AD7827 Analog Devices, AD7827 Datasheet

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AD7827

Manufacturer Part Number
AD7827
Description
3/5V, 1 MSPS, 8-Bit, Serial Interface Sampling ADC
Manufacturer
Analog Devices
Datasheet

Specifications of AD7827

Resolution (bits)
8bit
# Chan
1
Sample Rate
1MSPS
Interface
Ser
Analog Input Type
SE-Uni
Ain Range
Uni 2.0V,Uni 2.5V
Adc Architecture
Pipelined
Pkg Type
DIP,SOIC

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a
GENERAL DESCRIPTION
The AD7827 is a high speed, single channel, low power, analog-
to-digital converter with a maximum throughput of 1 MSPS that
operates from a single 3 V or 5 V supply. The AD7827 contains
a track/hold amplifier, an on-chip 2.5 V reference (2% toler-
ance), a 420 ns 8-bit half-flash ADC and a serial interface. The
serial interface is compatible with the serial interfaces of most
DSPs (Digital Signal Processors). The throughput rate of the
AD7827 is dependent on the clock speed of the DSP serial
interface.
The AD7827 combines the Convert Start and Power Down
signals at one pin, i.e., the CONVST pin. This allows a unique
automatic power-down at the end of a conversion to be imple-
mented. The logic level on the CONVST pin is sampled at the
end of a conversion and, depending on its state, the AD7827
powers down.
The AD7827 has one single-ended analog input with an input
span determined by the supply voltage. With a V
input range of the AD7827 is 0 V to 2 V and with V
5 V, the input range is 0 V to 2.5 V.
The parts are available in a small, 8-lead, 0.3" wide, plastic
dual-in-line package (DIP) and an 8-lead, small outline IC
(SOIC).
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
FEATURES
8-Bit Half-Flash ADC with 420 ns Conversion Time
8-Lead Package
On-Chip Track-and-Hold
On-Chip 2.5 V Reference with 2% Tolerance
Operating Supply Range: 3 V
Specifications @ 3 V and 5 V
DSP/Microcontroller Compatible Serial Interface
Automatic Power-Down at End of Conversion
Input Ranges
200 ns Acquisition Time
0 V to 2 V, V
0 V to 2.5 V, V
DD
DD
= 3 V
= 5 V
10% and 5 V
DD
of 3 V, the
DD
10%
equal to
3 V/5 V, 1 MSPS, 8-Bit, Serial Interface
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
PRODUCT HIGHLIGHTS
1. Fast Conversion Time
2. Built-In Track-and-Hold
3. Automatic Power-Down
4. An easy to use, fast serial interface allows direct interfacing to
The AD7827 has a conversion time of 420 ns. Faster conver-
sion times maximize the DSP processing time in a real time
system.
The analog input signal is held and a new conversion is initi-
ated on the falling edge of the CONVST signal. The CONVST
signal allows the sampling instant to be exactly controlled.
This feature is a requirement in many DSP applications.
The CONVST signal is sampled approximately 100 ns after
the end of conversion and depending on its state the AD7827
is powered down.
most popular DSPs with no external circuitry.
V
IN
V
REFIN
/V
REFOUT
T/H
FUNCTIONAL BLOCK DIAGRAM
BUF
2.5V
REF
World Wide Web Site: http://www.analog.com
HALF-FLASH
8-BIT
ADC
V
DD
V
DETECT
COMP
DD
GND
Sampling ADC
© Analog Devices, Inc., 1998
CONTROL
SERIAL
LOGIC
AD7827
PORT
AD7827
SCLK
D
RFS
CONVST
OUT

Related parts for AD7827

AD7827 Summary of contents

Page 1

... The AD7827 has one single-ended analog input with an input span determined by the supply voltage. With a V input range of the AD7827 and with the input range 2.5 V. The parts are available in a small, 8-lead, 0.3" wide, plastic dual-in-line package (DIP) and an 8-lead, small outline IC (SOIC) ...

Page 2

... AD7827–SPECIFICATIONS Parameter DYNAMIC PERFORMANCE Signal-to-(Noise + Distortion) Ratio 1 Total Harmonic Distortion 1 Peak Harmonic or Spurious Noise 1 Intermodulation Distortion 2nd Order Terms 3rd Order Terms DC ACCURACY Resolution 1 Integral Nonlinearity (INL) 1 Differential Nonlinearity (DNL) 1 Offset Error 1 Gain Error Minimum Resolution for Which No Missing Codes are Guaranteed ...

Page 3

... I 200 OUTPUT C PIN L 50pF I 200 A OH –3– Test Conditions/Comments 5 V 10% For Specified Performance 3 V 10% For Specified Performance 8 mA Typically Logic Inputs = Typically 24 mW valid delay. OUT = 5 V 10% and time required for an DD +2.1V AD7827 ...

Page 4

... ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7827 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality ...

Page 5

... The theoretical signal-to-(noise + distortion) ratio for an ideal 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 AD7827 it is defined as ...

Page 6

... V to the proximity of the CONVST and V mended to use decoupling capacitor first connected the AD7827 powers low current mode, i.e., power-down. A rising edge on the CONVST pin will cause the AD7827 to fully power up. For applications where power ...

Page 7

... DD REF REF Figure 6. Transfer Characteristic ANALOG INPUT The AD7827 has a single input channel with an input range 2 2.0 V, depending on the supply voltage (V ). This input range is automatically set on-chip DD “V detector” circuit operation of the ADC is detected ...

Page 8

... CONVST If the power-up time and the conversion time is 330 C), the AD7827 can be said to dissipate 30 mW for 1.33 s (worst case) during each conversion cycle. If the throughput rate is 100 kSPS, the cycle time and the average power dissipated during each cycle is (1.33/10) (30 mW) = 3.99 mW. ...

Page 9

... D OUT REV. 0 Mode 2 Operation (Automatic Power-Down) When the AD7827 is operated in Mode 2 (see Figure 14) it automatically powers down 530 ns after the falling edge of CONVST. The CONVST signal is brought low to initiate a conversion and is left logic low until 530 ns has elapsed after the falling edge of the CONVST pulse, i.e., before Point A or Point B in Figure 14, depending on the actual value of t Characteristics) ...

Page 10

... The D on the falling edge of the eighth SCLK after RFS goes low. The RFS output goes high again on the rising edge of the ninth SCLK. If the AD7827 does not receive a ninth SCLK, the RFS will be reset logic high by the next falling edge of CONVST. t ...

Page 11

... MICROPROCESSOR INTERFACING The Serial Interface on the AD7827 allows the part to be con- nected directly to a range of many different microprocessors and microcontrollers. This section explains how to interface the AD7827 with some of the more common DSP serial interface protocols. AD7827 to TMS320C5x The serial interface on the TMS320C5x uses a continuous serial clock and frame synchronization signals to synchronize the data transfer operations with peripheral devices such as the AD7827 ...

Page 12

... AD7827 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead Plastic DIP (N-8) 0.430 (10.92) 0.348 (8.84 0.280 (7.11) 0.240 (6.10 0.325 (8.25) 0.300 (7.62) 0.060 (1.52) PIN 1 0.015 (0.38) 0.210 (5.33) MAX 0.130 (3.30) 0.160 (4.06) MIN 0.115 (2.93) SEATING 0.022 (0.558) 0.100 0.070 (1.77) PLANE (2.54) 0.014 (0.356) 0.045 (1.15) BSC 8-Lead Small Outline Package (SO-8) 0 ...

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