ADC08161
500 ns A/D Converter with S/H Function and
2.5V Bandgap Reference
General Description
Using a patented multi-step A/D conversion technique, the
8-bit ADC08161 CMOS A/D converter offers 500 ns conver-
sion time, internal sample-and-hold (S/H), a 2.5V bandgap
reference, and dissipates only 100 mW of power. The
ADC08161 performs an 8-bit conversion with a 2-bit voltage
estimator that generates the 2 MSBs and two low-resolution
(3-bit) flashes that generate the 6 LBSs.
Input signals are tracked and held by the input sampling
circuitry,
eliminating
the
need
for
an
external
sample-and-hold. The ADC08161 can perform accurate con-
versions of full-scale input signals at frequencies from DC to
typically more than 300 kHz (full power bandwidth) without
the need of an external sample-and-hold (S/H).
For ease of interface to microprocessors, this part has been
designed to appear as a memory location or I/O port without
the need for external interfacing logic.
Key Specifications
n
Resolution
8 Bits
n
Conversion time (t
CONV
)
560 ns max (WR-RD Mode)
n
Full power bandwidth
300 kHz (typ)
n
Throughput rate
1.5 MHz min
n
Power dissipation
100 mW max
n
Total unadjusted error
1
/
2
LSB and
1 LSB max
Features
n
No external clock required
n
Analog input voltage range from GND to V
+
n
2.5V bandgap reference
Applications
n
Mobile telecommunications
n
Hard-disk drives
n
Instrumentation
n
High-speed data acquisition systems
Block Diagram
DS011149-1
June 1999
ADC08161
500
ns
A/D
Converter
with
S/H
Function
and
2.5V
Bandgap
Reference
2001 National Semiconductor Corporation
DS011149
www.national.com
Connection Diagram
Ordering Information
Industrial (-40C
T
A
85C)
Package
ADC08161CIWM
M20B
Pin Description
V
IN
This is the analog input. The input range is
GND50 mV
V
INPUT
V
+
+ 50 mV.
DB0DB7
TRI-STATE data outputs -- bit 0 (LSB)
through bit 7 (MSB).
WR /RDY
WR-RD Mode (Logic high applied to
MODE pin)
WR: With CS low, the conversion is
started on the rising edge of WR. The
digital result will be strobed into the output
latch at the end of conversion (
Figures 2,
3, 4).
RD Mode (Logic low applied to MODE
pin)
RDY: This is an open drain output (no
internal pull-up device). RDY will go low
after the falling edge of CS and returns
high at the end of conversion.
MODE
Mode: Mode (RD or WR-RD ) selection
input This pin is pulled to a logic low
through an internal 50 A current sink
when left unconnected.
RD Mode is selected if the MODE pin is
left unconnected or externally forced low.
A complete conversion is accomplished by
pulling RD low until output data appears.
WR-RD Mode is selected when a high is
applied to the MODE pin. A conversion
starts with the WR signal's rising edge and
then using RD to access the data.
RD
WR-RD Mode (logic high on the MODE
pin)
This is the active low Read input. With a
logic low applied to the CS pin, the
TRI-STATE data outputs (DB0DB7) will
be activated when RD goes low (
Figures
2, 3, 4).
RD Mode (logic low on the MODE pin)
With CS low, a conversion starts on the
falling edge of RD. Output data appears
on DB0DB7 at the end of conversion
(
Figures 1, 5).
INT
This is an active low output that indicates
that a conversion is complete and the data
is in the output latch. INT is reset by the
rising edge of RD.
GND
This is the power supply ground pin. The
ground pin should be connected to a
"clean" ground reference point.
V
REF-
, V
REF+
These are the reference voltage inputs.
They may be placed at any voltage be-
tween GND - 50 mV and V
+
+ 50 mV, but
V
REF+
must be greater than V
REF-
. Ideally,
an input voltage equal to V
REF-
produces
an output code of 0, and an input voltage
greater than V
REF+
- 1.5 LSB produces an
output code of 255.
For the ADC08161 an input voltage that
exceeds V
+
by more than 100 mV or is
below GND by more than 100 mV will
create conversion errors.
CS
This is the active low Chip Select input. A
logic low signal applied to this input pin
enables the RD and WR inputs. Internally,
the CS signal is ORed with RD and WR
signals.
OFL
Overflow Output. If the analog input is
higher than V
REF+
, OFL will be low at the
end of conversion. It can be used when
cascading two ADC08161s to achieve
higher resolution (9 bits). This output is
always active and does not go into
TRI-STATE as DB0DB7 do. When OFL
is set, all data outputs remain high when
the ADC08061's output data is read.
V
+
Positive power supply voltage input. Nomi-
nal operating supply voltage is +5V. The
supply pin should be bypassed with a
10 F bead tantalum in parallel with a 0.1
ceramic capacitor. Lead length should be
as short as possible.
V
REFOUT
The internal bandgap reference's 2.5V
output is available on this pin. Use a
220 F bypass capacitor between this pin
and analog ground.
