Datasheet

SENSORx REFx
28 16
DATAx CHx_OFFSET
¦ &+[B),1B',9,'(5 ¦
2 2
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39
LDC1612 , LDC1614
www.ti.com SNOSCY9A –DECEMBER 2014–REVISED MARCH 2018
Product Folder Links: LDC1612 LDC1614
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(1) Channels 2 and 3 are available only for LDC1614.
8.1.3.1 Data Offset
An offset value may be subtracted from each DATA value to compensate for a frequency offset or maximize the
dynamic range of the sample data. The offset values should be < ƒ
SENSORx_MIN
/ ƒ
REFx
. Otherwise, the offset
might be so large that it masks the LSBs which are changing.
Table 38. Frequency Offset Registers
CHANNEL REGISTER FIELD VALUE
0 OFFSET0, addr 0x0C OFFSET0 [15:0 ] ƒ
OFFSET0
= OFFSET0 × (ƒ
REF0
÷2
16
)
1 OFFSET1, addr 0x0D OFFSET1 [15:0 ] ƒ
OFFSET1
= OFFSET1 × (ƒ
REF1
÷2
16
)
2 OFFSET2, addr 0x0E OFFSET2 [15:0 ] ƒ
OFFSET2
= OFFSET2 × (ƒ
REF2
÷2
16
)
3 OFFSET3, addr 0x0F OFFSET3 [15:0 ] ƒ
OFFSET3
= OFFSET3 × (ƒ
REF3
÷2
16
)
The sensor frequency can be determined by:
where:
• DATAx = Channel x Conversion results from the DATAx_MSB and DATAx_LSB registers
• OFFSETx = Offset value set in the OFFSETx register (6)
8.1.4 Sensor Conversion Time
The LDC1612/LDC1614 provides a configurable conversion time by setting an internal register. The conversion
interval can be configured across a range of 1.2 µs to >26.2 ms with 16 bits of resolution. Note that it is possible
to configure the conversion interval to be significantly shorter than the time required to readback the DATAx
registers; when configured in this manner, older conversions for a channel are overwritten when new conversion
data is completed for each channel. The conversion interval is set in multiples of the reference clock period by
setting the RCOUNTx register value. The conversion time for any channel x is:
t
Cx
= (RCOUNTx × 16 + 4) /f
REFx
(7)
In general, a longer conversion time will provide a higher resolution inductance measurement. The maximum
setting, 0xFFFF, is required for full resolution. The reference count value should be chosen to support both the
required sample rate and the necessary resolution. Refer to the TI Application Note Optimizing L Measurement
Resolution for the LDC161x and LDC1101 for more information.
Table 39. Conversion Time Configuration Registers, Channels 0 - 3
(1)
CHANNEL REGISTER FIELD CONVERSION TIME
0 RCOUNT0, addr 0x08 RCOUNT0 [15:0] (RCOUNT0×16)/f
REF0
1 RCOUNT1, addr 0x09 RCOUNT1 [15:0] (RCOUNT1×16)/f
REF1
2 RCOUNT2, addr 0x0A RCOUNT2 [15:0] (RCOUNT2×16)/f
REF2
3 RCOUNT3, addr 0x0B RCOUNT3 [15:0] (RCOUNT3×16)/f
REF3
The typical channel switch delay time between the end of conversion and the beginning of sensor activation of
the subsequent channel is:
Channel Switch Delay = 692 ns + 5 / f
ref
(8)
The deterministic conversion time of the LDC allows data polling at a fixed interval. A data ready flag (DRDY)
can assert the INTB pin for use in interrupt driven system designs (see the STATUS register description in
Register Maps).