AMIS-30421 Datasheet, PDF (40/41 Pages) ON Semiconductor – Micro-Stepping Stepper Motor Bridge Controller

AMIS−30421
PACKAGE THERMAL CHARACTERISTICS
The AMIS−30421 is available in a NQFP44 package. For
cooling optimizations, the NQFP has an exposed thermal
pad which has to be soldered to the PCB ground plane. The
ground plane needs thermal vias to conduct the heat to the
bottom layer.
Figure 35 gives an example of good heat transfer. The
exposed thermal pad is soldered directly on the top ground
layer (left picture of Figure 35). It’s advised to make the top
ground layer as large as possible (see arrows Figure 35). To
improve the heat transfer even more, the exposed thermal
pad is connected to a bottom ground layer by using thermal
vias (see right picture of Figure 35). It’s advised to make this
bottom ground layer as large as possible and with as less as
possible interruptions.
For precise thermal cooling calculations the major
thermal resistances of the device are given (Table 4). The
thermal media to which the power of the devices has to be
given are:
• Static environmental air (via the case)
• PCB board copper area (via the exposed pad)
The major thermal resistances of the device are the Rth
from the junction to the ambient (Rth_ja) and the overall Rth
from the junction to exposed pad (Rth_jp). In Table 4 one can
find the values for the Rth_ja and Rth_jp, simulated according
to JESD−51.
The Rth_ja for 2S2P is simulated conform JEDEC
JESD−51 as follows:
• A 4−layer printed circuit board with inner power planes
and outer (top and bottom) signal layers is used
• Board thickness is 1,46mm (FR4 PCB material)
• The 2 signal layers: 70 um thick copper with an area of
5500 mm² copper and 20% conductivity
• The 2 power internal planes: 36 mm thick copper with
an area of 5500 mm² copper and 90% conductivity
The Rth_ja for 1S0P is simulated conform to JEDEC
JESD−51 as follows:
• A 1−layer printed circuit board with only 1 layer
• Board thickness is 1.46 mm (FR4 PCB material)
• The layer has a thickness of 70 mm copper with an area
of 5500 mm² copper and 20% conductivity
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Figure 35. PCB Ground Plane Layout Condition (left picture displays the top ground layer, right picture displays
the bottom ground layer)
ORDERING INFORMATION
Part No.
Peak Current
AMIS30421C4211G
NA
AMIS30421C4211RG
Temperature Range
−40°C to +170°C
Package
NQFP−44 (7 x 7 mm)
(Pb−Free)
Shipping^†
Units / Tube
Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
http://onsemi.com
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