RadiSys EPS-6315, Hardware Reference Manual, Page: 71 / 123

Chapter 5: Theory of operation
61
Power
The next table represents the estimated EPC-6315 power consumption.
1
Typical power measurement is 80% of maximum.
The 82600’s core logic of +2.5V is supplied by a linear regulator working from +5V.
The expected load current is 400mA.
The RTC portion of the 82600 is also limited to +2.5V. The RTC power pin is
therefore supplied through:
• A silicon diode connected to the +3.3V supply, and
• A silicon diode connected to a +3.0V Lithium button cell via optional Jn4
connector to the baseboard.
Power to EPC-6315 V
CORE
+1.15 V and V
CCT
+1.25V is supplied by a Linear
Technologies LTC1703 dual synchronous switching regulator along with external
FETs. The LTC1703 5 VID inputs are fixed with resistors to produce an output
voltage (V
CORE
) of +1.15V on the first controller. The second controller sets up its
output voltage through a resistor divider network to +1.25V, the AGTL termination
voltage, V
CCT
. LTC1703 can provide up to 25A output current per channel. The
current limit is set to 15 A for V
CORE
, and to 5 A for V
CCT
. The expected
maximum load current is 7A for V
CORE
.
A precision voltage reference in conjunction with a voltage comparator provides
monitoring of the +5V and +3.3V supplies. The outputs of the comparators
connect directly to the soft-start inputs for the switching regulator that creates
V
CORE
and V
CCT
. As soon as +3.3V and +5V planes are fully charged, the switcher
begins to power on and V
CCT
, and after V
CCT
is stable, V
CORE
comes up. Voltage
comparators monitor the status of V
CORE
, V
CCT
, +2.5V, +1.8V, and +1.5V power.
The outputs of the comparators are tied to the system power good line and cause
system reset on power failure. As soon as the voltages are valid, the board comes
out of reset.
This table includes the power requirements for the dual-die, +3.3V, nine
SDRAM ICs.
Table 5-4. Power estimates
Product configuration Voltage
Watts
Maximum
Typical
1
EPC6315-800-512
(800Mhz CPU, 133Mhz PSB, 512MB)
+3.3V 6.0W 4.8W
+5V 11.0W 8.8W
Total power 17.0W 13.6W
EPC6315-800-256
(800Mhz CPU, 133Mhz PSB, 256MB)
+3.3V 4.5W 3.6W
+5V 11.0W 8.8W
Total power 15.5W 12.4W