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SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
1
SP8527
Micropower Sampling 10-Bit A/D Converter
s
Low Cost
s
10-Bit Serial Sampling ADC
s
Guaranteed +1.0 LSB Max INL
s
8-Pin NSOIC Plastic Package
s
Low Power @ 230
A including
Automatic Shutdown: 1nA (typ)
s
Full differential input stage
s
Single Supply 3.0V to 5.5V operation
s
Digital Serial Interface
s
Sample Rate: 26.1
S
DESCRIPTION
The SP8527 is a very low power 10-Bit A/D converter. The SP8527 typically draws 230
A of
supply current when sampling at 38.3 kHz. Supply current drops linearly as the sample rate is
reduced. The ADC automatically powers down when not performing conversions, drawing only
leakage current. The SP8527 is available in 8-Pin NSOIC packages, specified over Commercial
and Industrial temperature ranges. The SP8527 is best suited for Battery-Operated Systems,
Portable Data Acquisition Instrumentation, Battery Monitoring, and Remote Sensing
applications. The serial port allows efficient data transfer to a wide range of microprocessors and
microcontrollers over 3 wires.
Internal
VCC
VCC
GND
REFL
DAC
REFL
Csample P
Csample N
+IN
-IN
SAR
PARALLEL TO
SERIAL SHIFT
REGISTER
10
CS/SHDN
SCLK
TIMING &
CONTROL LOGIC
Dout
VREF
COMPARATOR
INPUT
SWITCHES
SP8527 Block Diagram
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
2
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at
these ratings or any other above those indicated in the operation
sections of the specifications below is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect
reliability.
(TA=+25C unless otherwise noted) .....................................................
VCC to GND ................................................................................. 7.0V
Vin to GND .............................................................. -0.3 to VCC +0.3V
Digital input to GND ................................................ -0.3 to VCC +0.3V
Digital output to GND .............................................. -0.3 to VCC +0.3V
Operating Temperature Range
Commercial (J, K Version) ........................................... 0C to 70C
Industrial (A, B Version) .......................................... -40C to +85C
Lead Temperature (Solder 10Sec) ............................................ +300C
Storage Temperature .................................................. -65C to +150C
Power Dissipation to 70C ........................................................ 500mW
SPECIFICATIONS
Unless otherwise noted the following specifications apply for VCC=5V or 3.3V with limits applicable for Tmin to Tmax. Typical applies for Ta=25C.
VCC=5.0V
VCC=3.3V
PARAMETERS
MIN. TYP. MAX. MIN. TYP. MAX.
UNITS
CONDITIONS
DC ACCURACY
Resolution
10
10
Bits
Integral Linearity
K,B
+0.5 +1.0
+0.5 +1.0
LSB
Differential Linearity Error
K,B
+0.6 +2.0
+0.6 +2.0
LSB
Gain Error
K,B
+0.2 +2.0
+0.2 +2.0
LSB
Offset Error
K,B
+0.3 +2.0
+0.3 +3.0
LSB
ANALOG INPUT
Input Signal FS Range
0
V
ref
0
V
ref
Input Impedance
On Channel
20
20
pF
In Parallel with 100M
100
100
M
Off Channel
3
3
pF
In Parallel with 100M
100
100
M
Input Bias Current
.001
1
.001
1
A
Analog Input Range
-.05
V
CC
+.05 -.05
V
CC
+.05
Volts
CONVERSION SPEED
Sample Time
1.5
1.5
clock
See Timing Diagrams
cycles
Conversion Time
10
10
clock
See Timing Diagrams
cycles
Complete Cycle
38.3
25.5
kHz
See Timing Diagrams
Clock Period
2.0
3.0
S
See Timing Diagrams
Clock High Time
.9
1.4
S
See Timing Diagrams
Clock Low Time
.9
1.4
S
See Timing Diagrams
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
3
SPECIFICATIONS (cont.)
Unless otherwise noted the following specifications apply for VCC=5V or 3.3V with limits applicable for Tmin to Tmax. Typical applies for Ta=25C.
VCC=5.0V
VCC=3.3V
PARAMETERS
MIN. TYP. MAX. MIN. TYP. MAX.
