ZHCSHE0 December 2017 TMS320F28377D-EP
PRODUCTION DATA.
DESCRIPTION | VALUE (16-BIT MODE) | |
---|---|---|
Cp | Parasitic input capacitance | See Table 4-48 |
Ron | Sampling switch resistance | 700 Ω |
Ch | Sampling capacitor | 16.5 pF |
Rs | Nominal source impedance | 50 Ω |
Table 4-48 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 |
ADCINC2 | 5.5 | 6.9 |
ADCINC3 | 5.8 | 8.3 |
ADCINC4 | 5.0 | 6.4 |
ADCINC5 | 5.3 | 7.8 |
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 |
ADCIND5 | 4.3 | N/A |
ADCIN14 | 8.6 | 10.0 |
ADCIN15 | 9.0 | 11.5 |
These input models 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 TMS320F2837xD Dual-Core Delfino Microcontrollers Technical Reference Manual for more information.
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.