When designing a multi-rail power supply, the challenge increases exponentially with each additional rail, and designers must consider how to dynamically coordinate power sequencing and timing, power-on reset, fault monitoring, and proper response to protect the system. Designers know that as projects move from prototyping to production, the key to success in coping with this dynamic environment is flexibility, and solutions that minimize hardware and software changes are ideal solutions for development.
An ideal multi-rail power supply design approach is that from design to design, using only one IC, there is no need to change wiring throughout the life of the product. The IC autonomously monitors and ranks multiple power rails and collaborates with other ICs, none Seamlessly monitors multiple power regulators in the system to provide fault and reset management.When the system is connected to the I2C bus, designers can use powerful, PC-based software to configure the system in real time to visualize the system and debug the system.
The LTC2937 is a demand-fit, 6-channel voltage sequencer with EEPROM and a high-accuracy supervisor. Each of the 6 channels has two dedicated comparators that accurately monitor overvoltage and accuracy at ± 0.75% accuracy Undervoltage conditions. The comparator threshold can be set individually with 8-bit resolution from 0.2 V to 6 V. These comparators are fast with a 10 μs peak-inhibit propagation delay. Each sequencer channel has an enable output , Which controls the gate of an external voltage regulator or a pass FET.The policer voltage and sequencer timing are individually configurable to include up and down sequencing, sequencing timing parameters, and fault response. The built-in EEPROM fully automates the device and powers the system in the correct state for control. In addition, multiple LTC2937s can operate cooperatively to autonomically sequence up to 300 supplies in a single system and use a single Communication bus.
The LTC2937's autonomic fault-response behavior and debug registers control, view, and manage power failures. The LTC2937 automatically detects a fault condition and powers down the system in a coordinated manner. The device can remain powered down or attempt to power- Reorder the Power Supply In systems with a microcontroller and I2C / SMBus, the LTC2937 provides detailed information about the type and cause of the fault and the status of the system.The microcontroller can make a decision as to what to respond to or allow the LTC2937 to respond to itself.
Table 1: Programmable 6-Channel Sequencer and Supervisor with EEPROM
Power control of the three steps
A power cycle has three running steps: power-up sequencing, monitoring, and power-down sequencing. Figure 2 shows these phases for a typical system. At power-up sequencing, each power supply must wait and then within a specified time To the correct voltage. During the monitoring phase, each power supply must remain within the specified overvoltage and undervoltage limits. Each power supply must be in standby during power-down sequencing (the order is often different from the power-up sequencing) , Then power down for a set period of time, errors may occur at any time, causing a system failure The design challenge is to design a system where all these steps, as well as all variables, are easily configurable but must be carefully controlled.
When the ON input transitions to active, the power-up sequence starts. The LTC2937 is powered up in the up-sequence order, one at a time, and each is monitored to ensure that the supply voltage rises above the set threshold before the specified time. Any power supply that fails to meet set time requirements triggers a sort fault.
Providing a Sequencing Location Clock is a unique advantage of the LTC2937 Each lane is assigned a sort location (1 to 1023) and receives an enable signal when the LTC2937 counts a given ordinal location number. Channels with ordinal location 1 are always present If you change the system specification to require the two channels to be sorted in a different order then the sorted positions can be swapped and the second channel energized when counting to sorted position 1 to count to the sorted position The first channel is powered on at 2. Multiple LTC2937s can share the sequencing location information so that for all LTC2937 chips, the sequencing position N appears at the same time and the channels controlled by different chips can participate in the same ordering (see Figure 3 ).
The monitoring phase begins when the last channel powers up and crosses its undervoltage threshold During the monitoring phase, the LTC2937 uses its high-accuracy comparator to continuously monitor each of the input voltages to see if they exceed the overvoltage and undervoltage thresholds. The device ignores the small interference on the input signal and only triggers when the voltage exceeds the threshold by sufficient magnitude and lasts long enough. When the LTC2937 detects a fault, the device responds immediately to the set monitor fault response behavior In a typical situation, the device shuts down all power sources at the same time, asserts RESETB to the system, and then attempts to power-cycle in the normal startup sequence, preventing the power supply from supplying part of the system with no power to other parts or preventing System performs inconsistent fault recovery after a failure Multiple LTC2937s in a system share fault status information and respond to each other's faults in order to maintain complete coherency between the cooperating lanes as the fault resumes. Numerous programmable fault response behavior to meet many different system configuration needs.
The power-down sequencing phase begins when the ON input goes low, and the sequencing position clock begins counting again to power down the power supply, but all power-down sequencing parameters are not affected by the power-up sequencing parameters. The channels can be de-energized in any order Sequencing, and multiple LTC2937 chips coordinate the sequencing of all controlled supplies. Each supply must fall below its discharge threshold for a specified time limit on power-down sequencing, otherwise triggering sequencing failures. The LTC2937 is available with an optional The current source pulls down the supply voltage to effectively discharge the slowly changing power supply.
Sorting location clocks enforce event-based sort order, with each event waiting for an event to occur before continuing. The LTC2937 also allows a time-based ordering that can be used in systems that start the power rail at a predetermined point in time. Reconfigurable registers are both Available in time-based sorting mode, but also in event-based sorting mode.
LTpowerPlay makes things easy
The LTC2937 has a comprehensive set of powerful registers that are easy to control. The LTpowerPlay's graphical user interface (GUI) displays all of the information in the status and debug registers in a single, easy-to-use interface. The GUI is implemented on an I2C / SMBus ADI's any Power Systems Management IC, including the LTC2937, to configure one or more LTC2937s with just a few mouse clicks.
LTpowerPlay saves the setting on the PC and writes the setting to the EEPROM of the LTC2937. The GUI also shows all debugging information for system faults. LTpowerPlay shows when either supply is over or undervoltage or, After a failure, the GUI allows for complete control of system restarts. LTpowerPlay is an integral part of system performance during each phase of the design - starting, configuring, modulating, and operating.
in conclusion
The LTC2937 simplifies power sequencing and monitoring. The device forms a complete system requiring very little board space. The LTC2937 is extremely flexible and reconfigurable and operates autonomously with EEPROM registers. The LTC2937 operates independently Or with other chips in a large system to seamlessly coordinate the operation of up to 300 power supplies.