
Principles of Operation
50
September 2005
SCPS110
3.5.5 Power Switch Interface
The power switch interface of the PCIxx12 controller supports either the 3-pin serial interface or the 4-pin
parallel interface. The RSVD/VD0/VCCD1 pin selects whether the 3-pin serial interface or the 4-pin parallel
interface is used. If the RSVD/VD0/VCCD1 pin is sampled high on the rising edge of GRST, then the 3-pin
serial interface is used. If the RSVD/VD0/VCCD1 pin is sampled low on the rising edge of GRST, then the 4-pin
parallel interface is used. The 3-pin interface is implemented such that the controller can connect to both the
TPS2226 and TPS2228 power switches. Bit 10 (12V_SW_SEL) in the general control register (PCI offset 86h,
see Section 4.30) selects the power switch that is implemented. The controller defaults to use the control logic
for the TPS2228 power switch. See Table 33 and Table 36 below for the power switch control logic.
Table 33. TPS2228 Control Logic—xVPP/VCORE
AVPP/VCORE CONTROL SIGNALS
OUTPUT
V_AVPP/VCORE
BVPP/VCORE CONTROL SIGNALS
OUTPUT
V_BVPP/VCORE
D8(SHDN)
D0
D1
D9
OUTPUT
V_AVPP/VCORE
D8(SHDN)
D4
D5
D10
OUTPUT
V_BVPP/VCORE
1
0
X
0 V
1
0
X
0 V
1
0
1
0
3.3 V
1
0
1
0
3.3 V
1
0
1
5 V
1
0
1
5 V
1
0
X
Hi-Z
1
0
X
Hi-Z
1
0
Hi-Z
1
0
Hi-Z
1
1.8 V
1
1.8 V
0
X
Hi-Z
0
X
Hi-Z
Table 34. TPS2228 Control Logic—xVCC
AVCC CONTROL SIGNALS
OUTPUT
V_AVCC
BVCC CONTROL SIGNALS
OUTPUT
V_BVCC
D8(SHDN)
D3
D2
OUTPUT
V_AVCC
D8(SHDN)
D6
D7
OUTPUT
V_BVCC
1
0
0 V
1
0
0 V
1
0
1
3.3 V
1
0
1
3.3 V
1
0
5 V
1
0
5 V
1
0 V
1
0 V
0
X
Hi-Z
0
X
Hi-Z
Table 35. TPS2226 Control Logic—xVPP
AVPP CONTROL SIGNALS
OUTPUT
V_AVPP
BVPP CONTROL SIGNALS
OUTPUT
V_BVPP
D8(SHDN)
D0
D1
D9
OUTPUT
V_AVPP
D8(SHDN)
D4
D5
D10
OUTPUT
V_BVPP
1
0
X
0 V
1
0
X
0 V
1
0
1
0
3.3 V
1
0
1
0
3.3 V
1
0
1
5 V
1
0
1
5 V
1
0
X
12 V
1
0
X
12 V
1
X
Hi-Z
1
X
Hi-Z
0
X
Hi-Z
0
X
Hi-Z
Table 36. TPS2226 Control Logic—xVCC
AVCC CONTROL SIGNALS
OUTPUT
V_AVCC
BVCC CONTROL SIGNALS
OUTPUT
V_BVCC
D8(SHDN)
D3
D2
OUTPUT
V_AVCC
D8(SHDN)
D6
D7
OUTPUT
V_BVCC
1
0
0 V
1
0
0 V
1
0
1
3.3 V
1
0
1
3.3 V
1
0
5 V
1
0
5 V
1
0 V
1
0 V
0
X
Hi-Z
0
X
Hi-Z