TMC603A Datasheet, PDF (28/44 Pages) TRINAMIC Motion Control GmbH & Co. KG. – Three phase motor driver with BLDC back EMF commutation hallFX™ and current sensing

TMC603A DATA SHEET (V. 1.15 / 2009-Nov-19)
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Example:
f_OSC = 175 kHz, I_OUT = 0.2 A, V_VM = 48 V:
For continuous operation, a 330µH or 470µH coil would be required. The minimum inductivity
would be around 100µH.
Note:
Use an inductor, which has a sufficient nominal current rating. Keep switching regulator wiring
away from sensitive signals. When using an open core inductor, please pay special care to not
disturbing sensitive signals.
5.5.2 Charge pump
The Villard voltage doubler circuit relies on the switching regulator generating a square wave at the
switching transistor output with a height corresponding to the supply voltage. In order to work properly
the load drawn at +12V needs to be higher than the load drawn at the charge pump voltage. This
normally is satisfied when the IC is supplied by the step down regulator. For low voltage operation, the
charge pump voltage needs to be as high as possible to guarantee a high gate drive voltage, thus, a
dual Schottky diode should be used for the charge pump in low voltage applications.
5.5.3 Filter capacitors for switching regulator and charge pump
The filter capacitors in the switching regulator and the charge pump are required to provide current for
the high current spikes which are caused by switching up to three MOSFETs at the same time. The
required amount of charge can be estimated when looking at the MOSFETs gate charge. The gate
voltage should not drop significantly due to the switching event, e.g. only 100mV. Additionally, the 12V
filter capacitor provides charge for load spikes on the 12V net and filter switching ripple. In
applications, where board space is critical, lower capacitance values can be used.
Choice of filter capacitors in the switching regulator for different current requirements (example):
12V load current
<20mA
<20mA
<50mA
100mA
power MOSFET 12V filter capacitor
gate charge
(electrolytic/ceramic)
<20nC
22µF (or 4.7µF ceramic)
<50nC
22µF (or 10µF ceramic)
>50nC
47µF (or 10µF ceramic)
>50nC
100µF (or 10µF ceramic)
charge pump filter capacitor
(tantalum / ceramic)
1µF (e.g. ceramic)
2.2µF (e.g. ceramic)
4.7µF
4.7µF
5.5.4 Supply voltage filtering and layout considerations
As with most integrated circuits, ripple on the supply voltage should be minimized in order to
guarantee a stable operation and to avoid feedback oscillations via the supply voltages. Therefore,
use a ceramic capacitor of 100nF per supply voltage pin (VM to GND, VLS to GND and VCC to GND
and VCP to VM). Please pay attention to also keep voltage ripple on VCC pin low, especially when the
5V output is used to supply additional external circuitry. It also is important to make sure, that the
resistance of the power supply is low when compared to the load circuit. Especially high frequency
voltage ripple >1MHz should be suppressed using filter capacitors near the power bridge or near the
board power supply. The VM terminal is used, to detect short to GND situations, thus, it has to
correspond to the bridge power supply. In high noise applications, it may make sense to filter VCP
supply separately against ripple to GND. A large low ESR electrolytic capacitor across the bridge
supply (VM to GND) should also be used, because it effectively suppresses high frequency ripple. This
cannot be accomplished with ceramic capacitors. GND and GNDP pins should be tied to a common,
massive GND plane. Pay attention to power routing: Use short and wide, straight traces. The PCB
power supply should be placed near the driver bridge, where most current is consumed, to avoid
current drop in the plane between critical components like TMC603 and microcontroller. This is
especially is important to get a precise current measurement.
Copyright © 2009 TRINAMIC Motion Control GmbH & Co. KG