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The MAX5950 evaluation kit (EV kit) is a fully assembled
and tested surface-mount circuit board featuring a PWM
step-down DC-DC controller with integrated hot-swap
capabilities for PCIe® ExpressModule™. The circuit board
has an X8E PCIe ExpressModule form factor. The EV kit's
circuit uses a MAX5950 and two MAX5951 ICs in 32-pin
thin QFN packages. The MAX5950 EV kit provides outputs
of 1.2V at 2.5A, and 2.5V and 3.3V with each providing
1.25A.
The MAX5950 EV kit demonstrates the MAX5950 IC's
hot-swap inrush current control capabilities as well as
the MAX5950 and MAX5951 ICs' hiccup-mode output
short-circuit protection during normal operation. The
MAX5950 controls an external n-channel MOSFET for
inrush control during hot swapping. The EV kit can
operate over an 8V to 16V input range, however, it is
configured for 12V input operation by default. The
MAX5950 EV kit also includes connections for the PCIe
bus 3.3V auxiliary supply.
Additionally, the MAX5950 and MAX5951 PWM DC-DC
step-down controllers' lossless current sensing, digital
soft-start, startup synchronization, thermal shutdown,
and hiccup-mode output short-circuit current-limit
features can be evaluated using the EV kit. The VOUT1
circuit can also be reconfigured to evaluate an alternate
current-sense method using a resistor for the DC-DC
converter. The hot-swap and PWM undervoltage
lockouts (UVLO) can easily be reconfigured for other
set points. The MAX5950 EV kit can be reconfigured
for various startup tracking/sequencing modes such
as ratiometric-tracking, startup sequencing, PGOOD
sequencing. The EV kit is configured for PGOOD
sequencing by default.
To ease bench evaluation of the MAX5950 EV kit, a
MAX5950PB power board assembly is included with the
EV kit. The power board features bulk holdup capacitance
for the 12V and 3.3V auxiliary power rails providing
power to a single X8E PCIe connector. The power board
includes switches, HC logic, and LEDs to simulate hot
swapping a MAX5950 EV kit into a server's backplane utilizing
an X8E PCIe connector.
The MAX5950 EV kit is not optimized for size, but is
designed for ease of lab evaluation. See Appendix A,
which shows a compact reference design with the
same output voltages and currents. The reference
design is configured for PGOOD sequencing.
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