Analog Interface Circuits
4-2
4.1
Analog Interface Circuits
Two analog inputs and one analog output can be connected to the AIC10/11
device. The TLV320AIC10/11 EVM system has 4 input and 2 output
connectors that interface to external analog circuits via the two populated (U1
and U2) AIC10/11 devices. Refer to Figure 1–2 for these connections. For the
detail circuit design refer to Appendix A,
EVM System Schematics.
4.1.1
Input Offset Converter Circuits
The EVM board has two input offset or bias converter circuits. External analog
input to the offset bias circuits is via connectors J7 and J8. These circuits
provide analog input to the AURXFP/AURXM pins of the AIC10/11 U1 and to
the INP/INM input of AIC10/11 U2. Analog inputs to the bias circuits are
single-ended signals. The inputs are converted to a differential signal ranging
from 0 V to AVDD (AV
DD
=3.3 V to 5 V) with the offset centered at VMID. Note
that VMID=AV
DD
/2, and can range from 1.5 V to 2.5 V.
The input offset or bias converter circuits use the TI TLV2462 (U12 and U13).
The TLV2462 is a two-channel, low power, rail-to-rail input/output operational
amplifier designed for single-supply portable applications.
4.1.2
DAA Interface
By connecting jumpers W2 and W3 to position 2–3, and populating jumpers
W35 and W36, the CODEC U1 and U2 can be applied to interface with U11,
the data access arrangement (DAA) chip, for communication with a PSTN via
the standard RJ–11 modular jack J1. Refer to Table 2–5 for jumper
descriptions, and to Figure 2–3 for jumper locations,
Telephone line input is via J1. The INP/INM and OUTP/OUTM of the AIC10/11
CODEC device U1 are connected to RX+/RX– and TX+ and TX–, respectively,
of DAA U11. Device U1 also controls the off-hook (OH) signal of the DAA by
programming the FLAG pin, and detects the DAA ring-detection signal (RING)
through the ALTIN pin. CODEC device U2 controls the DAA Calling-ID (CID)
signal by programming the pin FLAG. The operational amplifier (U18), as a
logic buffer, provides the logic level to be used by the OH and CID pins of the
DAA device.
4.1.3
Microphone Interface
The built-in receiver operational amplifier circuit of AIC10/11 device U2 can be
programmed by the user to interface the device with the microphone input J12
(see Figure 1–1). The common mode of this on-chip circuit is referenced by
VMID to bias or offset the microphone input signal. Figure 4–1 shows the
recommended electret microphone interface to a TLV320AIC10/11 device.
It is important to note that the maximum current that can be drawn from the
VMID output pin is
5 mA. While the circuit in Figure 4–1 illustrates an electret
microphone, other types or models can be used without much trouble.
However, a different value for RP1 will be required.
Summary of Contents for TLV320AIC10 EVM
Page 1: ... January 2001 AAP Data Converters User s Guide SLWU003D ...
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