STLC1511

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3.5 Reference Voltages

3.6 Serial Interface

The serial interface on the AFE provides for transmis-

sion of transmit and receive data between the

STLC1511 and digital modem ASIC. This is accom-

plished with a two bit wide data stream in each direc-

tion plus the appropriate clocks. The data for the

transmit path is input to the AFE on the TXSIN[1:0]

pins and the data for the receive path is output on the

RXSOUT[1:0] pins.

The serial interface also consists of a 35.328MHz

clock (CK35M) which is generated in the STLC1510

and is used to retime the Tx data sent to the

STLC1511. It is also used in the STLC1511 to retime

the Rx data before it is sent to the digital chip.

A 4.416MHz pulse is also output from the STLC1511.

This pulse on pin FRMCLK is used to indicate the

start of the output and input data words. The align-

ment of the data to the FRMCLK signal is shown be-

low.

A diagram of this interface is show in Figure 11.

Note the MSB of each of the 8-bit registers is trans-

ferred first (MSB = b15/ b7.)

Note that the data word used by the converters is in

2’s complement notation.

Table 7. Reference Voltages/Currents

Unless otherwise noted, typical specifications apply for VCC = 5.0 V, temperature=25×C, nominal process and bias

and bias current.

Description

min

typ

max

Units

Comments

V3P75V Output voltage

3.6375

3.750

3.8625

Volts

measured at V3P75V

Output Referred Noise Voltage

at ANG

10

measured at V3P75V

TXDADC1 Output voltage

2.425

2.5V

2.575

Volts

measured at TXDADC1

TXDADC1 Output current

50

mA

measured at TXDADC1

External resistor at IREF

49

50

51

kW

assume 2%

External capacitor at V3P75V

0.22

mF

nV

Hz

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