Renesas ISL6421AERZ-T

Overview

ISL6421AERZ-T from Intersil is a single-output LNB supply and control voltage regulator with I²C interface, integrating a current-mode boost PWM and low-noise linear regulator for satellite set-top box antenna port power delivery. It delivers 450mA typical output current, supports programmable 13V/18V outputs via VSEL bit, includes 1V line-length compensation (LLC), and features factory-trimmed 22kHz tone generation for DiSEqC™ encoding.

For engineers reviewing the ISL6421AERZ-T datasheet, ISL6421AERZ-T pinout, ISL6421AERZ-T application, or ISL6421AERZ-T equivalent, key selection considerations include I²C-controlled dual-voltage output, integrated DiSEqC tone modulation, dynamic/programmable overcurrent protection, thermal shutdown flag visibility via I²C, and QFN-32 package compatibility with coaxial cable drop compensation.

Technical Context

The ISL6421AERZ-T employs a current-mode boost PWM followed by a linear post-regulator to minimize dissipation: VSW tracks VOUT + ~1.2V dropout, enabling efficient operation across 8–14V input while maintaining stable 13V/18V LNB output. Its internal 220kHz oscillator drives both PWM and tone circuitry, with the 22kHz tone derived via ÷10 division and wave shaping.

I²C interface operates at up to 400kHz with slave address 000100XX (ADDR pin selects LSB), supporting full read/write access to system registers SR1/SR2 for real-time control of EN, VSEL, LLC, ENT, DCL, and diagnostic flags OLF/OTF - all visible and modifiable during operation without reset.

Key Specifications

Pinout & Package

ISL6421AERZ-T is housed in a 32-lead 5×5 mm QFN package (JEDEC MO-220 VHHD-2 compliant), featuring an exposed thermal pad for enhanced heat dissipation and near chip-scale footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LNB supply and control applications.

Compared with MAX2102ETJ+T and LM4990MM/NOPB, the ISL6421AERZ-T provides superior system integration via I²C-configurable registers, real-time diagnostic visibility, and adaptive overcurrent protection - reducing BOM count and enabling firmware-driven LNB management in advanced STB platforms.

Availability

ISL6421AERZ-T is available at Aetrix Electronics and suitable for satellite set-top box front-end power delivery, DiSEqC™-compliant LNB control, and thermal-aware consumer electronics requiring stable component supply across extended temperature ranges (-20°C to +85°C).

Supply support for ISL6421AERZ-T 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 Corporation (now part of Renesas Electronics) is a U.S.-based analog and power management IC designer known for high-efficiency DC/DC converters, precision regulators, and interface solutions targeting consumer, industrial, and communications markets.

The ISL6421AERZ-T belongs to Intersil's satellite infrastructure power management product line, engineered specifically to consolidate LNB supply, DiSEqC™ tone generation, and intelligent protection into a single QFN device for next-generation STB and PVR platforms.

FAQ

What is the primary function of the ISL6421AERZ-T in satellite set-top box designs?

The ISL6421AERZ-T serves as a fully integrated LNB supply and control voltage regulator, delivering regulated 13V or 18V output to satellite low-noise blocks while generating DiSEqC™-compliant 22kHz tone signals. It combines a current-mode boost PWM, low-noise linear post-regulator, I²C interface, and diagnostics into a single QFN-32 package - eliminating discrete components traditionally needed for LNB bias and band switching in ISL6421AERZ-T-based STB designs.

How does the ISL6421AERZ-T compensate for voltage drop across long coaxial cables?

The ISL6421AERZ-T implements digital line-length compensation (LLC) via an I²C-configurable bit that increases the nominal output voltage by 1V - e.g., from 13V to 14V or 18V to 19V - to offset IR losses in RG-6 cables up to 50 meters. This feature is implemented entirely within the ISL6421AERZ-T's internal regulation loop and requires no external components, ensuring consistent LNB bias voltage at the antenna regardless of cable length.

Can the ISL6421AERZ-T generate DiSEqC™ tone signals without microcontroller intervention?

Yes - the ISL6421AERZ-T supports hardware-triggered DiSEqC™ tone generation via the DSQIN pin: driving DSQIN HIGH immediately enables the internal 22kHz oscillator and modulates VOUT, independent of I²C register settings. This allows direct connection to GPIO pins for burst-coded commands, while the ENT bit in SR1 provides software-controlled tone enable/disable. Both methods coexist in the ISL6421AERZ-T, offering flexibility for different STB firmware architectures.

What protection features are accessible through the I²C interface of the ISL6421AERZ-T?

The ISL6421AERZ-T exposes two real-time diagnostic flags via its I²C system registers: OLF (Overload Flag) in SR1 indicates active overcurrent condition, and OTF (Over Temperature Flag) in SR2 signals junction temperature exceeding 150°C. Both flags are readable at any time without interrupting operation, enabling host MCUs to implement predictive fault handling, thermal logging, and graceful degradation strategies - a capability unique to the ISL6421AERZ-T among LNB regulators.

Does the ISL6421AERZ-T require external components for stable 22kHz tone generation?

The ISL6421AERZ-T requires only a single external capacitor on the TCAP pin (≥1µF recommended) to set 22kHz tone rise/fall time - no crystal, resistor network, or op-amp is needed. The oscillator is factory-trimmed to 22kHz ±10% and internally divided from a 220kHz master clock, ensuring compliance with DiSEqC™ specifications without calibration. This TCAP-based timing control is intrinsic to the ISL6421AERZ-T's architecture and contributes to its high integration level.