85

INPUT VOLTAGE RANGE AND LSB VALUES

Input Voltage Range Defined As:

0V to +10V

0V to +5V

Analog Input Connected to Pin

2

3

Pin Connected to AGND

3

2

One Least Significant Bit (LSB)

2.44mV

1.22mV

OUTPUT TRANSITION VALUES

FFEH TO FFFH

+ FULL SCALE

+10V–3/2LSB

+5V–3/2LSB

+9.963V

+4.9982V

7FFH TO 800H

Mid Scale

4.9988V

2.4994V

000H to 001H

0V

1.22mV

0.6mV

Table 2. Input Voltages, Transition Voltages and LSB Values

FFE

+10V Range Offset and Gain

Offset — Apply 0.0012V to the +10V input at

pin 2. Adjust the offset potentiometer until the

LSB toggles on and off at code 0000 0000

0000

Gain — Apply 9.9963V to the +10V input at pin

2. Adjust the gain potentiometer until the LSB

toggles on and off at code 1111 1111 1110

FFE

Layout Considerations

Because of the high resolution and linearity of the

SP86XX Series, system design problems such as

groundpathresistanceandcontactresistancebecome

very important.

The input resistance of the SP86XX Series is 6.3k

Ω

or 4.2K

Ω (for the 10V and 5V ranges respectively).

connections as shown in Figure 2 should be used.

Calibration Procedure

Apply a precision input voltage source to your

chosen input range (10V range at pin 2 or 5V at

pin 3). Set the A/D to convert continuously.

Monitor the output code. Trim the offset first,

then gain. Use the appropriate input voltages

and output target codes for your chosen input

range as follows. The recommended offset cali-

bration voltage values eliminate interaction be-

tween the offset and gain calibration

+5V Range Offset and Gain

Offset — Apply 0.0006V to the +5V input at pin

3. Adjust the offset potentiometer until the LSB

toggles on and off at code 0000 0000 0000

000

Gain — Apply 4.9982V to the +5V input at pin

3. Adjust the gain potentiometer until the LSB

toggles on and off at code 1111 1111 1110

SP86XX

2

3

4

5

6

7

+10V

Input

GAIN ADJUST

100

Ω

10K

Ω

UNIPOLAR ZERO ADJUST

6.65K

Ω

–15V

+5V

SP86XX

2

3

4

5

6

7

GAIN ADJUST

+5V

Input

+5V

–15V

10K

Ω

30.1K

Ω

301

Ω

Figure 3. a) 10V Range b) 5V Range — With External Trims

a)

b)