UNITS
CONDITIONS
DIGITAL INPUTS
Input Low Voltage, VIL
0.8
0.8
Volts
V
DD
=5V
5%
Input High Voltage, VIH
2.0
2.0
Volts
V
DD
=5V
5%
Input Current IIN
+2.0
+2.0
A
Input Capacitance
3.0
3.0
pF
DIGITAL OUTPUTS
Data Format
Data Coding
See Timing Diagram
VOH
4.0
2.0
Volts
V
DD
=5V +5%, IOH=-0.4mA
VOL
0.4
0.4
Volts
V
DD
=5V +5%, IOL=+1.6mA
AC ACCURACY
Spurious free Dynamic
70
68
dB
For all FFT's
Range (SFDR)
(Full Differential Mode)
If V
CC
= 5V
fsample = 38.3kHz
fin = 15kHz
Total Harmonic Distortion (THD)
-70
-70
dB
Signal to Noise &
60
60
dB
If V
CC
= 3.3V
Distortion (SINAD)
fsample = 25.5kHz
fin = 12kHz
Signal to Noise (SNR)
61
61
dB
SAMPLING DYNAMICS
Acquisition Time to 0.05%
2
3
3
4.5
s
-3dB Small Signal BW
4
3
MHz
Aperture Delay
20
30
nS
Aperture Jitter
150
150
pS
Common-Mode Rejection Ratio
70
80
70
80
dB
f
CM
= 15kHz @ 5 volts
2.8kHz @ 3.3 volts
POWER SUPPLIES
Volts
V
CC
+3.0 +5.0 +5.5 +3.0 +3.3 +5.5
I
CC
Operation Mode
230
400
80
300
A
(CS=0) 38.3kHz, 5V conversion
rate. 25.5kHz 3.3 volts
Shutdown Mode
.001
0.5
.001
0.5
A
(CS=1)
Power Dissipation
Operating Mode
1.15
2
0.26 0.99
mW
Shutdown Mode
.005
2.5
.003
1.7
W
TEMPERATURE RANGE
Commercial
0 to +70C
0 to +70C
C
Industrial
-40 to +85C
-40 to +85C
C
Storage
-65 to +150C
-65 to +150C
C
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
4
PIN ASSIGNMENTS
Pin 1- V
REF
- Reference Voltage
Pin 2- +IN - Positive Input
Pin 3- -IN - Negative Input
Pin 4- GND - Ground
Pin 5- CS/SHDN - Chip Select Bar/Shutdown
Pin 6 - D
OUT
- Data Out
Pin 7- SCLK - Serial Clock
Pin 8- V
CC
- Supply
PIN DESCRIPTION
V
REF
+IN
-IN
GND
V
CC
SCLK
D
OUT
CS/SHDN
1
2
3
4
8
7
6
5
SP8527
w
w
w
w
SPECIFICATIONS (cont.)
Recommended Operating Conditions
VCC=5.0V
VCC=3.3V
SYMBOL
PARAMETERS
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
UNITS
V
CC
Supply Voltage
+3.0
+5.0
+5.5
+3.0
+3.3
+5.5
Volts
f
CLK
Clock Frequency
500
333
kHz
t
CYC
Total Cycle Time
26.1
39.2
S
t
suCS
Setup Time CSv
100
150
nS
Before CLK^
t
WHCLK
CLK High Time
.9
1.4
S
t
WLCLK
CLK Low Time
.9
1.4
S
t
WHCS
CS High Time between
100
150
nS
Data Transfers Cycles
t
SAMPLE
S/H Acquisition Time
2
2
SCLK Cycles
t
CONV
ADC Conversion Time
10
10
SCLK Cycles
t
CLK
Clock Period
2.0
3.0
S
t
en
SCLK to D
OUT
Enable
80
200
150
300
nS
t
DIS
CSN to D
OUT
Hi - Z
80
200
150
200
nS
t
R
D
OUT
Rise Time
5
25
10
50
nS
t
F
D
OUT
Fall Time
5
25
10
50
nS
t
HDO
D
OUT
Valid After SCLK
80
200
150
300
nS
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
5
The device features automatic shutdown and
will shutdown to a +0.5
A power level as CS
is brought high (de-selected). Power is propor-
tional to conversion duty cycle and varies from
230
A at 26.1
S (Duty cycle = 100%) to
5.75
A at 1.04 ms (Duty cycle = 2.5%).
Examples:
Conversion rate
I
CC
@ 5V
Duty Cycle
26.1
S
230
A
100%
52.2
S
115
A
50%
104
S
57.5
A
25%
1.04 mS
5.75
A
2.5%
The device is configured such that it
delivers serial data MSB first requiring 13 clock
periods for a full conversion. Please refer to the
timing diagram.
Circuit Operation
The SP8527 is a SAR converter with full
differential sampled front end, capacitive DAC,
precision comparator, Successive Approxima-
tions Register, control logic and data output reg-
ister. After the input is sampled and held the
conversion process begins. The DAC MSB is
set and its output is compared with the signal
input, if the DAC output is less than the input,
the comparator outputs a one which is latched
into the SAR and simultaneously made
available at the ADC serial output pin. Each bit
is tested in a similar manner until the SAR
contains a code which represents the signal input
to within +1/2 LSB. During this process the SAR
content has been shifted out of the ADC serially.
