View AD7828CQ_1068180.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

a
FEATURES 4 or 8 Analog Input Channels Built-In Track-and-Hold Function 10 kHz Signal Handling on Each Channel Fast Microprocessor Interface Single 5 V Supply Low Power: 50 mW Fast Conversion Rate: 2.5 s/Channel Tight Error Specification: 1/2 LSB
LC2MOS High Speed 4- and 8-Channel 8-Bit ADCs AD7824/AD7828
FUNCTIONAL BLOCK DIAGRAM
VREF (+) VREF (-) AIN1 AIN4 4-BIT FLASH ADC (4MSB) 4-BIT DAC VREF (+) 16 4-BIT FLASH ADC (4LSB) TIMING AND CONTROL CIRCUITRY RDY CS RD THREESTATE DRIVERS DB3 DB2 DB1 DB0 INT DB7 DB6 DB5 DB4
MUX*
AIN8
ADDRESS LATCH DECODE A0 A1 A2** *AD7824 - 4-CHANNEL MUX **AD7828 - 8-CHANNEL MUX A2 - AD7828 ONLY
GENERAL DESCRIPTION
PRODUCT HIGHLIGHTS
The AD7824 and AD7828 are high speed, multichannel, 8-bit ADCs with a choice of four (AD7824) or eight (AD7828) multiplexed analog inputs. A half-flash conversion technique gives a fast conversion rate of 2.5 s per channel, and the parts have a built-in track-and-hold function capable of digitizing full-scale signals of 10 kHz (157 mV/s slew rate) on all channels. The AD7824 and AD7828 operate from a single 5 V supply and have an analog input range of 0 V to 5 V, using an external 5 V reference. Microprocessor interfacing of the parts is simple, using standard Chip Select (CS) and Read (RD) signals to initiate the conversion and read the data from the three-state data outputs. The half-flash conversion technique means that there is no need to generate a clock signal for the ADC. The AD7824 and AD7828 can be interfaced easily to most popular microprocessors. The AD7824 and AD7828 are fabricated in an advanced, all ion-implanted, linear compatible CMOS process (LC2MOS) and have low power dissipation of 40 mW (typ). The AD7824 is available in a 0.3" wide, 24-lead "skinny" DIP, while the AD7828 is available in a 0.6" wide, 28-lead DIP and in 28-terminal surfacemount packages.
1. 4- or 8-channel input multiplexer gives cost effective, space-saving multichannel ADC system. 2. Fast conversion rate of 2.5 s/channel features a per-channel sampling frequency of 100 kHz for the AD7824 or 50 kHz for the AD7828. 3. Built-in track-and-hold function allows handling of four or eight channels up to 10 kHz bandwidth (157 mV/s slew rate). 4. Tight total unadjusted error spec and channel-to-channel matching eliminate the need for user trims. 5. Single 5 V supply simplifies system power requirements. 6. Fast, easy-to-use digital interface allows connection to most popular microprocessors with minimal external components. No clock signal is required for the ADC.
REV. F
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 that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/326-8703 (c) 2003 Analog Devices, Inc. All rights reserved.
= V AD7824/AD7828-SPECIFICATIONS (Vapply5toV,Mode(+) = 5 V, V noted. All specifications T to T , unless otherwise noted. Specifications 0.)
DD REF MIN MAX
REF
(-) = GND = O V, unless otherwise
Conditions/Comments
Parameter ACCURACY Resolution Total Unadjusted Error2 Minimum Resolution for which No Missing Codes Are Guaranteed Channel-to-Channel Mismatch REFERENCE INPUT Input Resistance VREF (+) Input Voltage Range VREF (-) Input Voltage Range ANALOG INPUT Input Voltage Range Input Leakage Current Input Capacitance3 LOGIC INPUTS RD, CS, A0, A1, and A2 VINH VINL IINH IINL Input Capacitance3 LOGIC OUTPUTS DB0-DB7 and INT VOH VOL IOUT (DB0-DB7) Output Capacitance3 RDY VOL4 IOUT Output Capacitance SLEW RATE, TRACKING3 POWER SUPPLY VDD IDD5 Power Dissipation Power Supply Sensitivity
NOTES 1 Temperature ranges are as follows:
K Version1 L Version B, T Versions 8 1 8 1/4 1.0/4.0 VREF (-)/ VDD GND/ VREF (+) VREF (-)/ VREF (+) 3 45 8 1/2 8 1/4 1.0/4.0 VREF (-)/ VDD GND/ VREF (+) VREF (-)/ VREF (+) 3 45 8 1 8 1/4 1.0/4.0 VREF (-)/ VDD GND/ VREF (+) VREF (-)/ VREF (+) 3 45
C, U Versions Unit 8 1/2 8 1/4 1.0/4.0 VREF (-)/ VDD GND/ VREF (+) VREF (-)/ VREF (+) 3 45 Bits LSB max Bits LSB max k min/k max V min/V max V min/V max
V min/V max A max pF typ Analog Input Any Channel 0 V to 5 V
2.4 0.8 1 -1 8
2.4 0.8 1 -1 8
2.4 0.8 1 -1 8
2.4 0.8 1 -1 8
V min V max A max A max pF max
Typically 5 pF
4.0 0.4 3 8 0.4 3 8 0.7 0.157 5 16 50 80 1/4
4.0 0.4 3 8 0.4 3 8 0.7 0.157 5 16 50 80 1/4
4.0 0.4 3 8 0.4 3 8 0.7 0.157 5 20 50 100 1/4
4.0 0.4 3 8 0.4 3 8 0.7 0.157 5 20 50 100 1/4
V min V max A max pF max V max A max pF max V/s typ V/s max V mA max mW typ mW max LSB max
ISOURCE = 360 A ISINK = 1.6 mA Floating State Leakage Typically 5 pF ISINK = 2.6 mA Floating State Leakage Typically 5 pF
5% for Specified Performance CS = RD = 2.4 V 1/16 LSB typ VDD = 5 V 5%
K, L Versions: 0C to 70C B, C Versions: -40C to +85C T, U Versions: -55C to +125C 2 Total Unadjusted Error includes offset, full-scale and linearity errors. 3 Sample tested at 25C by Product Assurance to ensure compliance. 4 RDY is an open-drain output. 5 See Typical Performance Characteristics. Specifications subject to change without notice.
