mlx90401 Melexis Company, mlx90401 Datasheet - Page 11

• Manufacturer Part Number: mlx90401
• Description: Brushless Dc Motor Controller Not For New Designs!
• Manufacturer: Melexis Company

9 FAQ
9.1 Bootstrap capacitor selection
When the top side is turned on charge is transferred from the bootstrap capacitor to the gate capacitance of
the N-channel power FET. The bootstrap capacitor value is chosen in function of the gate charge of the N-
channel power FETs used.
The charge on the bootstrap capacitor should be at least 20 times greater than the gate charge of the
power FET.
E.g. for the IRF530 N-channel power FET the total gate charge is specified as 26 nC. Therefore:
A value of 47 nF is chosen.
The maximum voltage drop due to the charge transfer at turn-on is:
Bootstrap capacitors up to 100nF can be applied.
9.2 Motor Noise
The MLX90401 defines its switching sequence based on the Hall input sequence and the state of the
60°/120° Select Input.
A 120° electrical sensor phasing motor operated with a 60° setting will most likely function, but will generate
clearly audible noise. Vice versa a 60° motor will generate noise when operated with a 120° setting.
Changing the setting of 60°/120° Select Input should remove the noise.
See also paragraph 7.9
sensor phasing, and how to connect the phases to the MLX90401 Hall sensor inputs.
10 Reliability Information
This Melexis device is classified and qualified regarding soldering technology, solderability and moisture
sensitivity level, as defined in this specification, according to following test methods:
3901090401
Rev 005
• IPC/JEDEC J-STD-020
• EIA/JEDEC JESD22-A113
• CECC00802
• EIA/JEDEC JESD22-B106
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•
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Moisture/Reflow Sensitivity Classification For Nonhermetic Solid State Surface Mount Devices
(Classification reflow profiles according to table 5-2)
Preconditioning of Nonhermetic Surface Mount Devices Prior to Reliability Testing
(Reflow profiles according to table 2)
Standard Method For The Specification of Surface Mounting Components (SMDs) of Assessed
Quality
Resistance to soldering temperature for through-hole mounted devices
A Forward/Reverse switch is present; the Brake switch could be omitted depending on the
application.
A jumper or fixed PCB track selects the type of motor (60/120 degrees electrical sensor spacing).
D1-3 and C6-8 are the bootstrap diode and capacitor.
Q1-6 are the 6 N-channel power FETs.
R3-8 smoothen the rise and fall times of the gate signals to reduce EMC emissions.
D4-6 are freewheel diodes.
C
dV
boot
gate
= 20 x Q
= dq / C
gate
boot
Logic table
/ V
= Q
gate
gate
= 20 x Q
/ C
for an explanation how to find out if a motor has 60° or 120° electrical
boot
= 26 nC / 47 nF = 553 mV.
gate
/ V
Page 11 of 13
REF
= 20 x 26 nC / 12 V = 43 nF.
Brushless DC Motor Controller
MLX90401
Data sheet
Oct/05