ZHCSDJ6E February 2015 – June 2018 LMH1218
PRODUCTION DATA.
The LMH1218 has receive-side equalization, and a key part is the Continuous Time Linear Equalizer (CTLE). This circuit operates on the received differential signal and compensates for frequency-dependent loss due to the transmission media. The CTLE applies gain to the input signal. This gain varies over frequency: higher frequencies are boosted more than lower frequencies. The CTLE works to restore the input signal to full amplitude across a wide range of frequencies.
The CTLE consists of 4 stages with each stage having two boost control bits. This allows 256 different boost settings. CTLE boost levels are determined by summing the boost levels of the 4 stages. The CTLE is configured manually. Refer to LMH1218 Programming Guide (SNLU174) on how to quickly select the most appropriate CTLE boost setting.
There are two CTLEs, one for each input, IN0 and IN1. Only one CTLE is enabled at a time, according to the user input channel selection. If IN0 is selected, the CTLE for IN0 is powered on and the IN1 CTLE is powered off. The CTLE compensates for up to 27 dB of loss at 6 GHz. The CTLE is able to handle low loss channels without over-equalizing by bypassing the CTLE.