UCD9222-EP_16 Datasheet, PDF (29/37 Pages) Texas Instruments – DIGITAL PWM SYSTEM CONTROLLER WITH 4-BIT, 6-BIT, OR 8-BIT VID SUPPORT

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APPLICATION INFORMATION
UCD9222-EP
SLVSBY1 – OCTOBER 2013
Automatic System Identification ( Auto-ID™)
By using digital circuits to create the control function for a switch-mode power supply, additional features can be
implemented. One of those features is the measurement of the open loop gain and stability margin of the power
supply without the use of external test equipment. This capability is called automatic system identification or
Auto-ID™. To identify the frequency response, the UCD9222 internally synthesizes a sine wave signal and
injects it into the loop at the Vref DAC. This signal excites the system, and the closed-loop response to that
excitation can be measured at another point in the loop. The UCD9222 measures the response to the excitation
at the output of the digital compensator. From the closed-loop response, the open-loop transfer function is
calculated. The open-loop transfer function may be calculated from the closed-loop response.
Note that since the compensator and DPWM are digital, their transfer functions are known exactly and can be
divided out of the measured open-loop gain. In this way the UCD9222 can accurately measure the power
stage/load plant transfer function in situ (in place), on the factory floor or in an end equipment application and
send the measurement data back to a host through the PMBus interface without the need for external test
equipment. Details of the Auto-ID™ PMBus measurement commands can be found in the UCD92xx PMBus
Command Reference (SLUU337).
Data Logging
The UCD9222 maintains a data log in non-volatile memory. This log tracks the peak internal and external
temperature sensor measurements, peak current measurements and fault history. The PMBus commands and
data format for the Data Logging can be found in the UCD92xx PMBus Command Reference (SLUU337).
Copyright © 2013, Texas Instruments Incorporated
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