LNBs supply and control IC with step-up and I2C interface# Technical Documentation: LNBH23QTR Low-Noise Block Downconverter with Integrated 13/18V and 22kHz Tone Switch
Manufacturer : STMicroelectronics
Document Version : 1.0
Date : October 26, 2023
---
## 1. Application Scenarios
### 1.1 Typical Use Cases
The LNBH23QTR is a monolithic, low-noise block downconverter (LNB) power supply and control IC designed primarily for satellite set-top boxes (STBs) and integrated digital televisions (iDTVs). Its core function is to provide a regulated, low-noise supply voltage to the external LNB, which is the front-end module on a satellite dish responsible for receiving the Ku-band (10.7–12.75 GHz) signal, amplifying it, and downconverting it to a lower intermediate frequency (L-band, 950–2150 MHz) for transmission via coaxial cable to the receiver.
Primary Functions in a Receiver System:
* Power Supply: Generates the precise 13V (Vertical Polarization) or 18V (Horizontal Polarization) DC voltage required to power the LNB module via the same coaxial cable that carries the RF signal (a scheme known as *DiSEqC™ power insertion*).
* Tone Switching: Integrates a 22kHz tone generator used for band selection. A continuous 22kHz signal superimposed on the supply voltage switches the LNB to the high band (11.7–12.75 GHz), while its absence selects the low band (10.7–11.7 GHz).
* Short-Circuit Protection: Features robust protection against output short-circuits and overcurrent conditions, which are common during installation or connector faults.
### 1.2 Industry Applications
1. Direct-to-Home (DTH) Satellite Television: The dominant application, found in millions of residential satellite receivers globally for services like DirecTV, DISH Network, Sky, and Freesat.
2. Community Satellite Distribution (SMATV): Used in head-end units that distribute satellite signals to multiple dwellings (apartments, hotels).
3. Automotive Satellite Systems: Employed in mobile satellite TV receivers for RVs, yachts, and luxury vehicles.
4. Professional VSAT Terminals: While higher-end VSATs may use more specialized components, the LNBH23QTR can be found in cost-sensitive, receive-only VSAT terminals for data backhaul or content distribution.
### 1.3 Practical Advantages and Limitations
Advantages:
* High Integration: Combines voltage regulators, a 22kHz tone generator, and control logic into a single 16-QFN package (3x3 mm), significantly reducing the bill of materials (BOM) and PCB footprint compared to discrete solutions.
* Low Dropout Voltage: The internal LDO regulators feature a low dropout voltage, enabling stable operation even with a modest (e.g., 19V) input supply, improving overall system efficiency.
* Excellent Noise Performance: Critical for LNB supply, as noise on the bias line can couple into the sensitive RF path. The IC is designed for very low output noise and high power supply rejection ratio (PSRR).
* DiSEqC 2.x Compatibility: The control interface is fully compatible with the Digital Satellite Equipment Control (DiSEqC) protocol, allowing for advanced switching between multiple LNBs or dishes via digital commands sent on the 22kHz tone.
* Robust Protection: Includes thermal shutdown, current limiting, and a timed short-circuit protection latch, enhancing field reliability.
Limitations:
* Fixed Output Voltages: The 13/18V outputs are fixed. For systems requiring non-standard voltages (e
