TI1 ADS574JP Microprocessor-compatible sampling cmos analog-to-digital converter Datasheet

®
ADS574
ADS
574
ADS
574
ADS
574
Microprocessor-Compatible Sampling
CMOS ANALOG-TO-DIGITAL CONVERTER
FEATURES
DESCRIPTION
● REPLACES ADC574 FOR NEW DESIGNS
● COMPLETE SAMPLING A/D WITH
REFERENCE, CLOCK AND
MICROPROCESSOR INTERFACE
● FAST ACQUISITION AND CONVERSION:
25µs max
● ELIMINATES EXTERNAL SAMPLE/HOLD
IN MOST APPLICATIONS
● GUARANTEED AC AND DC PERFORMANCE
The ADS574 is a 12-bit successive approximation
analog-to-digital converter using an innovative
capacitor array (CDAC) implemented in low-power
CMOS technology. This is a drop-in replacement for
ADC574 models in most applications, with internal
sampling, much lower power consumption, and capability to operate from a single +5V supply.
The ADS574 is complete with internal clock, microprocessor interface, three-state outputs, and internal
scaling resistors for input ranges of 0V to +10V, 0V to
+20V, ±5V, or ±10V. The maximum throughput time
for 12-bit conversions is 25µs over the full operating
temperature range, including both acquisition and conversion.
● SINGLE +5V SUPPLY OPERATION
● LOW POWER: 100mW max
● PACKAGE OPTIONS: 0.6" and 0.3" DIPs,
SOIC
Complete user control over the internal sampling function facilitates elimination of external sample/hold
amplifiers in most existing designs.
The ADS574 requires +5V, with –12V or –15V optional, depending on usage. No +15V supply is required. Available packages include 0.3" or 0.6" wide
28-pin plastic DIPs and 28-lead SOICs.
Status
Control
Inputs
20V Range
10V Range
2.5V Reference
Input
CDAC
Clock
–
Successive
Approximation
Register
+
Comparator
2.5V Reference
Output
Three-State Buffers
Bipolar Offset
Control Logic
Parallel
Data
Output
2.5V
Reference
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Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
© 1991 Burr-Brown Corporation
SBAS009
PDS-1104F
Printed in U.S.A. July, 1993
SPECIFICATIONS
ELECTRICAL
At TA = TMIN to TMAX , VDD = +5V, VEE = –15V to +5V, sampling frequency of 40kHz, and fIN = 10kHz, unless otherwise specified.
ADS574JE, JP, JU
PARAMETER
MIN
TYP
ADS574KE, KP, KU
MAX
RESOLUTION
MIN
TYP
12
MAX
UNITS
✻
Bits
INPUTS
ANALOG
Voltage Ranges: Unipolar
Bipolar
Impedance:
0 to +10V, ±5V
±10V, 0V to +20V
DIGITAL (CE, CS, R/C, AO, 12/8)
Voltages: Logic 1
Logic 0
Current
Capacitance
15
60
+2.0
–0.5
–5
0 to +10, 0 to +20
±5, ±10
✻
✻
21
84
+5.5
+0.8
+5
0.1
5
✻
✻
✻
V
V
kΩ
kΩ
✻
✻
✻
✻
✻
✻
✻
V
V
µA
pF
±1/2
✻
±4
LSB
LSB
LSB
TRANSFER CHARACTERISTICS
DC ACCURACY
At +25°C
Linearity Error
Unipolar Offset Error (adjustable to zero)
Bipolar Offset Error (adjustable to zero)
Full-Scale Calibration Error (1)
(adjustable to zero)
No Missing Codes Resolution (Diff. Linearity)
TMIN to TMAX (3)
Linearity Error
Full-Scale Calibration Error
Unipolar Offset
Bipolar Offset
No Missing Codes Resolution
AC ACCURACY (4)
Spurious Free Dynamic Range
Total Harmonic Distortion
Signal-to-Noise Ratio
Signal-to-(Noise + Distortion) Ratio
Intermodulation Distortion
(FIN1 = 10kHz, FIN2 = 11.5kHz)
TEMPERATURE COEFFICIENTS
Unipolar Offset
Bipolar Offset
Full-Scale Calibration
±1
±2
±10
±0.25
12
✻
12
±1
±0.47
±4
±12
12
73
69
68
±1/2
±0.37
±3
±5
12
78
–77
72
71
–75
76
–72
71
70
✻
✻
✻
✻
✻
–75
% of FS
Bits
LSB
% of FS
LSB
LSB
Bits
dB
dB
dB
dB
(5)
±1
±2
±12
✻
✻
✻
POWER SUPPLY SENSITIVITY
Change in Full-Scale Calibration(6)
+4.75V < VDD < +5.25V
±1/2
CONVERSION TIME (Including Acquisition Time)
tAQ + tC at 25°C:
8-Bit Cycle
12-Bit Cycle
12-Bit Cycle, TMIN to TMAX
SAMPLING DYNAMICS
Sampling Rate
Aperture Delay, tAP
With VEE = +5V
With VEE = 0V to –15V
Aperture Uncertainty (Jitter)
With VEE = +5V
With VEE = 0V to –15V
16
22
22
✻
✻
✻
18
25
25
ppm/°C
ppm/°C
ppm/°C
✻
LSB
✻
✻
✻
µs
µs
µs
✻
40
kHz
20
4.0
✻
✻
ns
µs
300
30
✻
✻
ps, rms
ns, rms
OUTPUTS
DIGITAL (DB11 - DB0, STATUS)
Output Codes: Unipolar
Bipolar
Logic Levels: Logic 0 (ISINK = 1.6mA)
Logic 1 (ISOURCE = 500µA)
Leakage, Data Bits Only, High-Z State
Capacitance
+2.4
–5
Unipolar Straight Binary (USB)
Bipolar Offset Binary (BOB)
+0.4
✻
+5
✻
0.1
5
®
ADS574
(2)
2
✻
✻
✻
✻
V
V
µA
pF
SPECIFICATIONS (CONT)
ELECTRICAL
At TA = TMIN to TMAX , VDD = +5V, VEE = –15V to +5V, sampling frequency of 40kHz, and fIN = 10kHz, unless otherwise specified.