The data appears at the DOUT pin MSB through
LSB in 13 clock periods. Note that the Chip
Select Bar pin must be toggled high between
conversions. The DOUT pin will be in a high
impedance state whenever Chip Select Bar is high.
After Chip Select Bar has been toggled and brought
low again, the converter begins a new conversion.
DESCRIPTION
The SP8527 is a 10 bit full differential
sampling ADC with a serial data interface. The
ADC samples and converts 10 bits of data in
26.1
S with a 5V supply voltage applied. The
SP8527 will also operate at a 3.3V supply at
39.2
S throughput. The device automatically
shuts down to a +0.5
A (MAX) level as soon
as the chip is deselected (CS=1). Serial data
output is available in an MSB first format.
FEATURES
The input sampling scheme is full differential,
where the maximum full scale range is V
REF
. The
signal is applied between +IN and -IN. The
signals applied at each input may both be
dynamic. This is in contrast with pseudo differ-
ential devices which must have input low held
at a constant level during conversion. The
converter will provide significant common mode
rejection because of the full differential
sampling. Each input independently must
remain between ground and Vcc to avoid
clamping the inputs. For proper conversion the
differential input (+IN - -IN) must be less than
or equal to Vref.
The device uses a capacitive DAC architecture
which provides the sampling behavior. This
results in full Nyquist performance at the
fastest throughput rate (38.3kHz) the device is
capable of.
The power supply voltage is variable from 3.0V
to 5.5V which provides supply flexibility. At the
5.0V supply level, conversion plus sampling
time is 26.1
S and supply current is 230
A
(1.15 mW). With a 3.3V supply the conversion
plus sampling time is 39.2
S and current is
reduced to 80
A (0.26 mW).
INPUT VOLTAGE
INPUT VOLTAGE
OUTPUT
(+IN - -IN)
AT V
REF
= 5V
CODE
0 LSB
0V
0000000000
1 LSB
0.0049V
0000000001
512 LSB
2.5000V
1000000000
1022 LSB
4.9902V
1111111110
1023 LSB
4.9951V
1111111111
ADC TRANSFER FUNCTION
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
6
Single Ended or Full
Differential Operation
The SP8527 has a balanced full differential front
end. The SP8527 can be used in this manner, or
it can be used in single-ended circuits as well.
For single-ended systems, simply tie the -IN to
the Reference Low of the input signal, which is
allowed to range from 0V to V
CC
. For a full
differential sampling configuration, both inputs
are sampled and held simultaneously. Because
of the balanced differential sampling, dynamic
common mode noise riding along the input
signal is cancelled above and beyond DC noise.
This is a significant improvement over psuedo-
differential sampling schemes, where the low
side of the input must remain constant during
the conversion, and therefore only DC noise (i.e.
signal offset) is cancelled. If AC common mode
noise is left to be converted along with the
differental component, the output signal will be
degraded.
Full differential sampling allows flexibility in
converting the input signal. If the signal low- side
is already tied to a ground elsewhere in the
system, it can be hardwired to the low side
input (i.e., -IN) which acts as a signal ground
sense, breaking a potential ground loop. It is also
possible to drive the inputs balanced differential,
as long as both inputs are within the power rails.
In this configuration, both the high and low
signals have the same impedance looking back
to ground, and therefore pick up the same noise
along the physical path from signal source (i.e.,
sensor, transducer, battery) to the converter. This
noise becomes common mode, and is cancelled
out by the differential sampling of the SP8527.
Layout Considerations
To preserve the high resolution and linearity of
the SP8527 attention must be given to circuit
board layout, ground impedance and bypassing.
A circuit board layout which includes separate
analog and digital ground planes will prevent
the coupling of noise into sensitive converter
circuits and will help to preserve the dynamic
performance of the device. In single ended
mode, the analog input signal should be
referenced to the ground pin of the converter.
This prevents any voltage drops that occur in
the power supply's common return from appearing
in series with the input signal.
In full differential mode, the high and low side
board traces should run close to each other, with
the same layout. This will insure that any noise
coupling will be common mode, and cancelled
by the converters (patent pending) full differential
architecture.
If separate analog and digital ground planes are
not possible, care should be used to prevent
coupling between analog and digital signals. If
analog and digital lines must cross, they should
do so at right angles. Parallel analog and digital
lines should be separated by a circuit board trace
which is connected to common.
