AS1538/AS1540
8 / 4 - C h a n n e l , 1 2 - B i t I ² C A n a l o g - t o - D i g i ta l C o n v e r t e r
D a ta S he e t
1 General Description
The AS1538/AS1540 are single-supply, low-power, 12-
bit data acquisition devices featuring a serial I²C inter-
face and an 8-channel (AS1538) or 4-channel (AS1540)
multiplexer.
The analog-to-digital (A/D) converters features a sam-
ple-and-hold amplifier an internal asynchronous clock
and an internal reference.
The combination of an I C serial, 2-wire interface and
micropower consumption makes the AS1538 and
AS1540 ideal for applications requiring the A/D con-
verter to be close to the input source in remote locations
and for applications requiring isolation.
The device is available in a TSSOP-16 or TQFN 4x4 16-
pin package.
2
2 Key Features
!
!
!
!
!
!
!
!
!
Single Supply: 2.7 to 5.25V
8-Channel Multiplexer (AS1538)
4-Channel Multiplexer (AS1540)
Sampling Rate: 50kSPS
No Missing Codes
Internal Reference: 2.5V
High Speed I C Interface at 3.4MHz
<1.5µA Full Shutdown Current
TSSOP-16 or TQFN 4x4 16-pin Package
2
3 Applications
The device is ideal for voltage-supply monitoring, iso-
lated data acquisition, transducer interfaces, battery-
operated systems, remote data acquisition or any other
analog-to-digital conversion application.
Figure 1. Block Diagram
CH0
CH1
CH2
CH3
CH4
CH5
AS1538 only
CH6
CH7
COM
8-Channel
MUX
Sample/
Hold
Amp
Successive Approximation Register
Serial
Interface
SDA
SCL
A0
A1
AS1538/AS1540
CDAC
Comparator
REF
IN/OUT
Buffer
Internal
2.5V
Reference
GND
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AS1538/AS1540
Data Sheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
+V
DD
SDA
CH0
N/C
CH0 1
CH1 2
CH2 3
CH3 4
CH4 5
CH5 6
CH6 7
CH7 8
16 +V
DD
15 SDA
14 SCL
CH1
CH2
CH3
N/C
1
2
16
15
14
13
12 SCL
11 A1
AS1538
13 A1
12 A0
11 COM
10 REF
IN/OUT
9 GND
AS1540
3
4
5
N/C
6
GND
7
REF
IN/OUT
8
COM
10 A0
9
N/C
Pin Descriptions
Table 1. Pin Descriptions
AS1538
-
1:8
9
10
11
12
13
14
15
16
-
AS1540
1:3,16
-
6
7
8
10
11
12
13
15
4, 5, 9, 14
Pin Name
CH0:CH3
CH0:CH7
GND
REF
IN/OUT
COM
A0
A1
SCL
SDA
+V
DD
NC
Description
Analog Input Channels 0 to 3
Analog Input Channels 0 to 7
Analog Ground
Internal Reference/External Reference Input
Analog Input Channel Common
Slave Address Bit 0
Slave Address Bit 1
Serial Clock
Serial Data
Power Supply Input.
2.7 to 5.25V.
Not Connected
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AS1538/AS1540
Data Sheet - 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
Electrical Character-
istics on page 4
is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Table 2. Absolute Maximum Ratings
Parameter
+V
DD
to GND
Digital Input Voltage to GND
Thermal Resistance
θ
JA
Operating Temperature Range
Storage Temperature Range
Junction Temperature (T
JMAX
)
ESD
1.5
-40
-65
Min
-0.3
-0.3
Max
+6
+V
DD
+
0.3
100
+85
+150
150
Units
V
V
°C/W
ºC
ºC
ºC
kV
HBM MIL-Std. 883E 3015.7
methods
The reflow peak soldering temperature (body
temperature) specified is in accordance with
IPC/JEDEC J-STD-020C “Moisture/Reflow
Sensitivity Classification for Non-Hermetic
Solid State Surface Mount Devices”.
The lead finish for Pb-free leaded packages is
matte tin (100% Sn).
on PCB
Comments
Package Body Temperature
+260
ºC
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AS1538/AS1540
Data Sheet - 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
Electrical Characteristics
+V
DD
=
+2.7
to +5.25V, V
REF
=
+2.5V
external, SCL = 3.4MHz, T
AMB
= -40 to +85ºC (unless otherwise specified).
