SMT4504

• Monitor, Sequence and Slew-Rate Control of Distributed Power and Point of Use Power Supplies
• Multi-voltage Processors, DSPs, ASICs used in Telecom, CompactPCI or server systems

The SMT4504 consists of several major functional blocks: the power supply monitors, the sequencing and tracking outputs; the programmable output circuitry; the timing and control block; the I2C interface and the nonvolatile memory array.

The analog acquisition system monitors all channels via the OV/UV sensors. The SMT4504 UV/OV sensors are the four power supply voltage channels and the VDD and VCTRL_SUP supplies. The setting of the OV/UV trip points is made via the I2C serial data port.

Once PWR_ON is asserted a programmable delay timer must first expire after which the PUP (Point of Use Power) output(s) so required are enabled. The PUPs are generally connected to the Enable pin of the converter controlled by the SMT4504 Any channel not requiring closed-loop tracking of the voltage is programmed to assert its output (PUP) once the previous sequence timer has expired. Otherwise all PUPs are asserted upon the completion of the PWR_ON delay timer.

The power supply manager block is also used to assign a given power supply a sequence position; sequence timeout period and track-up/down slew rate setting.These settings determine the time and the rate at which each supply is turned on. When more than one supply is assigned to a sequence position their voltages will be tracked during the period of time when they are turned on via the VCTRLX pins and monitored via the VMX pins.These events are controlled by the sequence and tracking block.

An additional feature of the SMT4504 allows the supplies that are assigned the same sequence position to be tracked at the same or different slew rates for applications requiring supplies to be started at the same time but to ramp up at different rates. (Figure 2A)

The next major block is a programmable output block.The SMT4504 provides a great deal of flexibility in choosing the fault trigger source for the fault outputs.The sources include multiple combinations of UV/OV conditions. The fault outputs' assertion polarities are also programmable.

Programming of the SMT4504 is performed over the industry standard I2C, 2-wire serial data interface. It allows configuration of the device, real-time control of the power-on/power-off processes and reading of the status registers. The bus interfaces the host to 4k bits of nonvolatile memory and the programmable configuration registers.The 4k bits of user configurable nonvolatile memory uses industry standard non-volatile memory technology.