ETC ADC-305-1 8-bit, 20mhz cmos a/d converter Datasheet

®
®
ADC-305
8-Bit, 20MHz
CMOS A/D Converters
FEATURES
•
•
•
•
•
•
•
8-bit resolution, 20MHz min. sampling rate
±½LSB max. differential nonlinearity error
18MHz input signal bandwidth
Subranging, S&H enclosed
+5V single power, low 85mW max. dissipation
CMOS compatible logic input
3-State TTL compatible output
INPUT/OUTPUT CONNECTIONS
GENERAL DESCRIPTION
DATEL's ADC-305 is an 8-bit, 20MHz sampling, CMOS,
subranging (two-pass) A/D converter. It processes signals at
speeds comparable to a full flash converter by using a subranging conversion technique with multiple comparator blocks,
each containing a sample and hold amplifier.
The ADC-305 features CMOS low power dissipation (60mW
typical) and a wide 18MHz (–1dB) input signal bandwidth.
The ADC-305-1 is packaged in 400 mil 24-pin DIP and the
ADC-305-3 in 300 mil 24-pin SOP.
Other features are CMOS compatible input logic, 3-state TTL
compatible output logic, +5V single power operation, self bias
mode and low cost.
PIN
1
2
3
4
5
6
7
8
9
10
11
12
FUNCTION
PIN
OUTPUT ENABLE (OE)
DGND
BIT 8 (LSB)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1 (MSB)
+DVS (+5V)
CLOCK INPUT (A/D CLK)
24
23
22
21
20
19
18
17
16
15
14
13
FUNCTION
DGND
REF. BOTTOM (VRB)
SELF BIAS 1 (VRBS)
AGND
AGND
ANALOG INPUT (VIN)
+AVS (+5V)
REFERENCE TOP (VRT)
SELF BIAS 2 (VRTS)
+AVS (+5V)
+AVS (+5V)
+DVS (+5V)
Both the ADC-305-1 and the ADC-305-3 have the same pin assignment.
24 DGND
OUTPUT ENABLE 1
REFERENCE
VOLTAGE
DGND 2
23 VRB
22 VRBS
BIT 8 (LSB) 3
BIT 7 4
BIT 6 5
LOWER
DATA
LATCHES
LOWER
ENCODER
(4 BIT)
B BLOCK
COMPARATORS
WITH S/H (4 BIT)
BIT 4 7
BIT 2 9
UPPER
DATA
LATCHES
BIT 1 (MSB) 10
LOWER
ENCODER
(4 BIT)
A BLOCK
COMPARATORS
WITH S/H (4 BIT)
UPPER
ENCODER
(4 BIT)
UPPER
COMPARATORS
WITH S/H (4 BIT)
18 +AVS
17 VRT
16 VRTS
15 +AVS
+DVS 11
A/D CLK 12
20 AGND
19 VIN
BIT 5 6
BIT 3 8
21 AGND
CLOCK
GENERATOR
14 +AVS
13 +DVS
Figure 1. Functional Block Diagram
DATEL, Inc., Mansfield, MA 02048-1151 (USA) • Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356 • Email: [email protected] • Internet www.datel.com
®
®
ADC-305
ABSOLUTE MAXIMUM RATINGS (TA = 25°C)
PARAMETERS
MIN
MAX
UNITS
Power Supply Voltage (+AVS, +DVS)
Analog Input Voltage (VIN)
Reference Input Voltage (VRT, VRB)
Digital Input Voltage (VIH, VIL)
Digital Output Voltage (VOH, VOL)
–0.5
–0.5
–0.5
–0.5
–0.5
+7
+AVS +0.5
+AVS +0.5
+DVS +0.5
+DVS +0.5
Volts
Volts
Volts
Volts
Volts
MIN.
TYP.
MAX.
UNITS
—
—
+0.5 to +2.5
11
—
—
Volts
pF
VRT to VRB
VRT
VRB
Offset Voltage
VRT
VRB
Self Bias I ➀ ➁VRBS
VRTS-VRBS
Self Bias II ➀ ➂VRTS
MAX.
