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Original question:

TPS65185: TPS65185 / Start up issue

TPS65185: TPS65185 / Start up issue of EVM

Kathrina Heil47
Prodigy 140 points
Part Number: TPS65185

Dear Team,

My customer is seeing similar issue as discussed in another thread which was followed up offline:

While testing the EVM, we found a problem: the VNEG and VPOS LDOs that generate +/- 15V do not successfully start up when there is a load drawing more than 30mA from their outputs (corresponding to resistors <500ohm).

Test steps:

  1. Connect 220ohm resistor between VPOS and GND, and another between VNEG and GND on the EVM kit.
  2. Enable TPS65185 by the jumpers as described in the user manual.
  3. The VNEG rail starts ramping up but stops at -8V, and won’t reach -15V. The VPOS stays at 0V. The boost converters seem running ok (VN=-16V, VB=+16V).

However, in case we enable TPS65185 with a smaller load connected (load resistors 560ohm), the TPS65185 can start up successfully. Afterwards if a greater load is connected, it can support that alright.

Is the LDO ramp-up current limited to just 30mA, although according to the DS the LDO should deliver up to 120mA?

Thanks for your support

Kathrina