ADC101S051CIMF Datasheet, PDF (15/24 Pages) Texas Instruments – Single Channel, 200 to 500 ksps, 10-Bit A/D Converter

ADC101S051
www.ti.com
SNAS303H – JULY 2005 – REVISED MARCH 2013
MODES OF OPERATION
The ADC has two possible modes of operation: normal mode, and shutdown mode. The ADC enters normal
mode (and a conversion process is begun) when CS is pulled low. The device will enter shutdown mode if CS is
pulled high before the tenth falling edge of SCLK after CS is pulled low, or will stay in normal mode if CS remains
low. Once in shutdown mode, the device will stay there until CS is brought low again. By varying the ratio of time
spent in the normal and shutdown modes, a system may trade-off throughput for power consumption, with a
sample rate as low as zero.
Normal Mode
The fastest possible throughput is obtained by leaving the ADC in normal mode at all times, so there are no
power-up delays. To keep the device in normal mode continuously, CS must be kept low until after the 10th
falling edge of SCLK after the start of a conversion (remember that a conversion is initiated by bringing CS low).
If CS is brought high after the 10th falling edge, but before the 16th falling edge, the device will remain in normal
mode, but the current conversion will be aborted, and SDATA will return to TRI-STATE (truncating the output
word).
Sixteen SCLK cycles are required to read all of a conversion word from the device. After sixteen SCLK cycles
have elapsed, CS may be idled either high or low until the next conversion. If CS is idled low, it must be brought
high again before the start of the next conversion, which begins when CS is again brought low.
After sixteen SCLK cycles, SDATA returns to TRI-STATE. Another conversion may be started, after t_QUIET has
elapsed, by bringing CS low again.
Shutdown Mode
Shutdown mode is appropriate for applications that either do not sample continuously, or it is acceptable to trade
throughput for power consumption. When the ADC is in shutdown mode, all of the analog circuitry is turned off.
To enter shutdown mode, a conversion must be interrupted by bringing CS high anytime between the second
and tenth falling edges of SCLK, as shown in Figure 23. Once CS has been brought high in this manner, the
device will enter shutdown mode, the current conversion will be aborted and SDATA will enter TRI-STATE. If CS
is brought high before the second falling edge of SCLK, the device will not change mode; this is to avoid
accidentally changing mode as a result of noise on the CS line.
Figure 23. Entering Shutdown Mode
Figure 24. Entering Normal Mode
To exit shutdown mode, bring CS back low. Upon bringing CS low, the ADC will begin powering up (power-up
time is specified in the Timing Specifications table). This power-up delay results in the first conversion result
being unusable. The second conversion performed after power-up, however, is valid, as shown in Figure 24.
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