ADS574JE, JP, JU
ADS574KE, KP, KU
PARAMETER
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
INTERNAL REFERENCE VOLTAGE
Voltage
Source Current Available for External Loads
+2.4
0.5
+2.5
+2.6
✻
✻
✻
✻
V
mA
VDD
+5.5
✻
✻
✻
✻
POWER SUPPLY REQUIREMENTS
Voltage: VEE (7)
VDD
Current: IEE (7) (VEE = –15V)
IDD
Power Dissipation (TMIN to TMAX)
(VEE = 0V to +5V)
TEMPERATURE RANGE
Specification
Operating:
Storage
–16.5
+4.5
–1
+13
+20
✻
✻
✻
V
V
mA
mA
65
100
✻
✻
mW
0
+70
✻
✻
°C
–40
–65
+85
+150
✻
✻
✻
✻
°C
°C
✻ Same specification as ADS574JE, JP, JU.
NOTES: (1) With fixed 50Ω resistor from REF OUT to REF IN. This parameter is also adjustable to zero at +25°C. (2) FS in this specification table means Full Scale
Range. That is, for a ±10V input range, FS means 20V; for a 0 to +10V range, FS means 10V. (3) Maximum error at TMIN and TMAX. (4) Based on using VEE =
+5V, which starts a conversion immediately upon a convert command. Using VEE = 0V to –15V makes the ADS574/ADS774 emulate standard ADC574 operation.
In this mode, the internal sample/hold acquires the input signal after receiving the convert command, and does not assume that the input level has been stable
before the convert command arrives. (5) Using internal reference. (6) This is worst case change in accuracy from accuracy with a +5V supply. (7) VEE is optional,
and is only used to set the mode for the internal sample/hold. When VEE = –15V, IEE = –1mA typ; when VEE = 0V, IEE = ±5µA typ; when VEE = +5V, IEE = +167µA
typ.
ELECTROSTATIC
DISCHARGE SENSITIVITY
ABSOLUTE MAXIMUM RATINGS
VEE to Digital Common ....................................................... +VDD to –16.5V
VDD to Digital Common .............................................................. 0V to +7V
Analog Common to Digital Common .................................................... ±1V
Control Inputs (CE, CS, AO, 12/8, R/C)
to Digital Common .................................................. –0.5V to VDD +0.5V
Analog Inputs (Ref In, Bipolar Offset, 10VIN )
to Analog Common ...................................................................... ±16.5V
20VIN to Analog Common .................................................................. ±24V
Ref Out .......................................................... Indefinite Short to Common,
Momentary Short to VDD
Max Junction Temperature ............................................................ +165°C
Power Dissipation ........................................................................ 1000mW
Lead Temperature (soldering,10s) ................................................. +300°C
Thermal Resistance, θJA : Plastic DIPs ........................................ 100°C/W
SOIC ................................................... 100°C/W
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits
may be more susceptible to damage because very small
parametric changes could cause the device not to meet its
published specifications.
PACKAGE/ORDERING INFORMATION
PRODUCT
PACKAGE
PACKAGE DRAWING
NUMBER(1)
SINAD(2)
TEMPERATURE
RANGE
LINEARITY
ERROR (LSB)
ADS574JE
ADS574KE
ADS574JP
ADS574KP
ADS574JU
ADS574KU
0.3" Plastic DIP
0.3" Plastic DIP
0.6" Plastic DIP
0.6" Plastic DIP
SOIC
SOIC
246
246
215
215
217
217
68
70
68
70
68
70
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
±1
±1/2
±1
±1/2
±1
±1/2
NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) SINAD is Signal-to-(Noise
and Distortion) expressed in dB.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
®
3
ADS574
CONNECTION DIAGRAM
4
–
R/C
5
CE
6
NC*
7
2.5V Ref
Out
8
Analog
Common
9
2.5V Ref
In
10
VEE (Mode Control)
11
Clock
2.5V
Reference
Bipolar 12
Offset
10V Range 13
20V Range
12 Bits
–
+
CDAC
14
*Not Internally Connected
®
ADS574
4
Nibble A
AO
Control
Logic
12
Bits
Nibble B
3
Three-State Buffers and Control
CS
Nibble C
2
Power-Up Reset
1
Succesive Approximation Register
+5VDC Supply
(VDD )
–
12/8
28
Status
27
DB11 (MSB)
26
DB10
25
DB9
24
DB8
23
DB7
22
DB6
21
DB5
20
DB4
19
DB3
18
DB2
17
DB1
16
DB0 (LSB)
15
Digital
Common
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VDD = VEE = +5V; Bipolar ±10V Input Range; sampling frequency of 40kHz; unless otherwise specified. All plots use 4096 point FFTs.
