DAC5687IPZP datasheet(42/79 Pages) TI

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CLK1

DA[15:0]

DB[15:0]

ts(DATA)

th(DATA)

AN+1

BN+1

T0039-01

B0053-09

CLK

Buffer

CLK

Buffer

PFD

Charge

Pump

VCO

Data

Latch

1 ´2

´1

CLK1

CLK1C

CLK2

LPF

pll_div(1:0)

PLLVDD

PLLLOCK

PLLVDD

DA[15:0]

DB[15:0]

interl

interp(1:0)

DAC

/2X2

DAC

X4L

DAC

Data

Lock

CLK2C

DAC5687

SLWS164E – FEBRUARY 2005 – REVISED SEPTEMBER 2006

A type-four phase-frequency detector (PFD) in the internal PLL compares this reference clock to a feedback

clock and drives the PLL to maintain synchronization between the two clocks. The feedback clock is generated

by dividing the VCO output by 1

×, 2×, 4×, or 8× as selected by the prescaler div(1:0). The output of the prescaler

is the DAC sample rate clock and is divided down to generate clocks at

÷2, ÷4, and ÷8. The feedback clock is

selected by the registers sel(1:0), which is fed back to the PFD for synchronization to the input clock. The

feedback clock is also used for the data input rate, so the ratio of DAC output clock to feedback clock sets the

interpolation rate of the DAC5687. The PLLLOCK pin is an output indicating when the PLL has achieved lock. An

external RC low-pass PLL filter is provided by the user at pin LPF. See the Low-Pass Filter section for

filter-setting calculations. This is the only mode where the LPF filter applies.

Figure 45. Dual-Bus Mode Timing Diagram (PLL Mode)

Figure 46. Clock Generation Architecture in PLL Mode

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