SNOSCY9 Data sheet

SNOSCY9A December 2014 – March 2018 LDC1612 , LDC1614

PRODUCTION DATA.

Package Options

Mechanical Data (Package|Pins)

DNT|12
- MPDS488B

Thermal pad, mechanical data (Package|Pins)

Orderable Information

8.1.6 Clocking Architecture

Optimum LDC1612/LDC1614 performance requires a clean reference clock with a limited frequency range. The device provides digital dividers for the ƒ_CLK and the sensor inputs to adjust the effective frequency. For most systems, the maximum permitted reference frequency provides the best performance. The dividers provide flexibility in system design so that the full range of sensor frequencies can be supported with available f_CLK. Each channel has a dedicated divider configuration.

Figure 57 shows the clock dividers and multiplexers of the LDC.

LDC1612 LDC1614 ldc1312-clocking-snoscz0.gif

Figure 57. Clocking Diagram

(1) LDC1614 only

In Figure 57, the key clocks are ƒ_INx, ƒ_REFx, and ƒ_CLK. ƒ_CLK is selected from either the internal clock source or external clock source (CLKIN). The frequency measurement reference clock, ƒ_REF, is derived from the ƒ_CLK source.

The internal oscillator (ƒ_INT) is highly stable across temperature and is suitable for applications when the maximum performance of the LDC1612/4 is not needed or when an external oscillator is not available. For precision applications, it is recommended to use an external oscillator for the reference clock; the external oscillator should offer the stability and accuracy requirements suitable for the application. Note that some internal functions, such as watchdog timers, always use ƒ_INT for timing.

The ƒ_INx clock is derived from sensor frequency for channel x, ƒ_SENSORx. ƒ_REFx and ƒ_INx must meet the requirements listed in Table 43, depending on whether ƒ_CLK (reference clock) is the internal or external clock.

Table 43. Clock Frequency Requirements

MODE⁽¹⁾	REFERENCE SOURCE	VALID ƒ_REFx RANGE	VALID ƒ_INx RANGE	SET FIN_DIVIDERx to	VALID SETTLECOUNTx SETTINGS	VALID RCOUNTx SETTINGS
Multi-Channel	Internal	ƒ_REFx≤ 55 MHz	< ƒ_REFx /4	≥ b0001 ⁽²⁾	> 3	> 8
Multi-Channel	External	ƒ_REFx ≤ 40 MHz
Single-Channel	Either external or internal	ƒ_REFx ≤ 35 MHz

(1) Channels 2 and 3 are only available for LDC1614

(2) If ƒ_SENSOR ≥ 8.75 MHz, then FIN_DIVIDERx must be ≥ 2

Table 44 shows the clock configuration registers. Each input channel has a dedicated configuration which can be set independently.

Table 44. Clock Configuration Registers

CHANNEL⁽¹⁾	CLOCK	REGISTER	FIELD	VALUE
All	ƒ_CLK = Reference Clock Source	CONFIG, addr 0x1A	REF_CLK_SRC [9]	b0 = internal oscillator is used as the reference clock b1 = external clock source is used as the reference clock
0	ƒ_REF0	CLOCK_DIVIDERS0, addr 0x14	FREF_DIVIDER0 [9:0]	ƒ_REF0 = ƒ_CLK / FREF_DIVIDER0
1	ƒ_REF1	CLOCK_DIVIDERS1, addr 0x15	FREF_DIVIDER1 [9:0]	ƒ_REF1 = ƒ_CLK / FREF_DIVIDER1
2	ƒ_REF2	CLOCK_DIVIDERS2, addr 0x16	FREF_DIVIDER2 [9:0]	ƒ_REF2 = ƒ_CLK / FREF_DIVIDER2
3	ƒ_REF3	CLOCK_DIVIDERS3, addr 0x17	FREF_DIVIDER3 [9:0]	ƒ_REF3 = ƒ_CLK / FREF_DIVIDER3
0	ƒ_IN0	CLOCK_DIVIDERS0, addr 0x14	FIN_DIVIDER0 [15:12]	ƒ_IN0 = ƒ_SENSOR0 / FIN_DIVIDER0
1	ƒ_IN1	CLOCK_DIVIDERS1, addr 0x15	FIN_DIVIDER1 [15:12]	ƒ_IN1 = ƒ_SENSOR1 / FIN_DIVIDER1
2	ƒ_IN2	CLOCK_DIVIDERS2, addr 0x16	FIN_DIVIDER2 [15:12]	ƒ_IN2 = ƒ_SENSOR2/ FIN_DIVIDER2
3	ƒ_IN3	CLOCK_DIVIDERS3, addr 0x17	FIN_DIVIDER3 [15:12]	ƒ_IN3 = ƒ_SENSOR3 / FIN_DIVIDER3

(1) Channels 2 and 3 are only available for LDC1614