SPRSP25A June 2018 – July 2018 TMS320F28035-EP
The core of the ADC contains a single 12-bit converter fed by two sample-and-hold circuits. The sample-and-hold circuits can be sampled simultaneously or sequentially. These, in turn, are fed by a total of up to 16 analog input channels. The converter can be configured to run with an internal band-gap reference to create true-voltage based conversions or with a pair of external voltage references (VREFHI/VREFLO) to create ratiometric-based conversions.
Contrary to previous ADC types, this ADC is not sequencer-based. It is easy for the user to create a series of conversions from a single trigger. However, the basic principle of operation is centered around the configurations of individual conversions, called SOCs, or Start-Of-Conversions.
Functions of the ADC module include:
|ADCCTL1||0x7100||1||Yes||Control 1 Register|
|ADCCTL2||0x7101||1||Yes||Control 2 Register|
|ADCINTFLG||0x7104||1||No||Interrupt Flag Register|
|ADCINTFLGCLR||0x7105||1||No||Interrupt Flag Clear Register|
|ADCINTOVF||0x7106||1||No||Interrupt Overflow Register|
|ADCINTOVFCLR||0x7107||1||No||Interrupt Overflow Clear Register|
|INTSEL1N2||0x7108||1||Yes||Interrupt 1 and 2 Selection Register|
|INTSEL3N4||0x7109||1||Yes||Interrupt 3 and 4 Selection Register|
|INTSEL5N6||0x710A||1||Yes||Interrupt 5 and 6 Selection Register|
|INTSEL7N8||0x710B||1||Yes||Interrupt 7 and 8 Selection Register|
|INTSEL9N10||0x710C||1||Yes||Interrupt 9 Selection Register (reserved Interrupt 10 Selection)|
|SOCPRICTL||0x7110||1||Yes||SOC Priority Control Register|
|ADCSAMPLEMODE||0x7112||1||Yes||Sampling Mode Register|
|ADCINTSOCSEL1||0x7114||1||Yes||Interrupt SOC Selection 1 Register (for 8 channels)|
|ADCINTSOCSEL2||0x7115||1||Yes||Interrupt SOC Selection 2 Register (for 8 channels)|
|ADCSOCFLG1||0x7118||1||No||SOC Flag 1 Register (for 16 channels)|
|ADCSOCFRC1||0x711A||1||No||SOC Force 1 Register (for 16 channels)|
|ADCSOCOVF1||0x711C||1||No||SOC Overflow 1 Register (for 16 channels)|
|ADCSOCOVFCLR1||0x711E||1||No||SOC Overflow Clear 1 Register (for 16 channels)|
|ADCSOC0CTL to ADCSOC15CTL||0x7120 – 0x712F||1||Yes||SOC0 Control Register to SOC15 Control Register|
|ADCREFTRIM||0x7140||1||Yes||Reference Trim Register|
|ADCOFFTRIM||0x7141||1||Yes||Offset Trim Register|
|COMPHYSTCTL||0x714C||1||Yes||Comparator Hysteresis Control Register|
|ADCRESULT0 to ADCRESULT15||0xB00 to 0xB0F||1||No||ADC Result 0 Register to ADC Result 15 Register|
ADC Connections if the ADC is Not Used
TI recommends keeping the connections for the analog power pins, even if the ADC is not used. Following is a summary of how the ADC pins should be connected, if the ADC is not used in an application:
When the ADC module is used in an application, unused ADC input pins should be connected to analog ground (VSSA).
Unused ADCIN pins that are multiplexed with AIO function should not be directly connected to analog ground. They should be grounded through a 1-kΩ resistor. This is to prevent an errant code from configuring these pins as AIO outputs and driving grounded pins to a logic-high state.
When the ADC is not used, be sure that the clock to the ADC module is not turned on to realize power savings.