GX1 Datasheet, PDF (191/247 Pages) National Semiconductor (TI) – Processor Series Low Power Integrated x86 Solution

Electrical Specifications (Continued)
6.5 DC CHARACTERISTICS
6.5.1 Input/Output DC Characteristics
Table 6-5 shows the input/output DC parameters for all the devices in the GX1 processor series.
Table 6-5. DC Characteristics (at Recommended Operating Conditions)
Symbol Parameter
Min
Typ
Max Units Comments
V_OL
V_OH
I_I
I_IH
I_IL
C_IN
C_OUT
C_CLK
Output Low Voltage
Output High Voltage
2.4
Input Leakage Current for all input pins
except those with internal pull up/pull downs
(PU/PDs).
Input Leakage Current for all pins with
internal PDs.
Input Leakage Current for all pins with
internal PUs.
Input Capacitance
Output or I/O Capacitance
CLK Capacitance
0.4
±10
200
–400
16
16
12
V
I_OL = 5 mA
V
I_OH = –2 mA
µA
0 < V_IN < V_CC3,
See Table 6-2
µA V_IH = 2.4 V,
See Table 6-2
µA V_IL = 0.35 V,
See Table 6-2
pF _{f = 1 MHz}¹
pF _{f = 1 MHz}¹
pF _{f = 1 MHz}¹
1. Not 100% tested.
6.5.2 DC Current
DC current is not a simple measurement. The CPU has
four power states and two functional characteristics that
determine how much current the processor uses at any
given point in time.
6.5.2.1 Definition of CPU Power States
The following DC characteristic tables list CPU core and
I/O current for four distinct CPU power states:
• On: All internal and external clocks with respect to the
processor are running and all functional blocks inside
the processor (CPU core, memory controller, display
controller, etc.) are actively generating cycles. This is
equivalent to the ACPI specification’s “S0” state.
• Active Idle: The CPU core has been halted, all other
functional blocks (including the display controller for
refreshing the display) are actively generating cycles.
This state is entered when a HLT instruction is executed
by the CPU core or the SUSP# pin is asserted. From a
user’s perspective, this state is indistinquishable from
the “On” state and is equivalent to the ACPI specifica-
tion’s “S1” state.
• Standby: The CPU core has been halted and all internal
clocks have been shut down. Externally, the SYSCLK
input continues to be driven. This is equivalent to the
ACPI specification’s “S2” or “S3” state.
• Sleep: Very similar to “Standby” except that the
SYSCLK input has been shut down as well. This is the
lowest power state the processor can be in with voltage
still applied to the device’s core and I/O supply pins. This
is equivalent to the ACPI specification’s “S4BIOS” state.
6.5.2.2 Definition and Measurement Techniques of
CPU Current Parameters
The following two parameters indicate processor current
while in the “On” state:
• Typical Average: Indicates the average current used by
the processor while in the “On” state. This is measured
by running typical Windows applications in a typical
display mode. In this case, 800x600x8 bpp at 75 Hz, 50
MHz DCLK using a background image of vertical stripes
(4-pixel wide) alternating between black and white with
power management disabled (to guarantee that the
processor never goes into the Active Idle state). This
number is provided for reference only since it can vary
greatly depending on the usage model of the system.
Note:
This typical average should not be confused with
the typical power numbers shown in Table 6-1 on
page 185. The numbers in Table 6-1 are based on
a combination of “On (Typical Average)” and
“Active Idle” states.
• Absolute Maximum: Indicates the maximum instanta-
neous current used by the processor. CPU core current
is measured by running the Landmark Speed 200^™
benchmark test (with power management disabled) and
measuring the peak current at any given instant during
the test. I/O current is measured by running Microsoft
Windows 98 and using a background image of vertical
stripes (1-pixel wide) alternating between black and
white at the maximum display resolution of
1280x1024x8 bpp at 75 Hz, 135 MHz DCLK.
Revision 1.0
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