SNLA267A March 2019 – June 2019 DS90UB953-Q1 , DS90UB954-Q1 , DS90UB960-Q1
The first mode, synchronous, is an internally generated clock. This clock reference is extracted from back channel on the bidirectional communications link, and the internal PLLs take the extracted signal to generate the required clocks. This allows multiple cameras within a system to operate in the same clock domain and allows more space on the PCB. As shown in Figure 4, REFCLK (f0) is input signal on the deserializer that is required for precise frequency operation. Refer to the REFCLK section in the 954 data sheet for more information. The RECLK specifications for the 953 states that REFCLK must range from 24 to 26 MHz, and this signal sends two bits across the back channel: high and low. As a result, multiply the REFCLK frequency by two when calculating the BC and FC rate. This is summarized in Table 5.