TMC249 / TMC249A DATA SHEET (V2.02 / Aug 12th, 2005)
7
Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG
Using additional Power Drivers
For higher voltage and higher output current it is possible to add external MOSFET gate drivers. Both,
dedicated transistor drivers are suitable, as well as a circuit based on standard HCMOS drivers. It is
important to understand the function of dedicated gate drivers for N-channel transistors: Since the
chopping also can be stopped in open load conditions, the gate drive circuit for the upper transistors
should allow for continuous ON conditions. In the schematic below this is satisfied by attaching a weak
additional charge pump oscillator and pumping the VS up to the high voltage supply. Do not enable
the TMC249, before the gate driver capacitors are charged to an appropriate voltage. A current
sensing comparator in the VM line pulling down the VT pin by some 100mV on overcurrent can be
added, if required. Since the TMC249 in this application can not sense switch-off of the transistor
gates to ensure break-before-make operation, the break before-make-delays have to be set by
capacitive loading of its transistor drive outputs. The capacitors CdHS and CdLS are charged /
discharged with the nominal gate current. The opposite output is not enabled, before the switching-off
output has been discharged to 0.5V. To calculate the timing, refer to the required logic levels of the
attached power driver, resp. the attached PMOS. For CdHS and CdLS 470pF give about 100ns. Both
circuits do not show decoupling capacitors and further details.
High current, high
voltage MOS, e.g.
SI4450
R
S
Coil
N
N
HA1
LA1
SRA
VT
TMC249/
TMC239
VS
small signal P-
MOS, e.g. BSS84
+12V
LS-
Driver
+V
M
e.g. 50V
HS-Driver
1µF
C
DHS
470p
C
DLS
470p
2n2
C-Pump
20kHz
ICM7555
to other
bridges
100R
4.7nF
opt.
22K
N
N
IR2101
12V
390R
390R
SLP
10K
Set HS and LS
current to 10mA
LED
grn*
*) The LED increases break-before-make
time and may be bridged if not desired
High voltage logic
level MOS bridge
R
S
Coil
N
N
P
P
HA1
LA1
SRA
VT
TMC249/
TMC239
VS
+V
S
+V
M
20..60V
C
DHS
C
DLS
1K
1/2 74HC244
on low side
+5V
1K
1/2 74HC244
on high side
VM-5.2V
1K
SLP
15K
set to 7 mA high-
side drive current
LM337
HV
120R
390R
ADJ
OUT
IN
55V low current
N-MOS
7..15V
100R
100R
GND
VCC
VCC
GND
/OE
/OE
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