ncp3122 ON Semiconductor, ncp3122 Datasheet - Page 18

• Manufacturer Part Number: ncp3122
• Description: Dual 2.0 A, Step-down Dc/dc Switching Regulator
• Manufacturer: ON Semiconductor

Sequencing of Output Voltages
supplies with different voltage levels. These systems often
require voltage sequencing between the core power supply
and the I/O power supply. Without proper sequencing,
latch-up failure or excessive current draw may occur that
could result in damage to the processor's I/O ports or the I/O
ports of a supporting system device such as memory, an
FPGA or a data converter. To ensure that the I/O loads are
not driven until the core voltage is properly biased, tracking
of the core supply and the I/O supply voltage is necessary.
sequencing for signal processing devices like DSPs, FPGAs,
and PLDs may create risks as to reliability or proper
functionality. The risk comes when there are active and
inactive power supply rails on the device for a long time.
During this time, the ESD structures, internal circuits and
components are stressed from interference between
different voltages (from the two separate power supply
Some microprocessors and DSP chips need two power
Designing a system without proper power supply
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NCP3122
18
rails). When these conditions persist on multi-supply
devices for long time periods (this is a cumulative
phenomenon), the life of the products (DSP, FPGA, and
PLD devices) is drastically reduced. The failure is often a
result of high currents flowing to the pins or the high voltage
difference between pins.
supplies generating different voltage levels for core and I/O
peripherals over time. NCP3122 offers ratiometric
sequencing, sequential sequencing and tracking sections to
manage the output voltages behavior during start-up and
power-down. Basically, the DSP, FPGA, and PLD
manufacturers do not specify the method of power
sequencing, but they do specify restrictions on the time or
voltage differences during power-up and power-down. The
power-up sequence for microprocessors should be finished
approximately within a few seconds to prevent the risks
mentioned above. For more information, see the
microprocessor manufacturers' datasheets.
In that case, the signal processors require multiple power