Datasheet

ADS7950, ADS7951, ADS7952, ADS7953
ADS7954, ADS7955, ADS7956, ADS7957
ADS7958, ADS7959, ADS7960, ADS7961
www.ti.com SLAS605A –JUNE 2008–REVISED JANUARY 2010
The device has two (high and low) programmable alarm thresholds per channel. If the input crosses these limits;
the device flags out an alarm on GPIO0/GPIO1 depending on the GPIO program register settings (refer to
Table 10). The alarm is asserted (under the alarm conditions) on the 12th falling edge of SCLK in the same
frame when a data conversion is in progress. The alarm output is reset on the 10th falling edge of SCLK in the
next frame.
The device offers a power-down feature to save power when not in use. There are two ways to powerdown the
device. It can be powered down by writing DI05 = 1 in the mode control register (refer to Table 1, Table 2, and
Table 5); in this case the device powers down on the 16th falling edge of SCLK in the next data frame. Another
way to powerdown the device is through GPIO in the case of the TSSOP packaged devices . GPIO3 can act as
the PD input (refer to Table 10, to assign this functionality to GPIO3). This is an asynchronous and active low
input. The device powers down instantaneously after GPIO3 (PD) = 0. The device will power up again on the CS
falling edge with DI05 = 0 in the mode control register and GPIO3 (PD) = 1.
CHANNEL SEQUENCING MODES
There are three modes for channel sequencing, namely Manual mode, Auto-1 mode, Auto-2 mode. Mode
selection is done by writing into the control register (refer to Table 1, Table 2, and Table 5). A new multiplexer
channel is selected on the second falling edge of SCLK (as shown in Figure 45) in all three modes.
Manual mode: When configured to operate in Manual mode, the next channel to be selected is programmed in
each frame and the device selects the programmed channel in the next frame. On powerup or after reset the
default channel is 'Channel-0' and the device is in Manual mode.
Auto-1 mode: In this mode the device scans pre-programmed channels in ascending order. A new multiplexer
channel is selected every frame on the second falling edge of SCLK. There is a separate ‘program register’ for
pre-programming the channel sequence. Table 3 and Table 4 show Auto-1 ‘program register’ settings.
Once programmed the device retains ‘program register’ settings until the device is powered down, reset, or
reprogrammed. It is allowed to exit and re-enter the Auto-1 mode any number of times without disturbing
‘program register’ settings.
The Auto-1 program register is reset to FFFF/FFF/FF/F hex for the 16/12/8/4 channel devices respectively upon
device powerup or reset; implying the device scans all channels in ascending order.
Auto-2 mode: In this mode the user can configure the program register to select the last channel in the scan
sequence. The device scans all channels from channel 0 up to and including the last channel in ascending order.
The multiplexer channel is selected every frame on the second falling edge of SCLK. There is a separate
‘program register’ for pre-programming of the last channel in the sequence (multiplexer depth). Table 6 lists the
‘Auto-2 prog’ register settings for selection of the last channel in the sequence.
Once programmed the device retains program register settings until the device is powered down, reset, or
reprogrammed. It is allowed to exit and re-enter Auto-2 mode any number of times, without disturbing the
‘program register’ settings.
On powerup or reset the bits D9-D6 of the Auto-2 program register are reset to F/B/7/3 hex for the 16/12/8/4
channel devices respectively; implying the device scans all channels in ascending order.
DEVICE PROGRAMMING AND MODE CONTROL
The following section describes device programming and mode control. These devices feature two types of
registers to configure and operate the devices in different modes. These registers are referred as ‘Configuration
Registers’. There are two types of ‘Configuration Registers’ namely ‘Mode control registers’ and ‘Program
registers’.
Mode Control Register
A ‘Mode control register’ is configured to operate the device in one of three channel sequencing modes, namely
Manual mode, Auto-1 Mode, Auto-2 Mode. It is also used to control user programmable features like range
selection, device power-down control, GPIO read control, and writing output data into the GPIO.
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Product Folder Link(s): ADS7950, ADS7951, ADS7952, ADS7953 ADS7954, ADS7955, ADS7956, ADS7957 ADS7958,
ADS7959, ADS7960, ADS7961