-2-
REV. F
AD7824/AD7828 TIMING CHARACTERISTICS1 (V
Parameter tCSS tCSH tAS tAH tRDY2 tCRD tACC13 tACC23 tlNTH2 tDH4 tP tRD Limit at 25 C (All Grades) 0 0 0 30 40 2.0 85 50 40 75 60 500 60 600 0 0 0 35 60 2.4 110 60 65 100 70 500 80 500
DD
= 5 V; VREF(+) = 5 V; VREF(-) = GND = 0 V, unless otherwise noted.)
Limit at TMIN, TMAX (T, U Grades) 0 0 0 40 60 2.8 120 70 70 100 70 600 80 400 Unit ns min ns min ns min ns min ns max s max ns max ns max ns typ ns max ns max ns min ns min ns max Conditions/Comments CS to RD Setup Time CS to RD Hold Time Multiplexer Address Setup Time Multiplexer Address Hold Time CS to RDY Delay. Pull-Up Resistor 5 k. Conversion Time, Mode 0 Data Access Time after RD Data Access Time after INT, Mode 0 RD to INT Delay Data Hold Time Delay Time between Conversions Read Pulsewidth, Mode 1
Limit at TMIN, TMAX (K, L, B, C Grades)
NOTES 1 Sample tested at 25C to ensure compliance. All input control signals are specified with t RISE = tFALL = 20 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V. 2 CL = 50 pF. 3 Measured with load circuits of Figure 1 and defined as the time required for an output to cross 0.8 V or 2.4 V. 4 Defined as the time required for the data lines to change 0.5 V when loaded with the circuits of Figure 2. Specifications subject to change without notice.
Test Circuits
DBN 3k DGND 100pF DBN 3k DGND 10pF
a. High-Z to VOH
a. VOH to High-Z
5V 3k DBN 100pF DGND DBN
5V 3k
10pF DGND
b. High-Z to VOL Figure 1. Load Circuits for Data Access Time Test
b. VOL to High-Z Figure 2. Load Circuits for Data Hold Time Test
REV. F
-3-
AD7824/AD7828
ABSOLUTE MAXIMUM RATINGS*
(TA = 25C, unless otherwise noted.)
VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V, 7 V Digital Input Voltage to GND (RD, CS, A0, A1, and A2) . . . . . . . . . -0.3 V, VDD + 0.3 V Digital Output Voltage to GND (DB0, DB7, RDY, and INT) . . . . . . . -0.3 V, VDD + 0.3 V VREF (+) to GND . . . . . . . . . . . . . . . . . VREF (-), VDD + 0.3 V VREF (-) to GND . . . . . . . . . . . . . . . . . . . . . . . . 0 V, VREF (+) Analog Input (Any Channel) . . . . . . . . . . -0.3 V, VDD + 0.3 V
Operating Temperature Range Commercial (K, L Versions) . . . . . . . . . . . . . . 0C to 70C Industrial (B, C Versions) . . . . . . . . . . . . . -40C to +85C Extended (T, U Versions) . . . . . . . . . . . . -55C to +125C Storage Temperature Range . . . . . . . . . . . . -65C to +150C Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . . 300C Power Dissipation (Any Package) to 75C . . . . . . . . . 450 mW Derates above 75C by . . . . . . . . . . . . . . . . . . . . . . 6 mW/C
*Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
CAUTION 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 AD7824/AD7828 feature 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.
WARNING!