SIGNAL/(NOISE + DISTORTION) vs
INPUT FREQUENCY AND AMBIENT TEMPERATURE
FREQUENCY SPECTRUM (±10V, 2kHz Input)
75
0
Magnitude (dB)
Signal/(Noise + Distortion) (dB)
S/(N + D) = 73.1dB
THD = –94.5dB
SNR = 73.1dB
–20
–40
–60
–80
–100
–55°C
70
+125°C
65
–120
0
5
15
10
0.1
20
1
FREQUENCY SPECTRUM (±10V, 19kHz Input)
100
FREQUENCY SPECTRUM (±1V, 19kHz Input)
0
0
S/(N + D) = 68.4dB
THD = –75.9dB
SNR = 69.3dB
–20
S/(N + D) = 53.3dB
THD = –74.5dB
SNR = 53.3dB
–20
–40
Magnitude (dB)
Magnitude (dB)
10
Input Frequency (kHz)
Frequency (kHz)
–60
–80
–100
–40
–60
–80
–100
–120
–120
0
5
15
10
0
20
5
10
Frequency (kHz)
POWER SUPPLY REJECTION
vs SUPPLY RIPPLE FREQUENCY
SPURIOUS FREE DYNAMIC RANGE, SNR AND THD
vs INPUT FREQUENCY
100
90
80
70
60
0.1
1
10
20
15
Frequency (kHz)
Power Supply Rejection Ratio (V/V in dB)
Spurious Free Dynamic Range, SNR, THD (dB)
+25°C
80
60
40
20
10
10
100
100
1k
10k
100k
1M
10M
Supply Ripple Frequency (Hz)
Input Frequency (kHz)
®
5
ADS574
THEORY OF OPERATION
approximation is made by connecting S2 to the reference and
S3 to GND, and latching S2 according to the output of the
comparator. After three successive approximation steps have
been made the voltage level at the comparator will be within
1/2LSB of GND, and a digital word which represents the
analog input can be determined from the positions of S1, S2
and S3.
In the ADS574, the advantages of advanced CMOS technology—high logic density, stable capacitors, precision analog
switches—and Burr-Brown’s state of the art laser trimming
techniques are combined to produce a fast, low power
analog-to-digital converter with internal sample/hold.
The charge-redistribution successive-approximation circuitry
converts analog input voltages into digital words.
OPERATION
A simple example of a charge-redistribution A/D converter
with only 3 bits is shown in Figure 1.
Analog
Input
Comparator
SC
4C
Signal
S
2C
S1
R
G
C
S2
R
L
o
g
i
c
G
S3
R
BASIC OPERATION
Figure 2 shows the minimum circuit required to operate the
ADS574 in a basic ±10V range in the Control Mode (discussed in detail in a later section.) The falling edge of a
Convert Command (a pulse taking pin 5 LOW for a minimum of 25ns) both switches the ADS574 input to the hold
state and initiates the conversion. Pin 28 (STATUS) will
output a HIGH during the conversion, and falls only after the
conversion is completed and the data has been latched on the
data output pins (pins 16 to 27.) Thus, the falling edge of
STATUS on pin 28 can be used to read the data from the
conversion. Also, during conversion, the STATUS signal
puts the data output pins in a High-Z state and inhibits the
input lines. This means that pulses on pin 5 are ignored, so
that new conversions cannot be initiated during the conversion, either as a result of spurious signals or to short-cycle
the ADS574.
Out
G
+
Reference
Input
–
FIGURE 1. 3-Bit Charge Redistribution A/D.
INPUT SCALING
Precision laser-trimmed scaling resistors at the input divide
standard input ranges (0V to +10V, 0V to +20V, ±5V or
±10V) into levels compatible with the CMOS characteristics
of the internal capacitor array.
The ADS574 will begin acquiring a new sample as soon as
the conversion is completed, even before the STATUS
output falls, and will track the input signal until the next
conversion is started. The ADS574 is designed to complete
a conversion and accurately acquire a new signal in 25µs
max over the full operating temperature range, so that
conversions can take place at a full 40kHz.
SAMPLING
While sampling, the capacitor array switch for the MSB
capacitor (S1) is in position “S”, so that the charge on the
MSB capacitor is proportional to the voltage level of the
analog input signal. The remaining array switches (S2 and
S3) are set to position “G”. Switch SC is closed, setting the
comparator input offset to zero.
