STMicroelectronics LNBS21PD

Overview

LNBS21PD from STMicroelectronics is a monolithic LNB supply and control IC in PowerSO-20 package, integrating step-up DC/DC controller, linear post-regulator, 22 kHz tone oscillator/detector, I²C interface, DiSEqC 2.x bi-directional support, and comprehensive protection (overcurrent, overtemperature, UVLO). It delivers regulated 13/18 V outputs with ±1 V cable compensation and supports master/slave loop-through operation for satellite TV receivers.

For engineers reviewing the LNBS21PD datasheet, LNBS21PD pinout, LNBS21PD application, or LNBS21PD equivalent, key selection considerations include its dual-mode current limiting (static/dynamic), factory-trimmed 22 kHz oscillator (±10% tolerance), I²C-addressable system register with diagnostic flags (OLF/OTF), and integrated DiSEqC modulation/demodulation path via DSQIN/DSQOUT pins.

Technical Context

The LNBS21PD implements a two-stage power architecture: a 220 kHz fixed-frequency step-up controller drives an external MOSFET to generate VUP (16–22 V), which feeds an internal linear post-regulator delivering precise 13/18 V output with dropout minimization logic. Its I²C interface uses a single 8-bit System Register (SR) with six writable bits controlling voltage select (VSEL), tone enable (TEN), loop-through (EN), cable compensation (LLC), current limit mode (ISEL), and pulsed limiting (PCL).

DiSEqC 2.x compliance is enabled through dedicated analog blocks: DSQIN accepts PWM-encoded DiSEqC data for tone modulation, while DETIN (AC-coupled) and DSQOUT provide tone-synchronous PWK demodulation with open-collector output. The 22 kHz oscillator is factory trimmed to 22 kHz ±10% and starts in <10 ms, enabling fast DiSEqC encoding.

Key Specifications

Pinout & Package

LNBS21PD is housed in a thermally enhanced PowerSO-20 package with exposed die pad for low-junction-to-case thermal resistance (2 °C/W). Pin numbering follows top-view layout per Figure 2 of the datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX2222ESE+ and SP8001D, LNBS21PD uniquely integrates step-up control, bi-directional DiSEqC, cable compensation, and pulsed current limiting - enabling full-featured, compact, and thermally robust LNB interfaces for next-generation satellite receivers.

Availability

LNBS21PD is available at Aetrix Electronics and suitable for satellite STB receivers, multiswitch controllers, PC tuner cards, and professional signal analyzers requiring stable component supply and long-term design continuity.

Supply support for LNBS21PD 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, designing and manufacturing microcontrollers, power ICs, sensors, and analog devices for automotive, industrial, and consumer markets.

LNBS21PD belongs to ST's LNB Interface IC product line, engineered specifically for satellite TV infrastructure to consolidate power regulation, DiSEqC signaling, and protection into a single monolithic solution for space-constrained, thermally demanding receiver designs.

FAQ

What is the purpose of the EXTM pin on the LNBS21PD?

The EXTM pin provides an external analog modulation input for custom LNB control signals. It accepts AC-coupled modulation sources (e.g., 10 Hz–40 kHz) with up to 400 mVpp amplitude and 260 Ω input impedance. When unused, it may be left floating; no pull-up/down is required. Its gain is 6 V/V, enabling direct voltage-controlled output adjustment beyond standard DiSEqC commands.

How does the LNBS21PD handle DiSEqC 2.x bi-directional communication?

LNBS21PD implements DiSEqC 2.x bi-directionality using three dedicated pins: DSQIN accepts PWM-encoded DiSEqC data for tone modulation, DETIN (AC-coupled) extracts the 22 kHz carrier from the bus, and DSQOUT outputs decoded PWK data as an open-collector logic signal. External LR termination (15 Ω at 22 kHz) on the OUT pin is required for full hardware compliance per EUTELSAT recommendations.

Can the LNBS21PD operate with a 5 V microcontroller I²C interface?

Yes - the LNBS21PD's SDA and SCL pins tolerate logic levels up to 7 V and specify VIH = 2 V and VIL = 0.8 V, making them fully compatible with both 3.3 V and 5 V microcontrollers. No level-shifting circuitry is required. The I²C interface operates up to 500 kHz and includes built-in UVLO reset that disables communication until VCC exceeds 7.3 V.

What happens to the LT1–LT2 loop-through path during thermal shutdown?

During thermal shutdown (junction temperature >150 °C), the LNBS21PD disables the step-up converter and linear regulator, sets the OTF flag HIGH, and opens the LT1–LT2 loop-through switch. This isolates the slave LNB path to prevent uncontrolled current flow. Normal loop-through operation resumes only after junction temperature cools to ≤140 °C and the OTF flag resets LOW.