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3. PMBus Interface Option ( /S Option )
The communications bus signals are powered by an external 3.3V power source pulled up with a 1.5kΩ resistor
3.1 HFE_2500 may have optional Power Management Bus (PMBus) hardware.
The PMBUS interface in the HFE2500 (/S option) includes:
• Monitoring the Output Voltage, Current and Temperature
• Programming the Output Voltage and current
• Programming the Maximum allowed output Voltage
• Programming the Supply On/OFF.
• Reading and Clearing Faults.
• Reading the Manufacturing Related Data (Model Name, Serial No, Manufacturing Date, etc)
• Storing the following conditions at AC Off
- Set Output voltage / current limit (OCP)
- Max allowed programmable output voltage
ATTENTION: If PMBus is used for voltage or current programming, the reference voltage will not be fixed to 5V but can be variable.
(Reference voltage will be used for voltage or current programming).
The PMBUS supports:
100KHz Operation.
Block Read Protocol
Group Command Protocol
Direct Data Format for Monitoring and Programming Functions
3.2 Addressing (A3, A2, A1, A0 inputs)
Four variable address lines allow up to 16 Supplies to be connected on a single bus.
PMBus uses 7 bit addressing.
There is constant part of address and variable part of address:
Constant part of address consists of 3 Most Significant Bits A6, A5, A4 and always equals 001.
Variable part of address consists of 4 Least Significant bits: A3, A2, A1, A0.
Value of these four bits have to be assigned by hardware connections of 4 pins of the PS connectors.
The Address lines (A3, A2, A1, A0) are internally pulled up by resistors to +5V.
The address lines can be left open for ‹1› address or connected to -S for ‹0› address.
So, available Address Space contains 16 possible addresses: from 0010000 to 0011111.
In case more than one unit is connected to PMBus, each unit must be set to its own unique address.
Duplicate addressing is not allowed.
For example:
first unit -- A3(J1.B10), A2(J1.B5), A1(J1.B14), A0(J1.B16) are not connected
second unit -- A0(J1.B16) is connected to -SENSE
third unit – A1(J1.B14) is connected to -SENSE
and so on.
Attention:
A3, A2, A1, A0 signals and -SENSE are NOT isolated from the Output Terminals.
Hot Plug:
When hot plugging a power supply into a live system, the supply takes about 1-2 seconds to configure
its address on the bus (based on the analog voltage levels present on the back plane).
3.3 SERIAL CLOCK
This line is clocked by the Controller which controls the PMBUS. It should be connected to +3.3V (referenced to
"Signal RTN") via a 1.5kΩ pull-up resistor.
3.4 SERIAL DATA
This is a Bi-Directional line which must be connected to +3.3V (referenced to Signal RTN) via a 1.5kΩ pull up resistor.
3.5 SMBALERT
SMBALERT is used to indicate to the HOST about any Faults/Error Conditions.
This line must be connected to +3.3V (referenced to Signal RTN) via a 1.5kΩ pull up resistor.
This Signal is HIGH to indicate that no fault/error is present. If some fault/error occurs, the signal will go LOW.
The Host system must poll multiple supplies after receiving SMBALERT to retrieve fault/warning information.
3.6 PMBus TYPICAL CONNECTION
"SIGNAL RETURN" and PMBus signals are isolated
from the Output terminals and Senses.
HFE2500
1.5k
Fig-3.6 PMBus Typical connection
15
– ADDRESS 0011111;
– ADDRESS 0011110;
– ADDRESS 0011101;
3.3V
1.5k
1.5k
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