
TMC239 DATA SHEET (V1.00 / Apr. 24th, 2003)
5
Copyright 2002, TRINAMIC Microchips GmbH
Selecting power transistors
Selection of power transistors for the TMC239 depends on required current, voltage and thermal
conditions. Driving transistors directly with the TMC239 is only limited by the gate capacity of these
transistors. If the total gate charge is too high, slope time increases and leads to a higher switching
power dissipation. Typical applications can reach a current in excess of 3A, while the maximum voltage
is limited to 30V. A total gate charge of below 10nC per transistor is recommended. The table below
shows a choice of transistors which can be driven directly by the TMC239. The maximum application
current mainly is a function of cooling and environment temperature. The given values are more
conservative. Peak currents typically can be higher by a factor of 1.5 for a limited time.
List of recommended transistors
Manufacturer
and type
Siliconix
SI 3552
Siliconix
SI 5504
ST Micro
STS2DNF30L
STS3DPF30L
IRF 5851
Package
(#Trans)
TSOP6
(1N,1P)
1206-8
(1N,1P)
SO8
(2N)
(2P)
TSOP6
(1N,1P)
SO8
(1N,1P)
Micro8
(1N,1P)
SO8
(1N,1P)
SOT363-6
(2P)
Volts N-type
Volts P-type
30V
30V
30V
30V
30V
30V
20V
20V
30V
30V
30V
30V
30V
30V
30V
RDS
ON
[Ohm]
0.105
0.200
0.085
0.165
0.11
0.15
0.090
0.135
0.10
0.25
0.11
0.20
0.08
0.13
0.480
Total gate
charge [nC]
2.5
3.0
5.0
5.5
4.5
5.5
6.0
6.0
6.9
6.1
7.8
7.5
4.7
4.1
0.86
Typical maximum
application current
1500mA
2000mA
2000mA
1500mA
IRF 9952
IRF 7509
2500mA
2000mA
Fairchild Semi
FDS 8333C
Siliconix
SI 1901
3000mA
200mA unipolar
Layout considerations
For optimal operation of the circuit a careful board layout is important, because of the combination of
high current chopper operation coupled with high accuracy threshold comparators. Please pay special
attention to massive grounding. Depending on the required motor current, either a single massive
ground plane or a ground plane plus star connection of the power traces may be used. The schematic
shows how the high current paths can be routed separately, so that the chopper current does not flow
through the system’s GND-plane. Tie the TMC239’s AGND and GND to the GND plane. Additionally,
use enough filtering capacitors located near to the board’s power supply input and small ceramic
capacitors near to the power supply connections of the TMC239. Use low inductance sense resistors,
or add a ceramic capacitor in parallel to each resistor to avoid high voltage spikes. In some
applications it may become necessary to introduce additional RC-filtering into the VT and SRA / SRB
line, as shown in the schematic, to prevent
spikes from triggering the short circuit
protection or the chopper comparator. If you
want to take advantage of the thermal
protection and diagnosis, ensure, that the
power transistors are very close to the
package, and that there is a good thermal
contact between the TMC239 and the external
transistors. Please be aware, that long or thin
GND traces to the sense resistors may add
substantial resistance and thus reduce output
current. The same is valid for the high side
shunt resistor.
+VM
GND
GND-
Plane
R
SB
R
SA
Bridge A
Bridge B
R
S
C
VM
100R
4.7nF
optional filter
VS
VT
TMC239
100R
100R
10nF
SRA
SRB
optional filter
AGND
GND
100nF