Company Products Tech.Info Notice    Dev.Tools Home > Developement Guide > FAQ FAQ HMS30C7202  :  ADCLCDPMU PLL RESETSDRAM SMI MMCUART CAN SPI USBTIMER PWM PS2 KEDGPIOAPPLICATION HMS30C7201  :  ADCPMU PLLETCAPPLICATION Q1.The register which is associated with ADC3 (AN3, battery check) is 8 bit wide. Is their any way to read the 10 bit ? A1.Unfortunately, there's no way to get 10bit values from battery check channels. Q2.I need to measure a voltage which exceeds the MCU Vdd. To scale this voltage I want to use resistors. To determine the proper resistor values he needs to know the ADC input resistance? A2.In 7201, ADC input voltage is sensed with capacitor. It means a capacitor serially connect with input pin. (Normally in ADC, input signal voltage pass through two or three transmission gates and then charge the internal capacitor) So input resistance of ADC is relative value of input voltage and leak current of capacitor and is not an exact value. In usual, effective input resistance of ADC is more than a couple of Mega Ohm. Q3.What is the input impedance or input current (whichever measurement you use) of each channel,the sound channel AN4 appears to have a much lower input impedance than the others? A3.There's no reason to have low impedance on only one channel.When analog mux(tranceiver) inside ADC is offed, it looks like open circuit. While analog mux of ADC is connected, channel pin goes to sample and hold circuit. We think if a channel connected, it could have relatively lower impedance than open circuit. ("relatively low value" than not connected channels) But even in this case, the lower impedance channel should have more than a couple of Mega Ohm order in nominal cases. Q4. What is the conversion time of the main battery and backup battery channels? A4. ADC needs 16 clocks (in 7201, 3.6864MHz is used for ADC operation) In one Battey check period, AD converion operation occur many times, but data stored in the same register.(user can get only the last one) And only in a certain internal state, battery check can be enable.Each battery check rate is 1/4 of Touch panel sample rate. Touch panel sample rate is mentioned in datasheet page 13-75.