ESD SENSITIVE DEVICE
PIN CONFIGURATIONS DIP/SOIC/SSOP
AIN4 AIN3 AIN2 AIN1 NC DB0 DB1 DB2 DB3
1 2 3 4 5 6 24 23 22 21
ORDERING GUIDE
VDD NC A0 A1 DB7
AIN6 1 AIN5
2
28 27 26 25 24
AIN7 AIN8 VDD A0 A1 A2
Model AD7824KN AD7824LN AD7824KR AD7824BQ AD7824CQ AD7824TQ* AD7824UQ* AD7828KN AD7828LN AD7828KP AD7828LP AD7828BQ AD7828CQ AD7828BR AD7828LRS AD7828TQ* AD7828UQ* AD7828TE* AD7828UE*
Temperature Range 0C to 70C 0C to 70C 0C to 70C -40C to +85C -40C to +85C -55C to +125C -55C to +125C 0C to 70C 0C to 70C 0C to 70C 0C to 70C -40C to +85C -40C to +85C -40C to +85C 0C to 70C -55C to +125C -55C to +125C -55C to +125C -55C to +125C
Total Unadjusted Package Error (LSBs) Option 1 1/2 1 1 1/2 1 1/2 1 1/2 1 1/2 1 1/2 +1 1/2 1 1/2 1 1/2 N-24 N-24 R-24 Q-24 Q-24 Q-24 Q-24 N-28 N-28 P-28A P-28A Q-28 Q-28 R-28 RS-28 Q-28 Q-28 E-28A E-28A
AIN4 3 AIN3 4 AIN2 5 AIN1 6 NC 7
AD7824
20
TOP VIEW 19 DB6 (Not to Scale) 18 DB5 7
8 9 17 16 15 14 13
AD7828
23
DB4 CS RDY VREF (+) VREF (-)
TOP VIEW 22 DB7 DB0 8 (Not to Scale) 21 DB6 DB1 9 DB2 10 DB3 11 RD 12 INT 13 GND 14
20 19 18 17 16 15
DB5 DB4 CS RDY VREF (+) VREF (-)
RD 10 INT 11 GND 12
NC = NO CONNECT
NC = NO CONNECT
PLCC
AIN3 AIN4 AIN5 AIN6 AIN7 AIN8 VDD
25 A0 24 A1
4
3
2
1
28 27 26 PIN 1 IDENTIFIER
AIN2 5 AIN1 6 NC 7 DB0 8 DB1 9 DB2 10 DB3 11
12 13 14 15
AD7828
TOP VIEW
(Not to Scale)
23 A2 22 DB7 21 DB6 20 DB5
*Available to /883B processing only. Contact our local sales office for military data sheet. For U.S. Standard Military Drawing (SMD) see DESC Drawing #5692-88764.
LCCC
AIN3 AIN4 AIN5 AIN6 AIN7 AIN8
4 3 2 1 28 27 26
19 DB4 16 17 18
VREF (-)
VREF (+)
INT
GND
RD
RDY
CS
VDD
AIN2 5 AIN1 6 NC 7
25 24
A0 A1 A2 DB7 DB6 DB5 DB4
NC = NO CONNECT
AD7828
TOP VIEW (Not to Scale)
23 22 21 20 19
DB0 8 DB1 9 DB2 10 DB3 11
12 13 14 15 16 17 18
VREF (-)
VREF (+)
INT
GND
RD
NC = NO CONNECT
RDY
CS
-4-
REV. F
Typical Performance Characteristics-AD7824/AD7828
3 14
tCRD - CONVERSION TIME - s
13
IDD - SUPPLY CURRENT - mA
12 VDD = 5V 11 VDD = 5.25V
2
10
VDD = 5V
9 VDD = 4.75V 1 -100 8 -100
-50 0 50 100 TA - AMBIENT TEMPERATURE - C
150
-50 0 50 100 TA - AMBIENT TEMPERATURE - C
150
TPC 1. Conversion Time vs. Temperature
TPC 4. Power Supply Current vs. Temperature (Not Including Reference Ladder)
2.0 VDD = 5V TA = 25 C
2.0 VDD = 5V VREF = 5V TA = 25 C
LINEARITY ERROR - LSB*
1.0
LINEARITY ERROR - LSB
0 VREF 256 1 2 VREF - V 3 4 5
1.5
1.5
1.0
0.5
0.5
0
0 300
400
500
600
700
800
900
*1LSB =
tP - ns
TPC 2. Accuracy vs. VREF [VREF = VREF (+) - VREF (-)]
TPC 5. Accuracy vs. tP
-36 -38 -40 -42 SNR - dB -44 -46 -48 -50 -52 ENCODE RATE = 400kHz INPUT SIGNAL = 5V p-p MEASUREMENT BANDWIDTH = 80kHz
10 VDD = 5V 8
OUTPUT CURRENT - mA
ISOURCE, V OUT = 2.4V 6
4 ISINK, V OUT = 0.4V 2
1
2
3
45 7 10 20 30 40 50 70 INPUT FREQUENCY - kHz
100
0 -100
-50 0 50 100 TA - AMBIENT TEMPERATURE - C
150
TPC 3. Signal Noise Ratio vs. Input Frequency
TPC 6. Output Current vs. Temperature
REV. F
-5-
AD7824/AD7828
OPERATIONAL DIAGRAM
The AD7824 is a 4-channel 8-bit ADC and the AD7828 is an 8-channel 8-bit ADC. Operational diagrams for both of these devices are shown in Figures 3 and 4. The addition of just a 5 V reference allows the devices to perform the analog-to-digital function.
