SX1781 View Datasheet(PDF) - Semtech Corporation

Part Name

Description

Manufacturer

SX1781

PLL Frequency Synthesizer with Integrated VCO

Semtech Corporation 

SX1781

PLL Frequency Synthesizer with integrated VCO

ADVANCED COMMUNICATIONS & SENSING

FINAL

DATASHEET

11. Output Buffer

The SX1781 device embeds a differential output buffer structure.

Figure 3. Output Buffer Structure

The output buffer structure described in Figure 3 allows using the SX1781 either single ended, or with the differential

outputs combined in a balun, hence leading to a higher drive level.

11.1. Single Ended Configuration

Out_P

Cs

Ls

Lc

50 ohms

Figure 4. Single-Ended Output Setting

Figure 4 describes the single-ended output setting, enabling a typical output power of -1dBm in a reactive matched 50 ohm

load, with the highest gain setting of the device. The choke inductor (denoted Lc) should be chosen to offer the highest

impedance at the output frequency. Whenever using the chip in single-ended configuration, the unused complementary

output should be terminated on a dissipative 50 ohms load.

11.2. Combined Differential Output

If additional power is required on a single-ended 50 ohms output port, the user can combine Out_P and Out_N outputs.

Typical output powers of up to +5dBm can hence be reached. To achieve this, the lumped-lattice balun configuration of

Rev 1 - November 2008

©2008 Semtech Corp.

Page 11

www.semtech.com

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