JAJSI48C March 2017 – October 2019 LMH1228
PRODUCTION DATA.
The LMH1228 has a continuous time linear equalizer (CTLE) block for IN0. The CTLE compensates for frequency-dependent loss due to the transmission media prior to the device input. The CTLE accomplishes this by applying variable gain to the input signal, thereby boosting higher frequencies more than lower frequencies. The CTLE block extends the signal bandwidth, restores the signal amplitude, and reduces ISI caused by the transmission medium.
IN0 has an on-chip 100-Ω termination and is designed for AC coupling, requiring a 4.7-μF, AC-coupling capacitor for minimizing base-line wander. The PCB equalizer can compensate up to 20 inches of board trace at data rates up to 11.88 Gbps. There are two adapt modes for IN0: AM0 manual mode and AM1 adaptive mode. In AM0 manual mode, fixed EQ boost settings are applied through user-programmable control. In AM1 adaptive mode, state machines automatically find the optimal EQ boost from a set of 16 predetermined settings defined in Registers 0x40-0x4F.
The HOST_EQ0 pin determines the IN0 adapt mode and EQ boost level. For normal operation, HOST_EQ0 = F is recommended. HOST_EQ0 pin logic settings are shown in Table 4. These HOST_EQ0 pin settings can be overridden by register control. For more information, refer to the LMH1228 and LMH1208 Programming Guide (SNAU206).
HOST_EQ0(1) | IN0± EQ BOOST | RECOMMENDED BOARD
TRACE IN0±(2) |
---|---|---|
H | All Rates: AM0 Manual Mode, EQ=0x00 | < 1 inch |
F | Normal Operation
12G to 3G Rates: AM1 Adaptive Mode 1.5G, 270M Rates: AM0 Manual Mode, EQ= 0x00 |
0-20 inches |
R | All Rates: AM0 Manual Mode, EQ=0x80 | 10-15 inches |
L | All Rates: AM0 Manual Mode, EQ=0x90 | 20 inches |