LINER LTC1852 8-channel, 10-bit/12-bit, 400ksps, low power, sampling adc Datasheet

LTC1852/LTC1853
8-Channel, 10-Bit/12-Bit,
400ksps, Low Power, Sampling ADCs
FEATURES
DESCRIPTION
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The 10-bit LTC®1852 and 12-bit LTC1853 are complete
8-channel data acquisition systems. They include a flexible
8-channel multiplexer, a 400ksps successive approximation analog-to-digital converter, an internal reference and a
parallel output interface. The multiplexer can be configured
for single-ended or differential inputs, two gain ranges and
unipolar or bipolar operation. The ADCs have a scan mode
that will repeatedly cycle through all 8 multiplexer channels
and can also be programmed to sequence through up to
16 addresses and configurations. The sequence can also
be read back from internal memory.
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Flexible 8-Channel Multiplexer
Single-Ended or Differential Inputs
Two Gain Ranges
Unipolar or Bipolar Operation
Scan Mode and Programmable Sequencer
Eliminate Configuration Software Overhead
Low Power: 3mW at 250ksps
2.7V to 5.5V Supply Range
Internal or External Reference Operation
Parallel Output Includes MUX Address
Nap and Sleep Shutdown Modes
Pin Compatible up-grade 1.25Msps 10-Bit LTC1850
and 12-Bit LTC1851
APPLICATIONS
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High Speed Data Acquisition
Test and Measurement
Imaging Systems
Telecommunications
Industrial Process Control
Spectrum Analysis
The reference and buffer amplifier provide pin strappable
ranges of 4.096V, 2.5V and 2.048V. The parallel output
includes the 10-bit or 12-bit conversion result plus the
4-bit multiplexer address. The digital outputs are powered from a separate supply allowing for easy interface
to 3V digital logic. Typical power consumption is 10mW
at 400ksps from a single 5V supply and 3mW at 250ksps
from a single 3V supply.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRAM
CH1
CONTROL LOGIC
AND
PROGRAMMABLE
SEQUENCER
CH2
CH3
CH4
8-CHANNEL
MULTIPLEXER
INTERNAL
CLOCK
CH5
M1
SHDN
CS
CONVST
RD
WR
DIFF
A2
A1
A0
UNI/BIP
PGA
M0
OVDD
CH6
CH7
COM
REFOUT
REFIN
REFCOMP
2.5V
REFERENCE
REF AMP
+
–
12-BIT
SAMPLING
ADC
DATA
LATCHES
OUTPUT
DRIVERS
BUSY
DIFFOUT/S6
A2OUT/S5
A1OUT/S4
A0OUT/S3
D11/S2
D10/S1
D9/S0
D8
D7
D6
D5
D4
D3
D2
D1
D0
Integral Linearity
1.0
0.5
INL ERROR (LSBs)
LTC1853
CH0
0
–0.5
–1.0
0
512 1024 1536 2048 2560 3072 3584 4096
CODE
1852 F01
OGND
18523 BD
18523fa
1
LTC1852/LTC1853
ABSOLUTE MAXIMUM RATINGS
OVDD = VDD (Note 1, 2)
Supply Voltage (VDD) ..................................................6V
Analog Input Voltage (Note 3) ..... – 0.3V to (VDD + 0.3V)
Digital Input Voltage (Note 4) .................... –0.3V to 10V
Digital Output Voltage ..................–0.3V to (VDD + 0.3V)
Power Dissipation ...............................................500mW
Ambient Operating Temperature Range
LTC1852C/LTC1853C .............................. 0°C to 70°C
LTC1852I/LTC1853I............................. –40°C to 85°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................. 300°C
PIN CONFIGURATION
LTC1852
LTC1853
TOP VIEW
TOP VIEW
CH0
1
48 M1
CH0
1
48 M1
CH1
2
47 SHDN
CH1
2
47 SHDN
CH2
3
46 CS
CH2
3
46 CS
CH3
4
45 CONVST
CH3
4
45 CONVST
CH4
5
44 RD
CH4
5
44 RD
CH5
6
43 WR
CH5
6
43 WR
CH6
7
42 DIFF
CH6
7
42 DIFF
CH7
8
41 A2
CH7
8
41 A2
COM
9
40 A1
COM
9
40 A1
REFOUT 10
39 A0
REFOUT 10
39 A0
REFIN 11
REFCOMP 12
38 UNI/BIP
REFIN 11
REFCOMP 12
37 PGA
38 UNI/BIP
37 PGA
GND 13
36 M0
GND 13
36 M0
VDD 14
35 OVDD
VDD 14
35 OVDD
VDD 15
34 OGND
VDD 15
34 OGND
GND 16
33 BUSY
GND 16
33 BUSY
DIFFOUT/S6 17
32 NC
DIFFOUT/S6 17
32 D0
A2OUT/S5 18
31 NC
A2OUT/S5 18
31 D1
A1OUT/S4 19
30 D0
A1OUT/S4 19
30 D2
A0OUT/S3 20
29 D1
A0OUT/S3 20
29 D3
D9/S2 21
28 D2
D11/S2 21
28 D4
D8/S1 22
27 D3
D10/S1 22
27 D5
D7/S0 23
26 D4
D9/S0 23
26 D6
D6 24
25 D5
D8 24
25 D7
FW PACKAGE
48-LEAD PLASTIC TSSOP
FW PACKAGE
48-LEAD PLASTIC TSSOP
TJMAX = 150°C, θJA = 110°C/W
TJMAX = 150°C, θJA = 110°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC1852CFW#PBF
LTC1852CFW#TRPBF
LTC1852CFW
48-Lead Plastic TSSOP (6.1mm)
0°C to 70°C
LTC1852IFW#PBF
LTC1852IFW#TRPBF
LTC1852IFW
48-Lead Plastic TSSOP (6.1mm)
–40°C to 85°C
LTC1853CFW#PBF
LTC1853CFW#TRPBF
LTC1853CFW
48-Lead Plastic TSSOP (6.1mm)
0°C to 70°C
LTC1853IFW#PBF
LTC1853IFW#TRPBF
LTC1853IFW
48-Lead Plastic TSSOP (6.1mm)
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
18523fa
2
LTC1852/LTC1853
CONVERTER CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VDD = 2.7V to 5.5V, REFCOMP < VDD (Notes 5,6)
PARAMETER
CONDITIONS
MIN
l
Resolution (No Missing Codes)
Integral Linearity Error
(Note 7)
Differential Linearity Error
Offset Error (Bipolar and Unipolar)
Gain = 1 (PGA = 1)
Gain = 2 (PGA = 0)
(Note 8)
REFCOMP ≥ 2V
LTC1852
TYP
10
MAX
UNITS
Bits
l
±0.25
±1
±0.35
±1
LSB
l
±0.25
±1
±0.25
±1
LSB
l
l
±0.5
±1
±2
±4
±1
±2
±6
±12
LSB
LSB
±0.5
±1
LSB
±2
±4
±4
±8
LSB
LSB
±0.5
±1
LSB
±2
±4
±4
±8
LSB
LSB
±0.5
±1
LSB
With External 4.096V Reference
Applied to REFCOMP (Note 12)
VDD = 4.75V to 5.25V, fS ≤ 400kHz
Unipolar Gain Error Match
Bipolar Gain Error
Gain = 1 (PGA = 1)
Gain = 2 (PGA = 0)
LTC1853
TYP
MIN
12
Offset Error Match (Bipolar and Unipolar)
Unipolar Gain Error
Gain = 1 (PGA = 1)
Gain = 2 (PGA = 0)
MAX
With External 4.096V Reference
Applied to REFCOMP (Note 12)
VDD = 4.75V to 5.25V, fS ≤ 400kHz
Bipolar Gain Error Match
Unipolar Gain Error
Gain = 1 (PGA = 1)
Gain = 2 (PGA = 0)
With External 2.5V Reference
Applied to REFCOMP
VDD = 2.7V to 5.5V, fS ≤ 250kHz
l
l
±1
±2
±3
±6
±1.5
±3
±8
±16
LSB
LSB
Bipolar Gain Error
Gain = 1 (PGA = 1)
Gain = 2 (PGA = 0)
With External 2.5V Reference
Applied to REFCOMP
VDD = 2.7V to 5.5V, fS ≤ 250kHz
l
l
±1
±2
±3
±6
±1.5
±3
±8
±16
LSB
LSB
Full-Scale Error Temperature Coefficient
15
15
ppm/°C
ANALOG INPUT
The l denotes the specifications which apply over the full operating temperature range, otherwise
specifications are at TA = 25°C. (Notes 5)
SYMBOL
PARAMETER
CONDITIONS
VIN
Analog Input Range (Note 9)
Unipolar, Gain = 1 (PGA = 1)
Unipolar, Gain = 2 (PGA = 0)
Bipolar, Gain = 1 (PGA = 1)
Bipolar, Gain = 2 (PGA = 0)
2.7V ≤ VDD ≤ 5.5V, REFCOMP ≤ VDD
MIN
TYP
MAX
0 – REFCOMP
0 – REFCOMP/2
± REFCOMP/2
±REFCOMP/4
l
UNITS
V
V
V
V
IIN
Analog Input Leakage Current
CIN
Analog Input Capacitance
tACQ
Sample-and-Hold Acquisition Time
tS(MUX)
Multiplexer Settling Time (Includes tACQ)
tAP
Sample-and-Hold Aperture Delay Time
