ADC with an SPI/MICROWIRE compatible serial interface.
This ADC includes an internal reference and a fully differ-
ential sample-and-hold circuit to reduce common-mode
noise. The internal conversion clock allows the external
serial output data clock (SCK) to operate at any frequency
up to 40MHz.
The LTC2308 operates from a single 5V supply and draws
just 3.5mA at a sample rate of 500ksps. The auto-shutdown
feature reduces the supply current to 200μA at a sample
rate of 1ksps.
The LTC2308 is packaged in a small 24-pin 4mm
×
4mm
QFN. The internal 2.5V reference and 8-channel multiplexer
further reduce PCB board space requirements.
The low power consumption and small size make the
LTC2308 ideal for battery operated and portable appli-
cations, while the 4-wire SPI compatible serial interface
makes this ADC a good match for isolated or remote data
acquisition systems.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
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■
■
■
12-Bit Resolution
500ksps Sampling Rate
Low Noise: SINAD = 73.3dB
Guaranteed No Missing Codes
Single 5V Supply
Auto-Shutdown Scales Supply Current with Sample
Rate
Low Power: 17.5mW at 500ksps
0.9mW Nap Mode
35μW Sleep Mode
Internal Reference
Internal 8-Channel Multiplexer
Internal Conversion Clock
SPI/MICROWIRE
TM
Compatible Serial Interface
Unipolar or Bipolar Input Ranges (Software Selectable)
Separate Output Supply OV
DD
(2.7V to 5.25V)
24-Pin 4mm
×
4mm QFN Package
APPLICATIONS
■
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High Speed Data Acquisition
Industrial Process Control
Motor Control
Accelerometer Measurements
Battery Operated Instruments
Isolated and/or Remote Data Acquisition
TYPICAL APPLICATION
5V
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
–140
8192 Point FFT, f
IN
= 1kHz
0.1μF
OV
DD
0.1μF
SDI
2.7V TO 5.25 V
f
SMPL
= 500kHz
SINAD = 73.6dB
THD = –89.5dB
0.1μF
10μF
AV
DD
10μF
DV
DD
LTC2308
CH0
CH1
CH2
CH0-CH7
CH4
ANALOG INPUTS
0V TO 4.096V UNIPOLAR
CH5
2.048V BIPOLAR
CH6
CH7
COM
CH3
ANALOG
INPUT
MUX
+
–
12-BIT
500ksps
ADC
SERIAL
PORT
SDO
SCK
CONVST
V
REF
SERIAL DATA LINK TO
ASIC, PLD, MPU, DSP
OR SHIFT REGISTER
INTERNAL
2.5V REF
2.2μF
MAGNITUDE (dB)
0
50
150
100
FREQUENCY (kHz)
200
250
2308 G03
REFCOMP
GND
0.1μF
10μF
2308 TA01
2308f
1
LTC2308
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
DV
DD
OV
DD
18 GND
17 SD0
25
16 SCK
15 SDI
14 CONVST
13 AV
DD
7
V
REF
8
REFCOMP
9 10 11 12
GND
GND
GND
AV
DD
GND
CH2
CH1
CH0
Supply Voltage (AV
DD
, DV
DD
, OV
DD
) ...........................6V
Analog Input Voltage (Note 3)
CH0 - CH7, COM, REF,
REFCOMP ....................(GND –0.3V) to (AV
DD
+ 0.3V)
Digital Input Voltage
(Note 3) ...................... (GND –0.3V) to (DV
DD
+ 0.3V)
Digital Output Voltage ..... (GND –0.3V) to (OV
DD
+ 0.3V)
Power Dissipation ...............................................500mW
Operating Temperature Range
LTC2308C ................................................ 0°C to 70°C
LTC2308I ............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
24 23 22 21 20 19
CH3 1
CH4 2
CH5 3
CH6 4
CH7 5
COM 6
UF PACKAGE
24-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 37°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC2308CUF#PBF
LTC2308IUF#PBF
TAPE AND REEL
LTC2308CUF#TRPBF
LTC2308IUF#TRPBF
PART MARKING*
2308
2308
PACKAGE DESCRIPTION
24-Lead (4mm
×
4mm) Plastic QFN
24-Lead (4mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
