data/text/DLP1/899534

TLV700: Reverse current issue

Part Number: TLV700 Hey E2E I have a situation where a battery is directly tied (with a MOSFET in series, to prevent charging) to Vout of the TLV700. Normally a 5V PSU is tied through a diode to V_in of the LDO, but in this test there is no input source. So when I attach this battery to V_out I see 40mA going into the LDO. I tried pulling CTRL of the LDO down, and it got me to 30mA. According to my measurements all the current is flowing in the LDO only, since I have isolated the circuit from the other parts. I am using a keysight N6705C for the current measurements. Is this normal behaviour? I placed a diode in series with the LDO to avoid back current - but I did not anticipate the LDO to drain all this current by itself!

Hi Emil, Yes, what you seem to be describing is normal, however it is important to note that it can damage the LDO. When Vout>Vin+0.3V this can cause reverse current (flowing from Vout to Vin) through an internal parasitic diode. This current is not limited by the LDO so this current can cause damage if too much current flows from Vout to Vin. For more information on reverse current please see the following blog post: <secret URL>/blogs_/b/powerhouse/archive/2018/07/25/ldo-basics-preventing-reverse-current-in-ldos

Yes I have followed that document, and chose "Use a diode before the LDO". If I have that, what kind of current should I expect to be drawn into the LDO (feedback resistors for example) if CTRL=OFF?

Hi Emil, I'm sorry I misunderstood and thought the diode was added after you found this issue. I have a few questions to help clarify a few things: When you mention pulling CTRL down, are you referring to the enable (EN) pin? When this occurs is the LDO in dropout?