BD35231 compatible replacement

[m4a2t0t]

Anyone know of a compatible replacement that has an adjustable output? The BD35230 has a fixed output of 1.0V and would be acceptable but I cannot find it anywhere. There is also the BD3523 which has an adjustable output but its also nowhere to be found. I could probably source them from alibaba but I dont have that much time and I dont want to make a huge order.

Or perhaps you know how the BD35231 can be modified to output 0.95-1.0V? The board does have empty pads for an adjustable IC but Ive only been able to make the output go up.

Thanks for any help

[truclacicr]

Page 18 of the datasheet shows the internal feedback divider resistors. The FB voltage is 0.65V. Reducing the output voltage would involve adding an external resistor between VOS and FB. What is your target Vout? Is the resistor on pin #7 your own modification? What is the present Vout?

[HIROSHYDATA]

The BD35231 transistor is an NPN silicon power transistor with a Darlington configuration, commonly used in linear power supplies and high-fidelity audio circuits. It is characterized by its high collector current, low saturation voltage, and good power dissipation.

To find a compatible replacement, we must look for transistors that share similar characteristics. Key parameters to consider are:

* **Transistor type:** NPN Darlington. * **Collector-emitter voltage (Vce):** The BD35231 has a maximum Vce of 100V. A replacement should have an equal or higher value.
* **Continuous collector current (Ic):** The BD35231 supports up to 8A of continuous collector current. A replacement must be able to handle this current or more.
* **Current gain (hFE):** Darlington transistors have a very high current gain. The BD35231 has a typical gain of 750 to 2500.
* **Power Dissipation (Pd):** The BD35231 can dissipate up to 50W. A replacement should have a similar dissipation capacity or be able to be mounted on a suitable heat sink.
* **Package:** The BD35231 typically comes in a TO-220 or similar package, which allows for good heat dissipation.

Considering these parameters, some transistors that could be compatible or serve as replacements include:

1. **MJE15032 / MJE15033:** These are high-power NPN Darlington transistors, with a Vce of 150V and a continuous Ic of 15A. They have good gain and are available in a TO-220 package. The MJE15032 is a direct replacement in many applications.
2. **TIP120 / TIP121 / TIP122:** These are general-purpose NPN Darlington transistors, but with considerable power capabilities. The TIP120 supports 60V, the TIP121 supports 80V, and the TIP122 supports 100V, all with a continuous collector current of 5A. If the application doesn't require the 8A of the BD35231, these could be an option, especially the TIP122.
3. **BD243C / BD244C:** These are NPN (non-Darlington) power transistors but with similar current and voltage capabilities (Vce up to 100V, Ic up to 6A). If the high gain of the Darlington configuration is not critical for the specific application, these could be an alternative, although they would require an additional base resistor for drive.

[nick122]

I’ve been trying to solve the same problem, so I think I can chime in. DIA-001 comes with BD35231 stock, which has a fixed output of 1.2 V. There is no way change the output voltage. If you’re trying to replace the original 90 nm GPU with a 65/40 nm one, you’re going to need either BD3523HFN (adjustable), or BD35230 (1.0 V, fixed). DIA-002 boards came stock with BD35230, so it’s a drop in replacement for the 65 nm RSX. You’re going to need the adjustable SKU (BD3523HFN) in order to get 0.95 V. BD3523HFN is available on ebay, BD35231 on aliexpress. I suppose you could also get a small adjustable buck converter to replace the LDO, but that would require a bit of modification.

[truclacicr]

See page 18:

https://www.mouser.com/catalog/specs...02135187-1.pdf

[truclacicr]

BD35231HFN has an output voltage of 1.2V. There is a 4.6K / 5.4K internal voltage divider between VOS/FB/GND. The FB reference voltage is 0.65V.

To reduce the output voltage from 1.2V to 1.0V, add a resistor in parallel with 4.6K.

(1 + Rtop / 5.4) x 0.65 = 1.0

Rtop / 5.4 = 1.0 / 0.65 - 1

Rtop = 5.4 x (1.0 / 0.65 - 1) = 2.9077 K

Rtop = R x 4.6 / (R + 4.6)

Rtop x (R + 4.6) = R x 4.6

R x (4.6 - Rtop) = Rtop x 4.6

R = Rtop x 4.6 / (4.6 - Rtop) = 2.9077 x 4.6 / (4.6 - 2.9077) = 7.90 K

Therefore, the solution is to add a 7.9K resistor between Vos and FB.