Datasheet

InitialDelay
Fully-SettledData
DRDY
Start
Condition
ADS1158
SBAS429D –JUNE 2008– REVISED MARCH 2011 www.ti.com
GPIO Linked START Pin Control
Power-Down mode. In Converting mode, the device
is actively converting channel data. The device power
The START pin can be controlled directly by software
dissipation is the highest in this mode. This mode is
by connecting externally a GPIO port pin to the
divided into two sub-modes: Auto-Scan and
START pin. (Note that an external pull-down resistor
Fixed-Channel.
is recommended to keep the GPIO from floating until
the GPIO is configured as an output). For this mode
The next mode is the Idle mode. In this mode, the
of control, the START pin is effectively controlled by
device is not converting channel data. The device
writing to the GPIO Data Register (GPIOD), with the
remains active, waiting for input to start conversions.
write operation setting or resetting the appropriate bit.
The power consumption is reduced from that of the
The data takes effect on the eighth falling edge of the
Converting mode. This mode also has two
data byte write. The START pin can then be
sub-modes: Standby and Sleep.
controlled by the serial interface.
The last mode is Power-Down mode. In this mode, all
functions of the converter are disabled to reduce
Initial Delay
power consumption to a minimum.
As seen in Figure 43, when a start convert condition
occurs, the first reading from ADS1158 is delayed for
CONVERTING MODES
a number of clock cycles. This delay allows fully
The ADS1158 has two converting modes: Auto-Scan
settled data to occur at the first data read. Data reads
and Fixed-Channel. In Auto-Scan mode, the channels
thereafter are available at the full data rate. The
to be measured are pre-selected in the address
number of clock cycles delayed before the first
register settings. When a convert condition is present,
reading is valid depends on the data rate setting, and
the converter automatically measures and sequences
whether exiting the Standby or Sleep mode. Table 8
through the channels either in a continuous loop or
lists the delayed clock cycles versus data rate.
pulse-step fashion, depending on the trigger
condition.
In Fixed-Channel mode, the channel address is
selected in the address register settings before
acquiring channel data. When a convert condition is
present, the device converts a single channel, either
continuously or in pulse-step fashion, depending on
the trigger condition. The data rate in this mode is
higher than in Auto-Scan mode because the input
channels are not indexed for each reading.
Figure 43. Start Condition to First Data
The selection of converting modes is set with bit
MUXMOD of register CONFIG0.
OPERATING MODES
The operating modes of the ADS1158 are defined in
three basic states: Converting mode, Idle mode, and
Table 8. Start Condition to DRDY Delay, Chop = 0, DLY[2:0] = 000
INITIAL DELAY (Standby Mode) INITIAL DELAY (Sleep Mode)
(f
CLK
cycles) (f
CLK
cycles)
DRATE[1:0] Fixed-Channel Auto-Scan Fixed-Channel Auto-Scan
11 802 708 866 772
10 1186 1092 1250 1156
01 2722 2628 2786 2692
00 8866 8772 8930 8836
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