SNOSCZ5B June 2015 – October 2024 FDC2112 , FDC2114 , FDC2212 , FDC2214
PRODUCTION DATA
Figure 7-3 shows the clock dividers and multiplexers of the FDC.
In Figure 7-3, the key clocks are fIN, fREF, and fCLK. fCLK is selected from either the internal clock source or external clock source (CLKIN) . The frequency measurement reference clock, fREF, is derived from the fCLK source. TI recommends that precision applications use an external controller clock that offers the stability and accuracy requirements needed for the application. The internal oscillator can be used in applications that require low cost and do not require high precision. The fINx clock is derived from sensor frequency for a channel x, fSENSORx. fREFx and fINx must meet the requirements listed in Table 7-1, depending on whether fCLK (controller clock) is the internal or external clock.
MODE(1) | CLKIN SOURCE | VALID fREFx RANGE (MHz) | VALID fINx RANGE | SET CHx_FIN_SEL to (2) | SET CHx_SETTLECOUNT to | SET CHx_RCOUNT to |
---|---|---|---|---|---|---|
Multi-channel | Internal | fREFx ≤ 55 | < fREFx /4 | Differential sensor configuration: b01: 0.01MHz to 8.75MHz (divide by 1) b10: 5MHz to 10MHz (divide by 2) Single-ended sensor configuration b10: 0.01MHz to 10MHz (divide by 2) | > 3 | > 8 |
External | fREFx ≤ 40 | |||||
Single-channel | Either external or internal | fREFx ≤ 35 |
Table 7-2 shows the clock configuration registers for all channels.
CHANNEL(1) | CLOCK | REGISTER | FIELD [ BIT(S) ] | VALUE |
---|---|---|---|---|
All | fCLK = Controller Clock Source | CONFIG, addr 0x1A | REF_CLK_SRC [9] | b0 = internal oscillator is used as the controller clock b1 = external clock source is used as the controller clock |
0 | fREF0 | CLOCK_DIVIDERS_CH0, addr 0x14 | CH0_FREF_DIVIDER [9:0] | fREF0 = fCLK / CH0_FREF_DIVIDER |
1 | fREF1 | CLOCK_DIVIDERS_CH1, addr 0x15 | CH1_FREF_DIVIDER [9:0] | fREF1 = fCLK / CH1_FREF_DIVIDER |
2 | fREF2 | CLOCK_DIVIDERS_CH2, addr 0x16 | CH2_FREF_DIVIDER [9:0] | fREF2 = fCLK / CH2_FREF_DIVIDER |
3 | fREF3 | CLOCK_DIVIDERS_CH3, addr 0x17 | CH3_FREF_DIVIDER [9:0] | fREF3 = fCLK / CH3_FREF_DIVIDER |
0 | fIN0 | CLOCK_DIVIDERS_CH0, addr 0x14 | CH0_FIN_SEL [13:12] | fIN0 = fSENSOR0 / CH0_FIN_SEL |
1 | fIN1 | CLOCK_DIVIDERS_CH1, addr 0x15 | CH1_FIN_SEL [13:12] | fIN1 = fSENSOR1 / CH1_FIN_SEL |
2 | fIN2 | CLOCK_DIVIDERS_CH2, addr 0x16 | CH2_FIN_SEL [13:12] | fIN2 = fSENSOR2 / CH2_FIN_SEL |
3 | fIN3 | CLOCK_DIVIDERS_CH3, addr 0x17 | CH3_FIN_SEL [13:12] | fIN3 = fSENSOR3 / CH3_FIN_SEL |