UNITS
Power Supply (+AVS, +DVS)
I A GND - D GND I
Power Supply Current
Power Dissipation
+4.75
—
—
—
+5.0
—
12
60
+5.25
100
17
85
Volts
mV
mA
mW
—
—
12.5
18
—
—
kΩ
MHz
230
4.5
+1.8
0
–10
0
+0.6
+1.96
+2.25
300
6.6
—
—
–35
+15
+0.64
+2.09
+2.39
450
8.7
+2.8
VRT
–60
+45
+0.68
+2.21
+2.53
Ω
mA
Volts
Volts
mV
mV
Volts
Volts
Volts
–40 to +85°C
–55 to +150°C
24-pin Plastic DIP
24-pin Plastic SOP
2.0 grams
0.3 grams
TECHNICAL NOTES
1. The ADC-305 has separate +AVS and +DVS pins. It is
recommended that both +AVS and +DVS be powered from a
single supply since a time lag between start up of separate
supplies could induce latch up. Other external logic circuits
must be powered from a separate digital supply. +DVS (pins
11 and 13) and +AVs (pins 14, 15 and 18) should be tied
together externally. DGND (pins 2 and 24) and AGND (pins
20 and 21) should also be tied together externally. Power
supply grounds must be connected at one point to the
ground plane directly beneath the device. Digital returns
should not flow through analog grounds.
REFERENCE INPUTS
Ref. Resitance
Ref. Current
Ref. Voltage ➀
TYP.
Operating Temp. Range
Storage Temp. Range
Package Type
ADC-305-1
ADC-305-3
Weight
ADC-305-1
ADC-305-3
(Specification are typical at TA = +25°C, +VRT = +2.5V, VRB = +0.5V, +AVS = +DVS =
+5v, fS = 20MHz sampling unless otherwise specified.)
Input Voltage Range (VIN) ➀
Input Capacitance
(VIN = 1.5Vdc+0.07VRMS)
Input Impedance
Input Signal Bandwidth
(VIN-2Vp-p, –1dB)
MIN.
PHYSICAL/ENVIRONMENTAL
FUNCTIONAL SPECIFICATIONS
ANALOG INPUTS
POWER REQUIREMENTS
DIGITAL INPUTS
2. Bypass all power lines to ground with a 0.1µF ceramic chip
capacitor in parallel with a 47µF electrolytic capacitor.
Locate the bypass capacitor as close to the unit as
possible.
Input Voltage (CMOS)
Logic Levels (VIH) "1"
Logic Level (VIL) "0"
Input Current (@VIH=+DVS)"1"
(@VIL=0) "0"
Clock Pulse Width TPW1
(A/D CLK)
TPW0
3. Even though the analog input capacitance is a low 15pF, it
is recommended that high frequency input be provided via
a high speed buffer amplifier. A parasitic oscillation may be
generated when a high speed amplifier is used. A 75 ohm
resister inserted between the output of an amplifier and the
analog input of the ADC-305 will improve the situation. A
resistor larger than 100 ohms may degrade linearity.
+4
—
—
—
25
25
—
—
—
—
—
—
—
+1
5
5
—
—
Volts
Volts
µA
µA
ns
ns
4. The input voltage range is determined by voltages applied
to VRB (Reference Bottom) and VRT (Reference Top). Keep
to the following equations;
DIGITAL OUTPUTS
Output Data
Output Voltage
Output Current ➃
Logic Level "1"
Logic Level "0"
Output Current ➄
Logic Level "1"
Logic Level "0"
Output Data Delay, Td
8-bit Binary Parallel
3-State TTL compatible
—
—
18
16
16
30
µA
µA
ns
8
20
—
—
—
—
—
—
—
—
—
—
4
30
±0.3
+0.5
1
0.5
—
—
0.5
—
—
±0.5
+1.3
—
—
Bit
MHz
MHz
ns
ps
LSB
LSB
%
deg
The analog input range is normally 2Vp-p.
Self Bias Mode
a. Tie VRB to VRBS, and tie VRT to VRTS respectively. The analog
input range in this case is +0.64V to +2.73V nominal.
PERFORMANCE
Resolution
Maximum Sampling Rate
Minimum Sampling Rate
Aperature Delay, TA
Aperature Jitter
Differential Linearity Error
Integral Linearity Error
Differential Gain Error ➅
Differential Phase Error ➅
Table 1. Digital Output Coding
OV
Zero
+0.9922V
+1.000V
+1/2FS –1LSB
+1/2FS
127
128
7F
80
0111
1000
1111
0000
0
00
0000
0000
➔
➔
➔
+1.9922V
2
DATA BITS OUT
MSB
LSB
CODE
➔
➃ OE=OV, VOH=+DVS–0.5V,
VOL=+0.4V
➄ OE=+DVS, VOH=+DVS, VOL=0V
➅ NTSC 40IRE mode ramp, 14.3MHz
sampling
STEP
DEC
HEX
VIN
➔
Footnotes:
➀ See Technical Note 4
➁ Short VRB (pin 23) to VRBS (pin 22).
