DA9116.005
22 November, 2005
GENERAL DESCRIPTION
recommended not to change the initial test register
value (00hex) in normal operation. For device testing
XMUTE pin is bidirectional. When the test register
bit 1 is high, XMUTE pin is output pin. Internal
signals can be directed to the pin. Note: In this state
the analog output is muted and new gain values
cannot be written into the gain register.
Main features
MAS9116 is a stereo digital volume control designed
for audio systems. The levels of the left and right
analog channels are set by the serial interface. Both
channels can be programmed independently.
Resistor values are decoded to 0.5 dB resolution by
using internal multiplexers for a gain from –111.5 to
+15.5 dB. The code for –112 dB activates mute for
maximum attenuation. MAS9116 operates from
single +5V supply and accepts input levels up to
18V.
Changing the gain of the channel
When new gain value is written into the gain register
the chip will activate zero crossing and delay
generator for the selected channel. MAS9116 will
wait until rising edge zero crossing is detected in the
input signal to ensure that there is no audible click
from the output of amplifier when gain is changed.
LIN is the input line for the left channel and RIN for
the right channel. If there are no zero crossings in
the signal, the gain is changed after typical 18ms
delay, since then the delay generator will provide
about 100ns pulse forcing the new value to be
latched. The delay generator´s delay has variation
but it is guaranteed that the delay is no longer than
50ms.
Interfaces
Control information is written into or read back from
the internal register via the serial control port. Serial
control port consists of a bi-directional pin for data
(DATA), chip select pin (XCS) and control clock
(CCLK) and supports the serial communication
protocol. All control instructions require two bytes of
data.
To shift the data in CCLK must be pulsed 16 times
when XCS is low. The data is shifted into the serial
input register on the rising edges of CCLK pulses.
The first 8 bits contain address information. The
second byte contains the control word. XCS must
return to high after the second byte. That is, after the
16th CCLK XCS must be returned to high. See the
timing diagram on page 11.
If new gain value has been written before zero
crossing or delay generator´s delay have occured
the previous gain value is overwritten, so the
previous value is not latched to the output. If it is
desired that each gain value will be latched to the
output there should be minimum 50ms delay
between each gain value writings.
Programming both gain registers at the same time
sets gain values first to the right channel and then to
the left channel.
The same process takes place for reading the
information. XCS will remain low for next 16 CCLK
pulses. The data is shifted out on the falling edges
of CCLK. When XCS is high, the DATA pin is in high
impedance state, which enables DATA pins of other
devices to be multiplexed together.
Programming gain into left and right channel using
separate commands causes gain values to be set in
the same order as the programming. If no zero
crossings occur in either channel, the firstly written
channel´s gain is changed after first channel´s delay
generator´s delay has passed. Only after that
second channel´s delay generator is started. In
these conditions the first channel gain is set after
maximum 50ms delay but second channel is set
after maximum 50ms+50ms = 100ms delay. To
guarantee that each written gain value will be set in
all conditions the maximum programming rate for
both channel gains separately is thus 1/100ms = 10
Hz.
On the PCB board the same DATA and CCLK lines
can be directed to every MAS9116 chip. If the XCS-
pin is not active (low), DATA-pin of that chip is in
high-impedance state. This allows using a simple
PCB board for multichannel audio systems.
Operating modes
When power is first applied, power-on reset
initializes control registers and sets MAS9116 into
mute state. The activation of the device requires that
XMUTE pin is high and a control byte with a greater
than the default value is written in the gain register. It
is possible to return to the mute stage either by
setting XMUTE pin low or writing zero (00hex) to the
gain register.
The device has special test register which is used
only for internal testing of the device. It is strongly
3 (18)
MAS [ MICRO ANALOG SYSTEMS ]
