CS5542 CS5543

14

DS109PP2

pins.

When entering calibration commands via the

DTEST lines, the calibration steps must follow a

specific sequence for the CS5542/CS5543 pair to

be properly calibrated. Figure 4 illustrates the cal-

ibration sequence for the CS5542/CS5543 chip set.

After the RST is issued, the chip set will be in the

normal mode. The first calibration step is the Input

Offset Voltage Cal mode.

The CS5542 is designed to digitize an input cur-

rent. This current is normally sourced from a pho-

todiode at the input of the chip. The Input Offset

Voltage Cal step is intended to remove any offset at

the front end of the modulator. This should be cal-

ibrated with no photodiode current present. If the

phototdiode is replaced with a resistor, the voltage

Table 1. Operation Modes

Notes: 1. MSW = Most Significant Word

2. LSW = Least Significant Word

Table 2. Control Modes

DATSEL[3:0]

DTEST[2:0]

FUNCTION

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

0 0 0

0 0 1

0 1 0

0 1 1

1 0 0

1 0 1

1 1 0

1 1 1

Normal Operation

Input Offset Voltage Cal

Noise Cal

System Offset Cal

Full-Scale Gain Cal (Uses ICAL input)

Full-Scale Gain Cal (Uses INL(INR) input)

Decimator and Modulator Power-Down

Modular Power Down

DTEST[2:0]

DATSEL[3:0]

FUNCTION

DATA TYPE

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0 0

0 0 0 1

0 0 1 0

0 0 1 1

0 1 0 0

0 1 0 1

0 1 1 0

0 1 1 1

1 0 0 0

1 0 0 1

1 0 1 0

1 0 1 1

1 1 X X

Normal Operation

Tri-State Dataout [3:0] Pins

Test Pattern #1

Test Pattern #2

Offset Cal Register Load

Offset Cal Register Load

Gain Cal Register Load

Noise Cal Register Load

Offset Cal Register Read

Offset Cal Register Read

Gain Cal Register Read

Noise Cal Register Read

Reserved

(SIGN, MSB first)

(- - -)

(MSW) (Note 1)

(LSW) (Note 2)

(MSW)

(LSW)

Note: Main Current Input must be idle for all calibration modes except for Gain Cal using INL(INR).

Normal

System

Reset

Input Offset

Voltage

Cal

Noise

Cal

System

Offset

Cal

INR(INL)

or ICAL

Gain Cal

Normal

Figure 4. Calibration Sequence CS5542/CS5543