STMicroelectronics LNBK20D2-TR

Overview

LNBK20D2-TR from STMicroelectronics is a monolithic linear voltage regulator in SO-20 package, designed to power and control two LNB downconverters via coaxial cable in satellite receivers. It delivers 13 V or 18 V (typ.) outputs with ±0.5 V load regulation, 400 mA guaranteed output current per channel, and integrated 22 kHz tone oscillator factory-trimmed to ±2 kHz for DiSEqC™ encoding.

For engineers reviewing the LNBK20D2-TR datasheet, LNBK20D2-TR pinout, LNBK20D2-TR application, or LNBK20D2-TR equivalent, key selection criteria include dual-port logic-selectable output voltage (13/18 V), dynamic overcurrent protection with 4.7 µF CEXT timing, bypass switch for slave operation, line-length compensation (+1 V), and dual-supply input selection (VCC1/VCC2) to minimize dissipation.

Technical Context

The device implements a dual-output linear regulator architecture with independent logic-controlled port enable (EN), selection (OSEL), and voltage set (VSEL) inputs. Each output supports fast 22 kHz tone modulation (ENT pin) with 5–15 µs rise/fall time and ±0.3 V amplitude, enabling DiSEqC™ burst coding without external components.

Overcurrent protection operates dynamically: upon fault detection on LNBA or LNBB, the affected output shuts down for t_OFF (1100 ms typical with 4.7 µF at CEXT), while OLF pin pulls low; after t_OFF, it resumes for t_ON = t_OFF/15 before cycling until fault clearance - reducing thermal stress during sustained short circuits.

Key Specifications

Pinout & Package

Package: SO-20 surface-mount package with 4 dedicated GND pins (pins 5, 6, 15, 16) serving both electrical grounding and thermal conduction to PCB heatsink. Thermal resistance R_thj-case = 15 °C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LNBP21D2-TR, LNBK20D2-TR trades 200 mA output headroom for lower cost and thermal footprint; versus SPS1001D2TR, it offers simpler tone-only control without DiSEqC™ data layer complexity or external oscillator dependency.

Availability

LNBK20D2-TR is available at Aetrix Electronics and suitable for dual-port satellite receivers, DiSEqC™-enabled dish positioners, single-dish dual-receiver systems, and professional signal distribution equipment requiring stable component supply and long-term lifecycle support.

Supply support for LNBK20D2-TR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in analog, power, and automotive ICs with strong heritage in broadcast and consumer electronics.

LNBK20D2-TR belongs to the LNBP series of LNB power regulators, engineered specifically for cost-sensitive satellite receiver designs requiring robust coaxial power delivery, DiSEqC™ tone generation, and thermal resilience in compact enclosures.

FAQ

What is the purpose of the CEXT pin and how does it affect protection timing?

The CEXT pin connects an external capacitor to ground to set the OFF-time (t_OFF) of the dynamic overcurrent protection circuit. With a 4.7 µF capacitor, t_OFF is 1100 ms; the ON-time (t_ON) is automatically t_OFF/15. This timing prevents thermal runaway during sustained shorts while allowing periodic re-attempts to restore power - critical for capacitive LNB loads that may exhibit inrush currents.

Can LNBK20D2-TR be used with a single 23 V supply instead of dual VCC1/VCC2?

Yes - both VCC1 and VCC2 can be tied to a common 23 V supply without functional impact. However, doing so increases power dissipation by ~30% when regulating to 13 V, since the higher input voltage creates greater dropout loss. The dual-supply architecture exists specifically to minimize heat in mixed-voltage applications; using only VCC2 is acceptable if thermal design accommodates the extra 0.6 W.

How does the bypass function work in slave mode, and what pins are involved?

In slave mode, the EN pin is held LOW, activating an internal electronic switch between the MI (Master Input) and LNBA pins. This routes the master receiver's LNB voltage directly to LNBA, disabling the local regulator. MI must be driven by the master's LNB output; LNBB remains under local control. No external components are needed - the function is fully integrated and requires only proper logic-level coordination between master and slave EN signals.

Is external filtering required on the EXTM pin, and what happens if left unconnected?

Yes - EXTM requires AC coupling via a DC-blocking capacitor (e.g., 100 nF) to isolate the modulating signal source from the IC's internal bias. If unused, EXTM may be left floating (not grounded), as it has no internal pull-up/down and draws negligible leakage current. Leaving it unconnected disables external modulation entirely, preserving default 22 kHz tone operation via ENT without interference or noise injection.