LDC1614RGHT datasheet(40/67 Pages) TI2

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LDC1612, LDC1614

SNOSCY9A – DECEMBER 2014 – REVISED MARCH 2018

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(1)

Channels 2 and 3 are available only in the LDC1614.

(2)

ƒREFx is the reference frequency configured for the channel.

8.1.4.1 Settling Time

When the LDC sequences through the channels in multi-channel mode, the dwell time interval for each channel

is the sum of 3 parts: sensor activation time + conversion time + channel switch delay.

The sensor activation time is the amount of settling time required for the sensor oscillation amplitude to stabilize,

as shown in Figure 53. The settling wait time is programmable and should be set to a value that is long enough

to allow stable oscillation. The settling wait time for channel x is given by:

tSx = (SETTLECOUNTx ×16)/ƒREFx

(9)

Table 40 illustrates the registers and values for configuring the settling time for each channel.

Table 40. Settling Time Register Configuration

CHANNEL(1)

FIELD

CONVERSION TIME(2)

SETTLECOUNT0, addr 0x10

SETTLECOUNT0 ['15:0]

(SETTLECOUNT0×16)/fREF0

SETTLECOUNT1, addr 0x11

SETTLECOUNT1 [15:0]

(SETTLECOUNT1×16)/fREF1

SETTLECOUNT2, addr 0x12

SETTLECOUNT2 [15:0]

(SETTLECOUNT2×16)/fREF2

SETTLECOUNT3, addr 0x13

SETTLECOUNT3 [15:0]

(SETTLECOUNT3×16)/fREF3

The SETTLECOUNTx for any channel x must satisfy:

SETTLECOUNTx

≥ QSENSORx × ƒREFx / (16 × ƒSENSORx)

where:

•

ƒSENSORx = Sensor Frequency of Channel x

•

ƒREFx = Reference frequency for Channel x

•

QSENSORx = Quality factor of the sensor on Channel x. The sensor Q can be calculated with:

(10)

(11)

Round the result to the next highest integer (for example, if Equation 10 recommends a minimum value of 6.08,

program the register to 7 or higher).

L, RP and C values can be obtained by using Texas Instrument’s WEBENCH

® for the coil design.

8.1.4.2 Sensor Activation

The LDC1612/LDC1614 provides option to either reduce the sensor activation time or to reduce the device

current consumption during the sensor activation time.

This can reduce the sensor activation time for higher-Q sensors by driving the maximum sensor drive current

during the sensor settling time. The maximum sensor drive current is nominally 1.56 mA. Sensors already

configured to use the maximum drive current setting (IDRIVEx = b11111) will see no change in operation based

on this setting.

This mode is selected by setting SENSOR_ACTIVATE_SEL to 0.

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