2–4

2.2.6

Frame-Sync Function

The frame-sync signal indicates that the device is ready to send and receive data. The data transfer from

DOUT and into DIN begins on the falling edge of the frame-sync signal.

The frame sync is generated internally and goes low on the rising edge of SCLK and remains low during

the 16-bit data transfer.

2.2.7

Multiplexed Analog Input

The two differential analog inputs (INP and INM or AUXP and AUXM) are multiplexed into the sigma-delta

modulator. The performance of the AUX channel is similar to the normal input channel. A simple RC

antialiasing filter must be connected to AUXP and AUXM (also INP and INM when used).

Digital Circuitry

Power Down

PWRDWN

Bit 6 is Programmed

Through a Secondary

Write Operation

Analog Circuitry

Power Down

Clear

(For Control

Reg. 1, Bit 6)

Internal TLC320AD56C

Figure 2–1. Internal Power-Down Logic

2.2.8

Analog Input

The signal applied to the terminals INM and INP (shown in Figure 2–2) should be differential to preserve

the device specifications. A single-ended input signal should always be converted to a differential input

signal prior to being used by the TLC320AD56C (see section 5 Application Information). The signal source

driving the analog inputs (INM, INP, AUXM, AUXP) should have a low source impedance for lowest noise

performance and accuracy. To obtain maximum dynamic range, the input signal should be centered at

midsupply. A simple RC antialiasing filter must be connected to INP and INM (also AUXP and AUXM if used).

2.2.9

Analog Output

The analog output swing across the OUTP and OUTM terminals depends on the value of the resistor used

from the IGAIN terminal to analog ground and the resistor load across the OUTP and OUTM terminals. Both

resistors can be used to set the output voltage swing and then gained to the desired value in the external

DAC output filter as shown in Figure 5–1 and Figure 5–2. With this external filter, the gain of the DAC channel

is –2.5 dB.

The resistor on the IGAIN terminal sets up the output current pumped and the resistor across OUTP and

OUTM is the load which converts the current output of the DAC to a voltage. Hence, the voltage swing across

OUTP and OUTM depends on the ratio of the load resistor to the value of the resistor from the IGAIN terminal

to analog ground. With 0 dB digital code applied to the DAC channel, the IGAIN resistor set at 27 k

Ω, and

a load resistor of 5 k

Ω, the output swing across OUTP and OUTM is –10.5 dB. The ratio of IGAIN resistance

to load resistance can be adjusted to get the desired voltage swing. For the best distortion performance,