AS1536/AS1537
1 2 - B i t , S i n g l e S u p p l y, L o w - P o w e r, 7 3 k s ps A / D C o n -
verters
D a ta s h e e t
1 General Description
The AS1536/AS1537 are low-power, 12-bit, 73ksps ana-
log-to-digital (A/D) converters specifically designed for
single-supply A/D applications. Superior AC characteris-
tics, very low power consumption, and robust packaging
make these ultra-small devices perfect for battery-pow-
ered analog-data collection devices.
The integrated successive-approximation register (SAR)
and a fast (1.5µs) sampling track/hold time provide an
economic and highly-reliable A/D conversion solution.
The AS1536/AS1537 operate from a single 2.7V to
5.25V supply. The AS1537 requires an external refer-
ence, using less power than the AS1536, however, the
AS1536 features an internal 2.5V reference.
As with the AS1537, the AS1536 can also be used with
an external reference, which uses the input range 0V to
V
REF
, including the positive supply range.
The AS1537 consumes only 3mW (V
DD
= 3V) at the
73ksps maximum sampling speed. Both devices feature
a low-current (0.3µA) shutdown mode, which reduces
power consumption at slower throughput rates.
Data accesses are made via the standard, high-speed
3-wire serial interface, which is SPI-, QSPI-, and
Microwire-compatible. Both devices contain an internal
clock, however, both devices also support an external
clock for increased flexibility.
The AS1536/AS1537 are available in an 8-pin SOIC-150
package.
2 Key Features
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12-Bit Resolution with 7.5µs Conversion Time
Sampling Rate: 73ksps
Straight Binary (Unipolar) Data Format
Single-Supply Operation:+2.7V to +5.25V
Internal 2.5V Reference (AS1536)
Low Power-Consumption:
- 4mW (73ksps, AS1536)
- 3mW (73ksps, AS1537)
- 66µW (1ksps, AS1537)
- 1µW (Shutdown Mode)
Integrated Track/Hold Amplifier
Internal Clock
SPI/QSPI/Microwire 3-Wire Serial Interface
Operating Temperature Range: -40 to +85ºC
8-pin SOIC-150 Package
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3 Applications
The devices are ideal for remote sensors, data-acquisi-
tion, data logging devices, lab instruments, or for any
other space-limited A/D devices with low power con-
sumption and single-supply requirements.
Figure 1. Block Diagram
1
VDD
7
CSN
8
SCLK
3
SHDNN
Control
Logic
Internal
Clock
Output
Shift
Register
6
DOUT
AS1536/AS1537
2
AIN
4
REF
Track/
Hold
12-Bit
SAR
2.5V
Ref
5
GND
AS1536
only
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AS1536/AS1537
Datasheet - Table of C o n t e n t
Contents
1 General Description
2 Key Features
3 Applications
4 Pinout
............................................................................................................................. 2
........................................................................................................................................ 2
.......................................................................................................................................... 2
..................................................................................................................................................... 4
................................................................................................................................................... 4
................................................................................................................. 5
Pin Description
5 Absolute Maximum Ratings
6 Electrical Characteristics
Timing Characteristics
...................................................................................................................... 6
........................................................................................................ 9
......................................................................................................................................... 8
7 Typical Operating Characteristics
8 Detailed Description
Analog Input
Track/Hold
External Clock
........................................................................................................................... 12
....................................................................................................................................................... 12
.......................................................................................................................................................... 13
.................................................................................................................................................... 13
............................................................................................................................................. 13
............................................................................................................................................... 15
................................................................................................................................... 15
..................................................................................................................... 16
Timing and Control
Transfer Function
Reducing Supply Current
External Reference
Initialization
Internal 2.5V Reference (AS1536)
............................................................................................................................................ 16
9 Application Information
Serial Interface
...................................................................................................................... 17
........................................................................................................................................................ 17
................................................................................................................................................... 17
....................................................................................................................................... 19
Layout Considerations
10 Package Drawings and Markings
11 Ordering Information
.................................................................................................... 20
....................................................................................................................... 21
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AS1536/AS1537
Datasheet - P i n o u t
4 Pinout
Figure 2. Pin Assignments (Top View)
VDD 1
8 SCLK
AIN 2
7 CSN
AS1536/
AS1537
SHDNN 3
6 DOUT
REF 4
5 GND
Pin Description
Table 1. Pin Descriptions
Pin Number
1
2
Pin Name
VDD
AIN
Description
Positive Supply Voltage.
+2.7V to +5.25V
Sampling Analog Input.
0V to V
REF
range.
Three-Level Shutdown Input.