Short VRT (pin 17) to VRTS (pin 16).
➂ Short VRB (pin 23) to A GND.
Short VRT (pin 17) to VRTS (pin 16).
b. Tie VRB to AGND, and tie VRT to VRTS respectively. The
analog input voltage range is 0 to +2.39V in this case.
➔
—
—
—
0V≤V RB≤V RT≤2.8V
1.8V≤V RT–VRB≤2.8V
➔
mA
mA
➔
—
—
➔
—
—
➔
–1.1
+3.7
+FS
255
FF
1111
1111
®
®
ADC-305
These values may differ from one device to another. Voltage
changes on the +5V supply have a direct influence on the
performance of the device. The use of external references is
recommended for applications sensitive to gain error.
longer TPW1 will improve linearity of the system for higher
frequency input signals.
7. The digital data outputs are 3-state and TTL compatible. To
enable the 3-state outputs, connect the OUTPUT ENABLE
(pin 1) to GND. To disable, connect it to +5V. It is
recommended that the data outputs be latched and buffered
through output registers.
External Reference Mode
Tie VRB to AGND, and apply +2V to VRT to use at 0 to +2V
input voltage range. The reference resistance between VRB
and VRT is about 300 ohms. It is important to make the
output impedance of the reference source small enough
while, at the same time, keeping sufficient drive capacity.
Insert a 0.1µF bypass ceramic chip capacitor between VRT
and GND to minimize the effect of the 20MHz clock
running nearby. See Figure 5.
8. Maximum 30ns (18ns typical) after the rising edge of the
Nth conversion pulse, the result of the (N-3) conversion can
be obtained. Data is stored firmly in an output register, such
as an 74LS574, using the rising edge of a start convert
pulse as a trigger. The (N–4) data is stored in this case. See
the timing diagrams, Figure 2 and 4.
5. Logic inputs are CMOS compatible. Normally a series 74HC
is used as a driver. It is recommended to pull up to +5V if
the device is driven with TTL.
9. The 20MHz sampling rate is guaranteed. It is not
recommended to use this device at sampling rates slower
than 500kHz because the droop characteristics of the
internal sample and holds will then exceed the limit
required to maintain the specified accuracy of the device.
6. The start convert (A/D CLK) pulse can be a 50% duty cycle
clock. Both TPW1 and TPW0 are 25ns minimum. A slightly
Ta
ANALOG
INPUT
N
TPW1
N+1
N+2
TPW0
N+3
N+4
N
N+1
CLOCK
DATA
OUTPUT
N-3
N-2
N-1
Td= 30ns max.
Figure 2. Timing Diagram
+DVS
+AVS
+DVS
OE
VIN
19
A/D CLK
+DGND
DGND
Digital Output Circuit, Bit1 through Bit 8
AGND
Equivalent Circuit for OE and A/D CLK
OE - Low data is output when high digital
output pins turn to high impedance.
Analog Input
+AVS
+AVS
VRT
VRB
17
23
VRBS
AGND
22
AGND
Voltage Reference (VRT,VRB)
Equivalent Circuit
Generates +0.6V
when shorted with VB
Figure 3. Equivalent Circuits
3
VRTS
16
Generates +2.6V
when shorted with VT
®
®
®
®
ADC-305
N+3
N+2
ANALOG INPUT
(VIN)
N+1
N
A/D CLK
UPPER
SAMPLING
COMPARATOR
BLOCK
S(N)
UPPER
OUTPUT
DATA
C(N)
MD(N-1)
LOWER
REFERENCE
VOLTAGE
S(1)
OUTPUT
DATA
S(N+2)
C(N-1)
S(N+3)
C(1)
S(3)
RV(N+2)
H(3)
