Datasheet

CODEx = INT
©
§
©
§
4096
VREF
x INx
VDD/2
C
HOLD
+
-
ROUT < 10k
Voltage
Source
INx
Sampling
Switch
Device Pin
LMP92001
SNAS507B –FEBRUARY 2011–REVISED APRIL 2012 www.ti.com
BLOCK COMMANDS
Block access functionality is discussed in Block Access.
Block Start Block End
Name Block Length in Bytes Comment
Address Address
BLK0 0x80 0x8B 24 Single command access to registers DAC[1:12]
BLK1 0x86 0x8B 12 Single command access to registers DAC[7:12]
BLK2 0x20 0x30 34 Single command access to registers ADC[1:17]
BLK3 0x28 0x30 18 Single command access to registers ADC[9:17]
BLK4 0x40 0x4B 24 Single command access to all LIHx and LILx registers
BLK5 0x46 0x4B 12 Single command access to all LILx registers
APPLICATION INFORMATION
ANALOG SENSE SUBSYSTEM
The device is capable of monitoring up to 16 externally applied voltages and an internal analog temperature
sensor. The system is centered around 12-bit SAR ADC fronted by a 17-input mux. Results of conversion are
stored in the registers corresponding to the given input channel. The register content can be read by the
supervisor via the I
2
C-compatible interface.
The ADC timing signals are derived from the on-board temperature compensated oscillator, which assures the
stable sampling interval.
In the applications where an instantaneous detection of the out-of-bounds condition is required the built in digital
window comparator function is provided on 6 of the input channels. This window comparator is capable of
triggering the external interrupts.
Sampling and Conversion
The external voltage is sampled onto the internal C
HOLD
capacitor. The TRACK period is controlled by the internal
oscillator, and its duration is t
TRACK
. The output impedance of the sensed voltage source and the analog input
capacitance C
INA
(which is dominated by C
HOLD
during TRACK time) limit the bandwidth of the input signal. It is
recommended to limit the output resistance ROUT of the sampled voltage source to 10 kΩ to assure 12-bit
accuracy of conversion.
Figure 14. ADC During TRACK Period
During the HOLD period, duration of t
HOLD
, all mux switches are in the off state, and charge captured on the hold
capacitor is measured to produce an ADC output code. The resulting output code is stored in the internal register
(ADCx) corresponding to the sampled analog input channel.
Typical ADC output code as a function of input voltage at device pin INx, x=1...16:
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