CONTROLLING THE ADS574
The Burr-Brown ADS574 can be easily interfaced to most
microprocessor systems and other digital systems. The
microprocessor may take full control of each conversion, or
the converter may operate in a stand-alone mode, controlled
only by the R/C input. Full control consists of selecting an
8- or 12-bit conversion cycle, initiating the conversion, and
reading the output data when ready—choosing either 12 bits
all at once, or the 8 MSB bits followed by the 4 LSB bits in
a left-justified format. The five control inputs (12/8, CS, A0,
R/C, and CE) are all TTL/CMOS-compatible. The functions
of the control inputs are described in Table II. The control
function truth table is shown in Table III.
CONVERSION
When a conversion command is received, switch S1 is opened
to trap a charge on the MSB capacitor proportional to the
analog input level at the time of the sampling command, and
switch SC is opened to float the comparator input. The charge
trapped in the capacitor array can now be moved between the
three capacitors in the array by connecting switches S1, S2, and
S3 to positions “R” (to connect to the reference) or “G” (to
connect to GND), thus changing the voltage generated at the
comparator input.
STAND-ALONE OPERATION
For stand-alone operation, control of the converter is accomplished by a single control line connected to R/C. In this
mode CS and A0 are connected to digital common and CE
and 12/8 are connected to +5V. The output data are presented as 12-bit words. The stand-alone mode is used in
systems containing dedicated input ports which do not
require full bus interface capability.
During the first approximation, the MSB capacitor is connected through switch S1 to the reference, while switches S2
and S3 are connected to GND. Depending on whether the
comparator output is HIGH or LOW, the logic will then
latch S1 in position “R” or “G”. Similarly, the second
®
ADS574
6
+5V
10µF
1
28
2
27 Bit 11 (MSB)
3
26 Bit 10
4
25 Bit 9
5
24 Bit 8
6
23 Bit 7
Status
Output
Convert Command
+5V
NC*
50Ω
(1)
50Ω
7
ADS574
8
21 Bit 5
9
20 Bit 4
10
19 Bit 3
11
18 Bit 2
12
17 Bit 1
Leave Unconnected 13
16 Bit 0 (LSB)
14
±10V
Analog
Input
22 Bit 6
15
*Not internally connected
NOTE: (1) Connect to ground or VEE for
emulation. Connect to +5 for control mode.
FIGURE 2. Basic ±10V Operation.
CONVERSION START
Conversion is initiated by a HIGH-to-LOW transition of
R/C. The three-state data output buffers are enabled when
R/C is HIGH and STATUS is LOW. Thus, there are two
possible modes of operation; data can be read with either a
positive pulse on R/C, or a negative pulse on STATUS. In
either case the R/C pulse must remain LOW for a minimum
of 25ns.
The converter initiates a conversion based on a transition
occurring on any of three logic inputs (CE, CS, and R/C) as
shown in Table III. Conversion is initiated by the last of the
three to reach the required state and thus all three may be
dynamically controlled. If necessary, all three may change
state simultaneously, and the nominal delay time is the same
regardless of which input actually starts the conversion. If it
is desired that a particular input establish the actual start of
conversion, the other two should be stable a minimum of
50ns prior to the transition of the critical input. Timing
relationships for start of conversion timing are illustrated in
Figure 5. The specifications for timing are contained in
Table V.
Figure 3 illustrates timing with an R/C pulse which goes
LOW and returns HIGH during the conversion. In this case,
the three-state outputs go to the high-impedance state in
response to the falling edge of R/C and are enabled for
external access of the data after completion of the conversion.
Figure 4 illustrates the timing when a positive R/C pulse is
used. In this mode the output data from the previous conversion is enabled during the time R/C is HIGH. A new
conversion is started on the falling edge of R/C, and the
three-state outputs return to the high-impedance state until
the next occurrence of a HIGH R/C pulse. Timing specifications for stand-alone operation are listed in Table IV.
The STATUS output indicates the current state of the converter by being in a high state only during conversion.
During this time the three state output buffers remain in a
high-impedance state, and therefore data cannot be read
during conversion. During this period additional transitions
of the three digital inputs which control conversion will be
ignored, so that conversion cannot be prematurely terminated or restarted. However, if A0 changes state after the
beginning of conversion, any additional start conversion
transition will latch the new state of A0, possibly resulting in
an incorrect conversion length (8 bits vs 12 bits) for that
conversion.
FULLY CONTROLLED OPERATION
Conversion Length
Conversion length (8-bit or 12-bit) is determined by the state
of the A0 input, which is latched upon receipt of a conversion start transition (described below). If A0 is latched
HIGH, the conversion continues for 8 bits. The full 12-bit
conversion will occur if A0 is LOW. If all 12 bits are read
following an 8-bit conversion, the 4LSBs (DB0-DB3) will
be LOW (logic 0). A0 is latched because it is also involved
in enabling the output buffers. No other control inputs are
latched.
