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TMC249_1 参数 Datasheet PDF下载

TMC249_1图片预览
型号: TMC249_1
PDF下载: 下载PDF文件 查看货源
内容描述: 大电流微步进电机驱动器与stallGuard ™ ,保护/诊断和SPI接口 [High current microstep stepper motor driver with stallGuard™, protection / diagnostics and SPI Interface]
分类和应用: 驱动器电机
文件页数/大小: 30 页 / 587 K
品牌: TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
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TMC249 / TMC249A DATA SHEET (V2.09 / 2009-Jul-30)  
22  
Oscillator Capacitor  
The PWM oscillator frequency can be set by an external capacitor. The internal oscillator uses a 28k  
resistor to charge / discharge the external capacitor to a trip voltage of 2/3 Vcc respectively 1/3 Vcc. It  
can be overdriven using an external CMOS level square wave signal. Do not set the frequency higher  
than 100kHz and do not leave the OSC terminal open! The two bridges are chopped with a phase shift  
of 180 degrees at the positive and at the negative edge of the clock signal.  
1
fOSC  
40 COSC [nF]  
fOSC:  
COSC:  
PWM oscillator frequency  
Oscillator capacitor in nF  
Table of oscillator frequencies  
fOSC typ. COSC  
16.7kHz 1.5nF  
20.8kHz 1.2nF  
25.0kHz 1.0nF  
30.5kHz 820pF  
36.8kHz 680pF  
44.6kHz 560pF  
Please remark that an unnecessary high frequency leads to high switching losses in the power  
transistors and in the motor. For most applications a chopper frequency slightly above audible range is  
sufficient. When audible noise occurs in an application, especially with mixed decay continuously  
enabled, the chopper frequency should be two times the audible range.  
Pull-up resistors on unused inputs  
The digital inputs all have integrated pull-up resistors, except for the ENN input, which is in fact an  
analog input. Thus, there are no external pull-up resistors required for unused digital inputs which are  
meant to be positive.  
Power supply sequencing considerations  
Upon power up, the driver initializes and switches off the bridge power transistors. However, in order  
for the internal startup logic to work properly, the Vcc supply voltage has to be at least 1.0V,  
respectively, the Vs supply voltage has to be at least 5.0V. When Vs goes up with Vcc at 0V, a medium  
current temporary cross conduction of the power stage can result at supply voltages between 2.4V and  
4.8V. In this voltage range, the upper transistors conduct, while the gates of the lower transistors are  
floating. While this typically does no harm to the driver, it may hinder the power supply from coming up  
properly, depending on the power supply start up behavior.  
There are two possibilities to prevent this from occurring:  
Add resistors from the LA and LB outputs to GND in the range of 1M keeping the low side N-  
channel MOSFETs gates at GND.  
Alternatively, either use a dual voltage power supply, or use a local regulator, generating the 5V or  
3.3V Vcc voltage.  
Please pay attention to the local regulator start up voltage: Some newer switching regulators do not  
start, before the input voltage has reached 5V. Therefore it is recommended to use a standard  
linear regulator like 7805 or LM317 series or a low drop regulator or a switching regulator like the  
LM2595, starting at relatively low input voltages.  
Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG