參數(shù)資料
型號: TMC249-SA
廠商: Electronic Theatre Controls, Inc.
英文描述: High Current Microstep Stepper Motor Driver with sensorless stall detection, protection / diagnostics and SPI Interface
中文描述: 大電流微步步進電機驅(qū)動器,帶有傳感器的失速檢測,保護/診斷和SPI接口
文件頁數(shù): 17/25頁
文件大?。?/td> 219K
代理商: TMC249-SA
TMC249 / TMC249A DATA SHEET (V2.02 / Aug 12th, 2005)
17
Copyright 2005, TRINAMIC Motion Control GmbH & Co KG
Making the circuit short circuit proof
In practical applications, a short circuit does not describe a static condition, but can be of very different
nature. It typically involves inductive, resistive and capacitive components. Worst events are
unclamped switching events, because huge voltages can build up in inductive components and result
in a high energy spark going into the driver, which can destroy the power transistors. The same is true
when disconnecting a motor during operation: Never disconnect the motor during operation!
There is no absolute protection against random short circuit conditions, but pre-cautions can be taken
to improve robustness of the circuit:
In a short condition, the current can become very high before it is interrupted by the short detection,
due to the blanking during switching and internal delays. The high-side transistors allow a high current
flowing for the selected blank time. The lower the external inductivity, the faster the current climbs. If
inductive components are involved in the short, the same current will shoot through the low-side
resistor and cause a high negative voltage spike at the sense resistor. Both, the high current and the
voltage spikes are a danger for the driver.
Thus there are a three things to be done, if short circuits are expected:
1. Protect SRA/SRB inputs using a series resistance
2. Increase R
SH
to limit maximum transistor current: Use same value as for sense resistors
3. Use as short as possible blank time
The second measure effectively limits short circuit current, because the upper driver transistor with its
fixed ON gate voltage of 6V forms a constant current source together with its internal resistance and
R
SH
. A positive side effect is, that only one type of low ohmic resistor is required. The drawback is, that
power dissipation increases. A high side short detection resistor of 0.33 Ohms limits maximum high
side transistor current to typically 4A. The schematic shows the modifications to be done.
However, the effectiveness of these measures should be tested in the given application.
+VM
GND
R
SB
R
SA
R
S
C
VM
100R
VS
VT
100R
100R
SRA
SRB
GND
100nF
R2
R
SH
=R
SA
=R
SB
Microstep: R2 = 27R
Fullstep: R2 = 18R
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