Using transistor with GPIO to switch another chip

[PKSHER]

Hello

I am using pin 1.15 of nrf52840 dongle with transistor with enable pin of another chip. The other chip is a wifi chip which I only want to switch on whenever I have data to send to that chip.

My software design is like this, switch on the chip, send the data and switch off the chip.

I have used a transistor circuit whose base pin when connected to high (3.3V), switches on the wifi chip and when connects to low (0V) switches it off. But when I try to do the same with the dongle, it is not working. The dongle is not able to supply 3.3V when connected to the transistor circuit, and when I disconnect the circuit, it supllies 3.3V. This may be related to current but I am using 10K base resistor. I am attached the picture for your reference.

I appreciate your suggestions.

Regards,

[Dmitry]

Hi,

Are you sure that your dongle gives 3.3V without load? It is powered from VDDH through internal regulator with default voltage 1.8V, you can change it to 3.3V in UICR (see REGOUT0 description in spec). Though I have no nrf52840 dongle to check...  Or you can replace NPN with n-MOS with low VGS threshold. 

[PKSHER]

Yes it is giving me 3.3V and the register stuff is active. But when I connect the transistor collector to the other chip. It then does not give me 3.3V although I set it high.