Renesas ISL6455IRZ-T5K

Overview

ISL6455IRZ-T5K from Intersil is a triple-output power management IC integrating one synchronous buck regulator (0.8V–2.5V, 600mA) and two ultra-low-noise adjustable LDOs (1.2V–3.3V, 300mA each), designed for FPGA and WLAN chipset power rails. It features integrated PMOS pass transistors, 750kHz fixed-frequency PWM operation, <30µVRMS LDO2 noise for VCO stability, and a programmable RESET output with 25ms timeout.

For engineers reviewing the ISL6455IRZ-T5K datasheet, ISL6455IRZ-T5K pinout, ISL6455IRZ-T5K application, or ISL6455IRZ-T5K equivalent, key selection criteria include PWM/LDO voltage adjustability via external resistors, dual independent enable controls (EN/EN_LDO), PG_PWM and PG_LDO status outputs, thermal shutdown at +150°C, and QFN-24 package compatibility with PCMCIA/MiniPCI form factors.

Technical Context

The ISL6455IRZ-T5K implements peak current-mode control with internal slope compensation in its synchronous buck stage, using integrated P-Channel and N-Channel MOSFETs (rDS(ON) = 170mΩ / 50mΩ). Its 750kHz oscillator supports external synchronization from 500kHz to 1MHz via the SYNC pin, and soft-start duration is fixed at 5.5ms.

Both LDOs employ internal 1.184V bandgap references, PMOS pass devices with 150mV dropout at 300mA, and dual-mode comparators for regulation monitoring. The RESET block asserts low for ≥25ms after VIN_PWM recovers above 2.77V (ISL6455 variant), with hysteresis of 20mV and CT-pin programmability.

Key Specifications

Pinout & Package

ISL6455IRZ-T5K uses a 24-lead QFN package (4mm × 4mm, 0.5mm pitch) with an exposed thermal pad on the underside, requiring direct connection to GND_LDO/PGND ground plane for thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triple-output power management applications.

Compared with ISL6455AIRZ-T5K, the ISL6455IRZ-T5K offers lower input voltage operation and tighter LDO noise specs but less PWM voltage headroom; versus TPS65283RGER, it trades higher current capability for RF-optimized dual-LDO integration and system-level supervision.

Availability

ISL6455IRZ-T5K is available at Aetrix Electronics and suitable for WLAN PCMCIA cards, FPGA-based embedded controllers, and handheld instrumentation requiring stable component supply across industrial temperature ranges (–40°C to +85°C).

Supply support for ISL6455IRZ-T5K 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

Intersil (now part of Renesas Electronics) is a semiconductor company specializing in precision analog, power management, and interface ICs for communications, computing, and industrial markets.

The ISL6455 product line was designed specifically for space-constrained wireless infrastructure and portable electronics, delivering highly integrated, low-noise multi-rail power solutions for WLAN, Bluetooth, and FPGA applications.

FAQ

What input voltage range does the ISL6455IRZ-T5K support for its PWM section?

The ISL6455IRZ-T5K PWM section supports an input voltage range of 3.0V to 3.6V, optimized for 3.3V ±10% systems. This is distinct from the ISL6455A variant, which requires 4.2V–5.5V. The VIN_PWM UVLO threshold is 2.65V (typical), ensuring reliable startup and shutdown behavior in 3.3V rail environments. The ISL6455IRZ-T5K must not be operated outside this range to maintain regulation integrity and avoid damage.

How is the RESET timeout period set on the ISL6455IRZ-T5K?

The RESET timeout period on the ISL6455IRZ-T5K is set by an external capacitor connected to the CT pin. With CT = 0.01µF, the minimum asserted time is 25ms; the relationship is linear at 2.5ms/nF. This allows precise tailoring of reset pulse width to match microprocessor requirements without external timing ICs. The ISL6455IRZ-T5K RESET block monitors VIN_PWM and holds the output low for the full CT-determined duration after crossing the 2.77V rising threshold.

Can the ISL6455IRZ-T5K power a VCO directly, and what ensures low phase noise?

Yes, the ISL6455IRZ-T5K can power a VCO directly via its LDO2 output, which delivers <30µVRMS output noise (10Hz–100kHz) at 10µF output capacitance. This ultra-low noise is achieved through internal PMOS pass transistor design, 33nF compensation capacitor (CC2), and dedicated low-noise error amplifier architecture. The ISL6455IRZ-T5K's LDO2 specification meets stringent phase noise requirements for 2.4GHz/5GHz synthesizers without requiring additional filtering stages.

What are the thermal management requirements for the ISL6455IRZ-T5K in continuous operation?

The ISL6455IRZ-T5K requires connection of its exposed thermal pad to a solid GND_LDO/PGND copper plane to achieve θJC = 6°C/W. For continuous operation at full load, junction temperature must remain below +150°C; with θJA = 42°C/W and ambient at +70°C, maximum allowable power dissipation is ~1.9W. Layout best practices include short, wide traces to the thermal pad, multiple vias to inner ground layers, and separation of analog (SGND/GND_LDO) and power (PGND) grounds at the pad.

How do the EN and EN_LDO pins function independently in power sequencing?

The EN pin controls only the synchronous buck regulator, while EN_LDO independently enables or disables both LDO1 and LDO2. This allows precise sequencing-for example, enabling the PWM rail first to power FPGA core logic, waiting for configuration completion (e.g., DONE pin assertion), then asserting EN_LDO to activate I/O and analog rails. Both pins accept CMOS-level signals referenced to VIN, and pulling either low reduces quiescent current to ≤10µA, supporting low-power standby modes in the ISL6455IRZ-T5K.