The ISL6504 and ISL6504A complement other power building blocks (voltage regulators) in ACPI compliant designs for microprocessor and computer applications. The IC integrates three linear controllers/regulators, switches, monitoring and control functions into a 16-pin wide body SOIC or 20-pin QFN 6 x 6 package. The ISL6504, ISL6504A operating mode (active output or sleep output) is selectable through two digital control pins, S3 and S5. A linear controller generates 3.3VDUAL/3.3VSB voltage from the plane's 5VSB output from the ATX power supply, powers the Southbridge, and passes transistors (S3, S4/S5) in sleep states through an external NPN PCI slot. In the active state (at S0 and S1/S2), the linear 3.3VDUAL/3.3VSB regulator uses an external N-channel MOSFET with the output directly connected to the 3.3V input supplied by ATX with minimal losses. The controller powers up the 5VDUAL aircraft, switching the ATX 5V output through an NMOS transistor in the active state, or the ATX 5VSB through a PMOS switch (or PNP) transistor in the S3 sleep state. In S4/S5 sleep state, the ISL6504 5VDUAL output is turned off. The S4/S5 sleep state is held during the 5VDUAL output of the ISL6504A. This is the only difference between the two parts; see Table 1. The internal linear regulated supply voltage is 1.2V The identification circuit (VID) is only in active state (S0 and S1/S2) and uses it as the input source for the internal 3V3 pin through element. In addition the internal regulator outputs a 1.5VSB chipset backup power supply, which uses the pin as an input 3V3DL source for its internal transmission components. The 3.3VDUAL/3.3VSB and 1.5VSB outputs are active as long as the ATX 5VSB voltage is applied to the chip.