Wide-Body Small-Outline Package
DS011149-14
See NS Package Number M20B
ADC08161
www.national.com
2
Absolute Maximum Ratings
(Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
+
)
6V
Logic Control Inputs
-0.3V to V
+
+ 0.3V
Voltage at Other Inputs and Outputs
-0.3V to V
+
+ 0.3V
Input Current at Any Pin (Note 3)
5 mA
Package Input Current (Note 3)
20 mA
Power Dissipation (Note 4)
875 mW
Lead Temperature (Note 5)
(Vapor Phase, 60 sec.)
+215C
(Infrared, 15 sec.)
+220C
Storage Temperature
-65C to +150C
ESD Susceptibility (Note 6)
750V
Operating Ratings
(Notes 1, 2)
Temperature Range
T
MIN
T
A
T
MAX
ADC08161CIWM
-40C
T
A
85C
Supply Voltage, (V
+
)
4.5V to 5.5V
Converter Characteristics
The following specifications apply for RD Mode, V
+
= 5V, V
REF+
= 5V, and V
REF-
= GND unless otherwise specified. Boldface
limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= 25C.
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 7)
(Note 8)
(Limit)
INL
Integral Non Linearity
V
REF
= 5V
1
LSB (max)
TUE
Total Unadjusted Error (Note 9)
V
REF
= 5V
1
LSB (max)
INL
Integral Non Linearity
V
REF
= 2.5V
1
LSB (max)
TUE
Total Unadjusted Error
V
REF
= 2.5V
1
LSB (max)
Missing Codes
V
REF
= 5V
0
Bits (max)
V
REF
= 2.5V
0
Bits (max)
Reference Input Resistance
700
500
(min)
700
1250
(max)
V
REF+
Positive Reference Input Voltage
V
REF-
V (min)
V
+
V (max)
V
REF-
Negative Reference
GND
V (min)
Input Voltage
V
REF+
V (max)
V
IN
Analog
(Note 10)
GND - 0.1
V (min)
Input Voltage
V
+
+ 0.1
V (max)
On-Channel Input Current
On Channel Input = 5V,
Off Channel Input = 0V
-0.4
-20
A (max)
(Note 11)
On Channel Input = 0V,
Off Channel Input = 5V
-0.4
-20
A (max)
(Note 11)
PSS
Power Supply Sensitivity
V
+
= 5V
5%,
V
REF
= 4.75V
1/16
1
/
2
LSB (max)
All Codes Tested
Effective Bits
V
IN
= 4.85 V
p-p
7.8
Bits
f
IN
= 20 Hz to 20 kHz
Full-Power Bandwidth
V
IN
= 4.85 V
p-p
300
kHz
THD
Total Harmonic Distortion
V
IN
= 4.85 V
p-p
0.5
%
f
IN
= 20 Hz to 20 kHz
S/N
Signal-to-Noise Ratio
V
IN
= 4.85 V
p-p
50
dB
f
IN
= 20 Hz to 20 kHz
IMD
Intermodulation Distortion
V
IN
= 4.85 V
p-p
50
dB
f
IN
= 20 Hz to 20 kHz
C
VIN
Analog Input Capacitance
25
pF
ADC08161
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3
AC Electrical Characteristics
The following specifications apply for V
+
= 5V, t
r
= t
f
= 10 ns, V
REF+
= 5V, V
REF-
= 0V unless otherwise specified. Boldface
limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 7)
Limit
(Note 8)
Units
(Limit)
t
WR
Write Time
Mode Pin to V
+
100
100
ns (min)
(
Figures 2, 3, 4)
t
RD
Read Time (Time from Rising Edge
Mode Pin to V
+
, (
Figure 2)
350
350
ns (min)
of WR to Falling Edge of RD )
t
RDW
RD Width
Mode Pin to GND (
Figure 5 )
200
250
ns (min)
400
400
ns (max)
t
CONV
WR -RD Mode Conversion Time
Mode Pin to V
+
, (
Figure 2 )
500
560
ns (max)
(t
WR
+ t
RD
+ t
ACC1
)
t
CRD
RD Mode Conversion Time
Mode Pin to GND, (
Figure 1 )
655
900
ns (max)
t
ACCO
Access Time (Delay from Falling
C
L
100 pF, Mode Pin to GND
640
900
ns (max)
Edge of RD to Output Valid)
(
Figure 1 )
t
ACC1
Access Time (Delay from
C
L
10 pF
45
ns
Falling Edge of RD
C
L
= 100 pF
50
110
ns (max)
to Output Valid)
Mode Pin to V
+
, t
RD
t
INTL
(
Figure 2 )
t
ACC2
Access Time (Delay from
C
L
10 pF
25
ns
Falling Edge of RD
C
L
= 100 pF
30
55
ns (max)
to Output Valid)
t
RD
>
t
INTL
,
(
Figures 3, 5)
t
1H
, t
0H
TRI-STATE Control
R
L
= 3 k
, C
L
= 10 pF
(Delay from Rising Edge
(
Figures 1, 2, 3, 4, 5)
30
60
ns (max)
of RD to HI-Z State)
t
INTL
Delay from Rising Edge of
Mode Pin = V
+
, C
L
= 50 pF
520
