SPRS902K October 2014 – February 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
DESCRIPTION | VALUE | |
---|---|---|
Cp | Parasitic input capacitance | See Table 6-10 |
Ron | Sampling switch resistance | 600 Ω |
Ch | Sampling capacitor | 16.5 pF |
Rs | Nominal source impedance | 50 Ω |
Table 6-10 shows the parasitic capacitance on each channel. Also, enabling a comparator adds approximately 1.4 pF of capacitance on positive comparator inputs and 2.5 pF of capacitance on negative comparator inputs.
ADC CHANNEL | Cp (pF) | |
---|---|---|
COMPARATOR DISABLED | COMPARATOR ENABLED | |
ADCINA0 | 12.9 | N/A |
ADCINA1 | 10.3 | N/A |
ADCINA2 | 5.9 | 7.3 |
ADCINA3 | 6.3 | 8.8 |
ADCINA4 | 5.9 | 7.3 |
ADCINA5 | 6.3 | 8.8 |
ADCINB0(1) | 117.0 | N/A |
ADCINB1 | 10.6 | N/A |
ADCINB2 | 5.9 | 7.3 |
ADCINB3 | 6.2 | 8.7 |
ADCINB4 | 5.2 | N/A |
ADCINB5 | 5.1 | N/A |
ADCIND0 | 5.3 | 6.7 |
ADCIND1 | 5.7 | 8.2 |
ADCIND2 | 5.3 | 6.7 |
ADCIND3 | 5.6 | 8.1 |
ADCIND4 | 4.3 | N/A |
ADCIN14 | 8.6 | 10.0 |
ADCIN15 | 9.0 | 11.5 |
This input model should be used along with actual signal source impedance to determine the acquisition window duration. See the Choosing an Acquisition Window Duration section of the TMS320F2807x Real-Time Microcontrollers Technical Reference Manual for more information. Also refer to Charge-Sharing Driving Circuits for C2000 ADCs and ADC Input Circuit Evaluation for C2000 MCUs for more details on evaluating ADC circuit performance.
The user should analyze the ADC input setting assuming worst-case initial conditions on Ch. This will require assuming that Ch could start the S+H window completely charged to VREFHI or completely discharged to VREFLO. When the ADC transitions from an odd-numbered channel to an even-numbered channel, or vice-versa, the actual initial voltage on Ch will be close to being completely discharged to VREFLO. For even-to-even or odd-to-odd channel transitions, the initial voltage on Ch will be close to the voltage of the previously converted channel.