VDD = 5V
– 0.5
tjitter
Sample-and-Hold Aperture Delay Time Jitter
VDD = 5V
2
psRMS
CMRR
Analog Input Common Mode Rejection Ratio
60
dB
DYNAMIC ACCURACY
±1
Between Conversions (Gain = 1)
Between Conversions (Gain = 2)
During Conversions
15
25
5
μA
pF
pF
pF
50
150
ns
50
150
ns
ns
TA = 25°C. (Notes 5)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
S/(N + D)
Signal-to-Noise Plus Distortion Ratio
40kHz Input Signal
72.5
dB
THD
Total Harmonic Distortion
40kHz Input Signal, First 5 Harmonics
–80
dB
SFDR
Spurious Free Dynamic Range
40kHz Input Signal
–85
dB
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LTC1852/LTC1853
INTERNAL REFERENCE
TA = 25°C. (Notes 5, 6)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
REFOUT Output Voltage
IOUT = 0
2.48
2.50
2.52
V
REFOUT Output Temperature Coefficient
IOUT = 0
±15
ppm/°C
REFOUT Line Regulation
2.7 ≤ VDD ≤ 5.5, IOUT = 0
0.01
LSB/V
Reference Buffer Gain
REFCOMP Output Voltage
External 2.5V Reference (VDD = 5V)
Internal 2.5V Reference (VDD = 5V)
REFCOMP Impedance
Impedance to GND, REFIN = VDD
1.6368
1.6384
1.6400
V/V
4.092
4.060
4.096
4.096
4.100
4.132
V
V
19.2
kΩ
DIGITAL INPUTS AND DIGITAL OUTPUTS
The ● denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. VDD = 5V (Note 5)
SYMBOL
PARAMETER
CONDITIONS
MIN
VIH
High Level Input Voltage
VDD = 5.25V
●
TYP
MAX
2.4
UNITS
V
VIL
Low Level Input Voltage
VDD = 4.75V
●
0.8
V
IIN
Digital Input Current
VIN = 0V to VDD
●
±5
μA
CIN
Digital Input Capacitance
VOH
High Level Output Voltage
VOL
Low Level Output Voltage
VDD = 4.75V, IO = –10μA
VDD = 4.75V, IO = – 200μA
●
VDD = 4.75V, IO = 160μA
VDD = 4.75V, IO = 1.6mA
●
IOZ
Hi-Z Output Leakage D11 to D0, A0, A1, A2OUT, DIFFOUT VOUT = 0V to VDD, CS High
1.5
pF
4.5
V
V
4
0.5
0.10
●
0.4
V
V
±10
μA
COZ
Hi-Z Capacitance D11 to D0
CS High (Note 9)
ISOURCE
Output Source Current
VOUT = 0V
–20
mA
ISINK
Output Sink Current
VOUT = VDD
30
mA
●
15
pF
DIGITAL INPUTS AND DIGITAL OUTPUTS
The ● denotes the specifications which apply over the full
operating temperature range, otherwise specifications are at TA = 25°C. VDD = 5V (Note 5)
SYMBOL
PARAMETER
CONDITIONS
MIN
VIH
High Level Input Voltage
VDD = 3.3V
●
TYP
MAX
1.9
UNITS
V
VIL
Low Level Input Voltage
VDD = 2.7V
●
0.45
V
IIN
Digital Input Current
VIN = 0V to VDD
●
±5
μA
CIN
Digital Input Capacitance
VOH
High Level Output Voltage
VOL
Low Level Output Voltage
VDD = 2.7V, IO = –10μA
VDD = 2.7V, IO = – 200μA
●
VDD = 2.7V, IO = 160μA
VDD = 2.7V, IO = 1.6mA
●
IOZ
Hi-Z Output Leakage D11 to D0, A0, A1, A2OUT, DIFFOUT VOUT = 0V to VDD, CS High
1.5
pF
2.5
V
V
2
0.05
0.10
●
0.4
V
V
±10
μA
COZ
Hi-Z Capacitance D11 to D0
CS High (Note 9)
ISOURCE
Output Source Current
VOUT = 0V
–10
mA
ISINK
Output Sink Current
VOUT = VDD
15
mA
●
15
pF
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LTC1852/LTC1853
POWER REQUIREMENTS
The ● denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VDD
Analog Positive Supply Voltage
(Note 10)
●
2.7
5.5
V
OVDD
Output Positive Supply Voltage
(Note 10)
●
2.7
5.5
V
IDD
Positive Supply Current
VDD = OVDD = 5V, fS = 400kHz
VDD = OVDD = 2.7V, fS = 250kHz
●
●
2
0.83
3
1.33
mA
mA
PDISS
Power Dissipation
VDD = OVDD = 5V, fS = 400kHz
VDD = OVDD = 2.7V, fS = 250kHz
●
●
10
2.25
15
4
mW
mW
IDDPD
Power Down Positive Supply Current
Nap Mode
Sleep Mode
SHDN = Low, CS = Low
SHDN = Low, CS = High
0.5
20
mA
μA
Power Down Power Dissipation
Nap Mode
Sleep Mode
VDD = VDD = OVDD = 5V, fS = 400kHz
SHDN = Low, CS = Low
SHDN = Low, CS = High
2.5
0.1
mW
mW
Power Down Power Dissipation
Nap Mode
Sleep Mode
VDD = VDD = OVDD = 3V, fS = 250kHz
SHDN = Low, CS = Low
SHDN = Low, CS = High
1.5
0.06
mW
mW
TIMING CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
fSAMPLE(MAX)
Maximum Sampling Frequency
VDD = 5.5V
VDD = 2.7V
●
●
Acquisition + Conversion
VDD = 5.5V
VDD = 2.7V
●
●
2.5
4.0
μs
μs
tCONV
Conversion Time
VDD = 5.5V
VDD = 2.7V
●
●
2.0
3.5
μs
μs
tACQ
Acquisition Time
(Note 13)
●
150
ns
t1
CS to RD Setup Time
(Notes 9, 10)
●
0
●
10
400
250
UNITS
kHz
kHz
ns
t2
CS to CONVST Setup Time
(Notes 9, 10)
t3
CS to SHDN Setup Time
(Notes 9, 10)
200
ns
t4
SHDN to CONVST Wake-Up Time
Nap Mode (Note 10)
Sleep Mode (Note 10)
200
10
ns
ms
t5
CONVST Low Time
(Notes 10, 11)
t6
CONVST to BUSY Delay
CL = 25pF
t7
Data Ready Before BUSY
t8
Delay Between Conversions
t9
Wait Time RD After BUSY
t10
Data Access Time After RD
(Note 10)
CL = 25pF
CL = 100pF
t11
50
RD Low Time
ns
10
●
60
35
ns
ns
●
20
15
●
50
ns
●
–5
ns
35
45
ns
ns
25
45
60
ns
ns
10
30
35
40
ns
ns
ns
●
●
●
●
t10
ns
ns
20
●
BUS Relinquish Time
0°C to 70°C
– 40°C to 85°C
t12
●
ns
ns
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LTC1852/LTC1853
TIMING CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. (Note 5)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
t13
CONVST High Time
(Note 10)
●
50
ns
t14
Latch Setup Time
(Note 10)
●
10
ns
t15
Latch Hold Time
(Notes 9, 10)
●
10
ns
t16
WR Low Time
(Note 10)
●
50
ns
t17
WR High Time
(Note 10)
●
50
ns
t18
M1 to M0 Setup Time
(Notes 9, 10)
●
10
ns
t19
M0 to BUSY Delay
M1 High
t20
M0 to WR (or RD) Setup Time
(Notes 9, 10)
●
t19
ns
t21
M0 High Pulse Width
(Note 10)
●
50
ns
t22
RD High Time Between Readback Reads
(Note 10)
●
50
ns
t23
Last WR (or RD) to M0
(Note 10)
●
10
ns
t24
M0 to RD Setup Time
(Notes 9, 10)
●
t19
ns
t25
M0 to CONVST
(Note 10)
●
t19
ns
t26
Aperture Delay
t27
Aperture Jitter
20
ns
– 0.5
ns
2
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 OGND and GND
wired together unless otherwise noted.
Note 3: When these pin voltages are taken below ground or above VDD,
they will be clamped by internal diodes. This product can handle input
currents of 100mA below ground or above VDD without latchup.
Note 4: When these pin voltages are taken below ground, they will be
clamped by internal diodes. This product can handle input currents of
100mA below ground without latchup. These pins are not clamped to VDD.
Note 5: VDD = 5V, fSAMPLE = 400kHz, tr = tf = 2ns unless otherwise
specified.
Note 6: Linearity, offset and full-scale specifications apply for a singleended input on any channel with COM grounded.
Note 7: Integral nonlinearity is defined as the deviation of a code from a
psRMS
straight line passing through the actual end points of the transfer curve.
The deviation is measured from the center of the quantization band.
Note 8: Bipolar offset is the offset voltage measured from – 0.5LSB when
the output code flickers between 1111 1111 1111 and 0000 0000 0000.
