ADM00902 Demonstration Board for EMC2103 User’s Guide
DS50002905A-page 38
2019 Microchip Technology Inc.
4.1.1
Power Selection
The fan and heat source power input (V
FAN
) is selectable through a 3-way jumper
assembly comprised of J3 and J4 with the following options:
• 5V USB (direct 5V option for 5V fans)
• 12V EXT (for an external power supply option)
• 12V BOOST (on-board boost switcher that is powered from the 5V USB input)
4.1.2
SHDN_SEL Pin Pull-up Selection
The J6 header provides easy access to all of the available pull-up values for the
SHDN_SEL pin. For the 15 k
, 22 k
, 33 k
and no jumper selection, the power-on
settings are loaded from the on-board EEPROM. See
Section 5.1.1
of the
“EMC2103
Data Sheet”
(DS20005250) for more mode/shutdown channel details.
4.1.3
Fan Connection and PWM Fan Driver
The fan is connected via a four contacts wire-to-board connector. The 3-pin jumper, J8,
is used to route the PWM output from the EMC2103-4 towards the switching driver for
a 3-wire fan (DRV option) or directly to the PWM pin of a 4-wire fan (FAN option). The
fan wiring color code for the 3-wire fan supplied in the kit is: Red = 12V, Black = GND,
Yellow = TACH. Depending on market availability, the provided fan can change in time.
If no jumper selection is made, the fan driver provides an unregulated output voltage
equal to the V
FAN
selection voltage.
The high-side DC/DC drive topology used (
) helps maintain the GND
connection for the tachometer output when driving 3-wire fans.
While the EMC2103-4 device can provide multiple frequency values for the PWM out-
put (ranging from 9.57 Hz to 26 kHz), the on-board Switch mode driver needs the
maximum frequency setting to operate properly without large ripple and audible noise.
FIGURE 4-2:
PWM Fan Drive.
displays the output voltage versus the PWM duty cycle for the fan provided
in the kit.
+
+12V
PWM
1
4
3
5
1
+12V
2
3
TACH
GND
GND
GND