®
7
ADS574
Binary (BIN) Output
Input Voltage Range and LSB Values
Defined As:
±10V
+5V
0V to +10V
0V to +20V
FSR
2n
n=8
n = 12
20V
2n
78.13mV
4.88mV
10V
2n
39.06mV
2.44mV
10V
2n
39.06mV
2.44mV
20V
2n
78.13mV
4.88mV
+ Full-Scale Calibration
Midscale Calibration (Bipolar Offset)
Zero Calibration ( – Full-Scale Calibration)
+10V – 3/2LSB
0 – 1/2LSB
–10V + 1/2LSB
+5V – 3/2LSB
0 – 1/2LSB
–5V + 1/2LSB
+10V – 3/2LSB
+5V – 1/2LSB
0 to +1/2LSB
+10V – 3/2LSB
±10V – 1/2LSB
0 to +1/2LSB
Analog Input Voltage Range
One Least Significant Bit
(LSB)
Output Transition Values
FFEH to FFFH
7FFFH to 800H
000H to 001H
TABLE I. Input Voltages, Transition Values, and LSB Values.
DESIGNATION
DEFINITION
FUNCTION
CE (Pin 6)
Chip Enable
(active high)
Must be HIGH (“1”) to either initiate a conversion or read output data. 0-1 edge may be used to initiate a
conversion.
CS (Pin 3)
Chip Select
(active low)
Must be LOW (“0”) to either initiate a conversion or read output data. 1-0 edge may be used to initiate a
conversion.
R/C (Pin 5)
Read/Convert
(“1” = read)
(“0” = convert)
Must be LOW (“0”) to initiate either 8- or 12-bit conversions. 1-0 edge may be used to initiate a conversion.
Must be HIGH (“1”) to read output data. 0-1 edge may be used to initiate a read operation.
AO (Pin 4)
Byte Address
Short Cycle
In the start-convert mode, AO selects 8-bit (AO = “1”) or 12-bit (AO = “0”) conversion mode. When reading
output data in two 8-bit bytes, AO = “0” accesses 8 MSBs (high byte) and AO = “1” accesses 4 LSBs and
trailing “0s” (low byte).
Data Mode Select
(“1” = 12 bits)
(“0” = 8 bits)
When reading output data, 12/8 = “1” enables all 12 output bits simultaneously. 12/8 = “0” will enable the
MSBs or LSBs as determined by the AO line.
12/8 (Pin 2)
TABLE II. Control Line Functions.
CE
CS
R/C
12/8
AO
OPERATION
0
X
↑
↑
1
1
1
1
1
1
1
X
1
0
0
↓
↓
0
0
0
0
0
X
X
0
0
0
0
↓
↓
X
X
X
X
X
X
X
X
1
0
0
X
X
0
1
0
1
0
1
X
0
1
None
None
Initiate 12-bit conversion
Initiate 8-bit conversion
Initiate 12-bit conversion
Initiate 8-bit conversion
Initiate 12-bit conversion
Initiate 8-bit conversion
Enable 12-bit output
Enable 8 MSBs only
Enable 4 LSBs plus 4
trailing zeroes
1
1
1
TABLE III. Control Input Truth Table.
READING OUTPUT DATA
When 12/8 is LOW, the data is presented in the form of two
8-bit bytes, with selection of the byte of interest accomplished by the state of A0 during the read cycle. When A0 is
LOW, the byte addressed contains the 8MSBs. When A0 is
HIGH, the byte addressed contains the 4LSBs from the
conversion followed by four logic zeros which have been
forced by the control logic. The left-justified formats of the
two 8-bit bytes are shown in Figure 7. Connection of the
ADS574 to an 8-bit bus for transfer of the data is illustrated
in Figure 8. The design of the ADS574 guarantees that the
A0 input may be toggled at any time with no damage to the
converter; the outputs which are tied together in Figure 8
cannot be enabled at the same time. The A0 input is usually
driven by the least significant bit of the address bus, allowing storage of the output data word in two consecutive
memory locations.
After conversion is initiated, the output data buffers remain
in a high-impedance state until the following four logic
conditions are simultaneously met: R/C HIGH, STATUS
LOW, CE HIGH, and CS LOW. Upon satisfaction of these
conditions the data lines are enabled according to the state of
inputs 12/8 and A0. See Figure 6 and Table V for timing
relationships and specifications.
In most applications the 12/8 input will be hard-wired in
either the high or low condition, although it is fully TTL and
CMOS-compatible and may be actively driven if desired.
When 12/8 is HIGH, all 12 output lines (DB0-DB11) are
enabled simultaneously for full data word transfer to a 12-bit
or 16-bit bus. In this situation the A0 state is ignored when
reading the data.
®
ADS574
8
S/H CONTROL MODE
AND ADC574 EMULATION MODE
tHRL
R/C
The basic difference between these two modes is the
assumptions about the state of the input signal both before
and during the conversion. The differences are shown in
Figure 9 and Table VI. In the Control Mode it is assumed
that during the required 4µs acquisition time the signal is not
slewing faster than the slew rate of the ADS574. No
assumption is made about the input level after the convert
command arrives, since the input signal is sampled and
conversion begins immediately after the convert command.
tDS
Status
tC
tHDR
tHS
High-Z-State
DB11-DB0
Data Valid
Data Valid
FIGURE 3. R/C Pulse Low—Outputs Enabled After Conversion.
R/C
tHRH
This means that a convert command can also be used to
switch an input multiplexer or change gains on a programmable gain amplifier, allowing the input signal to settle
before the next acquisition at the end of the conversion.
