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APPLICATION AND LAYOUT CONSIDERATIONS
POWER-SUPPLY BYPASSING
GROUNDING
VOLTAGE INPUT
A tantalum or aluminum electrolytic capacitor, between 1
μ
F and 10
μ
F, is recommended as an ac-coupling
capacitor at the inputs. Combined with the 30-k
characteristic input impedance, a 1-
μ
F coupling capacitor
establishes a 5.3-Hz cutoff frequency for blocking dc. The input voltage range can be increased by adding a
series resistor on the analog input line. This series resistor, when combined with the 30-k
input impedance,
creates a voltage divider and enables larger input ranges.
V
REF
INPUTS
A 4.7-
μ
F to 10-
μ
F tantalum capacitor is recommended between V
1, V
2, and AGND1 to ensure low source
impedance for the ADC references. These capacitors should be located as close as possible to the reference
pins to reduce dynamic errors on the ADC reference.
V
COM
INPUT
A 4.7-
μ
F to 10-
μ
F tantalum capacitor is recommended between V
COM
and AGND1 to ensure low source
impedance of the ADC and DAC common voltage. This capacitor should be located as close as possible to the
V
COM
pin to reduce dynamic errors on the dc common-mode voltage.
SYSTEM CLOCK
RESET CONTROL
If capacitors larger than 22
μ
F are used on V
REF
and V
COM
, external reset control (RST = low for the PCM3002,
PDAD = low and PDDA = low for the PCM3003) is required after the V
REF
, V
COM
transient response is settled.
EXTERNAL MUTE CONTROL
TYPICAL CONNECTION DIAGRAM
PCM3002
PCM3003
SBAS079A–OCTOBER 2000–REVISED OCTOBER 2004
The digital and analog power supply lines to PCM3002/3003 should be bypassed to the corresponding ground
pins with both 0.1-
μ
F ceramic and 10-
μ
F tantalum capacitors as close to the device pins as possible. Although
the PCM3002/3003 has three power-supply lines to optimize dynamic performance, the use of one common
power supply is generally recommended to avoid unexpected latch-up or pop noise due to power-supply
sequencing problems. If separate power supplies are used, back-to-back diodes are recommended to avoid
latch-up problems.
In order to optimize the dynamic performance of the PCM3002/3003, the analog and digital grounds are not
connected internally. The PCM3002/3003 performance is optimized with a single ground plane for all returns. It is
recommended to tie all PCM3002/3003 ground pins to the analog ground plane using low-impedance
connections. The PCM3002/3003 should reside entirely over this plane to avoid coupling high-frequency digital
switching noise into the analog ground plane.
The quality of the system clock can influence dynamic performance of both the ADC and DAC in the
PCM3002/3003. The duty cycle and jitter at the system-clock input pin should be carefully managed. When
power is supplied to the part, the system clock, bit clock (BCKIN), and word clock (LCRIN) also must be supplied
simultaneously. Failure to supply the audio clocks results in a power-dissipation increase of up to three times
normal dissipation and can degrade long-term reliability if the maximum power-dissipation limit is exceeded.
For power-down ON/OFF control without click noise, which is generated by a DC level change on the DAC
output, use of the external mute control is recommended. The control sequence, which is external mute ON,
codec power-down ON, SYSCLK stop and resume if necessary, codec power-down OFF, and external mute
OFF is recommended.
A typical connection diagram for the PCM3002/3003 is shown in Figure 51.
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