MC100EL38

The MC100EL38 is a low skew ÷2, ÷4, ÷8 clock generation chip designed explicitly for low skew clock generation applications. The internal dividers are synchronous to each other, therefore, the common output edges are all precisely aligned. The MC100EL38 can be driven by either a differential or single-ended ECL or, if positive power supplies are used, PECL input signal. In addition, by using the VBB output, a sinusoidal source can be AC coupled into the device (see Interfacing section of the ECLinPSE Data Book DL140/D). If a single-ended input is to be used, the VBB output should be connected to the CLKinput and bypassed to ground via a 0.01mF capacitor. The VBB output is designed to act as the switching reference for the input of the EL34 under single-ended input conditions, as a result, this pin can only source/sink up to 0.5mA of current.

The common enable (NE) is synchronous so that the internal dividers will only be enabled/disabled when the internal clock is already in the LOW state. This avoids any chance of generating a runt clock pulse on the internal clock when the MC100EL38 is enabled/disabled as can happen with an asynchronous control. An internal runt pulse could lead to losing synchronization between the internal divider stages. The internal enable flip-flop is clocked on the falling edge of the input clock, therefore, all associated specification limits are referenced to the negative edge of the clock input.

The Phase_Out output will go HIGH for one clock cycle whenever the ÷2 and the ÷4/6 outputs are both transitioning from a LOW to a HIGH. This output allows for clock synchronization within the system.

Upon startup, the internal flip-flops will attain a random state; therefore, for systems which utilize multiple MC100EL38s, the master reset (MR) input must be asserted to ensure synchronization. For systems which only use one LVEL38, the MR pin need not be exercised as the internal divider design ensures synchronization between the ÷2 and the ÷4/6 outputs of a single device.