LMP90100MHE National Semiconductor, LMP90100MHE Datasheet - Page 30

• Manufacturer Part Number: LMP90100MHE
• Description: AFE, SENSOR, 28TSSOP
• Manufacturer: National Semiconductor

Specifications of LMP90100MHE

• Brief Features: 24bit Low Power Sigma Delta ADC, Automatic Channel Sequencer
• Supply Voltage Range: 2.7V To 5.5V
• Operating Temperature Range: -40°C To +105°C
• Digital Ic Case Style: TSSOP
• No. Of Pins: 28
• Base: RoHS Compliant
• Ic Function: Multi-Channel, Low Power 24-bit Sensor AFE
• Rohs Compliant: Yes

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The
SENDIAG_FLAGS register and are described in further de-
tails below.
SHORT_THLD_FLAG:
The short circuit threshold flag is used to report a short-circuit
condition. It is set when the output voltage (VOUT) is within
the absolute Vthreshold. Vthreshold can be programmed us-
ing the 8-bit SENDIAG_THLDH register concatenated with
the 8-bit SENDIAG_THLDL register.
For
SENDIAG_THLDH = 0xFA, and SENDIAG_THLDL = 0x45.
In this case, Dthreshold = 0xFA45 = 64069d, and Vthreshold
can be calculated as:
When
SHORT_THLD_FLAG = 1; otherwise, SHORT_THLD_FLAG
= 0.
RAILS_FLAG:
The rails flag is used to detect if one of the sampled channels
is within 50mV of the rails potential (VA or VSS). This can be
further investigated to detect an open-circuit or short-circuit
condition. If the sampled channel is near a rail, then
RAILS_FLAG = 1; otherwise, RAILS_FLAG = 0.
Vthreshold = [(Dthreshold)(2)(VREF)] / [(Gain)(2
example,
sensor
(-38.2mV)
Vthreshold = [(64069)(2)(5V)] / [(1)(2
diagnostic
assume
Vthreshold = 38.2 mV
≤
VOUT
VREF
flags
are
=
≤
FIGURE 16. Sensor Diagnostic Flags Diagram
5V,
(38.2mV),
located
24
gain
)]
in
24
=
)]
then
the
1,
30
POR_AFT_LST_RD:
If POR_AFT_LST_READ = 1, then there was a power-on re-
set since the last time the SENDIAG_FLAGS register was
read. This flag's status is cleared when this bit is read, unless
this bit is set again on account of another power-on-reset
event in the intervening period.
OFLO_FLAGS:
OFLO_FLAGS is used to indicate whether the modulator is
over-ranged or under-ranged. The following conditions are
possible:
1.
2.
3.
4.
The condition of OFLO_FLAGS = 10b or 11b can be used in
conjunction with the RAILS_FLAG to determine the fault con-
dition.
SAMPLED_CH:
These three bits show the channel number for which the
ADC_DOUT and SENDIAG_FLAGS are available. This does
not necessarily indicate the current channel under conversion
because the conversion frame and computation of results
from the channels are pipelined. That is, while the conversion
is going on for a particular channel, the results for the previous
conversion (of the same or a different channel) are available.
OFLO_FLAGS = 0x0: Normal Operation
OFLO_FLAGS = 0x1: The modulator was not
overranged, but ADC_DOUT got clamped to 0x7f_ffff
(positive fullscale) or 0x80_0000 (negative full scale). For
example, if VREF = 5V, VIN = 2V, and gain = 128, then
OFLO_FLAGS would be 01b.
OFLO_FLAGS = 0x2: The modulator was over-ranged
towards +VREF.
OFLO_FLAGS = 0x3: The modulator was over-ranged
towards −VREF.
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