ADM00345 Microchip Technology, ADM00345 Datasheet - Page 18

• Manufacturer Part Number: ADM00345
• Description: Power Management IC Development Tools 3-Phase BLDC Snsrlss Fan Cntrllr
• Manufacturer: Microchip Technology
• Type: Other Power Managementr

Specifications of ADM00345

• Rohs: yes
• Product: Demonstration Boards
• Tool Is For Evaluation Of: MTD6505

MTD6505 3-Phase BLDC Sensorless Fan Controller Demo Board User’s Guide
2.3
DS52009A-page 18
HOW TO DEFINE THE CORRECT R
This section explains how to define the correct K
linked to the R
reduce the efficiency.
2.3.1
Follow the next steps to define the right R
1. Apply a constant stream of air to a fan that is not connected.
2. Using an oscilloscope, measure the waveform between two phases, when the
3. Measure the generated peak-to-peak voltage (V
4. Compute K
EQUATION 2-1:
K
rotation speed due to the air stream, should be close to the nominal fan rotation speed.
Table 2-1
TABLE 2-1:
M
should be constant, for all fan rotation speeds, but for the K
fan is rotating.
V
shows the corresponding K
Operation
BIAS
R
3.9 kΩ
24 kΩ
GND
PROG
PROG
(0Ω)
M
R
based on the measured V
PROG
(see
K
M
VALUE
COMPUTE
Table
2-1). An incorrect K
PROG
K
M
m
for different R
VALUE
=
K
PROG
3
2
1
0
M
V
------------
p-p
p p
2f
–
and f (in mV/Hz):
value:
M
value for a specific fan. The K
M
p-p
PROG
selection can create issues, or
) value and the frequency (f).
© 2011 Microchip Technology Inc.
values.
M
measurement, the fan
K
3.25 - 6.5
(mV/Hz)
6.5 - 13
M
26 - 52
13 - 26
Range
M
is