For the LTC1853 and between 11 1111 1111 and 00 0000 0000 for the
LTC1852.
Note 9: Guaranteed by design, not subject to test.
Note 10: Recommended operating conditions.
Note 11: The falling CONVST edge starts a conversion. If CONVST returns
high at a critical point during the conversion it can create small errors.
For the best results, ensure that CONVST returns high either within 400ns
after the start of the conversion or after BUSY rises.
Note 12: The analog input range is determined by the voltage on
REFCOMP. The gain error specification is tested with an external 4.096V
but is valid for any value of REFCOMP greater than 2V and less than
(VDD – 0.5V.)
Note 13: MUX address is updated immediately after BUSY falls.
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Linearity
0
1.0
8192 Point FFT with
fIN = 39.599kHz
–20
AMPLITUDE (dB)
DNL ERROR (LBS)
0.5
0
–40
–60
–80
–0.5
–100
–1.0
–120
0
4096
CODE
1852 F02
0
200
FREQUENCY (kHz)
1852 F03
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LTC1852/LTC1853
PIN FUNCTIONS
CH0 to CH7 (Pins 1 to 8): Analog Input Pins. Input pins can
be used single ended relative to the analog input common
pin or differentially in pairs (CH0 and CH1, CH2 and CH3,
CH4 and CH5, CH6 and CH7).
COM (Pin 9): Analog Input Common Pin. For single-ended
operation (DIFF = 0), COM is the “–” analog input. COM
is disabled when DIFF is high.
REFOUT (Pin 10): Internal 2.5V Reference Output. Bypass
to analog ground plane with 1μF.
REFIN (Pin 11): Reference Mode Select/Reference Buffer
Input. REFIN selects the reference mode and acts as the
reference buffer input. REFIN tied to ground (Logic 0) will
produce 2.048V on the REFCOMP pin. REFIN tied to the
positive supply (Logic 1) disables the reference buffer
to allow REFCOMP to be driven externally. For voltages
between 1V and 2.6V, the reference buffer produces an
output voltage on the REFCOMP pin equal to 1.6384 times
the voltage on REFIN (4.096V on REFCOMP for a 2.5V
input on REFIN).
REFCOMP (Pin 12): Reference Buffer Output. REFCOMP
sets the full-scale input span. The reference buffer produces
an output voltage on the REFCOMP pin equal to 1.6384
times the voltage on the REFIN pin (4.096V on REFCOMP
for a 2.5V input on REFIN). REFIN tied to ground will
produce 2.048V on the REFCOMP pin. REFCOMP can be
driven externally if REFIN is tied to the positive supply.
Bypass to analog ground plane with 10μF tantalum in
parallel with 0.1μF ceramic or 10μF ceramic.
GND (Pins 13, 16): Ground. Tie to analog ground plane.
VDD (Pins 14, 15): Positive Supply. Bypass to analog
ground plane with 10μF tantalum in parallel with 0.1μF
ceramic or 10μF ceramic.
DIFFOUT/S6 (Pin 17): Three-State Digital Data Output.
Active when RD is low. Following a conversion, the
single-ended/differential bit of the present conversion is
available on this pin concurrent with the conversion result.
In Readback mode, the single-ended/differential bit of the
current sequencer location (S6) is available on this pin.
The output swings between OVDD and OGND.
A2OUT/S5, A1OUT/S4, A0OUT/S3 (Pins 18 to 20): ThreeState Digital MUX Address Outputs. Active when RD is low.
Following a conversion, the MUX address of the present
conversion is available on these pins concurrent with the
conversion result. In Readback mode, the MUX address of
the current sequencer location (S5-S3) is available on these
pins. The outputs swing between OVDD and OGND.
D9/S2 (Pin 21, LTC1852): Three-State Digital Data Output.
Active when RD is low. Following a conversion, bit 9 of the
present conversion is available on this pin. In Readback
mode, the unipolar/bipolar bit of the current sequencer
location (S2) is available on this pin. The output swings
between OVDD and OGND.
D11/S2 (Pin 21, LTC1853): Three-State Digital Data Output.
Active when RD is low. Following a conversion, bit 11 of
the present conversion is available on this pin. In Readback
mode, the unipolar/bipolar bit of the current sequencer
location (S2) is available on this pin. The output swings
between OVDD and OGND.
D8/S1 (Pin 22, LTC1852): Three-State Digital Data Outputs.
Active when RD is low. Following a conversion, bit 8 of the
present conversion is available on this pin. In Readback
mode, the gain bit of the current sequencer location (S1)
is available on this pin. The output swings between OVDD
and OGND.
D10/S1 (Pin 22, LTC1853): Three-State Digital Data
Outputs. Active when RD is low. Following a conversion,
bit 10 of the present conversion is available on this pin.
In Readback mode, the gain bit of the current sequencer
location (S1) is available on this pin. The output swings
between OVDD and OGND.
D7/S0 (Pin 23, LTC1852): Three-State Digital Data Outputs.
Active when RD is low. Following a conversion, bit 7 of the
present conversion is available on this pin. In Readback
mode, the end of sequence bit of the current sequencer
location (S0) is available on this pin. The output swings
between OVDD and OGND.
18523fa
7
LTC1852/LTC1853
PIN FUNCTIONS
D9/S0 (Pin 23, LTC1853): Three-State Digital Data Outputs.
Active when RD is low. Following a conversion, bit 9 of the
present conversion is available on this pin. In Readback
mode, the end of sequence bit of the current sequencer
location (S0) is available on this pin. The output swings
between OVDD and OGND.
D6 to D0 (Pins 24 to 30, LTC1852): Three-State Digital
Data Outputs. Active when RD is low. The outputs swing
between OVDD and OGND.
D8 to D0 (Pins 24 to 32, LTC1853): Three-State Digital
Data Outputs. Active when RD is low. The outputs swing
between OVDD and OGND.
NC (Pins 31 to 32, LTC1852): No Connect. There is no
internal connection to these pins.
BUSY (Pin 33): Converter Busy Output. The BUSY output
has two functions. At the start of a conversion, BUSY will
go low and remain low until the conversion is completed.
The rising edge may be used to latch the output data.
BUSY will also go low while the part is in Program/Readback mode (M1 high, M0 low) and remain low until M0
is brought back high. The output swings between OVDD
and OGND.
OGND (Pin 34): Digital Data Output Ground. Tie to analog
ground plane. May be tied to logic ground if desired.
OVDD (Pin 35): Digital Data Output Supply. Normally tied
to 5V, can be used to interface with 3V digital logic. Bypass
to OGND with 10μF tantalum in parallel with 0.1μF ceramic
or 10μF ceramic.
UNI/BIP (Pin 38): Unipolar/Bipolar Select Input. Logic low
selects a unipolar input span, a high logic level selects a
bipolar input span.
A0 to A2 (Pins 39 to 41): MUX Address Input Pins.
DIFF (Pin 42): Single-Ended/Differential Select Input.
A low logic level selects single ended, a high logic level
selects differential.
WR (Pin 43): Write Input. In Direct Address mode, WR
low enables the MUX address and configuration input pins
(Pins 37 to 42). WR can be tied low or the rising edge of
WR can be used to latch the data. In Program mode, WR
is used to program the sequencer. WR low enables the
MUX address and configuration input pins (Pins 37 to 42).
The rising edge of WR latches the data and increments
the counter to the next sequencer location.
RD (Pin 44): Read Input. During normal operation, RD
enables the output drivers when CS is low. In Readback
mode (M1 high, M0 low), RD going low reads the current sequencer location, RD high advances to the next
sequencer location.
CONVST (Pin 45): Conversion Start Input. This active low
signal starts a conversion on its falling edge.
CS (Pin 46): Chip Select Input. The chip select input must
be low for the ADC to recognize the CONVST and RD inputs.
If SHDN is low, a low logic level on CS selects Nap mode;
a high logic level on CS selects Sleep mode.
M0 (Pin 36): Mode Select Pin 0. Used in conjunction with
M1 to select operating mode. See Table 5.
SHDN (Pin 47): Power Shutdown Input. A low logic level
will invoke the Shutdown mode selected by the CS pin.
CS low selects Nap mode, CS high selects Sleep mode.
Tie high if unused.
PGA (Pin 37): Gain Select Input. A high logic level selects
gain = 1, a low logic level selects gain = 2.
M1 (Pin 48): Mode Select Pin 1. Used in conjunction with
M0 to select operating mode. See Table 5.
