I am using a L6470H as step motor driver. The data sheet told me to use the following configuration for voltage pumping:


simulate this circuit – Schematic created using CircuitLab

(Value of C1 and C2 is not correct). I used a combined diode with 40V breakdown voltage, and 250 mA as forward current as D1 and D2 ((Datasheet)), after I assumed that the maximum voltage will be 2*12V. Nevertheless it burned on the first live test. What should be the maximum resistance of the diode? 48V? How can I calculate that?

Update: Apparently the problem was in the Driver, after VBOOT has a direct connection to GND, leading to 12V/20A max going through the diode array.

  • \$\begingroup\$ 40V/48V are not resistances of a diode. Are you talking about its breakdown voltage? You probably want to look for the diodes amp rating. \$\endgroup\$
    – PlasmaHH
    Commented Aug 14, 2015 at 10:33

1 Answer 1


The diode you used should be adequate. The BAT64 series come in several pinouts and it is not unheard-of for pin numbers to get mixed up on an SMT part footprint vs. schematic symbol.

Check directly with a multimeter on diode function that the pinout and wiring is what it should be.

  • \$\begingroup\$ The diode just smoked up, so measuring is out of question. But nevertheless the information about the diode is useful. Which else reasons could the failure have? \$\endgroup\$
    – arc_lupus
    Commented Aug 14, 2015 at 12:16
  • \$\begingroup\$ Faulty part(s) including the chip (unlikely) or a short (testing should detect it, perhaps even in your charred prototype). \$\endgroup\$ Commented Aug 14, 2015 at 12:20
  • \$\begingroup\$ You mean that a short circuit induced a too high current on the diode? \$\endgroup\$
    – arc_lupus
    Commented Aug 14, 2015 at 12:21
  • \$\begingroup\$ Sure- suppose the VBOOT pin was shorted to the grounded thermal pad under the chip- that would certainly do it. \$\endgroup\$ Commented Aug 14, 2015 at 13:24
  • \$\begingroup\$ It wasn't, the chip itself was faulty. \$\endgroup\$
    – arc_lupus
    Commented Aug 15, 2015 at 5:41

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