Because aperture jitter is minimized by the internal sample/
hold circuit, a high input frequency can be converted without
an external sample/hold.
tDS
Status
In the Emulation Mode, no assumption is made about the
input signal prior to the convert command. A delay time is
introduced between the convert command and the start of
conversion to allow the ADS574 enough time to acquire the
input signal before converting. The delay increases the
effective aperture time from 0.02µs to 4µs, but allows the
ADS574 to replace the ADC574 in any circuit. Any slewing
of the analog input prior to the convert command in existing
tC
tDDR
tHDR
High-Z
High-Z-State
Data Valid
DB11-DB0
FIGURE 4. R/C Pulse High — Outputs Enabled Only While
R/C Is High.
SYMBOL
tHRL
tDS
tHDR
tHRH
tDDR
PARAMETER
MIN
Low R/C Pulse Width
STS Delay from R/C
Data Valid After R/C Low
High R/C Pulse Width
Data Access Time
TYP
MAX
25
UNITS
150
ns
ns
ns
ns
ns
TYP
MAX
UNITS
60
30
20
20
0
20
200
ns
ns
ns
ns
ns
ns
ns
ns
150
ns
ns
ns
ns
ns
ns
ns
ns
ns
200
25
100
TABLE IV. Stand-Alone Mode Timing. (TA = TMIN to TMAX ).
SYMBOL
Convert Mode
tDSC
tHEC
tSSC
tHSC
tSRC
tHRC
tSAC
tHAC
Read Mode
tDD
tHD
tHL
tSSR
tSRR
tSAR
tHSR
tHRR
tHAR
tHS
PARAMETER
MIN
STS delay from CE
CE Pulse width
CS to CE setup
CS low during CE high
R/C to CE setup
R/C low during CE high
AO to CE setup
AO valid during CE high
50
50
50
50
50
0
50
Access time from CE
Data valid after CE low
Output float delay
CS to CE setup
R/C to CE setup
AO to CE setup
CS valid after CE low
R/C high after CE low
AO valid after CE low
STC delay after data valid
25
50
0
50
0
0
50
300
20
75
35
100
0
150
25
400
1000
TABLE V. Timing Specifications, Fully Controlled Operation. (TA = TMIN to TMAX ).
®
9
ADS574
tHEC
CE
CE
tSSR
tSSC
tHSR
CS
CS
tSRC
tHSC
tHRR
R/C
R/C
tHRC
tSRR
A0
A0
tSAC
tHAC
Status
Status
t X*
tDSC
tSAR
tHAR
High Impedance
DB11-DB0
tHS
DB11-DB0
High-Z
tHD
Data Valid
tDD
* tX includes tAQ + tC in ADC574
Emulation Mode, tC only in S/H Control Mode.
tHL
FIGURE 6. Read Cycle Timing.
FIGURE 5. Conversion Cycle Timing.
Word 1
Word 2
Processor
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
Converter
DB11 DB10
DB9
DB8
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
0
0
0
0
STATUS
28
DB11 (MSB)
27
FIGURE 7. 12-Bit Data Format for 8-Bit Systems.
2
12/8
4
AO
26
AO
25
24
Address
Bus
23
22
ADS574
21
20
19
18
17
DB0 (LSB)
16
Digital Common
15
FIGURE 8. Connection to an 8-Bit Bus.
®
ADS574
10
Data
Bus
tion Mode, system throughput can be speeded up, since the
input to the ADS574 can start slewing before the end of a
conversion (after the acquisition time), which is not possible
with existing ADC574s.
systems (due to multiplexers, sample/holds, etc. in front of
the converter) does not affect the accuracy of the ADS574
conversion in the Emulation Mode.
In both modes, as soon as the conversion is completed the
internal sample/hold circuit immediately begins slewing to
track the input signal.
INSTALLATION
Basically, the Control Mode is provided to allow full use of
the internal sample/hold, eliminating the need for an external sample/hold in most applications. As compared with
systems using separate sample/hold and A/D, the ADS574
in the Control Mode also eliminates the need for one of the
control signals, usually the convert command. The command that puts the internal sample/hold in the hold state also
initiates a conversion, reducing timing constraints in many
systems.
LAYOUT PRECAUTIONS
Analog (pin 9) and digital (pin 15) commons are not connected together internally in the ADS574, but should be
connected together as close to the unit as possible and to an
analog common ground plane beneath the converter on the
component side of the board. In addition, a wide conductor
pattern should run directly from pin 9 to the analog supply
common, and a separate wide conductor pattern from pin 15
to the digital supply common.
The Emulation Mode allows the ADS574 to be dropped into
almost all existing ADC574 sockets without changes to any
other existing system hardware or software. The input to the
ADS574 in the Emulation Mode does not need to be stable
before a convert command is received, so that multiplexers,
programmable gain amplifiers, etc., can be slewing quickly
any time before a convert command is given as long as the
analog input to the ADS574 is stable after the convert
command is received, as it needs to be in existing ADC574
systems for accurate operation. In fact, even in the Emula-
If the single-point system common cannot be established
directly at the converter, pin 9 and pin 15 should still be
connected together at the converter. A single wide conductor
pattern then connects these two pins to the system common.