1 AIN4
APPLYING THE AD7824/AD7828 REFERENCE AND INPUT
VDD 24 NC 23 A0 22
5V
ANALOG INPUTS 0V TO 5V
2 AIN3 3 AIN2 4 AIN1 5 NC 6 DB0
The two reference inputs on the AD7824/AD7828 are fully differential and define the zero to full-scale input range of the ADC. As a result, the span of the analog input voltage for all channels can easily be varied. By reducing the reference span, VREF (+) to VREF (-), to less than 5 V, the sensitivity of the converter can be increased (e.g., if VREF = 2 V then 1 LSB = 7.8 mV). The input/ reference arrangement also facilitates ratiometric operation. This reference flexibility also allows the input channel voltage span to be offset from zero. The voltage at VREF (-) sets the input level for all channels, which produces a digital output of all zeroes. Therefore, although the analog inputs are not themselves differential, they have nearly differential input capability in most measurement applications because of the reference design. Figures 5 to 7 show some of the configurations that are possible.
VIN (+) VIN (-) 5V 0.1 F 47 F AIN1 GND AD7824*
AD7824
A1 21 DB7 20 DB6 19 DB5 18 DB4 17 CS 16 RDY 15
P ADDRESS BUS
P 4LSB DATA BUS
7 DB1 8 DB2 9 DB3
P 4MSB DATA BUS
P CONTROL INPUT STATUS OUTPUT 5V
P CONTROL INPUT STATUS OUTPUT
10 RD 11 INT 12 GND
VREF (+) 14 VREF (-) 13
NC = NO CONNECT
Figure 3. AD7824 Operational Diagram
1 2
AD7828*
VDD VREF (+) VREF (-)
AIN6 AIN5 AIN4 AIN3 AIN2 AIN1 NC DB0 DB1 DB2 DB3 RD INT GND
AIN7 28 AIN8 27 VDD 26 A0 25 A1 24
ANALOG INPUTS 0V TO 5V 5V P ADDRESS BUS
ANALOG INPUTS 0V TO 5V
3 4 5 6 7 8
*ADDITIONAL PINS OMITTED FOR CLARITY. ONLY CHANNEL 1 SHOWN.
AD7828
A2 23 DB7 22 DB6 21 DB5 20 DB4 19 CS 18 RDY 17 P CONTROL INPUT STATUS OUTPUT 5V P 4MSB DATA BUS
Figure 5. Power Supply as Reference
VIN (+) VIN (-) 5V 0.1 F 47 F AD580 10 F 0.1 F VREF (-) AIN1 GND AD7824*
P 4LSB DATA BUS
9 10 11
AD7828*
VDD VREF (+)
P CONTROL INPUT STATUS OUTPUT
12 13 14
VREF (+) 16 VREF (-) 15
NC = NO CONNECT
Figure 4. AD7828 Operational Diagram
CIRCUIT INFORMATION BASIC DESCRIPTION
*ADDITIONAL PINS OMITTED FOR CLARITY. ONLY CHANNEL 1 SHOWN.
Figure 6. External Reference Using the AD580, Full-Scale Input is 2.5 V
VIN (+) AIN1 GND AD7824*
The AD7824/AD7828 uses a half-flash conversion technique whereby two 4-bit flash ADCs are used to achieve an 8-bit result. Each 4-bit flash ADC contains 15 comparators that compare the unknown input to a reference ladder to get a 4-bit result. For a full 8-bit reading to be realized, the upper 4-bit flash, the most significant (MS) flash, performs a conversion to provide the four most significant data bits. An internal DAC, driven by the four MSBs, then recreates an analog approximation of the input voltage. This analog result is subtracted from the input, and the difference is converted by the lower flash ADC, the least significant (LS) flash, to provide the four least significant bits of the output data. The most significant flash ADC also has one additional comparator to detect overrange on the analog input.
AD7828*
5V 0.1 F 47 F V1 V2 VDD DB7 VREF (+) VREF (-) DB0 DATA
*ADDITIONAL PINS OMITTED FOR CLARITY. ONLY CHANNEL 1 SHOWN. DATA = VIN (+) V1 - V2 256 (FOR ALL CHANNELS)
Figure 7. Input Not Referenced to GND
-6-
REV. F
AD7824/AD7828
INPUT CURRENT
Due to the novel conversion techniques employed by the AD7824/ AD7828, the analog input behaves somewhat differently than in conventional devices. The ADC's sampled-data comparators take varying amounts of input current depending on which cycle the conversion is in. The equivalent input circuit of the AD7824/AD7828 is shown in Figure 8. When a conversion starts (CS and RD going low), all input switches close, and the selected input channel is connected to the most significant and least significant comparators. Therefore, the analog input is simultaneously connected to 31 input capacitors of 1 pF each.
interest. It is important that the amplifier driving the AD7824/ AD7828 analog inputs have sufficient loop gain at the input signal frequency as to make the output impedance low. Suitable op amps for driving the AD7824/AD7828 are the AD544 or AD644.
