CDB42L73 Datasheet, PDF (6/36 Pages) Cirrus Logic – Ecaluation Borard for the CS42L73

CDB42L73
2.4 Analog Inputs
Line input (via 2x mono RCA jacks) and microphone input (via 2x mono 1/8-inch jacks) are available on the
CDB42L73. Analog input circuitry simply consists of DC-blocking capacitors and several resistors as shown
in the Typical Connections Diagram of the CS42L73 datasheet.
Button switch S2 engages the CS42L73’s MIC2 automute function when pressed.
Jumper pin blocks J54, J55, and J56 allow the user to evaluate the pseudo-differential analog input features
of the CS42L73. By default, shunts are placed on these jumper pin blocks to emulate a typical single-ended
input use case. When the shunts are removed, the pseudo-differential analog inputs will reject common-
mode noise effectively; this is especially useful for eliminating ground loop related problems from the analog
input source.
2.5 Analog Outputs
Line output (via 2x mono RCA jacks) and headphone output (via 1x stereo 1/8-inch jack) are available on
the CDB42L73. The line output also has a selectable first order low-pass filter commonly used with DACs;
this is done via jumper pin blocks J38 and J39. In addition, jumper pin blocks J36 and J37 allow the user to
evaluate the pseudo-differential line/headphone output capability of the CS42L73. By default, J36 and J37
are shunted to emulate a typical single-ended output use case. When the shunts are removed, the pseudo-
differential line/headphone outputs will reject common-mode noise effectively; this is especially useful for
eliminating ground loop related problems arising from an external connection to the line/headphone outputs.
The differential earphone, speakerphone, and speakerphone line outputs are provided via terminal blocks
J47, J48, and J52. Each of these outputs has a 1/8-inch jack in parallel to be used as the measurement
point when test loads are connected to the terminal blocks.
It should be noted that the CS35L01 Class-D amplifier (reference designator U13) may be used to amplify
the speakerphone line output. The CS35L01-amplified speakerphone line output may be selected by shunt-
ing jumper pin blocks J59 and J60 to the “AMP” position. This is useful when trying to achieve a stereo
speaker driver configuration; for example, the speakerphone output of the CS42L73 may be used as the left
speaker driver, while the amplified speakerphone line output may be used as the right speaker driver. The
CS35L01 may be enabled or disabled via FlexGUI by toggling bit 7 of address 0x01 in the “Micro” tab of the
Register Maps.
2.6 Control Port Interface
The Cirrus Logic FlexGUI software application (downloadable from http://www.cirrus.com/msasoftware)
provides users an easy and intuitive way to configure the CDB42L73. A Windows^®-compatible PC with USB
connectivity is required to run FlexGUI.
The CDB42L73’s onboard microcontroller handles the USB communication with FlexGUI and the control
port interface of the CS42L73. The control port interface of the CS42L73 is routed through jumper pin block
J21. When the pin columns marked “BOARD” are shunted (the default setting), the microcontroller handles
all communication between the FlexGUI application and the CS42L73. If external control is to be used in-
stead of FlexGUI, the shunts on J21 should be removed and the external signals wired in to the pin columns
marked “EXT CONN” (please note the GND pins on the right hand side).
2.7 Layout Reference
The CDB42L73 utilizes a six-layer PCB that allows for clean trace fanout from the CS42L73. There are also
dedicated ground planes between each routed layer, providing low-impedance return paths for high fre-
quency signals and improving shielding between layers. Local decoupling and fly capacitors for the
CS42L73 are placed as closely as possible to the device, with the critical components closest.
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