Internal Refernce voltage for KM14Z below desired value

[bharathpoonja]

Hi,

I have been working with KM14Z microcontroller to read the voltage and current through SAR ADC and the AFE module.

I am using the internal Vref as reference. The voltage i am getting in Vref is 0.26V, Vrefl is 0.1V and Vrefh is 0.28V.

Vref init module,

/* Vref Init */

VREF_Init (VREF_MODULE_CHOP_EN_ICOMP_EN_REG_EN_VREFL_EN_LPWR_CONFIG,

VREF_SWITCH_S1_H_S2_L_S3_L_BUFF_EN);

VREFL_Trim(3);

Actual Vref should be around 1.2V. Please help me understand the problem with the code

Thanks in Advance.

[isaacavila]

Hello Bharath,

What reference are you using? remember to measure VREF, VREFH and VREFL by using VSSA as reference.

Next image shows different positions for S1, S2 and S3 and what voltage is using every module, also notice that VREF pin should be 1.2V in your current configuration (S1 On, S2 Down, S3 Down):

So Vref is used as output (remember to enable VREFBUFOUTEN bit on SIM_MISC_CTL register).

I also corroborate this configuration by using vref_test example located at <KM128SWDRV_R4_1_2_PATH>\build\cw_10_6\projects\vref_test and it worked well.

How are you measuring this reference?

Regards,

Isaac

[bharathpoonja]

Thanks for the reply,

I changed the CHOPEN bit of VREF Trim Register to 1 (Chop oscillator enabled) after that I am getting Vref of 1.2V. Rest of the configurations were same.

Regards,

Bharath