Datasheet

CLASS
Maximum Power Used
by PD (W)
Resistor
R4 (I)
0 0.44 to 12.95 615
1 0.44 to 3.84 117
2 3.84 to 6.49 66.5
3 6.49 to 12.95 43.7
4 12.95 to 25.5 30.9
5 > 25.5 21.3
_________________________________________________________________ Maxim Integrated Products 5
MAX5974C Evaluation Kit
Evaluates: MAX5974C
The EV kit also demonstrates the full PD functionality of
the MAX5969B (U2), such as PD detection signature,
PD classification signature, inrush current control, and
UVLO. Resistors R14 and R4 set the PD detection sig-
nature and the PD classification signature, respectively.
The EV kit circuit accepts power from a wall adapter
DC power source. When a wall adapter power source
in the +37V to +57V range is applied at the PWR+ and
PWR- PCB pads, it always takes precedence over the
PSE source, allowing the wall adapter to power the EV kit
circuit. When applying a valid voltage source between
the PWR+ and PWR- PCB pads, the MAX5969B internal
isolation switch disconnects VSS from RTN, which allows
the wall adapter to supply power to the EV kit.
PD Classification Signature
The EV kit is configured for a Class 4 (12.95W to 25.5W)
PD classification by resistor R4. To reconfigure the PD
classification, replace surface-mount 0805 resistor R4.
Table 1 lists the PD classification options.
Wall Adapter Power Source (PWR+, PWR-)
The EV kit can also accept power from a wall adapter
DC power source, applied at the PWR+ and PWR- PCB
pads. The wall adapter power-source operating-voltage
range must be within +37V to +57V for the EV kit.
When the wall adapter power source is above +33.6V it
takes precedence over the PSE source. Once the wall
adapter power source is detected, the MAX5969B inter-
nal isolation switch disconnects VSS from RTN. The wall
adapter power is supplied to VDD (through diode D7)
and RTN. Once it takes over, the classification process
is disabled. Resistors R27 and R28 are available for
adjusting the EV kit wall adapter voltage for disabling the
PSE source.
When the wall adapter power source is below +27V the
PSE provides power through the RTN pin on U2. Diode
D7 prevents the PSE from backdriving the wall adapter
power source when it is below +7V.
Ethernet Data-Signal Interfacing
The EV kit features Ethernet jack J1 to interface with the
Ethernet data signals. J1 is provided for interfacing the EV
kit with the Ethernet data signals only. Refer to the RJ45
MagJack data sheet on the Bel Fuse website prior to inter-
facing the EV kit’s J1 jack with the Ethernet data signals.
Table 1. PD Classification Signature
Selection