| Electronics > Projects, Designs, and Technical Stuff |
| IN-1 nixie tube - fuzzy digits when driving with TPIC6B595 |
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| NivagSwerdna:
If you decide to re-think.... re-think in a HV5812 direction. |
| mikerj:
--- Quote from: DBecker on February 03, 2020, 01:42:42 pm ---From the datasheet, the TPIC6B595 has clamps on the output drivers. The part is rated for 50V, but the clamping voltage isn't specified. It's likely much higher but still under 180V, and all of the outputs are turning on slightly to draw enough current to drag the voltage down to the clamping voltage. --- End quote --- The headline in the datasheet says output clamp voltage is 50v, the absolute maximum Vds is specified as 50v and Vds breakdown is specified as 50v minimum @ 1mA. To me this strongly suggests a clamp voltage that is somewhat close to 50v. |
| DBecker:
--- Quote from: mikerj on February 04, 2020, 06:07:18 pm --- --- Quote from: DBecker on February 03, 2020, 01:42:42 pm ---From the datasheet, the TPIC6B595 has clamps on the output drivers. The part is rated for 50V, but the clamping voltage isn't specified. It's likely much higher but still under 180V, and all of the outputs are turning on slightly to draw enough current to drag the voltage down to the clamping voltage. --- End quote --- The headline in the datasheet says output clamp voltage is 50v, the absolute maximum Vds is specified as 50v and Vds breakdown is specified as 50v minimum @ 1mA. To me this strongly suggests a clamp voltage that is somewhat close to 50v. --- End quote --- I think that we agree that the maximum voltage is listed as 50V, and that any voltage over 50V exceeds the part's rating. I the statement that the clamp voltage is 50V, but I expect that actually means that the clamp voltage is above 50V but below the breakdown voltage of the output transistor. Anyway, 50V. |
| 2shy:
As I understand this output stage schematic of TPIC6B595, the drain voltages above 50 V should cause the internal clamping Zener diode to conduct, turning on the (previously turned off) output FET just a little bit to drop the drain voltage to around 50 V. In this case the drain-source channel should not break, right? |
| mikerj:
--- Quote from: 2shy on February 05, 2020, 07:03:53 am ---As I understand this output stage schematic of TPIC6B595, the drain voltages above 50 V should cause the internal clamping Zener diode to conduct, turning on the (previously turned off) output FET just a little bit to drop the drain voltage to around 50 V. In this case the drain-source channel should not break, right? --- End quote --- The zener clamps to protect the FET, so the FET should not be damaged provided excessive current isn't being dumped into the device. |
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