AD7823 Analog Devices, AD7823 Datasheet

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AD7823

Manufacturer Part Number
AD7823
Description
2.7 V to 5.5 V, 4.5 ms, 8-Bit ADC in 8-Lead microSOIC/DIP
Manufacturer
Analog Devices
Datasheet

Specifications of AD7823

Resolution (bits)
8bit
# Chan
1
Sample Rate
200kSPS
Interface
Ser
Analog Input Type
Diff-Uni
Ain Range
(Vref) p-p,Uni (Vref)
Adc Architecture
SAR
Pkg Type
DIP,SOIC,SOP

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a
GENERAL DESCRIPTION
The AD7823 is a high speed, low power, 8-bit A/D converter
that operates from a single 2.7 V to 5.5 V supply. The part con-
tains a 4 µs typ successive approximation A/D converter, inherent
track-and-hold functionality (with a pseudo differential input)
and a high speed serial interface that interfaces to most microcon-
trollers. The AD7823 is fully specified over a temperature range
of –40°C to +125°C.
By using a technique that samples the state of the CONVST
(convert start) signal at the end of a conversion, the AD7823
may be used in an automatic power-down mode. When used in
this mode, the AD7823 powers down automatically at the end
of a conversion and “wakes up” at the start of a new conversion.
This feature significantly reduces the power consumption of the
part at lower throughput rates. The AD7823 can also operate in
a high speed mode where the part is not powered down between
conversions. In this high speed mode of operation, the conver-
sion time of the AD7823 is 4 µs typ. The maximum throughput
rate is dependent on the speed of the serial interface of the
microcontroller.
The part is available in a small, 8-lead 0.3" wide, plastic dual-in-
line package (mini-DIP); in an 8-lead, small outline IC (SOIC);
and in an 8-lead microSOIC package.
PRODUCT HIGHLIGHTS
1. Complete, 8-Bit ADC in 8-Lead Package
2. Low Power, Single Supply Operation
3. Automatic Power-Down
4. Serial Interface
The AD7823 is an 8-bit 4 µs typ ADC with inherent track-
and-hold functionality and a high speed serial interface—all
in an 8-lead microSOIC package. V
V
is a high speed, low power, space saving ADC solution.
The AD7823 operates from a single 2.7 V to 5.5 V supply and
typically consumes only 9 mW of power. The power dissipa-
tion can be significantly reduced at lower throughput rates by
using the automatic power-down mode, e.g., at a throughput
rate of 10 kSPS the power consumption is only 570 µW.
The automatic power-down mode, whereby the AD7823
“powers down” at the end of a conversion and “wakes up”
before the next conversion, means the AD7823 is ideal for
battery powered applications. See Power vs. Throughput
Rate section.
An easy to use, fast serial interface allows connection to most
popular microprocessors with no external circuitry.
ADC in 8-Lead microSOIC/DIP
DD
V
V
IN+
IN–
to eliminate the need for an external reference. The result
AD7823
2.7 V to 5.5 V, 5 s, 8-Bit
FUNCTIONAL BLOCK DIAGRAM
V
DD
AGND
V
DD
/3
REDISTRIBUTION
CHARGE
V
DAC
COMP
REF
CLOCK
OSC
REF
CONTROL
CONVST
SERIAL
may be connected to
LOGIC
PORT
AD7823
D
SCLK
OUT

Related parts for AD7823

AD7823 Summary of contents

Page 1

... high speed, low power, space saving ADC solution. 2. Low Power, Single Supply Operation The AD7823 operates from a single 2 5.5 V supply and typically consumes only power. The power dissipa- tion can be significantly reduced at lower throughput rates by using the automatic power-down mode, e.g throughput rate of 10 kSPS the power consumption is only 570 µ ...

Page 2

... AD7823–SPECIFICATIONS Parameter DYNAMIC PERFORMANCE 1, 2 Signal to (Noise + Distortion) Ratio 1 Total Harmonic Distortion 1 Peak Harmonic or Spurious Noise 2 Intermodulation Distortion 2nd Order Terms 3rd Order Terms DC ACCURACY Resolution 1 Relative Accuracy 1 Differential Nonlinearity (DNL) 1 Gain Error 1 Offset Error 1 Total Unadjusted Error Minimum Resolution for Which ...

Page 3

... LSB –40°C to +125°C ± 1 LSB –40°C to +125° 200mA TO OUTPUT PIN C L 50pF I OH 200 A AD7823 Data Valid Delay OUT = 5 V ± 10% and the true bus relinquish time 8 Branding Package Information Option N-8 SO-8 C2Y RM-8 1.6V ...

Page 4

... Convert Start. Falling edge puts the track-and-hold into hold mode and initiates a conversion. A rising edge on the CONVST pin enables the serial port of the AD7823. This is useful in multipackage applications where a number of devices share the same serial bus. The state of this pin at the end of conversion also determines whether the part is powered down or not. ...

Page 5

... N-bit converter with a sine wave input is given by: Signal to (Noise + Distortion) = (6.02N + 1.76) dB Thus for an 8-bit converter, this is 50 dB. Total Harmonic Distortion Total harmonic distortion (THD) is the ratio of the rms sum of harmonics to the fundamental. For the AD7823 it is defined as ...

Page 6

... V IN+ CHARGE REDISTRIBUTION DAC CONTROL LOGIC The analog input of the AD7823 is made pseudo dif- ferential pair, V CLOCK OSC signal is applied to V the sampling capacitor is connected to V see Figure 8. This input scheme can be used to remove offsets that exist in a system. For example system had an offset of ...

Page 7

... ADC TRANSFER FUNCTION The output coding of the AD7823 is straight binary. The designed code transitions occur at successive integer LSB values (i.e., 1 LSB, 2 LSBs, etc.). The LSB size fer characteristic for the AD7823 is shown in Figure 11 below. 111...111 111...110 111...000 011...111 000 ...

Page 8

... V. If the power-up time is 1.5 µs operation is 10.5 mW and the conversion time is 5 µs, then the AD7823 can be said to dissipate 10.5 mW for 6.5 µs (worst case) during each conver- sion cycle. If the throughput rate is 10 kSPS, the cycle time is 100 µs, and the average power dissipated during each cycle is (6.5/100) × ...

Page 9

... CONVST signal low until the end of the conversion. The timing diagram in Figure 15 shows how to operate the part in this mode. If the AD7823 is powered down, the rising edge of the CONVST pulse causes the part to power up. When the part has powered up (≈ 1.5 µs after the rising edge of CONVST), the CONVST signal is brought low, and a conversion is initiated on this falling edge of the CONVST signal ...

Page 10

... AD7823 MICROPROCESSOR INTERFACING The serial interface on the AD7823 allows the parts to be directly connected to a range of many different microprocessors. This section explains how to interface the AD7823 with some of the more common microcontroller serial interface protocols. AD7823 to PIC16C6x/7x The PIC16C6x Synchronous Serial Port (SSP) is configured as an SPI Master with the Clock Polarity Bit = 0 ...

Page 11

... PIN 1 0.0256 (0.65) BSC 0.120 (3.05) 0.112 (2.84) 0.043 (1.09) 0.006 (0.15) 0.037 (0.94) 0.002 (0.05) 0.018 (0.46) SEATING 0.011 (0.28) 0.008 (0.20) PLANE 0.003 (0.08) AD7823 0.195 (4.95) 0.115 (2.93) 0.015 (0.381) 0.008 (0.204) 0.0196 (0.50 0.0099 (0.25) 0.0500 (1.27) 0.0160 (0.41) 0.120 (3.05) 0.112 (2.84 0.028 (0.71) 0.016 (0.41) ...

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