3 Replies Latest reply on Oct 8, 2019 1:25 AM by MoTa_728816

    PSoC4 Battery Power

    YSJE_3566666

      Hello everyone.

       

      I want to use CY8C4024LQI-S401 with battery directly.

       

      1. Is it possible to using battery from 3V to 1.8V without external component(DC/DC or LDO)?

        It is required long operating cycle so MCU should be powered until 1.8V from battery.

       

      2. I need a battery monitoring with MCU's ADC. But I think it may be impossible because battery voltage is variable (3V to 1.8V).

        I don't know exactly how to monitor battery in this system.  Do I have to use an external component(DC/DC or LDO) for ADC?

       

      Thanks.

        • 1. Re: PSoC4 Battery Power
          MoTa_728816

          Hi,

           

          (1) From PSoC 4 : PSoC 4000S Datasheet

          The device seems to be able to operate with 1.8 V to 5.5V External Supply.

           

          PSoC4_4000S_DS_Power.JPG

           

          (2) To monitor the battery level, may be using ADC with  "VCCD" as reference would do what you want.

          (Edited) At first I thought LPComp would be better,

          but using ADC with VCCD as VDDA and with external resister ladder  may work to monitor the battery voltage.

           

          (Edited) After writing above I noticed that this device does not have VDDA, if it's so I would do either

          (1) ADC with internal reference

          (2) 2ch ADC with 1 input from VCCD and the other from VDD

          (3) Use LPComp with VCCD and VDD

           

           

          moto

          • 2. Re: PSoC4 Battery Power
            YSJE_3566666

            Hi Motoo.

            Thanks for your reply.

             

            (2) I also was wondering about if how to monitor the battery without VDDA.

            As you mentioned, this device has no VDDA.

            I found below statement on datasheet.

            But I have no idea how to use Vref.

            Do you have an example with using internal reference to ADC?

             

             

            (Add)

            I found Comparator Component in PSoC Creator.

             

             

            Regards,

            YS

            • 3. Re: PSoC4 Battery Power
              MoTa_728816

              Dear YSJE-san,

               

              Yes, I think that LPComp sounds promising!

               

              On my side, I tried some tests with following setup.

              (Since I'm not quite adequate with analog, there must be some better way to test this though)

               

              As I don't have a board with 4000S, I used a board with 4100S, hoping they must be close enough.

               

              Then I provided power from CY8CKIT-042's 3.3V and GND via a 10K pot.

              And used 3 x 10K oham resistors to make analog input for ADC (should be around 1/3 of VDD)

              000-schematic.JPG

              At first I let the UART to report the voltage

               

              When the POT is max and oscilloscope reading was 3.29V, well about 1/3, right?

              ADC_3_29_Log.JPG

              Then the POT is about half way down.

              I could not make the VDD lower than 2.13V as the USB-UART's signal seems to be feeding power to the device.

              But anyway the number seems to be around 1/3 or so.

              ADC_2_13V.JPG

               

              Then I gave up UART, and let PWM's duty (compare) value change to see the change of VDD

               

              When VDD = 3.29V (PWM compare was set to 1000+ with period of 1500)

              ADC_3_29V.jpg

               

              When VDD = 1.88V

              ADC_1_88V.jpg

               

              When VDD = 1.63V, I wonder if this should work or not.

              Also around 1.8V or lower, the behavior of the device was not very stable.

              ADC_1_63V.bmp

              But as far as we could see the PWM pulse, it means that the program is running and ADC and PWM is working at the VDD voltage.

               

              So my conclusion for today is,

              Yes, up to VDD = ~1.8V, ADC was working

              No, I could not make sure if the ADC reading was linear or correct,

               

              But if you measure the ADC value via debugger with a reliable DC power supply unit which can control output voltage

              you should be able check if the ADC reading is linear down to 1.8V or so.

               

              Or I would just supply expected minimum voltage and use that ADC value as the lowest number to monitor the Power.

               

              Attached are projects

              adc_test_191008A (for CY8C4146LQI-S433)  (I tested with this)

              adc_test_191008   (for CY8C4024LQI-S401) (compile-able, but has not been tested)

               

              Best Regards,

              8-Oct-2019

              Motoo Tanaka

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