Table 3. Electrical Characteristics
Symbol
Analog Input
Parameter
Fullscale Input Span
Absolute Input Range
Negative Input
Capacitance
Leakage Current
Static Performance
No Missing Codes
Integral Linearity Error
Differential Linearity Error
Offset Error
Offset Error Match
Gain Error
Gain Error Match
1
1
Condition
Positive input, negative input
Positive input
Min
0
-0.3
-0.3
Typ
Max
V
REF
+V
DD
+ 0.3
+V
DD
+ 0.3
Unit
V
V
V
pF
Track Mode
Hold Mode
15
8
±0.1
12
±1
I
LEAK
µA
Bits
V
REF
= 2.5V, 1 LSB = 610µV
±0.75
±0.5
±0.5
±0.2
±1
±0.2
1
±1.5
±1
±6
±1
±6
±1
LSB
LSB
LSB
LSB
LSB
LSB
mV
Power Supply Rejection
Dynamic Performance
Throughput Frequency
Conversion Time
AC Accuracy
THD
Total Harmonic Distortion
Signal-to-Noise Ratio
Signal-to-Noise (+ Distortion)
Ratio
Spurious-Free Dynamic Range
Voltage Reference Output
Range
Internal Reference Drift
Output Impedance
Quiescent Current
Voltage Reference Input
Range
Input Resistance
Reference Input Current
PD = 01 Internal Ref. OFF, ADC ON
@ 50kSPS
1
2
50
6.67
V
IN
= 2.5V
P-P
@ 10kHz
V
IN
= 2.5V
P-P
@ 10kHz
V
IN
= 2.5V
P-P
@ 10kHz
V
IN
= 2.5V
P-P
@ 10kHz
2.475
-75
72
69.5
75
2.5
30
30
440
V
DD
1
4
2.525
kHz
µs
dB
dB
dB
dB
V
ppm/ºC
Ω
µA
V
GΩ
µA
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AS1538/AS1540
Data Sheet - 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
Table 3. Electrical Characteristics
Symbol
CMOS Digital I/O
V
IH
V
IL
V
OL
I
IH
I
IL
Input High Logic Level
Input Low Logic Level
Output Low Logic Level
Input High Leakage Current
Input Low Leakage Current
3mA sink current
V
IH
= +V
DD
V
IL
= GND
Straight binary
Specified performance
PD = 00 Full Power-Down
Analog Current in Static Mode,
3.6V
I
QSTAT
Analog Current in Static Mode,
5.25V
PD = 01 Internal Ref. OFF, ADC ON
PD = 10 Internal Ref. ON, ADC OFF
PD = 11 Internal Ref. ON, ADC ON
PD = 00 Full Power-Down
PD = 01 Internal Ref. OFF, ADC ON
PD = 10 Internal Ref. ON, ADC OFF
PD = 11 Internal Ref. ON, ADC ON
Quiescent Current at Full
Speed, 3.6V
I
Q
Quiescent Current at Full
Speed, 5.25V
PD = 01 Internal Ref. OFF, ADC ON
PD = 11 Internal Ref. ON, ADC ON
PD = 01 Internal Ref. OFF, ADC ON
PD = 11 Internal Ref. ON, ADC ON
2.7
0.04
400
500
800
0.04
450
550
850
500
850
650
915
5.25
1.2
500
600
900
1.5
550
650
950
600
950
800
1150
µA
µA
µA
µA
V
-1
+V
DD
x 0.7
-0.3
+V
DD
+ 0.5
+V
DD
x 0.3
0.4
1
V
V
V
µA
µA
Parameter
Condition
Min
Typ
Max
Unit
Data Format
Power Supply Requirements
+V
DD
Power Supply Voltage
1. Guaranteed by design and characterized on sample base.
2. THD measure out to 5th harmonic.
Timing Characteristics
+V
DD
=
+2.7
to 5.25V, T
AMB
= -40 to +85ºC (unless otherwise specified). All values referenced to V
IHMIN
and V
ILMAX
levels.
Table 4. Timing Characteristics
Symbol
f
SCL
t
BUF
T
HOLDSTART
t
LOW
t
HIGH
T
SETUPSTART
T
SETUPDATA
T
HOLDDATA
T
RISESCLK
1
Parameter
SCL Frequency
Bus Free Time Between
STOP and START Conditions
Hold Time for Repeated
START Condition
SCL Low Period
SCL High Period
Setup Time for Repeated
START Condition
Data Setup Time
Data Hold Time
SCL Rise Time
SCL Rise Time after
Repeated START Condition
and After an ACK Bit
Condition
Min
0.1
1.3
160
50
50
100
10
Typ
Max
3.4
Unit
MHz
µs
ns
75
75
ns
ns
ns
70
10
10
40
80
ns
ns
ns
ns
1
T
RISESCLK1
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