AD7730BRZ Analog Devices Inc, AD7730BRZ Datasheet - Page 10

• Manufacturer Part Number: AD7730BRZ
• Description: IC ADC BRIDGE TRANSDUCER 24-SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD7730BRZ

• Data Interface: DSP, Serial, SPI™
• Number Of Bits: 24
• Sampling Rate (per Second): 1.2k
• Number Of Converters: 1
• Power Dissipation (max): 125mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Resolution (bits): 24bit
• Sampling Rate: 1.2kSPS
• Input Channel Type: Differential, Single Ended
• Supply Voltage Range - Analog: 4.75V To 5.25V
• Package: 24SOIC W
• Resolution: 24 Bit
• Architecture: Delta-Sigma
• Number Of Adcs: 1
• Number Of Analog Inputs: 2
• Digital Interface Type: Serial (3-Wire, SPI)
• Input Type: Voltage
• Signal To Noise Ratio: 123 dB
• Polarity Of Input Voltage: Unipolar|Bipolar
• Number Of Elements: 1
• Sample Rate: 1.2KSPS
• Input Polarity: Unipolar/Bipolar
• Differential Input: Yes
• Power Supply Requirement: Analog and Digital
• Single Supply Voltage (typ): 5V
• Single Supply Voltage (min): 4.75V
• Single Supply Voltage (max): 5.25V
• Dual Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Power Dissipation: 125mW
• Integral Nonlinearity Error: 18ppm of FSR
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 24
• Package Type: SOIC W
• Input Signal Type: Differential
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7730LEBZ - BOARD EVALUATION FOR AD7730EVAL-AD7730EBZ - BOARD EVAL FOR AD7730
• Lead Free Status / Rohs Status: Compliant

AD7730/AD7730L
OUTPUT NOISE AND RESOLUTION SPECIFICATION
The AD7730 can be programmed to operate in either chop mode or nonchop mode. The chop mode can be enabled in ac-excited or
dc-excited applications; it is optional in dc-excited applications, but chop mode must be enabled in ac-excited applications. These
options are discussed in more detail in later sections. The chop mode has the advantage of lower drift numbers and better noise im-
munity, but the noise is approximately 20% higher for a given –3 dB frequency and output data rate. It is envisaged that the majority
of weigh-scale users of the AD7730 will operate the part in chop mode to avail themselves of the excellent drift performance and
noise immunity when chopping is enabled. The following tables outline the noise performance of the part in both chop and nonchop
modes over all input ranges for a selection of output rates. Settling time refers to the time taken to get an output that is 100% settled
to new value.
Output Noise (CHP = 1)
This mode is the primary mode of operation of the device. Table I shows the output rms noise for some typical output update rates
and –3 dB frequencies for the AD7730 when used in chopping mode (CHP of Filter Register = 1) with a master clock frequency of
4.9152 MHz. These numbers are typical and are generated at a differential analog input voltage of 0 V. The output update rate is
selected via the SF0 to SF11 bits of the Filter Register. Table II, meanwhile, shows the output peak-to-peak resolution in counts for
the same output update rates. The numbers in brackets are the effective peak-to-peak resolution in bits (rounded to the nearest 0.5
LSB). It is important to note that the numbers in Table II represent the resolution for which there will be no code flicker within a
six-sigma limit. They are not calculated based on rms noise, but on peak-to-peak noise.
The numbers are generated for the bipolar input ranges. When the part is operated in unipolar mode, the output noise will be the
same as the equivalent bipolar input range. As a result, the numbers in Table I will remain the same for unipolar ranges while the
numbers in Table II will change. To calculate the numbers for Table II for unipolar input ranges simply divide the peak-to-peak
resolution number in counts by two or subtract one from the peak-to-peak resolution number in bits.
Output
Data Rate Frequency
50 Hz
100 Hz
150 Hz
200 Hz*
400 Hz
*Power-On Default
Output
Data Rate Frequency
50 Hz
100 Hz
150 Hz
200 Hz*
400 Hz
*Power-On Default
Output Noise (CHP = 0)
Table III shows the output rms noise for some typical output update rates and –3 dB frequencies for the AD7730 when used in non-
chopping mode (CHP of Filter Register = 0) with a master clock frequency of 4.9152 MHz. These numbers are typical and are gen-
erated at a differential analog input voltage of 0 V. The output update rate is selected via the SF0 to SF11 bits of the Filter Register.
Table IV, meanwhile, shows the output peak-to-peak resolution in counts for the same output update rates. The numbers in brackets
are the effective peak-to-peak resolution in bits (rounded to the nearest 0.5 LSB). It is important to note that the numbers in Table
IV represent the resolution for which there will be no code flicker within a six-sigma limit. They are not calculated based on rms
noise, but on peak-to-peak noise.
The numbers are generated for the bipolar input ranges. When the part is operated in unipolar mode, the output noise will be the
same as the equivalent bipolar input range. As a result, the numbers in Table III will remain the same for unipolar ranges while the
numbers in Table IV will change. To calculate the number for Table IV for unipolar input ranges simply divide the peak-to-peak
resolution number in counts by two or subtract one from the peak-to-peak resolution number in bits.
–3 dB
1.97 Hz
3.95 Hz
5.92 Hz
7.9 Hz
15.8 Hz
–3 dB
1.97 Hz
3.95 Hz
5.92 Hz
7.9 Hz
15.8 Hz
SF
Word
2048
1024
683
512
256
SF
Word
2048
1024
683
512
256
Table II. Peak-to-Peak Resolution vs. Input Range and Update Rate (CHP = 1)
Table I. Output Noise vs. Input Range and Update Rate (CHP = 1)
Settling Time
Normal Mode
460 ms
230 ms
153 ms
115 ms
57.5 ms
Settling Time
Normal Mode
460 ms
230 ms
153 ms
115 ms
57.5 ms
Peak-to-Peak Resolution in Counts (Bits)
Typical Output RMS Noise in nV
Settling Time
Fast Mode
60 ms
30 ms
20 ms
15 ms
7.5 ms
Settling Time
Fast Mode
60 ms
30 ms
20 ms
15 ms
7.5 ms
–10–
Input Range
= 80 mV
115
155
200
225
335
Input Range
= 80 mV
230k (18)
170k (17.5)
130k (17)
120k (17)
80k (16.5)
Input Range
= 40 mV
75
105
135
145
225
Input Range
= 40 mV
175k (17.5)
125k (17)
100k (16.5)
90k (16.5)
55k (16)
Input Range
= 20 mV
55
75
95
100
160
Input Range
= 20 mV
120k (17)
90k (16.5)
70k (16)
65k (16)
40k (15.5)
Input Range
= 10 mV
40
60
70
80
110
Input Range
= 10 mV
80k (16.5)
55k (16)
45k (15.5)
40k (15.5)
30k (15)
REV. A