AD7870SQ Analog Devices Inc, AD7870SQ Datasheet - Page 13

• Manufacturer Part Number: AD7870SQ
• Description: IC ADC 12BIT SAMPLING 3V 24-CDIP
• Manufacturer: Analog Devices Inc

Specifications of AD7870SQ

• Rohs Status: RoHS non-compliant
• Number Of Bits: 12
• Sampling Rate (per Second): 100k
• Data Interface: Serial, Parallel
• Number Of Converters: 1
• Power Dissipation (max): 95mW
• Voltage Supply Source: Dual ±
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: 24-CDIP (0.300", 7.62mm)

Positive Full-Scale Adjust
Apply a voltage of 2.9978 V (FS/2 − 3/2 LSBs) at V
until the ADC output code flickers between 0111 1111 1110 and
0111 1111 1111.
Negative Full-Scale Adjust
Apply a voltage of −2.9993 V (−FS/2 + 1/2 LSB) at V
R2 until the ADC output code flickers between 1000 0000 0000
and 1000 0000 0001.
OFFSET AND FULL-SCALE ADJUSTMENT—
AD7876
The offset and full-scale adjustment for the AD7876 is similar
to that just outlined for the AD7870. The trim procedure, for
those applications that do require adjustment, is as follows:
apply a voltage of −2.44 mV (−1/2 LSB) at V
amp offset voltage until the ADC output code flickers between
1111 1111 1111 and 0000 0000 0000. Full-scale error can be
adjusted at either the first code transition (ADC negative full
scale) or the last code transition (ADC positive full scale). The
trim procedure for both case is as described in the following
sections (see Figure 13).
1
V
ADDITIONAL PINS OMITTED FOR CLARITY.
1
Figure 13. Offset and Full-Scale Adjust Circuit
10kΩ
500Ω
10kΩ
R1
R2
R3
10kΩ
R5
10kΩ
R4
AGND
V
AD7876
AD7870/
AD7875/
IN
1
and adjust the op
1
1
. Adjust R2
1
and adjust
Rev. C | Page 13 of 28
Positive Full-Scale Adjust
Apply a voltage of 9.9927 V (FS/2 − 3/2 LSBs) at V
until the ADC output code flickers between 0111 1111 1110 and
0111 1111 1111.
Negative Full-Scale Adjust
Apply a voltage of −9.9976 V (FS/2 + 1/2 LSB) at V
R2 until the ADC output code flickers between 1000 0000 0000
and 1000 0000 0001.
OFFSET AND FULL-SCALE ADJUSTMENT—
AD7875
Similar to the AD7870, most of the DSP applications in which
the AD7875 is used do not require offset and full-scale
adjustment. For applications that do require adjustment, offset
error must be adjusted before full-scale (gain) error. This is
achieved by applying an input voltage of 0.61 mV (1/2 LSB) to
V
the ADC output code flickers between 0000 0000 0000 and
0000 0000 0001. For full-scale adjustment, apply an input
voltage of 4.9982 V (FS − 3/2 LSBs) to V
the ADC output code flickers between 1111 1111 1110 and
1111 1111 1111.
1
in Figure 13 and adjusting the op amp offset voltage until
AD7870/AD7875/AD7876
1
and adjust R2 until
1
1
. Adjust R2
and adjust