INHERENT SAMPLE-HOLD
CS 2pF RS VIN AIN1 R MUX CS 12pF RON TO LS LADDER 1pF * * *
1pF
15LSB COMPARATORS
RON
1pF * * *
A major benefit of the AD7824's and AD7828's analog input structure is its ability to measure a variety of high speed signals without the help of an external sample-and-hold. In a conventional SAR type converter, regardless of its speed, the input must remain stable to at least 1/2 LSB throughout the conversion process if rated accuracy is to be maintained. Consequently, for many high speed signals, this signal must be externally sampled and held stationary during the conversion. The AD7824/AD7828 input comparators, by nature of their input switching, inherently accomplish this sample-and-hold function. Although the conversion time for AD7824/AD7828 is 2 s, the time for which any selected analog input must be 1/2 LSB stable is much smaller. The AD7824/AD7828 tracks the selected input channel for approximately 1 s after conversion start. The value of the analog input at that instant (1 s from conversion start) is the measured value. This value is then used in the least significant flash to generate the lower four bits of data.
SINUSOIDAL INPUTS
AD7824/ AD7828
TO MS LADDER
1pF
16MSB COMPARATORS
Figure 8. AD7824/AD7828 Equivalent Input Circuit
The input capacitors must charge to the input voltage through the on resistance of the analog switches (about 3 k to 6 k). In addition, about 14 pF of input stray capacitance must be charged. The analog input for any channel can be modelled as an RC network, as shown in Figure 9. As RS increases, it takes longer for the input capacitance to charge.
The AD7824/AD7828 can measure input signals with slew rates as high as 157 mV/s to the rated specifications. This means that the analog input frequency can be up to 10 kHz without the aid of an external sample-and-hold. Furthermore, the AD7828 can measure eight 10 kHz signals without a sample-and-hold. The Nyquist criterion requires that the sampling rate be twice the input frequency (i.e., 2 x 10 kHz). This requires an ideal antialiasing filter with an infinite roll-off. To ease the problem of antialiasing filter design, the sampling rate is usually much greater than the Nyquist criterion. The maximum sampling rate (FMAX) for the AD7824/AD7828 can be calculated as follows:
FMAX = 1 tCRD + t P
RS VIN
AIN1
R MUX 800 CS1 12pF
RON 350 CS2 2pF 31pF
FMAX =
1 = 400 kHz 2E - 6 + 0.5E - 6
Figure 9. RC Network Model
tCRD = AD7824/AD7828 Conversion Time tP = Minimum Delay Between Conversion This permits a maximum sampling rate of 50 kHz for each of the eight channels when using the AD7828 and 100 kHz for each of the four channels when using the AD7824.
The time for which the input comparators track the analog input is approximately 1 s at the start of conversion. Because of input transients on the analog inputs, it is recommended that a source impedance no greater than 100 be connected to the analog inputs. The output impedance of an op amp is equal to the open loop output impedance divided by the loop gain at the frequency of
REV. F
-7-
AD7824/AD7828
UNIPOLAR OPERATION
25k VIN 5V 40k 27k 12k 5V 0.1 F 47 F AD544 AIN1
The analog input range for any channel of the AD7824/AD7828 is 0 V to 5 V as shown in the unipolar operational diagram of Figure 10. Figure 11 shows the designed code transitions that occur midway between successive integer LSB values (i.e., 1/2 LSB, 3/2 LSB, 5/2 LSB, FS 3/2 LSBs). The output code is natural binary with 1 LSB = FS/256 = (5/256) V = 19.5 mV.
5V 0.1 F 47 F V REF 5V VIN 0V TO 5V VDD VREF (+) AIN1 VREF (-) GND
AD7824* AD7828*
5V
VREF (+) VDD VREF (-) GND DB7 DB0
AD7824* AD7828*
DB7 DB0
11111111
*ADDITIONAL PINS OMITTED FOR CLARITY. ONLY CHANNEL 1 SHOWN.
Figure 12. AD7824/AD7828 Bipolar 4 V Operation
*ADDITIONAL PINS OMITTED FOR CLARITY. ONLY CHANNEL 1 SHOWN.
11111110 11111101
FS = 8V 1LSB = FS/256
Figure 10. AD7824/AD7828 Unipolar 0 V to 5 V Operation
OUTPUT CODE
10000010 10000001 10000000 01111111 01111110 00000010 00000001 00000000 -FS + 1LSB 2 +FS 2
FULL-SCALE TRANSITION 11111111 11111110 11111101
OUTPUT CODE
1LSB = 00000011 00000010 00000001 00000000 0 1LSB 2LSB 3LSB AIN, INPUT VOLTAGE - LSB
FS 256
0V AIN, INPUT VOLTAGE - LSB
Figure 13. Ideal Input/Output Transfer Characteristic for 4 V Operation
FS FS - 1LSB
TIMING AND CONTROL
Figure 11. Ideal Input/Output Transfer Characteristic for Unipolar 0 V to 5 V Operation
BIPOLAR OPERATION
The circuit of Figure 12 is designed for bipolar operation. An AD544 op amp conditions the signal input (VIN) so that only positive voltages appear at AIN1. The closed loop transfer function of the op amp for the resistor values shown is given below: AIN 1 = (2.5 - 0.625VIN ) Volts The analog input range is 4 V and the LSB size is 31.25 mV. The output code is complementary offset binary. The ideal input/output characteristic is shown in Figure 13.
