For unidirectional up translation (lower voltage to higher voltage), the reference transistor is connected the same as for a down translation. A pullup resistor is required on the higher voltage side (Dn or Sn) to get the full HIGH level, because the GTL device only passes the reference source (S_REF) voltage as a HIGH when doing an up translation. The driver on the lower voltage side only needs pullup resistors if it is open drain.

Figure 9-4 Unidirectional Up Translation to Higher-Voltage Chipsets