Datasheet

LMP90100
SNAS510P –JANUARY 2011–REVISED MARCH 2013 www.ti.com
ScanMode1: Multiple-Channels Single Scan
LMP90xxx converts one or more channels starting from FIRST_CH to LAST_CH, and then enters the stand-by
state.
ScanMode2: Multiple-Channels Continuous Scan
LMP90xxx continuously converts one or more channels starting from FIRST_CH to LAST_CH, and then it
repeats this process.
ScanMode3: Multiple-Channels Continuous Scan with Burnout Currents
This mode is the same as ScanMode2 except that the burnout current is provided in a serially scanned fashion
(injected in a channel after it has undergone a conversion). Thus it avoids burnout current injection from
interfering with the conversion result for the channel.
The sensor diagnostic burnout currents are available for all four scan modes. The burnout current is further gated
by the BURNOUT_EN bit for each channel. ScanMode3 is the only mode that scans multiple channels while
injecting burnout currents without interfering with the signal. This is described in details in Burnout Currents.
SENSOR INTERFACE
LMP90100/LMP90098 contain two types of current sources: excitation currents (IB1 & IB2) and burnout currents.
They are described in the next sections.
IB1 & IB2 - Excitation Currents
IB1 and IB2 can be used for providing currents to external sensors, such as RTDs or bridge sensors. 100µA to
1000µA, in steps of 100µA, can be sourced by programming the ADC_AUXCN: RTD_CUR_SEL bits.
Refer to 3–Wire RTD to see how IB1 and IB2 can be used to source a 3-wire RTD.
Burnout Currents
As shown in Figure 48, the LMP90xxx contains two internal 10 µA burnout current sources, one sourcing current
from VA to VINP, and the other sinking current from VINN to ground. These currents are used for sensor
diagnostics and can be enabled for each channel using the CHx_INPUTCN: BURNOUT_EN bit.
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