
No. 7378 -15/17
LC75347E
Usage Notes
1. Data Transmission after Power is First Applied
The states of the internal analog switches are undefined when power is first applied. Applications should set up the
initial data immediately after power is applied (after VDD rises above 4.5 V). Applications should also mute the
outputs until the data has been set up and the outputs are stable.
To establish the states of the internal latches, set the bits D64 and D65 to 1 in the first data transferred after power is
first applied.
2. Zero Cross Switching Control
Zero cross switching is used by setting up data in which the zero cross control bits specify zero cross detection mode
(by setting bits D48 to D53 to 0) and transfer that data. Since these control bits are latched first, immediately after the
data is transferred, that is, on the fall of the CE signal, zero cross control can be performed with a single data transfer
operation when updating the volume control settings. If the zero cross control bits specify zero cross detection
disabled mode (by setting bits D48 to D53 to 1), the volume is switched on the fall of the CE signal at the end of the
data transfer.
3. Zero Cross Timer Setting
When the input signal is less than the detection sensitivity of the zero cross comparator, or if only a low-frequency
signal is being input, the state where the IC does not detect a zero cross will continue and the data will not be latched.
The zero cross timer allows applications to set a time at which data will be latched forcibly if the state where no zero
cross is detected continues.
For example, to set a time of 25 ms:
T = 0.69CR
Since the internal pull-up resistor is about 1 M
:
Applications usually set a time in the range 10 to 50 ms.
4. Notes on Serial Data Transfer
Cover the CL, DI, and CE pin signal lines with the ground pattern, or use shielded cables for these signals so that the
high-frequency digital signals transmitted on these lines do not enter the analog signal system.
C =
0.036
F
25
× 10–3
0.69
× 1.0 × 106