OPA192: Change in V+ if input grater than V+

Tensil Sebastian

Part Number: OPA192
Other Parts Discussed in Thread: OPA862

If my input is grater than VCC will the show leakage to the VCC

eg: V+=5V and V-=0V and ,my input is 32V . will this 32V show leakage to my V+ pins. Which i meant is will my V+ voltage will have any deviation from 5V. Will the V+ voltage increase from 5V.

So due to the delay in turn ON of the mosfet the divided voltage can man go garter than the V+

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 243080 points

The absolute maximum ratings imply that there are diodes from the input pins to V+.

If the input voltage is too large, a current will flow from the input into V+. If your circuit and your power supply are not able to sink that current, then V+ will indeed float up. (In any case, you must limit the diode current to less than 10 mA.)

If you add a 47 kΩ series resistor in front of the input, the diode current will be less than 1 mA. A 4.7 kΩ resistor between V+ and GND will then be able to prevent V+ from rising.

0 Tensil Sebastian over 3 years ago in reply to Clemens Ladisch

Prodigy 170 points

Thank you so much. I will update my circuit according to this.

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Tensil,

can you post a schematic?

Kai

0 Tamara M Alani over 3 years ago

TI__Genius 10850 points

Hi Tensil,

Thanks for your post. A schematic would be helpful.

0 Tensil Sebastian over 3 years ago

Prodigy 170 points

0 Tensil Sebastian over 3 years ago

Prodigy 170 points

0 kai klaas69 over 3 years ago in reply to Tensil Sebastian

Guru 140200 points

Hi Tensil,

I would add the diode clamp D1, the 6V8 zener diode Z1 and the Schottky diode SD1. For D1 the low leakage diode BAV199 could be chosen. Z1 protects the OPA862 (not shown here), as its positive supply voltage must not exceed 13V - 5V = 8V here. The Schottky diode SD1 is necessary to clamp the negative going positive (!) supply voltage to an as small value as possible. This to prevent the voltage regulator from going into latch-up and staying there! I strongly recommend to clamp the output voltages of all regulators by the help of suited Schottky diodes. I always use a 3A Schottky diode for this purpose :-)