C(3)
LD(N)
S(N+1)
H(N+1)
LD(N-3)
C(N+1)
S(N+3)
LD(N-1)
N-3
C(N+3)
MD(N+2)
RV(N+1)
LD(N-2)
H(0-1)
C(N+2)
MD(N+1)
RV(N)
H(1)
LOWER DATA A
LOWER
OUTPUT
DATA B
C(N+1)
MD(N)
RV(N-1)
LOWER
SAMPLING
COMPARATOR
A BLOCK
LOWER
SAMPLING
COMPARATOR
B BLOCK
S(N+1)
N-2
Figure 4. Timing Chart
4
H(N+3)
LD(N+1)
N-1
N
®
®
ADC-305
+5V(A)
+5V(D)
47µF
47µF
100µH
Bias
Adjust
0.1µF
0.1µF
0.1µF
13
14
11
1
20
0.1µF
15
10
2
19
0.1µF
16
9
3
18
17
8
4
17
18
7
5
16
6
6
20
5
7
14
21
4
8
13
22
3
9
12
23
2
10
11
24
1
VIN
(RIN = 75 Ω)
470µF 390
100
Gain
Adjust
2SC2785
2SC2785
22µF
120
0.1µF
2.2k
51
75
10k
2SC2785
0.1µF
680
2.2k
–5V(A)
+5V(A)
0.1µF
19
ADC-305
0.1µF
2SC2785
2k
74LS574
BIT 1 (MSB)
BIT 2
BIT 3
BIT 4
15
BIT 5
BIT 6
BIT 7
BIT 8 (LSB)
0.1µF
VRT
Adjust
510
VRB
Adjust
0.1µF
12
2SC2785
2k
1
14
2
13
3
4
510
11
74HC04
510
9
6
7
47µF
–5V(A)
Clock Input
(A/D CLK)
(RIN = 75Ω)
75
Figure 5. Typical Connection Diagram
LSB
20
0.6
+DVS=+AVS=+5V
VIN = 1kHz
Ta=25°C
15
Supply Current
Supply Current
20
15
10
SNR + THD vs. Input Signal Frequency
dB
+DVS=+AVS=+5V
FS = 20.48MHz
Ta=25°C
46
SNR + THD
mA
Diff. Linearity Error
mA
Differential Linearity Error vs.
Input Signal Frequency
Supply Current vs. Sampling Voltage
Supply Current vs. Sampling Rate
0.4
42
+DVS=+AVS=+5V
FS = 20.48MHz
Ta=25°C
38
0.2
5
10
36
5
10 15 20 25 30MHz
Sampling Rate
4.0
4.5
5.0
5.5V
Supply Voltage
2
4
6
8
Input Signal Frequency
Figure 6. Typical Performance Curves
5
10MHz
1
3
5
2
4
6 7MHz
Input Signal Frequency
®
®
ADC-305
MECHANICAL DIMENSIONS INCHES (MM)
1.195 ±0.010
(30.35 .±0.25)
ADC-305-1
24-Pin DIP (Plastic)
400mil 2.0g
13
24
0.339 ±0.008
(8.60 ±0.20)
ADC-305-1
1
12
0.400
(10.16)
0.152 ±0.010
(3.85 ±0.25)
0.118 MIN.
(3.00 MIN.)
0.011 ±0.003
(0.28 ±0.08)
0° to 15°
0.020 ±0.004
(0.50 ±0.10)
0.100 TYP.
(2.54)
SEATING
PLANE
0.020 MIN.
(0.50 MIN.)
0.047 ±0.006
(1.20 ±0.15)
ADC-305-3
24-Pin SOP (Plastic)
300mil 0.3g
0.596 ±0.010
(15.15 ±0.25)
24
13
1
0.307 ±0.012
(7.80 ±0.30)
0.213 ±0.008
(5.40 ±0.20)
ADC-305-3
12
0.078 ±0.011
(1.97 ±0.28)
0.272
(6.90)
0.007 ±0.005
(0.18 ±0.13)
0.050 TYP.
(1.27)
0.009 ±0.003
(0.23 ±0.08)
0.018 ± 0.004
(0.45 ± 0.10)
0.020 ±0.008
(0.50 ±0.20)
ORDERING INFORMATION
®
®
MODEL NUMBER
PACKAGE
ADC-305-1
ADC-305-3
24-Pin Plastic DIP 400 mil
24-Pin Plastic SOP 300 mil
ISO 9001
R
DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151
Tel: (508) 339-3000, (800) 233-2765 Fax: (508) 339-6356
Internet: www.datel.com Email: [email protected]
Data Sheet Fax Back: (508) 261-2857
E
G
I
S
T
E
R
E
D
DS-0342
6/98
DATEL (UK) LTD. Tadley, England Tel: (01256)-880444
DATEL S.A.R.L. Montigny Le Bretonneux, France Tel: 01-34-60-01-01
DATEL GmbH Munchen, Germany Tel: 89-544334-0
DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-354-2025
DATEL makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein
do not imply the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. The DATEL logo is a registered DATEL, Inc. trademark.
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