18523fa
8
LTC1852/LTC1853
PIN FUNCTIONS
NOMINAL (V)
TYP
PIN
NAME
MAX
1 to 8
9
10
REFOUT
2.5V Reference Output
11
REFIN
Reference Buffer Input
12
REFCOMP
Reference Buffer Output
13
GND
Ground
14
VDD
Positive Supply
2.7
5
5.5
15
VDD
Positive Supply
2.7
5
16
GND
Ground
17
DIFFOUT/S6
Single-Ended/Differential Output
18
A2OUT/S5
19
20
ABSOLUTE MAXIMUM (M)
MIN
MAX
DESCRIPTION
MIN
CH0 to CH7
Analog Inputs
0
VDD
–0.3
VDD + 0.3
COM
Analog Input Common Pin
0
VDD
–0.3
VDD + 0.3
–0.3
VDD + 0.3
VDD
–0.3
VDD + 0.3
–0.3
VDD + 0.3
–0.3
VDD + 0.3
–0.3
6
5.5
–0.3
6
–0.3
VDD + 0.3
OGND
0VDD
–0.3
VDD + 0.3
MUX Address Output
OGND
0VDD
–0.3
VDD + 0.3
A1OUT/S4
MUX Address Output
OGND
0VDD
–0.3
VDD + 0.3
A0OUT/S3
MUX Address Output
OGND
0VDD
–0.3
VDD + 0.3
21
D9/S2 (LTC1852)
Data Output
OGND
0VDD
–0.3
VDD + 0.3
21
D11/S2 (LTC1853)
Data Output
OGND
0VDD
–0.3
VDD + 0.3
22
D8/S1 (LTC1852)
Data Output
OGND
0VDD
–0.3
VDD + 0.3
22
D10/S1 (LTC1853)
Data Output
OGND
0VDD
–0.3
VDD + 0.3
23
D7/S0 (LTC1852)
Data Output
OGND
0VDD
–0.3
VDD + 0.3
23
D9/S0 (LTC1853)
Data Output
OGND
0VDD
–0.3
VDD + 0.3
24 to 30
D6 to D0 (LTC1852)
Data Outputs
OGND
0VDD
–0.3
VDD + 0.3
24 to 32
D8 to D0 (LTC1853)
Data Outputs
OGND
0VDD
–0.3
VDD + 0.3
31 to 32
NC (LTC1852)
No Connect
33
BUSY
Converter Busy Output
0VDD
–0.3
VDD + 0.3
34
OGND
Output Ground
–0.3
VDD + 0.3
35
OVDD
Output Supply
5.5
–0.3
6
2.5
0
2.5
4.096
0
0
OGND
0
2.7
5
36
M0
Mode Select Pin 0
0
VDD
–0.3
6
37
PGA
Gain Select Input
0
VDD
–0.3
6
38
UNI/BIP
Unipolar/Bipolar Input
0
VDD
–0.3
6
39 to 41
A0 to A2
MUX Address Inputs
0
VDD
–0.3
6
42
DIFF
Single-Ended/Differential Input
0
VDD
–0.3
6
43
WR
Write Input, Active Low
0
VDD
–0.3
6
44
RD
Read Input, Active Low
0
VDD
–0.3
6
45
CONVST
Conversion Start Input, Active Low
0
VDD
–0.3
6
46
CS
Chip Select Input, Active Low
0
VDD
–0.3
6
47
SHDN
Shutdown Input, Active Low
0
VDD
–0.3
6
48
M1
Mode Select Pin 1
0
VDD
–0.3
6
18523fa
9
LTC1852/LTC1853
APPLICATIONS INFORMATION
The LTC1852/LTC1853 are complete and very flexible
data acquisition systems. They consist of a 10-bit/12-bit,
400ksps capacitive successive approximation A/D converter with a wideband sample-and-hold, a configurable
8-channel analog input multiplexer, an internal reference
and reference buffer amplifier, a 16-bit parallel digital
output and digital control logic, including a programmable
sequencer.
CONVERSION DETAILS
The core analog-to-digital converter in the LTC1852/
LTC1853 uses a successive approximation algorithm and
an internal sample-and-hold circuit to convert an analog
signal to a 10-bit/12-bit parallel output. Conversion start
is controlled by the CS and CONVST inputs. At the start
of the conversion, the successive approximation register
(SAR) is reset. Once a conversion cycle is begun, it cannot
be restarted. During the conversion, the internal differential capacitive DAC output is sequenced by the SAR from
the most significant bit (MSB) to the least significant bit
(LSB). The outputs of the analog input multiplexer are
connected to the sample-and-hold capacitors (CSAMPLE)
during the acquire phase and the comparator offset is
nulled by the zeroing switches. In this acquire phase, a
minimum delay of 150ns will provide enough time for
the sample-and-hold capacitors to acquire the analog
signal. During the convert phase, the comparator zeroing
switches are open, putting the comparator into compare
mode. The input switches connect CSAMPLE to ground,
transferring the differential analog input charge onto the
summing junction. This input charge is successively
compared with the binary weighted charges supplied by
the differential capacitive DAC. Bit decisions are made by
the high speed comparator. At the end of the conversion,
the differential DAC output balances the input charges.
The SAR contents (a 10-bit/12-bit data word), which
represents the difference of the analog input multiplexer
outputs, and the 4-bit address word are loaded into the
14-bit/16-bit output latches.
DYNAMIC PERFORMANCE
Signal-to-(Noise + Distortion) Ratio
The signal-to-noise plus distortion ratio [S/(N + D)] is the
ratio between the RMS amplitude of the fundamental input
frequency and the RMS amplitude of all other frequency
components at the ADC output. The output is band limited to frequencies above DC to below half the sampling
frequency. The effective number of bits (ENOBs) is a
measurement of the resolution of an ADC and is directly
related to the S/(N + D) by the equation:
ENOB = [S/(N + D) – 1.76]/6.02
where ENOB is the effective number of bits and S/(N + D) is
expressed in dB. At the maximum sampling rate of 400kHz,
the LTC1852/LTC1853 maintain near ideal ENOBs up to
and beyond the Nyquist input frequency of 200kHz.
Total Harmonic Distortion
Total harmonic distortion is the ratio of the RMS sum
of all harmonics of the input signal to the fundamental
itself. The out-of-band harmonics alias into the frequency
band between DC and half the sampling frequency. THD
is expressed as:
THD= 20Log
V22 + V32 + V42 +...Vn2
V1
where V1 is the RMS amplitude of the fundamental
frequency and V2 through Vn are the amplitudes of the
second through nth harmonics. The LTC1852/LTC1853
have good distortion performance up to the Nyquist
frequency and beyond.
Intermodulation Distortion
If the ADC input signal consists of more than one spectral
component, the ADC transfer function nonlinearity can
produce intermodulation distortion (IMD) in addition to
THD. IMD is the change in one sinusoidal input caused
by the presence of another sinusoidal input at a different
frequency.
18523fa
10
LTC1852/LTC1853
APPLICATIONS INFORMATION
If two pure sine waves of frequencies fa and fb are applied
to the ADC input, nonlinearities in the ADC transfer function
can create distortion products at the sum and difference
frequencies of mfa ± nfb, where m and n = 0, 1, 2, 3, etc.
For example, the 2nd order IMD terms include (fa ± fb).
If the two input sine waves are equal in magnitude, the
value (in decibels) of the 2nd order IMD products can be
expressed by the following formula:
IMD ( fa ± fb) = 20Log
Amplitude at ( fa ± fb)
Amplitude at fa
Peak Harmonic or Spurious Noise
The peak harmonic or spurious noise is the largest spectral
component excluding the input signal and DC. This value
is expressed in decibels relative to the RMS value of a
full-scale input signal.
Full-Power and Full-Linear Bandwidth
The full-power bandwidth is that input frequency at which
the amplitude of the reconstructed fundamental is reduced
by 3dB for a full-scale input signal.
The full-linear bandwidth is the input frequency at which
the S/(N + D) has dropped to 68dB for the LTC1853 (11
effective bits) or 56dB for the LTC1852 (9 effective bits).
The LTC1852/LTC1853 have been designed to optimize
input bandwidth, allowing the ADC to undersample input
signals with frequencies above the converter’s Nyquist frequency. The noise floor stays very low at high frequencies;
S/(N + D) becomes dominated by distortion at frequencies
far beyond Nyquist.
ANALOG INPUT MULTIPLEXER
The analog input multiplexer is controlled using the
single-ended/differential pin (DIFF), three MUX address
pins (A2, A1, A0), the unipolar/bipolar pin (UNI/BIP) and
the gain select pin (PGA). The single-ended/differential
pin (DIFF) allows the user to configure the MUX as eight
single-ended channels relative to the analog input common pin (COM) when DIFF is low or as four differential
pairs (CH0 and CH1, CH2 and CH3, CH4 and CH5, CH6
and CH7) when DIFF is high. The channels (and polarity in
the differential case) are selected using the MUX address
inputs as shown in Table 1. Unused inputs (including
the COM in the differential case) should be grounded to
prevent noise coupling.
Table 1. Multiplexer Address Table
MUX ADDRESS
DIFF A2
SINGLE-ENDED CHANNEL SELECTION
A1
A0 CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 COM
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
+
+
–
+
–
+
–
+
–
+
–
+
–
+
MUX ADDRESS
DIFF A2
–
–
DIFFERENTIAL CHANNEL SELECTION
A1
A0 CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 COM
1
0
0
0
+
–
1
0
0
1
–
+
1
0
1
0
1
0
1
1
1
1
0
0
+
–
–
+
*
*
+
–
*
–
+
*
*
*
1
1
0
1
1
1
1
0
+
–
*
1
1
1
1
–
+
*
*Not used in differential mode. Connect to AGND.
In addition to selecting the MUX channel, the LTC1852/
LTC1853 also allows the user to select between two gains
and unipolar or bipolar inputs for a total of four input spans.
PGA high selects a gain of 1 (the input span is equal to the
voltage on REFCOMP). PGA low selects a gain of 2 where
the input span is equal to half of the voltage on REFCOMP.
