TLFD500PN

3.3 V INTEGRATED G.LITE ANALOG FRONT END

SLAS207B – JUNE 1999 – REVISED MAY 2000

5

POST OFFICE BOX 655303

Terminal Functions (Continued)

TERMINAL

I/O

DESCRIPTION

NAME

NO.

I/O

DESCRIPTION

NC

36,53, 58,

63

No connection. Keep floating.

PLLSEL

42

I

Selects between VCXO mode and DPLL mode. If the pin is tied high PLL mode is selected.

Pin should be tied low for VCXO mode. Cannot be left floating.

PWRDN

17

I

Power-down pin. When PWRDN is pulled low the device goes into power-down mode. The

default state of this pin is low.

REFM

45

O

Negative reference filter node. This terminal is provided for low-pass filtering of the internal

band-gap reference. The optimal ceramic capacitor value is 10

µF (tantalum) and 0.1 µF

(ceramic), connected to analog ground. The nominal dc voltage at this terminal is 0.5 V.

REFP

46

O

Positive reference filter node. This terminal is provided for low-pass filtering of the internal

band-gap reference. The optimal ceramic capacitor value is 10

µF (tantalum) 0.1 µF

(ceramic), connected to analog ground. The nominal dc voltage at this terminal is 2.5 V.

RESET

38

I

Device reset input pin. Initializes all the device’s internal registers to their default values.

The default state of this pin is low.

RXBANDGAP

43

O

RX channel band-gap filter node. This terminal is provided for decoupling of the 1.5-V

band-gap reference. The optimal capacitor value is 10

µF (tantalum) and 0.1 µF (ceramic).

This node should not be used as a voltage source.

RXINP

70

I

RX channel stage 3 positive input. The input is self-biased at AVDD_RX/2.

RXINM

71

I

RX channel stage 3 negative input. The input is self-biased at AVDD_RX/2.

SCLK

19

O

Serial port shift clock (transmit and receive)

SDR

20

I

Serial data receive from DSP

SDX

18

O

Serial data transmit to DSP

TXBANDGAP

14

O

TX channel band-gap filter node. This terminal is provided for decoupling of the 1.5-V

band-gap reference. The optimal capacitor value is 10

µF (tantalum) and 0.1 µF (ceramic).

This node should not be used as a voltage source.

TXOUTP

5

O

TX channel positive output

TXOUTM

6

O

TX channel negative output

VCXOCNTL

13

O

DAC output to control onboard VCXO

VMID_RX

50

I/O

Decoupling Vmid for ADC. Add 10

µF (tantalum) and 0.1 µF (ceramic) capacitors to analog

ground.

VSS

80

I

Substrate. Connect to analog ground.

detailed description

transmit

The transmit channel is powered by a high performance DAC. The transmit channel update rate is 276 kHz.

The DAC is a 14-bit DAC at 4.416-MHz. This provides 16X oversampling. A band-pass filter limits the output

of the transmitter to a frequency range of 30 kHz to 138 kHz. A differential amplifier drives the output into the

external line driver. The differential amplifier has programmable attenuation for added flexibility. The transmitter

high-pass filter can be bypassed by writing the appropriate bit to the filter bypass control register (BCR).

The output spectrum of the DAC complies with the nonoverlapped power spectrum density (PSD) mask

specified in the ITU draft recommendation G.992.2 for G.Lite.

The TXPAA is a programmable-attenuation amplifier. It provides 0 dB to 24 dB of attenuation in1-dB steps. The

TXPAA is controlled via the PAA control register (PCR). For details about register programming see the register

programming section.