CONVERTER AND MULTIPLEXER CHARACTERISTICS
PARAMETER
Resolution (No Missing Codes)
Integral Linearity Error
Differential Linearity Error
Bipolar Zero Error
Bipolar Zero Error Drift
Bipolar Zero Error Match
Unipolar Zero Error
Unipolar Zero Error Drift
Unipolar Zero Error Match
(Note 7)
(Note 7)
(Note 6)
CONDITIONS
The
●
denotes the specifications
which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Notes 4, 5)
MIN
●
●
●
●
TYP
±0.3
±0.25
±1
0.002
±0.3
±0.5
0.002
±0.3
MAX
±1
±1
±6
±3
±3
±2
UNITS
Bits
LSB
LSB
LSB
LSB/°C
LSB
LSB
LSB/°C
LSB
12
●
●
●
2308f
2
LTC2308
The
●
denotes the specifications
which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C. (Notes 4, 5)
PARAMETER
Bipolar Full-Scale Error
Bipolar Full-Scale Error Drift
Bipolar Full-Scale Error Match
Unipolar Full-Scale Error
Unipolar Full-Scale Error Drift
Unipolar Full-Scale Error Match
External Reference (Note 8)
External Reference
●
CONVERTER AND MULTIPLEXER CHARACTERISTICS
CONDITIONS
External Reference (Note 8)
External Reference
MIN
●
TYP
±1
0.05
±0.5
±1.5
0.05
±0.4
MAX
±9
±3
±8
±3
UNITS
LSB
LSB/°C
LSB
LSB
LSB/°C
LSB
●
●
ANALOG INPUT
SYMBOL
V
IN+
V
IN–
V
IN+
– V
IN–
I
IN
C
IN
CMRR
PARAMETER
The
●
denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
(Note 9)
Unipolar (Note 9)
Bipolar (Note 9)
V
IN
= V
IN+
– V
IN–
(Unipolar)
V
IN
= V
IN+
– V
IN–
(Bipolar)
Sample Mode
Hold Mode
●
●
●
●
●
●
MIN
–0.05
–0.05
–0.05
TYP
MAX
AV
DD
AV
DD
/2
AV
DD
UNITS
V
V
V
V
V
Absolute Input Range (CH0 to CH7)
Absolute Input Range (CH0 to CH7,
COM)
Input Differential Voltage Range
Analog Input Leakage Current
Analog Input Capacitance
Input Common Mode Rejection Ratio
0 to REFCOMP
±REFCOMP/2
±1
55
5
70
μA
pF
pF
dB
The
●
denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C and A
IN
= –1dBFS. (Notes 4, 10)
SYMBOL
SINAD
SNR
THD
SFDR
PARAMETER
Signal-to-(Noise + Distortion) Ratio
Signal-to-Noise Ratio
Total Harmonic Distortion
Spurious Free Dynamic Range
Channel-to-Channel Isolation
Full Linear Bandwidth
–3dB Input Linear Bandwidth
Aperture Delay
Transient Reponse
Full-Scale Step
CONDITIONS
f
IN
= 1kHz
f
IN
= 1kHz
f
IN
= 1kHz, First 5 Harmonics
f
IN
= 1kHz
f
IN
= 1kHz
(Note 11)
●
●
●
●
DYNAMIC ACCURACY
MIN
71
71
TYP
73.3
73.4
–90
–90
–109
700
25
13
240
MAX
UNITS
dB
dB
–78
–80
dB
dB
dB
kHz
MHz
ns
ns
2308f
3
LTC2308
The
●
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
PARAMETER
V
REF
Output Voltage
V
REF
Output Tempco
V
REF
Output Impedance
V
REFCOMP
Output Voltage
V
REF
Line Regulation
CONDITIONS
I
OUT
= 0
I
OUT
= 0
–0.1mA ≤ I
OUT
≤ 0.1mA
I
OUT
= 0
AV
DD
= 4.75V to 5.25V
●
INTERNAL REFERENCE CHARACTERISTICS
MIN
2.47
TYP
2.50
±25
8
4.096
0.8
MAX
2.53
UNITS
V
ppm/°C
kΩ
V
mV/V
The
●
denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 4)
SYMBOL
V
IH
V
IL
I
IN
C
IN
V
OH
V
OL
I
OZ
C
OZ
I
SOURCE
I
SINK
PARAMETER
High Level Input Voltage
Low Level Input Voltage
High Level Input Current
Digital Input Capacitance
High Level Output Voltage
Low Level Input Voltage
Hi-Z Output Leakage
Hi-Z Output Capacitance
Output Source Current
Output Sink Current
OV
DD
= 4.75V, I
OUT
= –10μA
OV
DD
= 4.75V, I
OUT
= –200μA
OV
DD
= 4.75V, I
OUT
= 160μA
OV
DD
= 4.75V, I
OUT
= 1.6mA
V
OUT
= 0V to OV
DD
, CONVST High
CONVST High
V
OUT
= 0V
V
OUT
= OV
DD
●
●
●
DIGITAL INPUTS AND DIGITAL OUTPUTS
CONDITIONS
DV
DD
= 5.25V
DV
DD
= 4.75V
V
IN
= V
DD
MIN
●
●
●
TYP
MAX
0.8
±10
UNITS
V
V
μA
pF
V
V
2.4
5
4.74
4
0.05
0.4
±10
15
–10
10
V
V
μA
pF
mA
mA
