WM8746 Wolfson Microelectronics plc, WM8746 Datasheet - Page 29

• Manufacturer Part Number: WM8746
• Description: 24-bit, 192khz 6-channel Dac With Volume Control
• Manufacturer: Wolfson Microelectronics plc

WM8746
DECOUPLING APPLICATIONS INFORMATION
SUPPLY PINS DESCRIPTION
DC ELECTRICAL CHARACTERISTICS
DECOUPLING EXAMPLES
w
PARAMETER
Analogue supply current
Digital supply current
Analogue supply current
Digital supply current
PIN
11
15
16
20
24
28
1
AVDD2
AGND1
AGND2
AVDD1
DGND
DVDD
NAME
CAP
AVDD2, DVDD and CAP. Also recommended are 10µF capacitors for AVDD, DVDD and CAP.
These are a general guideline and are dependent on the amount of noise present in the system.
If there is excessive noise on the supply, such as may be present in a commercial DVD receiver with
motors and switching amplifiers, additional filtering will be required. The supply AVDD2 is the
reference voltage for the DAC. It has no supply noise rejection, so any noise on this pin will affect the
DAC outputs. There is not much current drawn on this supply pin. Supply AVDD1 does have supply
rejection and draws most of the analogue supply current.
Figure 25 Decoupling Example 1
In Figure 25, there is a single analogue supply that is fairly noisy. The AVDD1 and DVDD pins can
tolerate this, but the AVDD2 needs additional filtering. The schematic illustrates a suitable solution.
For proper decoupling, 0.1µF surface-mount ceramic capacitors are recommended for AVDD1,
Analogue output
SYMBOL
Supply
Supply
Supply
Supply
Supply
Supply
TYPE
Digital Positive Supply.
Digital GND
Analogue Positive DAC Reference
Analogue Internal Mid-Rail Reference De-Coupling Point
Analogue GND
Analogue GND
Analogue VDD
TEST CONDITIONS
AVDD = 3.3V
DVDD = 3.3V
AVDD = 5V
DVDD = 5V
MIN
DESCRIPTION
TYP
58
22
57
11
PD, October 2008, Rev 4.2
MAX
Production Data
UNIT
mA
mA
mA
mA
29