TMC5031 DATASHEET (Rev. 1.11 / 2016-APR-28)
13
3.3 External VCC Supply
Supplying VCC from an external supply is advised, when cooling of the chip is critical, e.g. at high
environment temperatures in combination with high supply voltages (16V), as the linear regulator is a
major source of on-chip power dissipation. It must be made sure that the external VCC supply comes
up before or synchronously with the 5VOUT supply, because otherwise the power-up reset event may
be missed by the TMC5031. A diode from 5VOUT to VCC ensures this, in case the external voltage
regulator is not a low drop type linear regulator. In order to prevent overload of the internal 5V
regulator when using this diode, an additional series resistor has been added to VSA.
An alternative for reduced power dissipation is using a lower supply voltage for VSA, e.g. 6V to 12V.
If power dissipation is critical, but no external supply is available, the clock frequency can be reduced
as a first step by supplying external 12MHz clock.
22n
The diode is mandatory to satisfy power-up
conditions!
+VM
VCP
charge pump
100n
220R
VSA
5V Voltage
regulator
5VOUT
100n
4.7µ
+5V
VCC
LL4148
470n
Figure 3.4 Using an external 5V supply to reduce linear regulator power dissipation
3.3.1 Internal Regulator Bridged
In case a clean external 5V supply is available, it can be used for complete supply of analog and
digital part (Figure 3.5). The circuit will benefit from a well-regulated supply, e.g. when using a +/-1%
regulator. A precise supply guarantees increased motor current precision, because the voltage at
5VOUT directly is the reference voltage for all internal units of the driver, especially for motor current
control. For best performance, the power supply should have low ripple to give a precise and stable
supply at 5VOUT pin with remaining ripple well below 5mV. Some switching regulators have a higher
remaining ripple, or different loads on the supply may cause lower frequency ripple. In this case,
increase capacity attached to 5VOUT. In case the external supply voltage has poor stability or low
frequency ripple, this would affect the precision of the motor current regulation as well as add
chopper noise.
Well-regulated, stable
supply, better than +-5%
+5V
VSA
5V Voltage
regulator
5VOUT
4.7µ
10R
VCC
470n
Figure 3.5 Using an external 5V supply to bypass internal regulator
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