UNI/BIP low selects a unipolar input span, UNI/BIP high
selects a bipolar input span. Table 2 summarizes the possible input spans.
Table 2. Input Span Table
INPUT SPAN
UNI/BIP
PGA
0
0
0 – REFCOMP/2
0 – 2.048V
0
1
0 – REFCOMP
0 – 4.096V
1
0
± REFCOMP/4
±1.024V
1
1
±REFCOMP/2
±2.048V
REFCOMP = 4.096V
18523fa
11
LTC1852/LTC1853
APPLICATIONS INFORMATION
The LTC1852/LTC1853 have a unique differential sampleand-hold circuit that allows rail-to-rail inputs. The ADC will
always convert the difference of the “+” and “–” inputs
independent of the common mode voltage. The common
mode rejection holds up to high frequencies. The only
requirement is that both inputs can not exceed the AVDD
power supply voltage or ground. When a bipolar input
span is selected the “+” input can swing ± full scale relative to the “–” input but neither input can exceed AVDD or
go below ground.
Integral nonlinearity errors (INL) and differential nonlinearity errors (DNL) are independent of the common mode
voltage, however, the bipolar offset will vary. The change
in bipolar offset is typically less than 0.1% of the common
mode voltage.
input(s) must settle after the small current spike before
the next conversion starts (settling time must be less than
150ns for full throughput rate).
Choosing an Input Amplifier
Choosing an input amplifier is easy if a few requirements
are taken into consideration. First, to limit the magnitude
of the voltage spike seen by the amplifier from charging
the sampling capacitor, choose an amplifier that has a low
output impedance (<100Ω) at the closed-loop bandwidth
frequency. For example, if an amplifier is used in a gain
of +1 and has a unity-gain bandwidth of 50MHz, then the
output impedance at 50MHz should be less than 100Ω.
The second requirement is that the closed-loop bandwidth
must be greater than 10MHz to ensure adequate smallsignal settling for full throughput rate. The following list
is a summary of the op amps that are suitable for driving
the LTC1852/LTC1853, more detailed information is available in the Linear Technology Databooks, the LinearView™
CD-ROM and on our web site at www.linear-tech.com.
Some AC applications may have their performance limited
by distortion. Most circuits exhibit higher distortion when
signals approach the supply or ground. THD will degrade
as the inputs approach either power supply rail. Distortion can be reduced by reducing the signal amplitude
and keeping the common mode voltage at approximately
midsupply.
LT®1360: 50MHz Voltage Feedback Amplifier. ± 2.5V to
±15V supplies. 5mA supply current. Low distortion.
Driving the Analog Inputs
LT1363: 70MHz Voltage Feedback Amplifier. ± 2.5V to ±15V
supplies. 7.5mA supply current. Low distortion.
The inputs of the LTC1852/LTC1853 are easy to drive. Each
of the analog inputs can be used as a single-ended input
relative to the input common pin (CH0-COM, CH1-COM,
etc.) or in pairs (CH0 and CH1, CH2 and CH3, CH4 and
CH5, CH6 and CH7) for differential inputs. Regardless
of the MUX configuration, the “+” and “–” inputs are
sampled at the same instant. Any unwanted signal that is
common mode to both inputs will be reduced by the common mode rejection of the sample-and-hold circuit. The
inputs draw only one small current spike while charging
the sample-and-hold capacitors at the end of conversion.
During conversion, the analog inputs draw only a small
leakage current. If the source impedance of the driving
circuit is low, then the LTC1852/LTC1853 inputs can be
driven directly. As source impedance increases, so will
acquisition time. For minimum acquisition time with high
source impedance, a buffer amplifier should be used. The
only requirement is that the amplifier driving the analog
LT1364/LT1365: Dual and Quad 70MHz Voltage Feedback
Amplifiers. ±2.5V to ±15V supplies. 7.5mA supply current
per amplifier. Low distortion.
LT1468/LT1469: Single and Dual 90MHz Voltage Feedback
Amplifier. ± 5V to ±15V supplies. 7mA supply current per
amplifier. Lowest noise and low distortion.
LT1630/LT1631: Dual and Quad 30MHz Rail-to-Rail Voltage Feedback Amplifiers. Single 3V to ±15V supplies.
3.5mA supply current per amplifier. Low noise and low
distortion.
LT1632/LT1633: Dual and Quad 45MHz Rail-to-Rail Voltage
Feedback Amplifiers. Single 3V to ±15V supplies. 4.3mA
supply current per amplifier. Low distortion.
LT1806/LT1807: Single and Dual 325MHz Rail-to-Rail
Voltage Feedback Amplifier. Single 3V to ± 5V supplies.
13mA supply current. Lowest distortion.
LinearView is a trademark of Linear Technology Corporation.
18523fa
12
LTC1852/LTC1853
APPLICATIONS INFORMATION
LT1809/LT1810: Single and Dual 180MHz Rail-to-Rail
Voltage Feedback Amplifier. Single 3V to ±15V supplies.
20mA supply current. Lowest distortion.
LT1812/LT1813: Single and Dual 100MHz Voltage Feedback Amplifier. Single 5V to ±5V supplies. 3.6mA supply
current. Low noise and low distortion.
or DAC. If REFIN is tied low, the internal 2.5V reference
divided by 2 (1.25V) is connected internally to the input
of the reference buffer resulting in 2.048V on REFCOMP.
If REFIN is tied high, the reference buffer is disabled and
REFCOMP can be tied to REFOUT to achieve a 2.5V span
or driven with an external reference or DAC. Table 3 summarizes the Reference modes.
Input Filtering
Table 3. Reference Mode Table
The noise and the distortion of the input amplifier and
other circuitry must be considered since they will add to
the LTC1852/LTC1853 noise and distortion. Noisy input
circuitry should be filtered prior to the analog inputs to
minimize noise. A simple 1-pole RC filter is sufficient for
many applications. For instance, a 200Ω source resistor
and a 1000pF capacitor to ground on the input will limit
the input bandwidth to 800kHz.The capacitor also acts
as a charge reservoir for the input sample-and-hold and
isolates the ADC input from sampling glitch sensitive
circuitry. High quality capacitors and resistors should be
used since these components can add distortion. NPO
and silver mica type dielectric capacitors have excellent
linearity. Carbon surface mount resistors can also generate
distortion from self heating and from damage that may
occur during soldering. Metal film surface mount resistors
are much less susceptible to both problems.
MODE
REFERENCE
The LTC1852/LTC1853 includes an on-chip, temperature
compensated, curvature corrected, bandgap reference
that is factory trimmed to 2.500V and has a very flexible
3-pin interface. REFOUT is the 2.5V bandgap output, REFIN
is the input to the reference buffer and REFCOMP is the
reference buffer output. The input span is determined by
the voltage appearing on the REFCOMP pin as shown in
Table 2. The reference buffer has a gain of 1.6384 and
is factory trimmed by forcing an external 2.500V on the
REFIN pin and trimming REFCOMP to 4.096V. The 3-pin
interface allows for three pin-strappable Reference modes
as well as two additional external Reference modes. For
voltages on the REFIN pin ranging from 1V to 2.6V, the
output voltage on REFCOMP will equal 1.6384 times the
voltage on the REFIN pin. In this mode, the REFIN pin can
be tied to REFOUT to use the internal 2.5V reference to get
4.096V on REFCOMP or driven with an external reference
REFIN
REFCOMP
0V Input
2.048V Output
1v to 2.6 Input
1.6384V to 4.26V Output
(1.6384 • REFIN)
5V Input
Input, 19.2kΩ to Ground
REFIN Tied Low
REFIN is Buffer Input
REFIN Tied High
Full Scale and Offset
In applications where absolute accuracy is important,
offset and full-scale errors can be adjusted to zero during a calibration sequence. Offset error must be adjusted
before full-scale error. Zero offset is achieved by adjusting the offset applied to the “–” input. For single-ended
inputs, this offset should be applied to the COM pin. For
differential inputs, the “–” input is dictated by the MUX
address. For zero offset error, apply 0.5LSB (actual voltage will vary with input span selected) to the “+” input
and adjust the offset at the “–” input until the output code
flickers between 0000 0000 0000 and 0000 0000 0001
for the LTC1853 and between 00 0000 0000 and 00 0000
0001 for the LTC1852.
As mentioned earlier, the internal reference is factory
trimmed to 2.500V. To make sure that the reference buffer
gain is not compensating for trim errors in the reference,
REFCOMP is trimmed to 4.096V with an extremely accurate
external 2.5V reference applied to REFIN. Likewise, to make
sure that the full-scale gain trim is not compensating for
errors in the reference buffer gain, the input full-scale gain
is trimmed with an extremely accurate 4.096V reference
applied to REFCOMP (REFIN = 5V to disable the reference
buffer). This allows the use of either a 2.5V reference applied
to REFIN or a 4.096V reference applied to REFCOMP to
achieve accurate results. Full-scale errors can be trimmed
to zero by adjusting the appropriate reference voltage. For
unipolar inputs, an input voltage of FS – 1.5LSBs should
be applied to the “+” input and the appropriate reference
18523fa
13
LTC1852/LTC1853
APPLICATIONS INFORMATION
adjusted until the output code flickers between 1111 1111
1110 and 1111 1111 1111 for the LTC1853 and between
11 1111 1110 and 11 1111 1111 for the LTC1852.