The reference pin on the SP8527 should be kept
as clean as possible. A noise signal of 4.88mV
(for VREF = 5.0V) will produce 1 lsb of error
in the output code. For convenience, the VREF
pin can be tied to the VCC pin, but now the same
care should be taken with the VCC pin as with
the VREF pin. Whether or not VCC is tied to
VREF, the VCC pin should always be bypassed
to the GROUND pin with a parallel combination
of a 6.8
F tantalum and a 0.1
F ceramic
capacitor. To maintain maximum system
accuracy, the supply connected to the VCC pin
should be well isolated from digital supplies and
wide load variations. A separate conductor from
the supply regulator to the A/D converter will
limit the effects of digital switching elsewhere
in the system. Power supply noise can degrade
the converters performance. Especially corrupting
are noise and spikes from a switching
power supply.
To avoid introducing distortion when driving the
A/D converter input, the input signal source
should be able to charge the SP8527's equivalent
20 pF of input capacitance from zero volts to
the signal level in 1.5 clock periods.
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
7
SP8527 Timing Diagram
FIGURE 1. MSB FIRST TIMING
FIGURE 2. DETAILED TIMING
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
8
Icc vs. Sampling Rate
(Clock Rate = 333kHz)
Vcc = 3.3V
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
10
100
1000
10000
100000
Icc (
A)
conversion time (
s)
Icc vs. Sampling Rate
(Clock Rate = 500kHz)
Vcc = 5V
50.0
0.0
10
100
1000
10000
100000
Icc (
A)
conversion time (
s)
100.0
150.0
200.0
250.0
Vcc = 5V
Vref = 5V
Vcc = 3.3V
Vref = 3.3V
+1
+1
-1
-1
DNLE
INLE
Input CMRR
Vcc = 5V
20
0
10.0E+0
CMRR (dB)
common mode frequency(Hz)
40
60
80
100
100.0E+0 1.0E+3
10.0E+3 100.0E+3 1.0E+6
+1
+1
-1
-1
DNLE
INLE
0
512
1023
0
512
1023
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
9
Icc vs. Temperature
250
240
230
220
210
200
-50
A
temperature (C)
-25
0
25
50
75
100
125
Gain vs. Temperature
1.5
1.0
.05
0.00
-1.0
-1.5
-50
LSB
temperature (C)
-25
0
25
50
75
100
125
-0.5
Offset vs. Temperature
1.5
1.0
.05
0
-1.0
-1.5
-50
LSB
temperature (C)
-25
0
25
50
75
100
125
-0.5
FFT 20 dB/div
0Hz
Spectral Density (dB)
1.3kHz/div
10.4kHz
SNR =
THD =
SINAD =
SFDR =
Vinamp =
Fund Freq =
61.26 dB
-70.7 dB
60.79 dB
70.43 dB
-0.49 dB
9.885kHz
Spurious Free Dynamic Range
50
1000
SFDR (dB)
input frequency (Hz)
65
70
75
80
10000
SINAD
50
1000
SINAD (dB)
input frequency (Hz)
64
66
68
70
10000
Signal to Noise Ratio
1000
SNR (dB)
input frequency (Hz)
10000
Total Harmonic Distortion
-80
1000
THD (dB)
input frequency (Hz)
-65
-60
-55
-50
10000
60
55
62
60
58
56
52
50
64
66
68
70
62
60
58
56
52
54
54
-75
-70
For all plots, V
CC
= 5V, Conversion Rate = 38.3kHz.
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
10
D
ALTERNATE
END PINS
(BOTH ENDS)
D1 = 0.005" min.
(0.127 min.)
E
PACKAGE: PLASTIC
DUALINLINE
(NARROW)
DIMENSIONS (Inches)
Minimum/Maximum
(mm)
A = 0.210" max.
(5.334 max).
E1
C
L
A2
A1 = 0.015" min.
(0.381min.)