In either case, the common return of the analog input signal
should be referenced to pin 9 of the ADC. This prevents any
voltage drops that might occur in the power supply common
returns from appearing in series with the input signal.
S/H CONTROL MODE
(Pin 11 Connected to +5V)
SYMBOL
PARAMETER
TYP
MAX
tAQ + tC
Throughput Time:
12-bit Conversions
8-bit Conversions
22
16
25
18
Conversion Time:
12-bit Conversions
8-bit Conversions
Acquisition Time
Aperture Delay
Aperture Uncertainty
18
12
4
20
0.3
tC
tAQ
tAP
tJ
MIN
ADC574 EMULATION MODE
(Pin 11 Connected to 0V to –15V)
MIN
TYP
MAX
UNITS
22
16
25
18
µs
µs
µs
µs
µs
ns
ns
18
12
4
4000
30
TABLE VI. Conversion Timing, TMIN to TMAX.
R/C
tC
tAP
S/H Control Mode
Pin 11 connected to +5V.
Signal
Acquisition
Conversion
tAQ
Signal
Acquisition
tC
tAP
ADC574 Emulation Mode*
Pin 11 connected to VEE or ground.
Signal
Acquisition
Conversion
Signal
Acquisition
tAQ
*In the ADC574 Emulation Mode, a convert command triggers a delay that
allows the ADS574 enough time to acquire the input signal before converting.
FIGURE 9. Signal Acquisition and Conversion Timing.
®
11
ADS574
POWER SUPPLY DECOUPLING
On the ADS574, +5V (to Pin 1) is the only power supply
required for correct operation. Pin 7 is not connected internally, so there is no problem in existing ADC574 sockets
where this is connected to +15V. Pin 11 (VEE) is only used
as a logic input to select modes of control over the sampling
function as described above. When used in an existing
ADC574 socket, the –15V on pin 11 selects the ADC574
Emulation Mode. Since pin 11 is used as a logic input, it is
immune to typical supply variations.
+VCC
Unipolar
Offset
Adjust
R1
100kΩ
Full-Scale
Adjust
R2
10
Ref In
8
Ref Out
12
Bipolar Offset
100Ω
ADS574
100kΩ
2.5V
–VCC
100Ω
R3
The +5V supply should be bypassed with a 10µF tantalum
capacitor located close to the converter to promote noisefree operations, as shown in Figure 2. Noise on the power
supply lines can degrade the converter’s performance. Noise
and spikes from a switching power supply are especially
troublesome.
10V
Range
13
Analog
Input
14
20V
Range
9
RANGE CONNECTIONS
The ADS574 offers four standard input ranges: 0V to +10V,
0V to +20V, ±5V, or ±10V. Figures 10 and 11 show the
necessary connections for each of these ranges, along with
the optional gain and offset trim circuits. If a 10V input
range is required, the analog input signal should be connected to pin 13 of the converter. A signal requiring a 20V
range is connected to pin 14. In either case the other pin of
the two is left unconnected. Pin 12 (Bipolar Offset) is
connected either to Pin 9 (Analog Common) for unipolar
operation, or to Pin 8 (2.5V Ref Out), or the external
reference, for bipolar operation. Full-scale and offset adjustments are described below.
Analog
Common
FIGURE 10. Unipolar Configuration.
Full-Scale Adjust
R2
10
Ref In
8
Ref Out
12
Bipolar Offset
100Ω
ADS574
2.5V
100Ω
Bipolar
Offset
Adjust
R1
Analog
Input
10V
Range
20V
Range
14
The input impedance of the ADS574 is typically 84kΩ in the
20V ranges and 21kΩ in the 10V ranges. This is significantly higher than that of traditional ADC574 architectures,
reducing the load on the input source in most applications.
9
INPUT STRUCTURE
13
Figure 12 shows the resistor divider input structure of the
ADS574. Since the input is driving a capacitor in the CDAC
during acquisition, the input is looking into a high imped-
Analog
Common
FIGURE 11. Bipolar Configuration.
If the 10V analog input range is used (either bipolar or
unipolar), the 20V range input (pin 14) should be shielded
with ground plane to reduce noise pickup.
Pin 14
68kΩ
Pin 13
34kΩ
20V Range
Coupling between analog input and digital lines should be
minimized by careful layout. For instance, if the lines must
cross, they should do so at right angles. Parallel analog and
digital lines should be separated from each other by a pattern
connected to common.
10V Range
34kΩ
If external full scale and offset potentiometers are used, the
potentiometers and associated resistors should be as close as
possible to the ADS574.
Pin 12
Bipolar
Offset
17kΩ
10kΩ
FIGURE 12. ADS574 Input Structure.
®
ADS574
12
Capacitor
Array
CALIBRATION
ance node as compared with traditional ADC574 architectures, where the resistor divider network looks into a comparator input node at virtual ground.
