AD7870JNZ Analog Devices Inc, AD7870JNZ Datasheet - Page 16

• Manufacturer Part Number: AD7870JNZ
• Description: IC ADC 12BIT LC2MOS 100KHZ 24DIP
• Manufacturer: Analog Devices Inc

Specifications of AD7870JNZ

• Data Interface: Serial, Parallel
• Number Of Bits: 12
• Sampling Rate (per Second): 100k
• Number Of Converters: 1
• Power Dissipation (max): 95mW
• Voltage Supply Source: Dual ±
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 24-DIP (0.300", 7.62mm)
• Resolution (bits): 12bit
• Sampling Rate: 100kSPS
• Input Channel Type: Single Ended
• Supply Voltage Range - Analog: ± 4.75V To ± 5.25V
• Supply Current: 8mA
• Number Of Elements: 1
• Resolution: 12Bit
• Architecture: SAR
• Sample Rate: 100KSPS
• Input Polarity: Bipolar
• Input Type: Voltage
• Rated Input Volt: ±3V
• Differential Input: No
• Power Supply Requirement: Dual
• Single Supply Voltage (typ): Not RequiredV
• Single Supply Voltage (min): Not RequiredV
• Single Supply Voltage (max): Not RequiredV
• Dual Supply Voltage (typ): ±5V
• Dual Supply Voltage (min): ±4.75V
• Dual Supply Voltage (max): ±5.25V
• Power Dissipation: 95mW
• Integral Nonlinearity Error: ±0.5LSB(Typ)
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Through Hole
• Pin Count: 24
• Package Type: PDIP
• Input Signal Type: Single-Ended
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

AD7870/AD7875/AD7876
The Mode 2 timing diagram for byte and serial data is shown in
Figure 17. For a two-byte data read, the lower byte (DB0 – DB7)
has to be accessed first since HBEN must be low to start conver-
sion. The ADC behaves like slow memory for this first read,
but the second read to access the upper byte of data is a normal
read. Operation of the serial functions is identical between
Mode 1 and Mode 2. The timing diagram of Figure 17 shows
both a noncontinuously and a continuously running SCLK
(dashed line).
DYNAMIC SPECIFICATIONS
The AD7870 and AD7875 are specified and 100% tested for
dynamic performance specifications as well as traditional dc
specifications such as integral and differential nonlinearity.
Although the AD7876 is not production tested for ac
parameters, its dynamic performance is similar to the AD7870
and AD7875. The ac specifications are required for signal
processing applications such as speech recognition, spectrum
analysis and high speed modems. These applications require
information on the ADC’s effect on the spectral content of the
SSTRB
1
2
3
SDATA
TIMES
EXTERNAL 4.7kΩ PULL-UP RESISTOR.
EXTERNAL 2kΩ PULL-UP RESISTOR;
HBEN
SCLK
BUSY
CONTINUOUS SCLK (DASHED LINE) WHEN 12/8/CLK = –5V;
NONCONTINUOUS WHEN 12/8/CLK = 0V.
DATA
CS
RD
2
3
2
1
t
15
,
t
t
15
16
, AND
t
19
THREE-STATE
BUSY
DATA
t
t
16
20
CS
RD
TRACK-AND-HOLD
GOES INTO HOLD
t
ARE THE SAME FOR A HIGH BYTE READ AS FOR A LOW BYTE READ.
10
t
15
LEADING
ZEROS
t
t
TRACK-AND-HOLD RETURNS TO TRACK
11
16
Figure 16. Mode 2 Timing Diagram, 12-Bit Parallel Read
Figure 17. Mode 2 Timing Diagram, Byte or Serial Read
TRACK-AND-HOLD
GOES INTO HOLD
t
12
THREE-STATE
AND ACQUISITION TIME BEGINS
t
DB11 DB10
CONVERT
TRACK-AND-HOLD RETURNS TO TRACK
SERIAL DATA
AND ACQUISITION TIME BEGINS
Rev. C | Page 16 of 28
t
CONVERT
t
DB0
2
t
8
input signal. Thus, the parameters for which the AD7870 and
AD7875 are specified include SNR, harmonic distortion,
intermodulation distortion and peak harmonics. These terms
are discussed in more detail in the following sections.
Signal-to-Noise Ratio (SNR)
SNR is the measured signal-to-noise ratio at the output of the
ADC. The signal is the rms magnitude of the fundamental.
Noise is the rms sum of all the nonfundamental signals up
to half the sampling frequency (FS/2) excluding dc. SNR is
dependent upon the number of quantization levels used in
the digitization process; the more levels, the smaller the
quantization noise. The theoretical signal-to-noise ratio for
a sine wave input is given by
where N is the number of bits. Thus for an ideal 12-bit
converter, SNR = 74 dB.
Note that a sine wave signal is of very low distortion to the V
input which is sampled at a 100 kHz sampling rate. A fast
t
t
14
17
t
DB7 TO DB0
13
SNR = (6.02N + 1.76) dB
VALID
DATA
t
7
t
17
DB11 TO DB0
t
18
VALID
DATA
t
20
t
7
t
18
t
6
DB11 TO DB8
t
6
VALID
DATA
t
7
IN
(1)