690
ns (max)
WR to Falling Edge of INT
(
Figures 3, 4)
t
INTH
Delay from Rising Edge of
C
L
= 50 pF,
50
95
ns (max)
RD to Rising Edge of INT
(
Figures 1, 2, 3, 5)
t
INTH
Delay from Rising Edge of
C
L
= 50 pF, (
Figure 4)
45
95
ns (max)
WR to Rising Edge of INT
t
RDY
Delay from CS to RDY
Mode Pin = 0V, C
L
= 50 pF,
25
45
ns (max)
R
L
= 3 k
, (
Figure 1)
t
ID
Delay from INT
R
L
= 3 k
, C
L
= 100 pF
0
15
ns (max)
to Output Valid
(
Figure 4)
t
RI
Delay from RD to INT
Mode Pin = V
+
, t
RD
t
INTL
60
115
ns (max)
(
Figure 2)
t
N
Time between End of RD
(
Figures 1, 2, 3, 4, 5)
50
50
ns (min)
and Start of New Conversion
t
CSS
CS Setup Time
(
Figures 1, 2, 3, 4, 5)
0
0
ns (max)
t
CSH
CS Hold Time
(
Figures 1, 2, 3, 4, 5)
0
0
ns (max)
DC Electrical Characteristics
The following specifications apply for V
+
= 5V unless otherwise specified. Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
;
all other limits T
A
= T
J
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 7)
Limit
(Note 8)
Units
(Limit)
V
IH
Logic "1" Input Voltage
V
+
= 5.5 V
CS, WR, RD, A0, A1, A2 Pins
2.0
V (min)
Mode Pin
3.5
ADC08161
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4
DC Electrical Characteristics
(Continued)
The following specifications apply for V
+
= 5V unless otherwise specified. Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
;
all other limits T
A
= T
J
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 7)
Limit
(Note 8)
Units
(Limit)
V
IL
Logic "0" Input Voltage
V
+
= 4.5V
CS, WR, RD, A0, A1, A2 Pins
0.8
V (max)
Mode Pin
1.5
I
IH
Logic "1" Input Current
V
H
= 5V
CS, RD, A0, A, A2 Pins
0.005
1
WR Pin
0.1
3
A (max)
Mode Pin
50
200
I
IL
Logic "0" Input Current
V
L
= 0V
CS, RD, WR, A0, A1, A2
Mode Pins
-0.005
-2
A (max)
V
OH
Logic "1" Output Voltage
V
+
= 4.75V
I
OUT
= -360 A
2.4
V (min)
DB0DB7, OFL, INT
I
OUT
= -10 A
4.5
V (min)
DB0DB7, OFL, INT
V
OL
Logic "0" Output Voltage
V
+
= 4.75V
I
OUT
= 1.6 mA
0.4
V (max)
DB0DB7, OFL, INT, RDY
I
O
TRI-STATE Output Current
V
OUT
= 5.0V
0.1
3
A (max)
DB0DB7, RDY
V
OUT
= 0V
-0.1
-3
A (max)
DB0DB7, RDY
I
SOURCE
Output Source Current
V
OUT
= 0V
-26
-6
mA (min)
DB0DB7, OFL, INT
I
SINK
Output Sink Current
V
OUT
= 5V
24
7
mA (min)
DB0DB7, OFL, INT, RDY
I
C
Supply Current
CS = WR = RD = 0
11.5
20
mA (max)
C
OUT
Logic Output Capacitance
5
pF
C
IN
Logic Input Capacitance
5
pF
Bandgap Reference Electrical Characteristics
The following specifications apply for V
+
= 5V unless otherwise specified. Boldface limits apply for T
MIN
to T
MAX
; all other
limits T
A
= T
J
= 25C.
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 7)
(Note 8)
(Limit)
V
REFOUT
Internal Reference Output Voltage
2.5
2.0%
V (max)
V
REF
/
T
Internal Reference Temperature
40
ppm/C
Coefficient
V
REF
/
I
L
Internal Reference Load
Sourcing (0
I
L
+10 mA)
0.01
0.1
%/mA (max)
Regulation
Line Regulation
4.75V
V
+
5.25V
0.5
6.0
mV (max)
I
SC
Short Circuit Current
V
REV
= 0V
35
mA (max)
V
REF
/
t
Long Term Stability
200
ppm/kHr
Start-Up Time
V
+
: 0V
5V, C
L
= 220 F
40
ms
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating
the device beyond its specified operating ratings. Operating Ratings indicate conditions for which the device is functional, but do not guarantee performance limits.
For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some
performance characteristics may degrade when the device is not operated under the listed test conditions.
ADC08161
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5
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