Power Requirements

The HT specification defines the link supply voltage requirements and the power consumption allowed by HT transmitters and receivers.

Power Supply Voltage

Single fixed power supply provides power to all the transmitter and receiver circuits. The HT link supply voltage (VLDT, or Voltage _{Lightning Data Transport} ) is rated at:

1.2 volts ± 5%

It is possible to have tight tolerance on VLDT (+-5%) on the power supply voltage output because most HyperTransport signals are differential with minimal current transients on simultaneous switching signals. The tight tolerance requirement on the supply voltage ensures that less power supply feedback noise will propagate through the system.

Differential Pair Power Consumption

The power consumption associated with the transmitter and receiver of each differential signaling pair is defined by the specification. Table 14-2 on page 367 lists these parameters. Note that the values are based on specified values of R _ON and R _TT as described in the next section.

Table 14-2. Differential Pair Power Consumption

Parameter	Min (mW)	Typical (mW)	Max (mW)
DC power per output signal pair (P DC )	5.9	7.2	9.0
AC power per differential pair, transmitter (P TAC )			53.0
AC power per differential pair, receiver (P RAC )			13.0
AC power per differential signal pair, total (P AC )			66.0