ZHCSHX3A December 2014 – March 2018 LDC1312 , LDC1314
PRODUCTION DATA.
The multi-channel package of the LDC enables the user to save board space and support flexible system design. For example, temperature drift can often cause a shift in component values, resulting in a shift in resonant frequency of the sensor. Using a second sensor as a reference or in a differential configuration provides the capability to cancel out temperature shifts and other environmental variations. When operated in multi-channel mode, the LDC sequentially samples the selected channels - only one channel is active at any time while the other selected channels are held in an inactive state. In single channel mode, the LDC samples a single channel, which is selectable. Refer to Inactive Channel Sensor Connections for more details on inactive channels.
Inactive channels have the corresponding INAx and INBx pins tied to ground. The following table shows the registers and values that are used to configure either multi-channel or single channel modes.
MODE | REGISTER | FIELD | VALUE(1) |
---|---|---|---|
Single channel | CONFIG, addr 0x1A | ACTIVE_CHAN [15:14] | 00 = chan 0 |
01 = chan 1 | |||
10 = chan 2 | |||
11 = chan 3 | |||
MUX_CONFIG addr 0x1B | AUTOSCAN_EN [15] | 0 = continuous conversion on a single channel (default) | |
Multi-channel | MUX_CONFIG addr 0x1B | AUTOSCAN_EN [15] | 1 = continuous conversion on multiple channels |
MUX_CONFIG addr 0x1B | RR_SEQUENCE [14:13] | 00 = Ch0, Ch 1 | |
01 = Ch0, Ch 1, Ch 2 | |||
10 = Ch0, CH1, Ch2, Ch3 |
The digitized sensor measurement for each channel (DATAx) represents the ratio of the sensor frequency to the reference frequency. The data outputs represent the 12 MSBs of a 16-bit result. With the FIN_DIVIDER set to 1 and OFFSET set to 0, the sensor frequency can be calculated from:
The following table illustrates the registers that contain the fixed point sample values for each channel.
CHANNEL(1) | REGISTER | FIELD NAME [BITS(S) ] | VALUE |
---|---|---|---|
0 | DATA0, addr 0x00 | DATA0 [11:0] | 12 bit conversion results
0x000 = sensor under range condition 0xfff = sensor over range condition |
1 | DATA1, addr 0x02 | DATA1 [11:0] | 12 bit conversion results.
0x000 = sensor under range condition 0xfff = sensor over range condition |
2 | DATA2, addr 0x04 | DATA2 [11:0] | 12 bit conversion result.
0x000 = sensor under range condition 0xfff = sensor over range condition |
3 | DATA3, addr 0x06 | DATA3 [11:0] | 12 bit conversion result.
0x000 = sensor under range condition 0xfff = sensor over range condition |