POWER REQUIREMENTS
SYMBOL
AV
DD
DV
DD
OV
DD
I
DD
PARAMETER
Analog Supply Voltage
Digital Supply Voltage
Output Driver Supply Voltage
Supply Current
Nap Mode
Sleep Mode
Power Dissipation
Nap Mode
Sleep Mode
The
●
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
MIN
4.75
4.75
2.7
C
L
= 25pF
CONVST = 5V, Conversion Done
CONVST = 5V, Conversion Done
●
●
●
TYP
5
5
3.5
180
7
17.5
0.9
35
MAX
5.25
5.25
5.25
4.2
400
20
UNITS
V
V
V
mA
μA
μA
mW
mW
μW
P
D
2308f
4
LTC2308
TIMING CHARACTERISTICS
SYMBOL
f
SMPL(MAX)
f
SCK
t
WHCONV
t
HD
t
SUDI
t
WHCLK
t
WLCLK
t
WLCONVST
t
HCONVST
t
CONV
t
ACQ
t
REFWAKE
t
dDO
t
hDO
t
en
t
dis
t
r
t
f
t
CYC
PARAMETER
Maximum Sampling Frequency
Shift Clock Frequency
CONVST High Time
Hold Time SDI After SCK↑
Setup Time SDI Valid Before SCK↑
SCK High Time
SCK Low Time
CONVST Low Time During Data Transfer
Hold Time CONVST Low After Last SCK↓
Conversion Time
Acquisition Time
REFCOMP Wakeup Time (Note 12)
SDO Data Valid After SCK↓
SDO Hold Time After SCK↓
SDO Valid After CONVST↓
Bus Relinquish Time
SDO Rise Time
SDO Fall Time
Total Cycle Time
7th SCK↑ to CONVST↑ (Note 9)
C
REFCOMP
= 10μF, C
REF
= 2.2μF
C
L
= 25pF (Note 9)
C
L
= 25pF
C
L
= 25pF
C
L
= 25pF
C
L
= 25pF
C
L
= 25pF
●
●
●
●
The
●
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. (Note 4)
CONDITIONS
●
●
MIN
TYP
MAX
500
40
UNITS
kHz
MHz
ns
ns
ns
ns
ns
ns
ns
(Note 9)
●
●
●
20
2.5
0
10
10
410
20
1.3
240
200
10.8
4
11
11
4
4
2
15
15
12.5
1.6
f
SCK
= f
SCK(MAX)
f
SCK
= f
SCK(MAX)
(Note 9)
(Note 9)
●
●
●
●
●
●
μs
ns
ms
ns
ns
ns
ns
ns
ns
μs
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All voltage values are with respect to ground with AV
DD
, DV
DD
and
OV
DD
wired together (unless otherwise noted).
Note 3:
When these pin voltages are taken below ground or above V
DD
,
they will be clamped by internal diodes. These products can handle input
currents greater than 100mA below ground or above V
DD
without latchup.
Note 4:
AV
DD
= 5V, DV
DD
= 5V, OV
DD
= 5V, f
SMPL
= 500kHz, internal
reference unless otherwise specified.
Note 5:
Linearity, offset and full-scale specifications apply for a single-
ended analog input with respect to COM.
Note 6:
Integral nonlinearity is defined as the deviation of a code from a
straight line passing through the actual endpoints of the transfer curve.
The deviation is measured from the center of the quantization band.
Note 7:
Bipolar zero error is the offset voltage measured from –0.5LSB
when the output code flickers between 0000 0000 0000 and 1111 1111
1111. Unipolar zero error is the offset voltage measured from +0.5LSB
when the output code flickers between 0000 0000 0000 and
0000 0000 0001.
Note 8:
Full-scale bipolar error is the worst-case of –FS or +FS untrimmed
deviation from ideal first and last code transitions and includes the effect
of offset error. Unipolar full-scale error is the deviation of the last code
transition from ideal and includes the effect of offset error.
Note 9:
Guaranteed by design, not subject to test.
Note 10:
All specifications in dB are referred to a full-scale ±2.048V input
with a 2.5V reference voltage.
Note 11:
Full linear bandwidth is defined as the full-scale input frequency
at which the SINAD degrades to 60dB or 10 bits of accuracy.
Note 12:
REFCOMP wakeup time is the time required for the REFCOMP pin
to settle within 0.5LSB at 12-bit resolution of its final value after waking up
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