AD7707BR Analog Devices Inc, AD7707BR Datasheet - Page 26

• Manufacturer Part Number: AD7707BR
• Description: A/D Converter (A-D) IC
• Manufacturer: Analog Devices Inc

Specifications of AD7707BR

• Peak Reflow Compatible (260 C): No
• No. Of Bits: 16 Bit
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Features: 3V/5V, 1mW, 2?Channel, 16?Bit
• Package / Case: 20-SOIC
• Rohs Status: RoHS non-compliant
• Number Of Bits: 16
• Sampling Rate (per Second): 500
• Data Interface: DSP, MICROWIRE™, QSPI™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 1mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD7707
In buffered mode, the analog inputs look into the high impedance
inputs stage of the on-chip buffer amplifier. C
this buffer amplifier such that source impedances do not affect
the charging of C
current of 1 nA. In buffered mode, large source impedances
result in a small dc offset voltage developed across the source
impedance, but not in a gain error.
INPUT SAMPLE RATE
The modulator sample frequency for the AD7707 remains at
f
selected gain. However, gains greater than 1 are achieved by a
combination of multiple input samples per modulator cycle and
a scaling of the ratio of reference capacitor to input capacitor. As
a result of the multiple sampling, the input sample rate of the
device varies with the selected gain (see Table 27). In buffered
mode, the input impedance is constant. In unbuffered mode,
where the analog input looks directly into the sampling capacitor,
the effective input impedance is 1/C
input sampling capacitance and f
CLKIN
/128 (19.2 kHz at f
SAMP
. This buffer amplifier has an offset leakage
CLKIN
= 2.4576 MHz) regardless of the
S
is the input sample rate.
SAMP
× f
S
where C
SAMP
is charged via
SAMP
is the
Rev. B | Page 26 of 52
Table 27. Input Sampling Frequency vs. Gain
Gain
1
2
4
8 to 128
BIPOLAR/UNIPOLAR INPUTS
The analog inputs on the low level input channels on the AD7707
can accept either unipolar or bipolar input voltage ranges with
respect to LOCOM.
The high level input channel handles true bipolar signals of ±10 V
max
Bipolar or unipolar options are chosen by programming the
B /U bit of the setup register. This programs the channel for
either unipolar or bipolar operation. Programming the channel
for either unipolar or bipolar operation does not change any of
the channel conditions, it simply changes the data output coding
and the points on the transfer function where calibrations occur.
In unipolar operation, the output coding is straight binary. In
bipolar mode, the output coding is offset binary.
for guaranteed operation.
Input Sampling Frequency (f
f
2 × f
4 × f
8 × f
CLKIN
/64 (38.4 kHz at f
CLKIN
CLKIN
CLKIN
/64 (76.8 kHz at f
/64 (76.8 kHz at f
/64 (307.2 kHz at f
CLKIN
CLKIN
CLKIN
= 2.4576 MHz)
CLKIN
=2.4576 MHz)
=2.4576 MHz)
= 2.4576 MHz)
S
)