OPTIONAL EXTERNAL FULL-SCALE
AND OFFSET ADJUSTMENTS
To understand how this circuit works, it is necessary to
know that the input range on the internal sampling capacitor
is from 0V to +3.33V, and the analog input to the ADS574
must be converted to this range. Unipolar 20V range can be
used as an example of how the divider network functions. In
20V operation, the analog input goes into pin 14. Pin 13 is
left unconnected and pin 12 is connected to analog common
pin 9. From Figure 12, it is clear that the input to the
capacitor array will be the analog input voltage on pin 14
divided by the resistor network (68kΩ + 68kΩ || 17kΩ). A
20V input at pin 14 is divided to 3.33V at the capacitor
array, while a 0V input at pin 14 gives 0V at the capacitor
array.
Offset and full-scale errors may be trimmed to zero using
external offset and full-scale trim potentiometers connected
to the ADS574 as shown in Figures 10 and 11 for unipolar
and bipolar operation.
CALIBRATION PROCEDURE—
UNIPOLAR RANGES
If external adjustments of full-scale and offset are not
required, replace R2 in Figure 10 with a 50Ω, 1% metal film
resistor, omitting the other adjustment components. Connect
pin 12 to pin 9.
If adjustment is required, connect the converter as shown in
Figure 10. Sweep the input through the end-point transition
voltage (0V + 1/2LSB; +1.22mV for the 10V range, +2.44mV
for the 20V range) that causes the output code to be DB0 ON
(HIGH). Adjust potentiometer R1 until DB0 is alternately
toggling ON and OFF with all other bits OFF. Then adjust
full scale by applying an input voltage of nominal full-scale
minus 3/2LSB, the value which should cause all bits to be
ON. This value is +9.9963V for the 10V range and +19.9927V
for the 20V range. Adjust potentiometer R2 until bits DB1DB11 are ON and DB0 is toggling ON and OFF.
The main effect of the 10kΩ internal resistor on pin 12 is to
provide offset adjust response the same as that of traditional
ADC574 architectures without needing to change the external trimpot values.
SINGLE SUPPLY OPERATION
The ADS574 is designed to operate from a single +5V
supply, and handle all of the unipolar and bipolar input
ranges, in either the Control Mode or the Emulation Mode as
described above. Pin 7 is not connected internally. This is
where +12V or +15V is supplied on traditional ADC574s.
Pin 11, the –12V or –15V supply input on traditional
ADC574s, is used only as a logic input on the ADS574.
There is a resistor divider internally on pin 11 to reduce that
input to a correct logic level within the ADS574, and this
resistor will add 10mW to 15mW to the power consumption
of the ADS574 when –15V is supplied to pin 11. To
minimize power consumption in a system, pin 11 can be
simply grounded (for Emulation Mode) or tied to +5V (for
Control Mode.)
CALIBRATION PROCEDURE—BIPOLAR RANGES
If external adjustments of full-scale and bipolar offset are
not required, replace the potentiometers in Figure 11 by
50Ω, 1% metal film resistors.
If adjustments are required, connect the converter as shown
in Figure 11. The calibration procedure is similar to that
described above for unipolar operation, except that the offset
adjustment is performed with an input voltage which is
1/2LSB above the minus full-scale value (–4.9988V for the
±5V range, –9.9976V for the ±10V range). Adjust R1 for
DB0 to toggle ON and OFF with all other bits OFF. To
adjust full-scale, apply a DC input signal which is 3/2LSB
below the nominal plus full-scale value (+4.9963V for ±5V
range, +9.9927V for ±10V range) and adjust R2 for DB0 to
toggle ON and OFF with all other bits ON.
There are no other modifications required for the ADS574 to
function with a single +5V supply.
®
13
ADS574
PACKAGE OPTION ADDENDUM
www.ti.com
29-Sep-2009
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
Lead/Ball Finish
MSL Peak Temp (3)
ADS574AU
OBSOLETE
SOIC
DW
28
TBD
Call TI
Call TI
ADS574AU/1K
OBSOLETE
SOIC
DW
28
TBD
Call TI
Call TI
ADS574JE
ACTIVE
PDIP
NT
28
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
N / A for Pkg Type
ADS574JEG4
ACTIVE
PDIP
NT
28
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
N / A for Pkg Type
ADS574JP
ACTIVE
PDIP
NTD
28
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
N / A for Pkg Type
TBD
Call TI
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
TBD
Call TI
Call TI
Call TI
ADS574JP-2
OBSOLETE
PDIP
NTD
28
ADS574JPG4
ACTIVE
PDIP
NTD
28
Call TI
ADS574JU
OBSOLETE
SOIC
DW
28
ADS574JU/1K
OBSOLETE
SOIC
DW
28
TBD
Call TI
ADS574KE
ACTIVE
PDIP
NT
28
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
N / A for Pkg Type
ADS574KEG4
ACTIVE
PDIP
NT
28
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
N / A for Pkg Type
ADS574KP
ACTIVE
PDIP
NTD
28
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
N / A for Pkg Type
ADS574KPG4
ACTIVE
PDIP
NTD
28
13
Green (RoHS &
no Sb/Br)
CU NIPDAU
N / A for Pkg Type
ADS574KU-2
OBSOLETE
SOIC
DW
28
TBD
Call TI
N / A for Pkg Type
Call TI
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
29-Sep-2009
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 2
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