JAJSEA6B December 2017 – February 2019 LMH5401-SP
PRODUCTION DATA.
The LMH5401-SP can be operated using split supplies. One of the most common supply configurations is ±2.5 V. In this case, VS+ is connected to 2.5 V, VS– is connected to –2.5 V, and the GND pins are connected to the system ground. As with any device, the LMH5401-SP is impervious to what the levels are named in the system. In essence, using split supplies is simply a level shift of the power pins by –2.5 V. If everything else is level-shifted by the same amount, the device does not detect any difference. With a ±2.5-V power supply, the CM range is 0 V ±1 V; the input has a slightly larger range of –2.5 V to 1 V. This design has certain advantages in systems where signals are referenced to ground, and as noted in the ADC Input Common-Mode Voltage Considerations—DC-Coupled Input section, for driving ADCs with low input common-mode voltage requirements in dc-coupled applications. With the GND pin connected to the system ground, the power-down threshold is 1.2 V, which is compatible with most logic levels from 1.5-V CMOS to 2.5-V CMOS.
As noted previously, the absolute supply voltage values are not critical. For example, using a 4-V VS+ and a
–1-V VS– still results in a 5-V supply condition. As long as the input and output common-mode voltages remain in the optimum range, the amplifier can operate on any supply voltages from 3.3 V to 5.25 V. When considering using supply voltages near the 3.3-V total supply, be very careful to make sure that the amplifier performance is adequate. Setting appropriate common-mode voltages for large-signal swing conditions becomes difficult when the supply voltage is below 4 V.