B
B1
e = 0.100 BSC
(2.540 BSC)
e
A
= 0.300 BSC
(7.620 BSC)
A2
B
B1
C
D
E
E1
L
0.115/0.195
(2.921/4.953)
0.014/0.022
(0.356/0.559)
0.045/0.070
(1.143/1.778)
0.008/0.014
(0.203/0.356)
0.735/0.775
(18.669/19.685)
0.300/0.325
(7.620/8.255)
0.240/0.280
(6.096/7.112)
0.115/0.150
(2.921/3.810)
0/ 15
(0/15)
0.115/0.195
(2.921/4.953)
0.014/0.022
(0.356/0.559)
0.045/0.070
(1.143/1.778)
0.008/0.014
(0.203/0.356)
0.355/0.400
(9.017/10.160)
0.300/0.325
(7.620/8.255)
0.240/0.280
(6.096/7.112)
0.115/0.150
(2.921/3.810)
0/ 15
(0/15)
22PIN
8PIN
14PIN
16PIN
0.115/0.195
(2.921/4.953)
0.014/0.022
(0.356/0.559)
0.045/0.070
(1.143/1.778)
0.008/0.014
(0.203/0.356)
1.145/1.155
(29.083/29.337)
0.300/0.325
(7.620/8.255)
0.240/0.280
(6.096/7.112)
0.115/0.150
(2.921/3.810)
0/ 15
(0/15)
0.115/0.195
(2.921/4.953)
0.014/0.022
(0.356/0.559)
0.045/0.070
(1.143/1.778)
0.008/0.014
(0.203/0.356)
0.780/0.800
(19.812/20.320)
0.300/0.325
(7.620/8.255)
0.240/0.280
(6.096/7.112)
0.115/0.150
(2.921/3.810)
0/ 15
(0/15)
18PIN
0.115/0.195
(2.921/4.953)
0.014/0.022
(0.356/0.559)
0.045/0.070
(1.143/1.778)
0.008/0.014
(0.203/0.356)
0.880/0.920
(22.352/23.368)
0.300/0.325
(7.620/8.255)
0.240/0.280
(6.096/7.112)
0.115/0.150
(2.921/3.810)
0/ 15
(0/15)
20PIN
0.115/0.195
(2.921/4.953)
0.014/0.022
(0.356/0.559)
0.045/0.070
(1.143/1.778)
0.008/0.014
(0.203/0.356)
0.980/1.060
(24.892/26.924)
0.300/0.325
(7.620/8.255)
0.240/0.280
(6.096/7.112)
0.115/0.150
(2.921/3.810)
0/ 15
(0/15)
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
11
D
E
H
PACKAGE: PLASTIC
SMALL OUTLINE (SOIC)
(NARROW)
DIMENSIONS (Inches)
Minimum/Maximum
(mm)
8PIN
A
A1
L
B
e
h x 45
A
A1
B
D
E
e
H
h
L
0.053/0.069
(1.346/1.748)
0.004/0.010
(0.102/0.249
0.014/0.019
(0.35/0.49)
0.189/0.197
(4.80/5.00)
0.150/0.157
(3.802/3.988)
0.050 BSC
(1.270 BSC)
0.228/0.244
(5.801/6.198)
0.010/0.020
(0.254/0.498)
0.016/0.050
(0.406/1.270)
0/8
(0/8)
14PIN
0.053/0.069
(1.346/1.748)
0.004/0.010
(0.102/0.249)
0.013/0.020
(0.330/0.508)
0.337/0.344
(8.552/8.748)
0.150/0.157
(3.802/3.988)
0.050 BSC
(1.270 BSC)
0.228/0.244
(5.801/6.198)
0.010/0.020
(0.254/0.498)
0.016/0.050
(0.406/1.270)
0/8
(0/8)
16PIN
0.053/0.069
(1.346/1.748)
0.004/0.010
(0.102/0.249)
0.013/0.020
(0.330/0.508)
0.386/0.394
(9.802/10.000)
0.150/0.157
(3.802/3.988)
0.050 BSC
(1.270 BSC)
0.228/0.244
(5.801/6.198)
0.010/0.020
(0.254/0.498)
0.016/0.050
(0.406/1.270)
0/8
(0/8)
SP8527DS/01
SP8527 Micropower Sampling 10-Bit A/D Converter
Copyright 2000 Sipex Corporation
12
ORDERING INFORMATION
Model ........................................................ Linearity (LSB) ..................... Temperature Range ............................................................... Package
SP8527BN ..........................................................
1.0 .................................... 40C to +85C .............................................. 8-pin, 0.3" Plastic DIP
SP8527KN ..........................................................
1.0 ..................................... 0C to +70C ............................................... 8-pin, 0.3" Plastic DIP
SP8527BS ..........................................................
1.0 .................................... 40C to +85C ......................................... 8-pin, 0.15" Plastic SOIC
SP8527KS ..........................................................
1.0 ..................................... 0C to +70C .......................................... 8-pin, 0.15" Plastic SOIC
Please consult the factory for pricing and availability on a Tape-On-Reel option.
Corporation
SIGNAL PROCESSING EXCELLENCE
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others.
Sipex Corporation
Headquarters and
Sales Office
22 Linnell Circle
Billerica, MA 01821
TEL: (978) 667-8700
FAX: (978) 670-9001
e-mail: sales@sipex.com
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
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