OPA462: OPA462 Connection

Hi Hunzhe,

Junzhe Zhang said:

1. Can I drive the OPA462 at ±24V if I want to output ±14mA, with a frequency of 5K and a load of up to 1.5K.

Here is an example. It looks like that you may require to increase the supply rail, since ±14mA*1.5kohm = ±21V, where the output voltage swing is limited to due voltage drop across the output driver stage. 

OPA462 Howland 14mA 07052025.TSC

If you have other questions, please let me know. 

Best,

Raymond

Hi Raymond,

Thanks a lot for your reply. I ran a simulation and it seems like a ±24V supply would be enough to meet my desired output?

For my second question, I would like you to help me confirm whether my understanding is correct. Thanks a lot.

Best,

Junzhe

By the way, I would like to ask how to provide ±90V for OPA462? I try to find some DC-DC converter but I have not find any totally match it.

Best,

Junzhe

Hi Junzhe, 

For high voltage amplifier, both OPA462, OPA455 and OPA454 should work for the application. 

However, if you have to use AC/DC or DC/DC converter, you may have to consider isolated flyback, push-pull converters. You may also use charge pump or AC/DC + Rectifier converter and DC booster converter to generate +/-90Vdc or similar voltage rails (e.g., LM5020, LM5155 ).  For medical application, these power system has to be isolated or you can use DC battery or supercapacitor pack as the power sources (I would recommend to use Li+ battery as the battery pack). You are dealing with the medical applications, where lower-medium power, Galvano isolation, good regulation and  safety feature are must for the requirement compliance. 

The constant current pulse application may require to use Howland Current Pump. The V-to-I application notes are:

https://www.ti.com/lit/an/snoa474a/snoa474a.pdf?ts=1751813583713&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.ti.com/lit/an/sboa437a/sboa437a.pdf?ts=1751811855942&ref_url=https%253A%252F%252Fsearch.brave.com%252F

https://www.ti.com/lit/an/sboa436/sboa436.pdf?ts=1751826871134&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.tij.co.jp/lit/ug/slau502/slau502.pdf?ts=1722198902909

The slau502 may be the best option, if you are using battery powered system. 

BTW, the human muscle equivalent impedance is not pure resistor. The simple equivalent Spice model is a resistor in series with a capacitor. 

If you have other questions, please let me know. 

Best,

Raymond

Hi Raymond, 

Thanks for your answer and suggestions, that's helpful.

Could you please help me with this:

2. For the connections for pins 1, 5, 8 and the powerPAD, can I just connect 1, 5, 8 directly to ground and the powerPAD to my -24V?

Best,

Junzhe

Hi Junzhe, 

Junzhe Zhang said:

2. For the connections for pins 1, 5, 8 and the powerPAD, can I just connect 1, 5, 8 directly to ground and the powerPAD to my -24V?

The OPA462's thermal pad shall be connected to the most negative rail of the IC design. If Vee is -24Vdc, the thermal pad should be connected to -24Vdc. 

The pin1, 5 are the IC's status pins and their logic voltage are REFERENCED to pin8 or E/D COM pin.  The E/D COM pin's voltage is defined by the user, see the captured table above. The pin1 and pin5's logic voltage is referenced above E/D COM defined by the table. 

You may connect pin8 (E/D COM) to GND within the OPA462's supply voltage range (see defined range above), but the pin1 and pin5 have to be up to 5.5Vdc above the E/D COM's voltage reference. And pin5 or the Status Flag is an open drain configuration, and required to be pull-up to 5Vdc above E/D COM pin with 10kohm resistor. 

Attached is the OPA462EVM, which you can purchase from TI E-store or authorized TI distributors.  

https://www.ti.com/lit/ug/sbou175/sbou175.pdf?ts=1751898933834&ref_url=https%253A%252F%252Fwww.google.com%252F

If you have other questions, please let me know. 

Best,

Raymond

Hi Raymond,

My understanding is that since I don't need the Flag pin 5, I leave it floating. Because I use a ±80V power supply, I connect pin 1 E/D com to GND. Then I divide my +80V power supply through the following circuit, and connect VF3 to E/D, so that the voltage of E/D is E/D Com +5, which meets the requirements, and the device can work. Can you confirm that my design is correct?

Best,

Junzhe