TMS320F2810, TMS320F2812
DIGITAL SIGNAL PROCESSORS
SPRS174B
–
APRIL 2001
–
REVISED SEPTEMBER 2001
69
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251
–
1443
enhanced analog-to-digital converter (ADC) module (continued)
To obtain the specified accuracy of the ADC, proper board layout is very critical. To the best extent possible,
traces leading to the ADCIN pins should not run in close proximity to the digital signal paths. This is to minimize
switching noise on the digital lines from getting coupled to the ADC inputs. Furthermore, proper isolation
techniques must be used to isolate the ADC module power pins (such as V
CCA
, V
REFHI
, and V
SSA
) from the
digital supply.
Notes:
1.
The ADC registers are accessed at the SYSCLKOUT rate. The internal timing of the ADC module is
controlled by the high-speed peripheral clock (HSPCLK).
2.
The behavior of the ADC module based on the state of the ADCENCLK and HALT signals is as follows:
ADCENCLK:
On reset, this signal will be low. While reset is active-low (XRS) the clock to the register will still
function. This is necessary to make sure all registers and modes go into their default reset state. The analog
module will however be in a low-power inactive state. As soon as reset goes high, then the clock to the
registers will be disabled. When the user sets the ADCENCLK signal high, then the clocks to the registers
will be enabled and the analog module will be enabled. There will be a certain time delay (ms range) before
the ADC is stable and can be used.
HALT:
This signal only affects the analog module. It does not affect the registers. If low, the ADC module is
powered. If high, the ADC module goes into low-power mode. The HALT mode will stop the clock to the CPU,
which will stop the HSPCLK. Therefore the ADC register logic will be turned off indirectly.
P