reset and startup problem with stand alone msp430g2553 board

[ilpaso 0]

Hi,

After some months of launchpad experiences I'm developing my first stand alone board.

 

On the board there are these smd components for now.

MSP430G2553 Tsop28pins

Voltage regulator at 3,3V

Anaren RF module.

A led with 150ohm resistor.

 

I think I've a problem with the sturtup and reset.

There are 2 decoupling ceramics capacitors for the voltage regulator (about 4,7uF)

There is a 100nF capacitor connected ad VCC and GND 10mm far from the microcontroller.

There is a 47K resistor between Vcc and the RESET pin.

 

 

Often if I connect the battery (nominal 3.7V) the circuit works well but it is not stable.

Often it doesn't start.

 

Sometimes when it doesn't work there is a 1V across the 47K resistor. If I decrease the resistor value it works better but there are the same problems.

 

 

I tried to remove the RF module and write a simple led blink program (I use Energia IDE) but the problems are the same.

 

Thank you for your help.

 

ilpaso

 

 

 

 

[simpleavr 399]

You are feeding 3.7V to a 3.3V voltage regulator, I assume from your description. Usually you need to feed regulator higher voltage, even with a LDO (low-drop-out) like a 1117 you still need to feed it w/ at least 4.5V. You need to read the specification / datasheet for your regulator.

 

I would just remove the voltage regulator and have 3.7V direct powering the MCU.

[ilpaso 0]

I've used a LDO with a higher input voltage with same problem.

I've removed the voltage regulator with an input of 3.5V with same problem.

[grahamf72 169]

A 10nF capacitor between the reset pin and ground should solve your problems.

 

 

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