For bipolar inputs, an input voltage of FS – 1.5LSBs should
be applied to the “+” input and the appropriate reference
adjusted until the output code flickers between 0111 1111
1110 and 0111 1111 1111 for the LTC1853 and between
01 1111 1110 and 01 1111 1111 for the LTC1852.
also function as output bits when reading the contents of
the programmable sequencer. During readback, a 7-bit
status word (S6-S0) containing the contents of the current sequencer location is available when RD is low. The
individual bits of the status word are outlined in Figure 1.
During readback, the D8 to D0 pins (LTC1853) or D6 to
D0 pins (LTC1852) remain high impedance irrespective
of the state of RD.
These adjustments as well as the factory trims affect all
channels. The channel-to-channel offset and gain error
matching are guaranteed by design to meet the specifications in the Converter Characteristics table.
Unipolar Transfer Characteristic
(UNI/BIP = 0)
1111...1111
1111...1110
The data format of the conversion result is automatically
selected and determined by the UNI/BIP input pin. If
the UNI/BIP pin is low indicating a unipolar input span
(0 – REFCOMP assuming PGA = 1), the format for the
data is straight binary with 1 LSB = FS/4096 (1mV for
REFCOMP = 4.096V). For the LTC1853 and 1LSB = FS/1024
(4mV for REFCOMP = 4.096V) for the LTC1852.
If the UNI/BIP pin is high indicating a bipolar input span
(± REFCOMP/2 for PGA = 1), the format for the data is two’s
complement binary with 1 LSB = [(+FS) – (–FS)]/4096
(1mV for REFCOMP = 4.096V). For the LTC1853 and 1LSB
= [(+FS) – (–FS)]/1024 (4mV for REFCOMP = 4.096V) for
the LTC1852.
In both cases, the code transitions occur midway between successive integer LSB values (i.e., –FS + 0.5LSB,
–FS + 1.5LSB, ... –1.5LSB, –0.5LSB, 0.5LSB, 1.5LSB, ...
FS – 1.5LSB, FS – 0.5LSB).
1000...0001
1000...0000
0111...1111
0111...1110
0000...0010
0000...0001
0000...0000
FS = VREFCOMP
0
FS – 1LBS
INPUT VOLTAGE (V)
18523 F01A
Bipolar Transfer Characteristic
(UNI/BIP = 1)
0111...1111
0111...1110
BIPOLAR
ZERO
0111...1101
OUTPUT CODE
The LTC1852/LTC1853 have a 14 bit/16-bit parallel output. The output word normally consists of a 10-bit/12-bit
conversion result data word and a 4-bit address (three
address bits A2OUT, A1OUT, A0OUT and the DIFFOUT bit).
The output drivers are enabled when RD is low provided
the chip is selected (CS is low). All 14/16 data output pins
and BUSY are supplied by OVDD and OGND to allow easy
interface to 3V or 5V digital logic.
OUTPUT CODE
1111...1101
OUTPUT DATA FORMAT
0000...0001
0000...0000
1111...1111
1111...1110
1000...0010
1000...0001
V
FS = REFCOMP
2
1000...0000
–FS
S6
S5
–1LBS 0 1LBS
INPUT VOLTAGE (V)
S4
S3
A1
A2
A0
MUX ADDRESS
SINGLE-ENDED/
DIFFERENTIAL BIT
S2
FS – 1LBS
18523 F01B
S1
S0
PGA BIT
END OF
UNIPOLAR/
BIPOLAR BIT SEQUENCE BIT
18523 F01
The three most significant bits of the data word (D11, D10
and D9 for the LTC1853; D9, D8 and D7 for the LTC1852)
Figure 1. Readback Status Word
18523fa
14
LTC1852/LTC1853
APPLICATIONS INFORMATION
BOARD LAYOUT AND BYPASSING
To obtain the best performance from the LTC1852/LTC1853,
a printed circuit board with ground plane is required. The
ground plane under the ADC area should be as free of
breaks and holes as possible, such that a low impedance
path between all ADC grounds and all ADC decoupling
capacitors is provided. It is critical to prevent digital noise
from being coupled to the analog inputs, reference or
analog power supply lines. Layout for the printed circuit
board should ensure that digital and analog signal lines are
separated as much as possible. In particular, care should
be taken not to run any digital track alongside an analog
signal track or underneath the ADC.
An analog ground plane separate from the logic system
ground should be established under and around the ADC.
Pin 34 (OGND), Pin 13 (GND), Pin 16 (GND) and all other
analog grounds should be connected to this single analog ground point. The bypass capacitors should also be
connected to this analog ground plane. No other digital
grounds should be connected to this analog ground plane.
In some applications, it may be desirable to connect the
OVDD to the logic system supply and OGND to the logic
system ground. In these cases, OVDD should be bypassed
to OGND instead of the analog ground plane.
Low impedance analog and digital power supply common
returns are essential to the low noise operation of the
ADC and the foil width for these tracks should be as wide
as possible. In applications where the ADC data outputs
and control signals are connected to a continuously active microprocessor bus, it is possible to get errors in the
conversion results. These errors are due to feedthrough
from the microprocessor to the sucessive approximation
comparator. The problem can be eliminated by forcing the
microprocessor into a WAIT state during conversions or
by using three-state buffers to isolate the ADC bus. The
traces connecting the pins and bypass capacitors must be
kept short and should be made as wide as possible.
The LTC1852/LTC1853 have differential inputs to minimize noise coupling. Common mode noise on the “+”
and “–” inputs will be rejected by the input CMRR. The
LTC1852/LTC1853 will hold and convert the difference
between whichever input is selected as the “+” input and
whichever input is selected as the “–” input. Leads to the
inputs should be kept as short as possible.
SUPPLY BYPASSING
High quality, low series resistance ceramic 10μF bypass
capacitors should be used. Surface mount ceramic capacitors such as Murata GRM235Y5V106Z016 provide
excellent bypassing in a small board space. Alternatively,
10μF tantalum capacitors in parallel with 0.1μF ceramic
capacitors can be used. Bypass capacitors must be located
as close to the pins as possible. The traces connecting the
pins and the bypass capacitors must be kept short and
should be made as wide as possible.
DIGITAL INTERFACE
Internal Clock
The A/D converter has an internal clock that eliminates the
need of synchronization between the external clock and
the CS and RD signals found in other ADCs. The internal
clock is factory trimmed to achieve a typical conversion
time of 1400ns, and a maximum conversion time over
the full operating temperature range of 2μs. No external
adjustments are required. The guaranteed maximum
acquisition time is 150ns. In addition, a throughput
time of 2.5μs and a minimum sampling rate of 400ksps
is guaranteed.
CS
t3
SHDN
18523 F02
Figure 2. CS to SHDN Setup Timing
SHDN
t4
CONVST
18523 F03
Figure 3. SHDN to CONVST Wake-Up Timing
18523fa
15
LTC1852/LTC1853
APPLICATIONS INFORMATION
the ADC has been selected (i.e., CS is low). Once initiated,
it cannot be restarted until the conversion is complete.
Converter status is indicated by the BUSY output. BUSY
is low during a conversion. If CONVST returns high at a
critical point during the conversion it can create small
errors. For the best results, ensure that CONVST returns
high either within 400ns after the start of the conversion
or after BUSY rises.
CS
t2
CONVST
t1
RD
18523 F04
Figure 4. CS to CONVST and RD Setup Timing
Figures 5 through 9 show several different modes
of operation. In modes 1a and 1b (Figures 5 and 6),
CS and RD are both tied low. The falling edge of
CONVST starts the conversion. The data outputs
are always enabled and data can be latched with the
BUSY rising edge. Mode 1a shows operation with a narrow
logic low CONVST pulse. Mode 1b shows a narrow logic
high CONVST pulse.
Power Shutdown
The LTC1852/LTC1853 provide two power shutdown
modes, Nap and Sleep, to save power during inactive
periods. The Nap mode reduces the power to 2.5mW and
leaves only the digital logic and reference powered up.
The wake-up time from Nap to active is 200ns. In Sleep
mode, all bias currents are shut down and only leakage
current remains—about 20μA. Wake-up time from sleep
mode is much slower since the reference circuit must
power-up and settle to 0.005% for full 12-bit accuracy
(0.02% for full 10-bit accuracy). Sleep mode wake-up time
is dependent on the value of the capacitor connected to
the REFCOMP (Pin 12). The wake-up time is 10ms with
the recommended 10μF capacitor.
In mode 2 (Figure 7), CS is tied low. The falling edge of
CONVST signal again starts the conversion. Data outputs are in three-state until read by the MPU with the
RD signal. Mode 2 can be used for operation with a shared
MPU databus.
In slow memory and ROM modes (Figures 8 and 9),CS is
tied low and CONVST and RD are tied together. The MPU
starts the conversion and reads the output with the RD
signal. Conversions are started by the MPU or DSP (no
external sample clock).
Shutdown is controlled by Pin 47 (SHDN); the ADC is in
shutdown when it is low. The shutdown mode is selected
with Pin 46 (CS); low selects Nap (Figures 2 and 3).
