The LMH1219 is designed to provide flexibility in supply rails. There are two ways to power the LMH1219:

• Single Supply Mode (2.5 V): This mode offers ease of use, with the internal circuitry receiving power from the on-chip 1.8 V regulator. In this mode, 2.5 V is applied to VDD_CDR, VIN, and VDDIO. See Figure 39 for more details.
• Dual Supply Mode (2.5 V and 1.8 V): This mode provides lower power consumption. In this mode, 1.8 V is connected to both VIN and VDD_LDO. VDD_CDR, and VDDIO are powered from a 2.5 V supply. See Figure 40 for more details.
• When Dual Supply Mode is used, the 2.5 V supply for VDD_CDR and VDDIO should be powered before or at the same time as the 1.8 V supply that powers VIN and VDD_LDO.

Figure 39. Typical Connection for Single 2.5 V Supply

Figure 40. Typical Connection for Dual 2.5 V and 1.8 V Supply

For power supply de-coupling, 0.1-μF surface-mount ceramic capacitors are recommended to be placed close to each VDD_CDR, VIN, VDD_LDO, and VDDIO supply pin to VSS. Larger bulk capacitors (for example, 10 µF and 1 µF) are recommended for VDD_CDR and VIN. Good supply bypassing requires low inductance capacitors. This can be achieved through an array of multiple small body size surface-mount bypass capacitors in order to keep low supply impedance. Better results can be achieved through the use of a buried capacitor formed by a VDD and VSS plane separated by 2-4 mil dielectric in a printed circuit board.