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ADM1041A Datasheet(PDF) 3 Page - Analog Devices |
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ADM1041A Datasheet(HTML) 3 Page - Analog Devices |
3 / 56 page ADM1041A Rev. 0 | Page 3 of 56 GENERAL DESCRIPTION The ADM1041A is a secondary-side and management IC spec- ifically designed to minimize external component counts and to eliminate the need for manual calibration or adjustment on the secondary-side controller. The principle application of this IC is to provide voltage control, current share, and housekeeping functions for single output in N+1 server power supplies. The ADM1041A is manufactured with a 5 V CMOS process and combines digital and analog circuitry. An internal EEPROM provides added flexibility for trimming timing and voltage and selecting various functions. Programming is done via an SMBus serial port that also allows communication capability with a microprocessor or microcontroller. The usual configuration using this IC is on a one-per-output voltage rail. Output from the IC can be wire-OR’ed together or bused in parallel and read by a microprocessor. A key feature on this IC is support for an OrFET circuit when higher efficiency or power density is required. SAMPLE APPLICATION CIRCUIT DESCRIPTION Figure 1 shows a sample application circuit using the ADM1041A. The primary side is not detailed and the focus is on the secondary side of the power supply. The ADM1041A controls the output voltage from the power supply to the designed programmed value. This programmed value is determined during power supply design and is digitally adjusted via the serial interface. Digital adjustment of the current sense and current limit is also calibrated via the serial interface, as are all of the internal timing specifications. The control loop consists of a number of elements, notably the inputs to the loop and the output of the loop. The ADM1041A takes the loop inputs and determines what, if any, adjustments are needed to maintain a stable output. To maintain a stable loop, the ADM1041A uses three main inputs: • Remote voltage sense • Load current sense • Current sharing information In this example, a resistor divider senses the output current as a voltage drop across a sense resistor (RS) and feeds a portion into the ADM1041A. Remote local voltage sense is monitored via VS+ and VS− pins. Finally, current sharing information is fed back via the share bus. These three elements are summed together to generate a control signal (VCMP), which closes the loop via an optocoupler to the primary side PWM controller. Another key feature of the ADM1041A is its control of an OrFET. The OrFET causes lower power dissipation across the OR'ing diode. The main function of the OrFET is to disconnect the power supply from the load in the event of a fault occurring during steady state operation, for example, if a filter capacitor or rectifier fails and causes a short. This eliminates the risk of bringing down the load voltage that is supplied by the redun- dant configuration of other power supplies. In the case of a short, a reverse voltage is generated across the OrFET. This reverse voltage is detected by the ADM1041A and the OrFET is shut down via the FG pin. This intervention prevents any interruption on the power supply bus. The ADM1041A can then be interrogated via the serial interface to determine why the power supply has shut down. This application circuit also demonstrates how temperature can be monitored within a power supply. A thermistor is connected between the VDD and MON2 pins. The thermistor’s voltage varies with temperature. The MON2 input can be programmed to trip a flag at a voltage corresponding to an overheating power supply. The resulting action may be to turn on an additional cooling fan to help regulate the temperature within the power supply. RSENSE ADM1041A PWM + PRIMARY DRIVER OPTO- COUPLER AC PULSE SENSE DIFF CURRENT SENSE OrFET CONTROL ERROR AMP EEPROM AND RAM AND TRIM SMBus CURRENT SHARE DIFF LOAD AND LOCAL VOLTAGE SENSE VOLT, TEMP MONITOR AND FAULT DETECTION SOFT START SHARE BUS μC ( μC OR STANDALONE OPERATION) LOAD Figure 2. Application Block Diagram Differences Between the ADM1041A and ADM1041 For all new designs, it is recommended to use the ADM1041A. The parts differ as follows: • The ADM1041 allows the internal VREF voltage reference to be accessed at Pin 18. This is not accessible using the ADM1041A. • The ADM1041A has longer V DD OK debounce and VDDOV debounce than the ADM1041. • The GND_OK Disable bit (Register 11h) does not disable when using the ADM1041. It does disable when using the ADM1041A. |
Número de pieza similar - ADM1041A_15 |
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