The AD7824/AD7828 has two digital inputs for timing and control. These are Chip Select (CS) and Read (RD). A READ operation brings CS and RD low, which starts a conversion on the channel selected by the multiplexer address inputs (see Table I). There are two modes of operation as outlined by the timing diagrams of Figures 14 and 15. Mode 0 is designed for microprocessors that can be driven into a WAIT state. A READ operation (i.e., CS and RD are taken low) starts a conversion and data is read when conversion is complete. Mode l does not require microprocessor WAIT states. A READ operation initiates a conversion and reads the previous conversion results.
Table I. Truth Table for Input Channel Selection
AD7824 A1 A0 0 0 1 1 0 1 0 1
A2 0 0 0 0 1 1 1 1
AD7828 A1 A0 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1
Channel AIN1 AIN2 AIN3 AIN4 AIN5 AIN6 AIN7 AIN8
-8-
REV. F
AD7824/AD7828
MODE 0 MODE 1
Figure 14 shows the timing diagram for Mode 0 operation. This mode can only be used for microprocessors that have a WAIT state facility, whereby a READ instruction cycle can be extended to accommodate slow memory devices. A READ operation brings CS and RD low, which starts a conversion. The analog multiplexer address inputs must remain valid while CS and RD are low. The data bus (DB7-DB0) remains in the three-state condition until conversion is complete. There are two converter status outputs on the AD7824/AD7828, interrupt (INT) and ready (RDY), which can be used to drive the microprocessor READY/WAIT input. The RDY is an open-drain output (no internal pull-up device) that goes low on the falling edge of CS and goes high impedance at the end of conversion when the 8-bit conversion result appears on the data outputs. If the RDY status is not required, the external pull-up resistor can be omitted and the RDY output tied to GND. The INT goes low when conversion is complete and returns high on the rising edge of CS or RD.
Mode 1 operation is designed for applications where the microprocessor is not forced into a WAIT state. A READ operation takes CS and RD low, which triggers a conversion (see Figure 15). The multiplexer address inputs are latched on the rising edge of RD. Data from the previous conversion is read from the three-state data outputs (DB7-DB0). This data may be disregarded if not required. Note that the RDY output (open drain output) does not provide any status information in this mode and must be connected to GND. At the end of conversion, INT goes low. A second READ operation is required to access the new conversion result. This READ operation latches a new address into the multiplexer inputs and starts another conversion. INT returns high at the end of the second READ operation, when CS or RD returns high. A delay of 2.5 s must be allowed between READ operations.
CS
tCSS
RD
tCSH
tCSS
tAS
ANALOG CHANNEL ADDRESS ADDRESS VALID
tP
tAS
ADDRESS VALID
tAH
RDY
tRDY
INT
tINTH tCRD
tACC2
DATA VALID
tDH
DATA
HIGH IMPEDANCE
Figure 14. Mode 0 Timing Diagram
CS
tCSS
RD
tRD
tCSH
tCSS
tRD
tCSH
tP tAS
ANALOG CHANNEL ADDRESS ADDRESS VALID
tAS
ADDRESS VALID
tAH tCRD tINTH
INT
tAH tINTH
tACC1
DATA OLD VALID
tDH
tACC1
NEW VALID
tDH
Figure 15. Mode 1 Timing Diagram
REV. F
-9-
AD7824/AD7828
MICROPROCESSOR INTERFACING
The AD7824/AD7828 is designed to interface to microprocessors as Read Only Memory (ROM). Analog channel selection, conversion start, and data read operations are controlled by CS, RD, and the channel address inputs. These signals are common to all memory peripheral devices.
Z80 MICROPROCESSOR
to any of the addresses in Table II starts a conversion and reads the conversion result. MOVE x B $C000, D0 Once conversion has begun, the MC68000 inserts WAIT states until INT goes low, asserting DTACK at the end of conversion. The microprocessor then places the conversion results into the D0 register.
A23 ADDRESS BUS A1 A0 A1
Figure 16 shows a typical AD7824/AD7828-Z80 interface. The AD7824/AD7828 is operating in Mode 0. Assume the ADC is assigned a memory block starting at address C000. The following LOAD instruction to any of the addresses listed in Table II will start a conversion of the selected channel and read the conversion result. LD B, (C000) At the beginning of the instruction cycle when the ADC address is selected, RDY asserts the WAIT input so that the Z80 is forced into a WAIT state. At the end of conversion, RDY returns high and the conversion result is placed in the B register of the microprocessor.
