lm4921itlx National Semiconductor Corporation, lm4921itlx Datasheet - Page 12

• Manufacturer Part Number: lm4921itlx
• Description: Low Voltage I2s 16-bit Stereo Dac With Stereo Headphone Power Amplifiers And Volume Control
• Manufacturer: National Semiconductor Corporation

www.national.com
VOLUME CONTROL
The internal Stereo Volume Control is set by changing bits 7 through 11 in the SPI interface, as shown in table 3 below. The zero
dB setting is for 3V VDD operation and the +3dB is for 5V VDD.
BYPASS CHARGE RATE BIT 12
This control pin allows the user to change the Bypass
Capacitor's charge rate by a factor of two. Setting this bit at
zero will set the circuit to it's normal 1x rate. Setting the bit to
High will double the charge rate and allow the part to turn on
faster with a slight degradation in turn on click/pop noise.
SPI CONTROL INTERFACE BUS (J1)
SPI DATA: This is the serial data pin.
SPI CLK: This is the clock input pin.
SPI ENABLE: This is the SPI enable pin.
Gain (dB)
HP_L & HP_R
-43.5
-42.0
-40.5
-39.0
-37.5
-36.0
-34.5
-33.0
-31.5
-30.0
-28.5
-27.0
-25.5
-24.0
-22.5
-21.0
-19.5
-18.0
-16.5
-15.0
-13.5
-12.0
-10.5
-9.0
-7.5
-6.0
-4.5
-3.0
-1.5
0.0
1.5
3.0
Bit 11
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Table 3. Volume Control Settings
Bit 10
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
12
BITS 5, 13,14, and 15
Bits 13, 14, and 15 are all reserve bits and must be set to low/
zero/ground.
Bit 5 must be set High.
Bit 9
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Bit 8
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Bit 7
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1