ADCLK846

Rev. A | Page 12 of 16

CLOCK OUTPUTS

Each driver consists of a differential LVDS output or two single-

ended CMOS outputs (always in phase). When the LVDS driver

is enabled, the corresponding CMOS driver is in tristate. When

the CMOS driver is enabled, the corresponding LVDS driver is

powered down and tristated. Figure 21 and Figure 22 display

the equivalent output stage.

OUTx

OUTx

3.5mA

3.5mA

Figure 21. LVDS Output Simplified Equivalent Circuit

OUTxA

OUTxB

Figure 22. CMOS Equivalent Output Circuit

CONTROL AND FUNCTION PINS

Logic Select for CTRL_A

CTRL_A selects either CMOS (high) or LVDS (low) logic for

Output 1 and Output 0. This pin has an internal 200 kΩ pull-

down resistor.

Logic Select for CTRL_B

CTRL_B selects either CMOS (high) or LVDS (low) logic for

Output 5, Output 4, Output 3, and Output 2. This pin has an

internal 200 kΩ pull-down resistor.

Sleep Mode

SLEEP powers down the chip except for the band gap. The

input is active high, which puts the outputs into a high-Z state.

This pin has a 200 kΩ pull-down resistor. The control pins are

operational during sleep mode.

POWER SUPPLY

Best practice recommends bypassing the power supply on

the PCB with adequate capacitance (>10 μF) and bypassing

all power pins with adequate capacitance (0.1 μF) as close to

the part as possible. The layout of the ADCLK846 evaluation

board (ADCLK846/PCBZ) provides a good layout example.

Exposed Metal Paddle

The exposed metal paddle on the ADCLK846 package is an

electrical connection, as well as a thermal enhancement. For

the device to function properly, the paddle must be properly

attached to ground (GND). The ADCLK846 dissipates heat

through its exposed paddle. The PCB acts as a heat sink for the

ADCLK846. The PCB attachment must provide a good thermal

path to a larger heat dissipation area, such as the ground plane

on the PCB. This requires a grid of vias from the top layer down

to the ground plane. See Figure 23 for an example.

VIAS TO GND PLANE

Figure 23. PCB Land Example for Attaching Exposed Paddle