A15 ADDRESS BUS A0 A0 A1 A2** A1 A0
A2
A0 AS R/W MC68000 CLR 7474 D 5k DTACK D7 Q CK RDY DB7 DATA BUS D0 DB0 5V EN ADDRESS DECODE CS RD
A1
A2**
AD7824* AD7828*
A2
MREQ 5V Z80 5k WAIT RD D7
EN
ADDRESS DECODE
CS RDY RD DB7 DATA BUS D0 DB0
AD7824* AD7828*
*LINEAR CIRCUITRY OMITTED FOR CLARITY. ** FOR THE AD7828 ONLY
Figure 17. AD7824/AD7828-MC68000 Interface
TMS32010 MICROCOMPUTER
A TMS32010 interface is shown in Figure 18. The AD7824/ AD7828 is operating in Mode 1 (i.e., no P WAIT states). The ADC is mapped at a port address. The following I/O instruction starts a conversion and reads the previous conversion result into the accumulator. IN, A PA (PA = PORT ADDRESS) The port address (000 to 111) selects the analog channel to be converted. When conversion is complete, a second I/O instruction (IN, A PA) reads the up-to-date data into the accumulator and starts another conversion. A delay of 2.5 s must be allowed between conversions.
PA2 PA1 PA0 TMS32010 MEN DEN D7 DATA BUS D0 DB0 CS RD DB7 A2** A1 A0
*LINEAR CIRCUITRY OMITTED FOR CLARITY. ** FOR THE AD7828 ONLY
Figure 16. AD7824/AD7828-Z80 lnterface
Table II. Address Channel Selection
Address C000 C001 C002 C003 C004 C005 C006 C007
AD7824 Channel 1 2 3 4
AD7828 Channel 1 2 3 4 5 6 7 8
AD7824* AD7828*
MC68000 MICROPROCESSOR
Figure 17 shows an MC68000 interface. The AD7824/AD7828 is operating in Mode 0. Assume the ADC is again assigned a memory block starting at address C000. A MOVE instruction
*LINEAR CIRCUITRY OMITTED FOR CLARITY. ** FOR THE AD7828 ONLY
Figure 18. AD7824/AD7828-TMS32010 Interface
-10-
REV. F
AD7824/AD7828
5V BAND-PASS FILTER 1 BAND-PASS FILTER 2 SPEECH INPUT AMP BAND-PASS FILTER 7 BAND-PASS FILTER 8 5V AIN7 AIN8 VREF (+) VREF (-) GND AIN1 AIN2 DB7 VDD CS RD
5V VDD AIN1 AIN2 AIN3 AIN4 CS RD INT DB7 DB0 A1 A0 SAMPLE PULSE 15V 10V WR DB7 DB0 A1 A0 VSS VDD VREF VOUT A VOUT B VOUT C VOUT D DGND AGND VO1 VO 2 VO 3 VO 4
AD7226
AD7828
DB0 A2 A1 A0
DATA
AD7824
VREF (+) VREF (-) GND
Figure 19. Speech Analysis Using Real-Time Filtering
Figure 20. 4-Channel Fast Infinite Sample-and-Hold
OUTLINE DIMENSIONS 24-Lead Plastic Dual-in-Line Package [PDIP] (N-24)
Dimensions shown in inches and (millimeters)
1.185 (30.01) 1.165 (29.59) 1.145 (29.08)
24 1 13 12
0.295 (7.49) 0.285 (7.24) 0.275 (6.99) 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.150 (3.81) 0.135 (3.43) 0.120 (3.05) 0.015 (0.38) 0.010 (0.25) 0.008 (0.20)
0.180 (4.57) MAX 0.150 (3.81) 0.130 (3.30) 0.110 (2.79)
0.015 (0.38) MIN
0.022 (0.56) 0.018 (0.46) 0.014 (0.36)
0.100 (2.54) BSC
0.060 (1.52) SEATING 0.050 (1.27) PLANE 0.045 (1.14)
COMPLIANT TO JEDEC STANDARDS MO-095AG CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
28-Lead Plastic Dual-in-Line Package [PDIP] (N-28)
Dimensions shown in inches and (millimeters)
1.565 (39.7) 1.380 (35.1)
28 15
0.580 (14.73) 0.485 (12.32)
1 14
0.100 (2.54) BSC 0.250 (6.35) MAX 0.200 (5.05) 0.115 (2.93)
0.015 (0.39) MIN
0.625 (15.87) 0.600 (15.24)
0.195 (4.95) 0.125 (3.18)
0.022 (0.558) 0.014 (0.356)
0.70 (1.77) 0.30 (0.77)
SEATING PLANE
0.015 (0.381) 0.008 (0.204)
COMPLIANT TO JEDEC STANDARDS MS-011AB CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
REV. F
-11-
AD7824/AD7828
OUTLINE DIMENSIONS 24-Lead Standard Small Outline Package [SOIC] Wide Body (R-24)
Dimensions shown in millimeters and (inches)
15.60 (0.6142) 15.20 (0.5984)
24
13
7.60 (0.2992) 7.40 (0.2913)
1 12
10.65 (0.4193) 10.00 (0.3937)
2.65 (0.1043) 2.35 (0.0925) 0.30 (0.0118) 0.10 (0.0039) 1.27 (0.0500) BSC 0.51 (0.020) 0.33 (0.013) 8 0 SEATING 0.32 (0.0126) PLANE 0.23 (0.0091)
0.75 (0.0295) 0.25 (0.0098)
45
COPLANARITY 0.10
1.27 (0.0500) 0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-013AD CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
28-Lead Standard Small Outline Package [SOIC] Wide Body (R-28)
