SSM2319

Rev. 0 | Page 16 of 20

Operating Modes

•

SYNCI = external clock. SYNCO is a buffered clock output

sourced from an external clock signal. One clock cycle after

the internal modulator detect signal is released, an irregular

pulse appears on MCLK before the first buffered output signal

begins on SYNCO, as shown in Figure 39.

The SYNC operating modes include the following:

•

Initial SYNC startup. An internal reference signal, REF, is

released after one complete internal clock cycle (MCLK).

After REF is released, another internal signal, MOD, waits

127 internal clock cycles. This operates as a training signal

to determine the SYNCI/SYNCO connection. During this

time, SYNCO is the internal clock signal.

SD

REF

MOD

SYNCI

SYNCO

MCLK

INTERNAL

SIGNAL

SYNCI = CLKIN

•

SYNCI = GND or VDD. SYNCO stops generating pulses.

The modulator is controlled by an internal clock signal, as

shown in Figure 37.

SD

REF

MOD

SYNCI

SYNCO

MCLK

INTERNAL

SIGNAL

SYNCI = GND

Figure 39. SYNCI = External Clock

•

SYNCI = GND, transitions to clock. When the SYNCI pin is

connected to GND first but then transitions to a clock signal,

SYNCO generates several internal clock signals before finally

being synchronized to the external clock signal, as shown

in Figure 40.

SD

REF

MOD

SYNCI

SYNCO

MCLK

INTERNAL

SIGNAL

SYNCI = GND TO CLKIN

Figure 37. SYNCI = GND or VDD

•

SYNCI = SYNCO. SYNCO is the delayed clock signal of

SYNCI, as shown in Figure 38.

SD

REF

MOD

SYNCI

SYNCO

MCLK

INTERNAL

SIGNAL

SYNCI = SYNCO

Figure 40. SYNCI = GND to Clock Input

•

SYNCI = CLK, transitions to GND. When SYNCI is

connected to a clock signal but then transitions to GND,

the SYNCO pin immediately stops generating a clock signal.

After a short clock loss detect time, the internal modulator

synchronizes to the internal clock signal, as shown

in Figure 41.

Figure 38. SYNCI = SYNCO

SD

REF

MOD

SYNCI

SYNCO

MCLK

INTERNAL

SIGNAL

SYNCI = CLKIN TO GND

CLK LOSS

DETECT

Figure 41. SYNCI = Clock Input to GND