Pulling this pin low puts the AS1536/AS1537
in shutdown mode, down to 4µA (max) supply current. The devices are fully
operational with this pin high or floating.
Note:
For the AS1536, pulling this pin high enables the internal reference; let-
ting this pin float disables the internal reference allowing for the use of an
external reference. See also pin 4.
A/D Conversion Reference Voltage.
This pin serves as the internal 2.5V
reference output for the AS1536; bypass this pin with a 4.7µF capacitor.
This pin also serves as the external reference voltage input for the AS1537, or
for AS1536 if the internal reference is disabled. Bypass this pin with a
minimum of 0.1µF when using an external reference. See also pin 3.
Analog and Digital Ground
Serial Data Output.
Data changes state at SCLK’s falling edge.
Note:
This pin is high-impedance when pin CSN is high.
Active-Low Chip Select.
The falling edge of this pin initiates a conversion.
Note:
When this pin is high, DOUT is high-impedance.
Serial Clock Input.
This pin clocks data out at rates up to 2.1MHz.
3
SHDNN
4
REF
5
6
7
8
GND
DOUT
CSN
SCLK
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AS1536/AS1537
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in
Table 2
may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in
Section 6 Electrical
Characteristics on page 6
is not implied. Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
Table 2. Absolute Maximum Ratings
Parameter
VDD to GND
AIN to GND
REF to GND
Digital Inputs to GND
DOUT to GND
DOUT Current
Continuous Power Dissipation
(T
AMB
= +70ºC)
Operating Temperature Range
Storage Temperature Range
-40
-60
Min
0.3
-0.3
-0.3
-0.3
-0.3
-25
Max
+7
V
DD
+
0.3V
V
DD
+
0.3V
V
DD
+
0.3V
V
DD
+
0.3V
+25
471
+85
+150
Units
V
V
V
V
V
mA
mW
ºC
ºC
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/JEDEC J-STD-020D “Moisture/Reflow
Sensitivity Classification for non-hermetic
Solid State Surface Mount Devices”.
Derate 5.88mW/ºC above +70ºC
Comments
Package-Body Peak Temperature
260
°C
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AS1536/AS1537
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
DD
= +2.7V to +5.25V, 73ksps, f
SCLK
= 2.1MHz (50% duty cycle); AS1536:4.7µF capacitor at REF, AS1537: external
reference; V
REF
= 2.5V applied to REF; T
AMB
= T
MIN
to T
MAX
(unless otherwise specified).
Table 3. Electrical Characteristics
Symbol
DC Accuracy
1
Parameter
Conditions
Min
Typ
Max
Units
Resolution
Relative Accuracy
DNL
2
12
±1
No missing codes over temperature
±1
±6
±6
±1
Bits
LSB
LSB
LSB
LSB
ppm/°C
Differential Non-Linearity
Offset Error
Gain Error
3
Gain Temperature Coefficient
Dynamic Specifications
(10kHz sine-wave input, 0V to 2.5Vp-p, 73ksps, f
SCLK
=2.1MHz)
SINAD
THD
SFDR
Signal-to-Noise + Distortion
Ratio
Total Harmonic Distortion
Spurious-Free Dynamic Range
Small-Signal Bandwidth
Full-Power Bandwidth
Conversion Rate
t
CONV
t
ACQ
Conversion Time
Track/Hold Acquisition Time
Throughput Rate
t
AP
Aperture Delay
Aperture Jitter
Analog Input
Input Voltage Range
Input Capacitance
Internal Reference
(AS1536 only)
REF
Output Voltage
REF
Short-Circuit Current
REF
Temperature Coefficient
Load Regulation
C
REFBYP
6
4
67
Up to the 5th harmonic
80
-3dB rolloff
70.5
-83
88
2.5
2.5
-80
dB
dB
dB
MHz
MHz
5.5
7.5
1.5
µs
µs
ksps
ns
ps
f
SCLK
= 2.1MHz
Figure 27 on page 14
7
<50
73
0
21
V
REF
V
pF
T
AMB
= +25ºC
5
2.47
2.50
2.53
45
V
mA
ppm/°C
mV
µF
AS1536
0 to 0.2mA output load
4.7
±30
0.35
Capacitive Bypass at
REF
External Reference
(V
REF
= 2.5V)
Input Voltage Range
Input Current
Input Resistance
REF
Input Current in Shutdown
C
REFBYP
Capacitive Bypass at
REF
SHDNN = 0V
0.1
18
1.00
100
25
±0.01
10
V
DD
+
50mV
150
V
µA
kΩ
µA
µF
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