In slow memory mode, the processor applies a logic low
to RD ( = CONVST), starting the conversion. BUSY goes
low, forcing the processor into a Wait state. The previous
conversion result appears on the data outputs. When
the conversion is complete, the new conversion results
Timing and Control
Conversion start and data read operations are controlled by
three digital inputs: CONVST, CS and RD (Figure 4). A logic
“0” applied to the CONVST pin will start a conversion after
tCONV
t5
CONVST
t8
t6
BUSY
t7
DATA
DATA (N – 1)
DATA N
18523 F05
Figure 5. Mode 1a CONVST Starts a Conversion. Data Outputs Always Enabled (CS = RD = 0)
18523fa
16
LTC1852/LTC1853
APPLICATIONS INFORMATION
t8
tCONV
t5
t13
CONVST
t6
t6
BUSY
t7
DATA
DATA (N – 1)
DATA N
18523 F06
Figure 6. Mode 1b CONVST Starts a Conversion, RD = CS = 0
tCONV
t5
t8
CONVST
t13
t6
BUSY
t9
t12
RD
t10
DATA
t11
DATA N
18523 F07
Figure 7. Mode 2 CONVST Starts a Conversion. Data is Read by RD, CS = 0
tCONV
t8
RD = CONVST
t11
t6
BUSY
t10
DATA
t7
DATA (N – 1)
DATA N
DATA N
DATA (N + 1)
18523 F08
Figure 8. Slow Memory Mode Timing, CS = 0
tCONV
t8
CONVST
t6
t11
BUSY
t10
DATA
DATA (N – 1)
DATA N
18523 F09
Figure 9. ROM Mode Timing, CS = 0
18523fa
17
LTC1852/LTC1853
APPLICATIONS INFORMATION
appear on the data outputs; BUSY goes high releasing the
processor, and the processor takes RD ( = CONVST) back
high and reads the new conversion data.
In ROM mode, the processor takes RD ( = CONVST) low,
starting a conversion and reading the previous conversion
result. After the conversion is complete, the processor can
read the new result and initiate another conversion.
MODES OF OPERATION
Direct Address Mode
The simplest mode of operation is the Direct Address
mode. This mode is selected when both the M1 and M0
pins are low. In this mode, the address input pins directly
control the MUX and the configuration input pins directly
control the input span. The address and configuration
input pins are enabled when WR is low. WR can be tied
low if the pins will be constantly driven or the rising edge
of WR can be used to latch and hold the inputs for as long
as WR is held high.
Scan Mode
Scan mode is selected when M1 is low and M0 is high.
This mode allows the converter to scan through all of
the input channels sequentially and repeatedly without
the user having to provide an address. The address
input pins (A2 to A0) are ignored but the DIFF, PGA and
UNI/BIP pins are still enabled when WR is low. As in the
direct address mode, WR can be held low or the rising
edge of WR can be used to latch and hold the information
on these pins for as long as WR is held high. The DIFF
pin selects the scan pattern. If DIFF is held low, the scan
pattern will consist of all eight channels in succession,
single-ended relative to COM (CH0-COM, CH1-COM,
CH2-COM, CH3-COM, CH4-COM, CH5-COM, CH6-COM,
CH7-COM, repeat). At the maximum conversion rate the
throughput rate for each channel would be 400ksps/8 or
50ksps. If DIFF is held high, the scan pattern will consist
of four differential pairs (CH0-CH1, CH2-CH3, CH4-CH5,
CH6-CH7, repeat). At the maximum conversion rate, the
throughput rate for each pair would be 400ksps/4 or
100ksps. It is possible to drive the DIFF input pin while
the part is in Scan mode to achieve combinations of
single-ended and differential inputs. For instance, if the
A0OUT pin is tied to the DIFF input pin, the scan pattern
will consist of four single-ended inputs and two differential
pairs (CH0-COM single-ended, CH1-COM single-ended,
CH2-CH3 differential, CH4-COM single-ended, CH5-COM
single-ended, CH6-CH7 differential, repeat).
The scan counter is reset to zero whenever the M0 pin
changes state so that the first conversion after M0 rises
will be MUX Address 000 (CH0-COM single-ended or CH0CH1 differential depending on the state of the DIFF pin).
A conversion is initiated by the falling edge of CONVST.
After each conversion, the address counter is advanced
(by one if DIFF is low, by two if DIFF is high) and the MUX
address for the present conversion is available on the address output pins (DIFFOUT, A2OUT to A0OUT) along with
the conversion result.
Program/Readback Mode
The LTC1852 and LTC1853 include a sequencer that can
be programmed to run a sequence of up to 16 locations
containing a MUX address and input configuration. The
MUX address and input configuration for each location
are programmed using the DIFF, A2 to A0, UNI/BIP and
PGA pins and are stored in memory along with an end-ofsequence (EOS) bit that is generated automatically. The
six input address and configuration bits plus the EOS bit
can be read back by accessing the 7-bit readback status
word (S6-S0) through the data output pins. The sequencer
memory is a 16 × 7 block of memory represented by the
block diagram in Figure 10.
DIFF
A2
A1
A0
UNI/BIP
PGA
EOS
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
LOCATION 0000
LOCATION 0001
LOCATION 0010
LOCATION 1110
LOCATION 1111
18523 F10
Figure 10. Sequencer Memory Block Diagram
18523fa
18
LTC1852/LTC1853
APPLICATIONS INFORMATION
The sequencer is accessed by taking the M1 mode pin
high. With M1 high, the sequencer memory is accessed
by taking the M0 mode pin low. This will cause BUSY to
go low, disabling conversions during the programming
and readback of the sequencer. The sequencer is reset
to location 0000 whenever M1 or M0 changes state. One
of these signals should be cycled prior to any read or
write operation to guarantee that the sequencer will be
programmed or read starting at location 0000.
The sequencer is programmed sequentially starting from
location 0000. RD and WR should be held high, the appropriate signals applied to the DIFF pin, the A2 to A0 MUX
address pins, the UNI/BIP pin and the PGA pin and WR
taken low to write to the memory. WR going high will latch
the data into memory and advance the pointer to the next
sequencer location. Up to 16 locations can be programmed
and the last location written before M0 is taken back high
will be the last location in the sequence. After 16 writes,
the pointer is reset to location 0000 and any subsequent
writes will erase all of the previous contents and start a
new sequence.
The sequencer memory can be read by holding WR high
and strobing RD. Taking RD low accesses the sequencer
memory and enables the data output pins. The sequencer
should be reset to location 0000 before beginning a read
operation (by applying a positive pulse to MO). The seven
output bits will be available on the DIFFOUT/S6, A2OUT/S5,
A1OUT/S4, A0OUT/S3, D11/S2, D10/S1 and D9/S0 pins
(LTC1853) or DIFFOUT/S6, A2OUT/S5, A1OUT/S4, A0OUT/S3,
D9/S2, D8/S1 and D7/S0 pins (LTC1852). The D8 to D0
(LTC1853) or D6 to D0 (LTC1852) data output pins will
remain high impedance during readback. RD going high
will return the data output pins to a high impedance state
and advance the pointer to the next location. A logic 1
on the D9/S0 (D7/S0) pin indicates the last location in
the current sequence but all 16 locations can be read by
continuing to clock RD. After 16 reads, the pointer is reset
to location 0000. When all programming and/or reading
of the sequencer memory is complete, M0 is taken high.
BUSY will come back high enabling CONVST and indicating
that the part is ready to start a conversion.
Sequence Run Mode
Once the sequencer is programmed, M0 is taken high.
BUSY will also come back high enabling CONVST and
the next falling CONVST will begin a conversion using the
MUX address and input configuration stored in location
0000 of the sequencer memory. After each conversion,
the sequencer pointer is advanced by one and the MUX
address ( the actual channel or channels being converted,
not the sequencer pointer) for the present conversion
is available on the address output pins along with the
conversion result. When the sequencer finishes converting the last programmed location, the sequencer pointer
will return to location 0000 for the next conversion. The
sequencer will also reset to location 0000 anytime the M1
or M0 pin changes state.
The contents of the sequencer memory will be retained
as long as power is contiuously applied to the part. This
allows the user to switch from Sequence Run mode to
either Direct Address or Scan Mode and back without
losing the programmed sequence. The part can also be
disabled using CS or shutdown in Nap or Sleep mode
without losing the programmed sequence. Table 5 outlines
the operational modes of the LTC1852/LTC1853. Figures 11
and 12 show the timing diagrams for writing to, reading
from and running a sequence.
