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AD7150BRMZ

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P29
AD7150
Rev. 0 | Page 12 of 28
SENSITIVITY
In adaptive threshold mode, the output comparator threshold is
set as a defined distance (sensitivity) above the data average,
below the data average, or both, depending on the selected
threshold mode of operation (see
Figure 31). The sensitivity
value is programmable in the range 0 to 255 LSBs of the 12-bit
CDC converter (see the
Register Descriptions section).
NEGATIVE
THRESHOLD
POSITIVE
THRESHOLD
DATA AVERAGE
OUTPUT ACTIVE
TIME
SENSITIVITY
DAT
A
SENSITIVITY
0
6517-039
Figure 31. Threshold Sensitivity
HYSTERESIS
In adaptive threshold mode, the comparator features hysteresis.
The hysteresis is fixed to one-fourth of the threshold sensitivity
and can be programmed on or off. The comparator does not
have hysteresis in the fixed threshold mode.
OUTPUT
POSITIVE
THRESHOLD
DATA AVERAGE
OUTPUT ACTIVE
TIME
HYSTERSIS
DAT
A
06517-040
Figure 32. Threshold Hysteresis
TIMEOUT
In the case of a large, long change in the capacitive input, when
the data average adapting to a new condition may take too long,
a timeout can be set.
The timeout becomes active (counting) when the CDC data
goes outside the band of data average ± sensitivity. When the
timeout elapses (a defined number of CDC conversions is
counted), the data average (and thus the thresholds), is forced to
follow the new CDC data value immediately (see
Figure 33).
The timeout can be set independently for approaching (for change
in data toward the threshold) and for receding (for change in data
away from the threshold). See
Figure 34, Figure 35, and the
Register Descriptions section.
D
A
T
A
A
V
ERAGE
+ SENSITIVITY
LARGE CHANGE IN DATA
DATA AVERAGE
DATA AVERAGE
– SENSITIVITY
TIME
TIMEOUT
06517-041
Figure 33. Threshold Timeout After a Large Change in CDC Data
INPUT C
A
PACITANCE
THRESHOLD
OUTPUT
DATA AVERAGE
OUTPUT ACTIVE
TIME
TIMEOUT APPROACHING
06517-042
Figure 34. Approaching Timeout in Negative Threshold Mode
Shortens False Output Trigger
INPUT
C
A
PACITANCE
LARGE CHANGE
THRESHOLD
OUTPUT
OUTPUT ACTIVE
TIME
TIMEOUT RECEDING
0
6517-043
Figure 35. Positive Timeout in Negative Threshold Mode
Shortens Period of Missing Output Trigger
AD7150
Rev. 0 | Page 13 of 28
AUTOCAPDAC ADJUSTMENT
In adaptive threshold mode, the part can dynamically adjust the
CAPDAC to keep the CDC in an optimal operating capacitive
range. When the AutoDAC function is enabled, the CAPDAC
value is automatically incremented when the data average
exceeds three-fourths of the CDC full range, and the CAPDAC
value is decremented when the data average goes below one-
fourth of the CDC full range. The AutoDAC increment or
decrement step depends on the selected CDC capacitive input
range. See the
Setup Registers section.
POWER-DOWN TIMER
In power sensitive applications, the AD7150 can be set to
automatically enter power-down mode after a programmed
period of time in which the outputs have not been activated.
The AD7150 can be then returned to a normal operational
mode either via the serial interface or by the power supply
off/on sequence.
POWER SUPPLY MONITOR
When the AD7150 V
DD
power supply voltage drops below a
defined level needed for correct CDC operation, the on-chip
power supply monitor stops the adaptive threshold logic and
holds it in reset. After the V
DD
reaches the required level, the
threshold logic is released, and the data average is reset to the
value of the first conversion finished at the correct power supply
voltage.
This feature prevents the adaptive threshold from being set
incorrectly after a very slow rise of the V
DD
voltage or from
being corrupted by accidental drops in the V
DD
voltage.
The other AD7150 functions continue working below the
power supply monitor threshold, down to approximately
1.0V..1.8V, the exact level depending on the manufacturing
process variation. In the region of the low V
DD
voltage, the part is
still accessible via the serial interface and continues conversion.
However, the conversion results may be incorrect and,
therefore, the data should not be considered valid if the part
operates below the power supply monitor threshold.
The status of the power supply monitor can be determined by
reading the PwrDown bit in the AD7150 status register.
AD7150
Rev. 0 | Page 14 of 28
REGISTER DESCRIPTIONS
Table 5. Register Summary
Pointer Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Register (Dec) (Hex) R/W Default Value
PwrDown
DacStep2
OUT2
DacStep1
OUT1 C1/C2
RDY2 RDY1
Status 0 0x00 R
0 1 0 1 0 0 1 1
Ch1 Data High 1 0x01 R 0x00
Ch1 Data Low 2 0x02 R 0x00
Ch2 Data High 3 0x03 R 0x00
Ch2 Data Low 4 0x04 R 0x00
Ch1 Average High 5 0x05 R 0x00
Ch1 Average Low 6 0x06 R 0x00
Ch2 Average High 7 0x07 R 0x00
Ch2 Average Low 8 0x08 R 0x00
Ch1 Sensitivity (in adaptive threshold mode)/Threshold High Byte (in fixed threshold mode)
Ch1 Sensitivity
Ch1 Threshold High
9 0x09 R/W
0x08
Ch1 Timeout (in adaptive threshold mode)/Threshold Low Byte (in fixed threshold mode)
Ch1 Timeout
Ch1 Threshold Low
10 0x0A R/W
0x86
RngH1 RngL1 –
Hyst1
ThrSettling1 (4-bit value)
Ch1 Setup 11 0x0B R/W
0 0 0 0 0x0B
Ch2 Sensitivity (in adaptive threshold mode)/Threshold High Byte (in fixed threshold mode)
Ch2 Sensitivity
Ch2 Threshold High
12 0x0C R/W
0x08
Ch2 Timeout (in adaptive threshold mode)/Threshold Low Byte (in fixed threshold mode)
Ch2 Timeout
Ch2 Threshold Low
13 0x0D R/W
0x86
RngH2 RngL2 –
Hyst2
ThrSettling2 (4-bit value)
Ch2 Setup 14 0x0E R/W
0 0 0 0 0x0B
ThrFixed ThrMD1 ThrMD0 EnCh1 EnCh2 MD2 MD1 MD0
Configuration 15 0x0F R/W
0 0 0 1 1 0 0 1
– – Power-Down Timeout (6-bit value)
Power-Down Timer 16 0x10 R/W
0 0 0x00
DacEn1 DacAuto1 DacValue1 (6-bit value)
Ch1 CAPDAC 17 0x11 R/W
1 1 0x00
DacEn2 DacAuto2 DacValue2 (6-bit value)
Ch2 CAPDAC 18 0x12 R/W
1 1 0x00
Serial Number 3 19 0x13 R Serial Number – Byte 3 (MSB)
Serial Number 2 20 0x14 R Serial Number – Byte 2
Serial Number 1 21 0x15 R Serial Number – Byte 1
Serial Number 0 22 0x16 R Serial Number – Byte 0 (LSB)
Chip ID 23 0x17 R Chip Identification Code
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P29

AD7150BRMZ

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Buy AD7150BRMZ
Manufacturer:
Analog Devices Inc.
Description:
Data Acquisition ADCs/DACs - Specialized 2-CH CDC wt adaptive threshold IC
Lifecycle:
New from this manufacturer.
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