AMIS-30523 Datasheet, PDF (5/35 Pages) ON Semiconductor – CAN Micro-Stepping Motor Driver

AMIS−30523
Table 3. THERMAL RESISTANCE
Thermal Resistance
Junction−to−Exposed Pad
Junction−to−Ambient (Rth_J−A)
Package
(Rth_J−EP)
1S0P Board
2S2P Board
Unit
QFN−52
0.95
60
30
K/W
EQUIVALENT SCHEMATICS
Following figure gives the equivalent schematics of the user relevant inputs and outputs. The diagrams are simplified
representations of the circuits used.
4k
IN
Rpd
OUT
TYPE 1: CLR Input
4k
IN
TYPE 4: DO and ERR Open
Drain Outputs
R_out
SLA
TYPE 2: CLK, DI, CS, NXT, DIR Inputs
VDD
VDD
VBB
VBB
TYPE 5: SLA Analog Output
TYPE 3: V_DD and V_BB Power Supply
Figure 3. In− and Output Equivalent Diagrams
PACKAGE THERMAL CHARACTERISTICS
The AMIS−30523 is available in a QFN−52 package. For
cooling optimizations, the QFN 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 4 gives an example for good power
distribution solutions.
For precise thermal cooling calculations the major
thermal resistances of the device are given. 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 thermal resistances are presented in Table 5: DC
Parameters Motor Driver.
The major thermal resistances of the device are the Rth
from the junction to the ambient (Rth_J−A) and the overall Rth
from the junction to exposed pad (Rth_J−EP). In Table 3 one
can find the values for the Rth_J−A and Rth_J−EP, simulated
according to JESD−51:
The Rth_J−A 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 1.46 mm (FR4 PCB material)
• The 2 signal layers: 70 mm thick copper with an area of
5500 mm² copper and 20% conductivity
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