Dimensions shown in millimeters and (inches)
18.10 (0.7126) 17.70 (0.6969)
28
15
7.60 (0.2992) 7.40 (0.2913)
1 14
10.65 (0.4193) 10.00 (0.3937)
2.65 (0.1043) 2.35 (0.0925) 0.30 (0.0118) 0.10 (0.0039) COPLANARITY 0.10 8 0 1.27 (0.0500) 0.51 (0.0201) SEATING 0.32 (0.0126) PLANE BSC 0.33 (0.0130) 0.23 (0.0091)
0.75 (0.0295) 0.25 (0.0098)
45
1.27 (0.0500) 0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-013AE CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
-12-
REV. F
AD7824/AD7828
OUTLINE DIMENSIONS 24-Lead Ceramic DIP - Glass Hermetic Seal [CERDIP] (Q-24)
Dimensions shown in inches and (millimeters)
0.005 (0.13) MIN
24
0.098 (2.49) MAX
13
0.310 (7.87) 0.220 (5.59)
PIN 1
1 12
0.200 (5.08) MAX
1.280 (32.51) MAX
0.060 (1.52) 0.015 (0.38) 0.150 (3.81) MIN
0.320 (8.13) 0.290 (7.37) 0.015 (0.38) 0.008 (0.20)
0.200 (5.08) 0.125 (3.18) 0.023 (0.58) 0.014 (0.36)
0.100 (2.54) BSC
0.070 (1.78) SEATING PLANE 0.030 (0.76)
15 0
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
28-Lead Ceramic DIP - Glass Hermetic Seal [CERDIP] (Q-28)
Dimensions shown in inches and (millimeters)
0.100 (2.54) MAX
28 15
0.005 (0.13) MIN
PIN 1
1 14
0.610 (15.49) 0.500 (12.70)
0.225(5.72) MAX
1.490 (37.85) MAX
0.015 (0.38) MIN 0.150 (3.81) MIN
0.620 (15.75) 0.590 (14.99)
0.200 (5.08) 0.125 (3.18) 0.026 (0.66) 0.014 (0.36)
0.100 (2.54) BSC
0.070 (1.78) SEATING 0.030 (0.76) PLANE
15 0
0.018 (0.46) 0.008 (0.20)
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
28-Terminal Ceramic Leaded Chip Carrier [LCC] (E-28A)
Dimensions shown in inches and (millimeters)
0.300 (7.62) REF 0.075 (1.91) REF
19 18 26 25
0.100 (2.54) 0.064 (1.63)
0.020 (0.51) MIN 0.028 (0.71) 0.022 (0.56)
0.458 (11.63) SQ 0.442 (11.23)
0.458 (11.63) MAX SQ
0.05 (1.27) BSC
BOTTOM VIEW
1
28
0.075 (1.91) REF
11
0.15 (3.81) REF
4 5
12
0.088 (2.24) 0.054 (1.37)
0.055 (1.40) 0.045 (1.14)
0.095 (2.41) 0.075 (1.90)
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
REV. F
-13-
AD7824/AD7828
OUTLINE DIMENSIONS
28-Lead Shrink Small Outline Package [SSOP] (RS-28)
Dimensions shown in millimeters
10.50 10.20 9.90
28
15
5.60 5.30 5.00
1 14
8.20 7.80 7.40
2.00 MAX
1.85 1.75 1.65
0.10 COPLANARITY 0.25 0.09
0.05 MIN
0.65 BSC
0.38 0.22
SEATING PLANE
8 4 0
0.95 0.75 0.55
COMPLIANT TO JEDEC STANDARDS MO-150AH
28-Lead Plastic Leaded Chip Carrier [PLCC] (P-28A)
Dimensions shown in inches and (millimeters)
0.180 (4.57) 0.165 (4.19) 0.056 (1.42) 0.042 (1.07)
26 25
0.048 (1.22) 0.042 (1.07)
0.020 (0.51) MIN 0.021 (0.53) 0.013 (0.33)
4
0.048 (1.22) 0.042 (1.07)
5
TOP VIEW
(PINS DOWN) 11 12 19 18
0.050 (1.27) BSC
0.032 (0.81) 0.026 (0.66) 0.040 (1.02) 0.025 (0.64)
0.430 (10.9) 0.390 (9.9)
BOTTOM VIEW
(PINS UP)
0.456 (11.582) SQ 0.450 (11.430) 0.495 (12.57) SQ 0.485 (12.32)
0.120 (3.05) 0.090 (2.29)
COMPLIANT TO JEDEC STANDARDS MO-047AB CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
-14-
REV. F
AD7824/AD7828 Revision History
Location 1/03--Data Sheet changed from REV. E to REV. F. Page
Edits to ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Edits to DIP/SOIC/SSOP, LCCC, AND PLCC Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Edit to Figure 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Edits to Circuit Information Basic Description section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Edits to Input Current section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Edit to Figure 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Edit to Figure 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4/02--Data Sheet changed from REV. D to REV. E.
Edits to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
REV. F
-15-
-16-
C01323-0-1/03 (F)
PRINTED IN U.S.A.

▲Up To Search▲

Price & Availability of AD7828CQ

	To Download AD7828CQ Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .