BTS6403

[SHARIF-ALSHAMI]

I have designed an evaluation board to test performance of that amplifier before I embed it in my final design. I followed passive components values recommended in the datasheet. I was using 5Vcc and 3.3 Venb from my power supply. the problem is the amplifier temperature increase to a very high value (burns my finger) and very rapidly just two three seconds I start powering on the amplifier and current was very high also up to 420 miliamps. I checked Vcc to ground DC resistance it was about 0.85 Mohms and 1.6Mohms Venb to ground. it also heats up if Venb is floating and not connected to a logic status(HIGH/LOW). well I know this amplifier is designed for 5V operations but I tried connecting it to 3.3 volts for Vcc it was a stable (no overheating) but gain was around 20 db and current was around 67 milliamps. please advise 

NOTE. it heats up even with no RF signal injected at the input pin

[SHARIF-ALSHAMI]

@ErikaC  any updates ?

[ErikaC]

Hello,

Sorry for the delay in replying.

Please see my observations below:

1.  RFin and RFout : Cin and Cout are stated as 18 pF and 3.9pF. The values of C1 and C2 are critical for power on/off settling time. When the value for those capacitors is increased significantly the switching speed is affected. In your Schematic these capacitors are 20pF and 4pF.

2. Vcc1 and Vcc2 : In NXP Reference design C6, C11 and C4, C12 decoupling capacitors respectively bypass VCC1 and VCC2. 

C4 and C6 preferably should be located as close as possible < 1 mm to the device, to avoid AC leakage via the bias lines.

In your case these capacitors are C3 and C2 for VCC1 but I do not see decoupling capacitors for VCC2.

In your PCB these capacitors are not located as close as possible.

3. Proper grounding of the GND: I recommend connecting N.C. pins to GND to improve the thermal dissipation.

4. Enable: To limit the current, a 5.6 kΩ resistor can be used in series.

You can check this information in the application note AN13844 https://www.nxp.com/docs/en/application-note/AN13844.pdf

Hope this helps!

[SHARIF-ALSHAMI]

Thank you @ErikaC for the time and effort you did to reveiw my design and write these recomendations, but Erika I did neither complain about the amplifier on/off setling time nor about noise in the signal. I did notice these issues in my design but I donot think any of these should raise the temprature so high, I did compine Vcc1 and Vcc2 and attached to them a common decoupling capacitors because I thought this might work because this is a design of a development board and it doesnot contain any other active components that may introduce high noise in the dc biase and dc power source is clean (checked by oscilliscope). Erica the amplifier temperature shoots up in a mater of 2 or 3 seconds after I connect 5 V dc power. Current consumption reaches 400 milliamps. Some times it stablize while being powered by 3.3V. I have alrady gone through the document you shared before and I did try Instaling 5kohms in series with Venb it didnot solve the issue but what did help was instaling 20 ohms resistor in series with common Vcc line (which was strange thing to me) so I think maybe there is an issue with the amplifier bias circuit and I think it is in the full batch because I have tried 3 amplifiers (was from same tape/reel) and they all produce same temprature issue

[ErikaC]

Hello,

Could you please share your schematic and Layout?

[SHARIF-ALSHAMI]

please find attached design file

note: passive components values:

Venb= 3.3V, Vcc1,2= 5V

R1 = 10 kohms, R2= 1KOHMS

C1= 20 PF, C2= 10NF, C3= 10 UF, C4= 4PF

D1= LED, D2= SHOTCKEY DIOD

J1= sma input, J2=sma output

[ErikaC]

I can not see any file attached. 

[SHARIF-ALSHAMI]

@ErikaC  I have uploaded the files again. if you still cannot see them please supply me with an Email address and I will send them to it