLEWR = 11 V/µs, ISLEWR = 1.3 A/µs), 20–250 kHz programmable oscillator, and dual-polarity regulation capability (±1.25 V FB reference / –2.5 V NFB reference). It is used in medical instrumentation and isolated industrial supplies where EMI < 100 µV_P-P is required.

For engineers reviewing the LT1533CS#TRPBF datasheet, LT1533CS#TRPBF pinout, LT1533CS#TRPBF application, or LT1533CS#TRPBF equivalent, key selection criteria include its dual 1A switch architecture, independent slew rate programming via RVSL/RCSL pins, ±2.5V feedback compliance, 2.7–23V input range, and SO-16 narrow package thermal performance (θ_JA = 100°C/W).

Technical Context

The LT1533CS#TRPBF employs a fixed-frequency current-mode control architecture with internal slope compensation, enabling stable operation up to 45.5% duty cycle and inherent cycle-by-cycle current limiting. Its dual out-of-phase outputs drive push-pull transformer topologies while supporting unregulated 50% duty cycle mode via the DUTY pin.

Slew control is implemented through two independent feedback loops: one regulating collector voltage dV/dt (via RVSL), the other regulating emitter current dI/dt (via RCSL), both referenced to external resistors. The VC pin serves simultaneously as error amplifier output, current limit threshold, and soft-start node - with clamp voltages at 0.1 V (low) and 1.33 V (high).

Key Specifications

Pinout & Package

LT1533CS#TRPBF is housed in a 16-pin narrow SOIC (SO-16) package with exposed pad not present; θ_JA = 100°C/W. Pin 9 (GND) is signal ground; Pin 16 (PGND) is dedicated power switch emitter return with 25 nH recommended trace inductance for slew loop stability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-output switching regulator applications.

Compared with LTC3891EFE#PBF and LM5180QPWPRQ1, the LT1533CS#TRPBF uniquely delivers integrated dual 1A switches, programmable dV/dt and di/dt control, and native ±2.5 V feedback - making it irreplaceable in EMI-sensitive dual-rail applications where component count, layout simplicity, and intrinsic noise suppression are critical.

Availability

LT1533CS#TRPBF is available at Aetrix Electronics and suitable for medical instrumentation, precision data acquisition, and industrial isolated supplies requiring stable component supply across extended product lifecycles.

Supply support for LT1533CS#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. (ADI) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies.

The LT1533CS#TRPBF belongs to ADI's legacy Linear Technology power management portfolio, engineered specifically for ultralow-noise switching regulation in precision analog and measurement systems where EMI compliance is non-negotiable.

FAQ

What is the maximum allowable input voltage for LT1533CS#TRPBF?

The absolute maximum input voltage (VIN) for LT1533CS#TRPBF is 30 V, but the recommended operating range is 2.7 V to 23 V. Operation above 23 V risks exceeding safe junction temperature due to increased power dissipation in the internal switches and regulator. The device enters undervoltage lockout below 2.55 V, and sustained operation within the 2.7–23 V window ensures full specification compliance across temperature.

How does the LT1533CS#TRPBF achieve ultralow EMI performance?

The LT1533CS#TRPBF achieves ultralow EMI by enabling independent control of output voltage slew rate (via RVSL pin) and output current slew rate (via RCSL pin), reducing high-frequency harmonic content by up to 40 dB. Unlike conventional switchers, it avoids sharp edges in both dV/dt and di/dt domains - directly suppressing conducted and radiated emissions at the source rather than relying solely on filtering.

Can LT1533CS#TRPBF regulate both positive and negative output voltages simultaneously?

Yes, LT1533CS#TRPBF can regulate both polarities simultaneously using its dedicated FB pin (for +VOUT, regulated to +1.25 V) and NFB pin (for –VOUT, regulated to –2.5 V). When both pins are active, the IC prevents either rail from exceeding its setpoint - though load regulation is compromised under mismatched loading. This dual-feedback capability eliminates the need for separate negative regulators in bipolar supply designs.

What is the function of the DUTY pin on LT1533CS#TRPBF?

The DUTY pin on LT1533CS#TRPBF forces the internal power switches into a fixed 50% duty cycle mode when grounded - overriding normal current-mode control. This mode operates at half the oscillator frequency and is optimized for push-pull transformer topologies. When left floating or pulled high, the DUTY pin enables standard variable-duty-cycle regulation based on feedback error.

Does LT1533CS#TRPBF include thermal protection?

Yes, LT1533CS#TRPBF includes thermal shutdown protection that disables both output drivers and pulls the VC pin low when junction temperature exceeds 125°C. Recovery occurs automatically once temperature falls below the hysteresis threshold. This feature protects against catastrophic failure during overload or poor heatsinking - complementing cycle-by-cycle current limiting and undervoltage lockout for comprehensive fault coverage.