Table 5
M1
M0
WR
RD
COMMENTS
Direct Address
0
0
0
0
0
OE
OE
Address and Configuration are Driven from External Pins
Address and Configuration are Latched on Rising Edge of WR or Falling Edge of CONVST
Scan
0
0
1
1
0
OE
OE
Address is Provided by Internal Scan Counter, Configuration is Driven from External Pins
Configuraton is Latched on Rising Edge of WR or Falling Edge of CONVST
Program
1
0
1
Write Sequencer Location, WR Low Enables Inputs, Rising Edge of WR Latches Data and
Advances to Next Location
Readback
1
0
1
Sequence Run
1
1
X
OPERATION MODE
Read Sequencer Location, Falling Edge of RD Enables Output, Rising Edge of RD
Advances to Next Location
OE
Run Programmed Sequence, Falling Edge of CONVST Starts Conversion and Advances to
Next Location
18523fa
19
20
Hi-Z
D6 TO D0 (LTC1852)
D8 TO D0 (LTC1853)
S6 TO S0
Hi-Z
L0CATION 0001
L0CATION 0000
PGA
BUSY
L0CATION 0001
L0CATION 0000
UNI/BIP
t19
L0CATION 0001
L0CATION 0000
A2 TO A0
t16
L0CATION 0001
t17
L0CATION 0000
t20
t18
DIFF
RD
WR
CONVST
M0
M1
t23
LOCATION
0000
t11
t24
Figure 11. Sequencer I/O
L0CATION n
L0CATION n
L0CATION n
L0CATION n
t14
t15
t22
t10
LOCATION
0001
t12
LOCATION
n
LOCATION
n+1
t23
18523 F11
LTC1852/LTC1853
APPLICATIONS INFORMATION
18523fa
Hi-Z
DIFFOUT
A2OUT TO A0OUT
D9 TO D0 (LTC1852)
D11 TO D0 (LTC1853)
L0CATION 0010
L0CATION 0010
L0CATION 0010
L0CATION 0010
t23
t25
t6
CONVERT
0000
t8
DATA
0000
CONVERT
0001
Figure 12. Programming and Running a Sequence
L0CATION 0001
L0CATION 0000
PGA
BUSY
L0CATION 0001
L0CATION 0000
UNI/BIP
t19
L0CATION 0001
L0CATION 0000
t15
A2 TO A0
t14
L0CATION 0001
t16
t17
L0CATION 0000
t20
t18
DIFF
RD
WR
CONVST
M0
M1
t7
DATA
0001
CONVERT
0010
t11
t10
DATA
0010
t5
CONVERT
0000
DATA
0000
18523 F12
LTC1852/LTC1853
APPLICATIONS INFORMATION
18523fa
21
LTC1852/LTC1853
TYPICAL APPLICATIONS
LTC1853 Hardwired for 8-Channel Single-Ended Scan with Unipolar 0V to 4.096V Operation
5V
10μF
0.1μF
15
14
VDD
VDD
M1 48
M0 36
LTC1853
5V
CS 46
1 CH0
CONVST 45
CONTROL LOGIC
AND
PROGRAMMABLE
SEQUENCER
2 CH1
3 CH2
INPUT
CONFIGURATION:
ALL 8 CHANNELS
SINGLE ENDED
TO COM
CH0–CH7:
0V TO 4.096V
5V
SHDN 47
4 CH3
RD 44
CONVERT
CLOCK
WR 43
DIFF 42
A2 41
A1 40
A0 39
8-CHANNEL
MULTIPLEXER
5 CH4
INTERNAL
CLOCK
UNI/BIP 38
PGA 37
6 CH5
OVDD 35
7 CH6
BUSY 33
8 CH7
DIFFOUT/S6 17
9 COM
A1OUT/S4 19
5V
2.7V TO VDD
10μF
0.1μF
A2OUT/S5 18
A0OUT/S3 20
2.5V
10 REFOUT
2.5V
REFERENCE
1μF
D11/S2 21
+
–
12-BIT
SAMPLING
ADC
DATA
LATCHES
OUTPUT
DRIVERS
D10/S1 22
D9/S0 23
D8 24
D7 25
11 REFIN
D6 26
REF AMP
D5 27
1.6384X
4.096V
0.1μF
D4 28
D3 29
12 REFCOMP
D2 30
10μF
D1 31
D0 32
GND
13
GND
16
OGND 34
18523 TA01
18523fa
22
LTC1852/LTC1853
TYPICAL APPLICATIONS
LTC1853 Hardwired for 4-Channel Differential Scan with Bipolar ±1.024V Operation
5V
10μF
14
0.1μF
15
VDD
VDD
M1 48
M0 36
LTC1853
+
–
+
INPUT
CONFIGURATION:
4 DIFFERENTIAL
CHANNELS: ±1.024V
–
+
–
+
–
SHDN 47
CS 46
1 CH0
5V
5V
CONVST 45
RD 44
CONTROL LOGIC
AND
PROGRAMMABLE
SEQUENCER
2 CH1
3 CH2
WR 43
DIFF 42
A2 41
4 CH3
CONVERT
CLOCK
5V
A1 40
A0 39
8-CHANNEL
MULTIPLEXER
5 CH4
INTERNAL
CLOCK
UNI/BIP 38
6 CH5
PGA 37
7 CH6
BUSY 33
8 CH7
DIFFOUT/S6 17
9 COM
A1OUT/S4 19
5V
OVDD 35
3V TO 5V
0.1μF
10μF
A2OUT/S5 18
A0OUT/S3 20
2.5V
10 REFOUT
D11/S2 21
2.5V
REFERENCE
1μF
12-BIT
SAMPLING
ADC
+
–
DATA
LATCHES
OUTPUT
DRIVERS
D10/S1 22
D9/S0 23
D8 24
D7 25
11 REFIN
D6 26
REF AMP
D5 27
D4 28
1.6384X
4.096V
0.1μF
D3 29
12 REFCOMP
D2 30
10μF
D1 31
D0 32
GND
OGND 34
GND
13
18523 TA02
16
PACKAGE DESCRIPTION
FW Package
48-Lead Plastic TSSOP (6.1mm)
(Reference LTC DWG # 05-08-1651 Rev A)
48
12.40 – 12.60*
(.488 – .496)
25
0.95 ±0.10
48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25
8.4 ±0.10
6.2 ±0.10
7.9 – 8.3
(.311 – .327)
1
24
0.32 ±0.05
0.50 BSC
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
RECOMMENDED SOLDER PAD LAYOUT
6.0 – 6.2**
(.236 – .244)
1.10
(.0433)
MAX
0.25
REF
0° – 8°
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
-T0.10 C
-C-
0.09 – 0.20
0.45 – 0.75
(.0035 – .008)
(.018 – .029)
3. DRAWING NOT TO SCALE
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE
0.50
(.0197)
BSC
0.17 – 0.27
(.0067 – .0106)
TYP
0.05 – 0.15
(.002 – .006)
FW48 TSSOP REV A 1005
18523fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However,
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC1852/LTC1853
TYPICAL APPLICATION
Data buffering using two IDT7202LA15 1k x 9-bit FIFOs
allows rapid collection of 1024 samples and simple interface
to low power, low speed, 8-bit microcontrollers. Data and
channel information are clocked in simultaneously and read
out as two bytes using READ HIGH FIFO and READ LOW
FIFO lines. In the event of bus contention, resistors limit
peak output current. If both FIFOs are read completely or
reset before a burst of conversions, the empty, half full,
and full flags from only one FIFO need to be monitored.
The retransmit inputs may also be tied together. Retransmit
may be used to read data repeatedly, allowing a memory
limited processor to perform transform and filtering functions that would otherwise be difficult.
0.1μF
INPUT
CONFIGURATION:
ALL 8 CHANNELS
SINGLE ENDED TO COM
CH0–CH7: 0V TO 4.096V
5V
5V
5V
0.1μF
10μF
14
OVDD 35
15
VDD
VDD
25
M0 36
5V
SHDN 47
5V
CS 46
1 CH0
CONTROL LOGIC
AND
PROGRAMMABLE
SEQUENCER
3 CH2
4 CH3
8-CHANNEL
MULTIPLEXER
INTERNAL
CLOCK
27
4
RD 44
5
WR 43
6
DIFF 42
1
A2 41
A1 40
8
A0 39
22
UNI/BIP 38
PGA 37
6 CH5
26
3
CONVST 45
2 CH1
2
24
M1 48
LTC1853
5 CH4
0.1μF
10μF
5V
28
IDT7202LA15 13
D8
Q8
8 × 1k
18
D7
Q7
18
D6
Q6
17
D5
Q5
16
D4
Q4
12
D3
Q3
11
D2
Q2
10
D1
Q1
9
D0
Q0
15
WR
R
READ_HIGH_FIFO
21
FF
EF
HIGH_FIFO_EMPTY
20
RS
HF
HIGH_FIFO_HALF_FULL
23
RT
HIGH BYTE_FIFO_RETRANSMIT
GND
XI
7
14
7 CH6
BUSY 33
8 CH7
DIFFOUT/S6 17
HIGH_FIFO_FULL_FLAG
A2OUT/S5 18
LOW_FIFO_FULL_FLAG
9 COM
A1OUT/S4 19
10 REFOUT
11 REFIN
+
–
12-BIT
SAMPLING
ADC
DATA
LATCHES
OUTPUT
DRIVERS
REF AMP
1μF
1.6384X
GND
REFCOMP
12
4.096V
0.1μF
GND
13
D10/S1 22
5V
D9/S0 23
D8 24
2
D7 25
24
D6 26
25
D5 27
26
D4 28
27
D3 29
3
D2 30
4
D1 31
5
D0 32
6
OGND 34
1
8
16
22
*CONVERT
CLOCK
UP TO 1024
10μF
D5
D4
D3
D2
D1
D0
0.1μF
D11/S2 21
2.5V
REFERENCE
D6
FIFO_RESET
A0OUT/S3 20
2.5V
8-BIT
DATA BUS
D7
28
IDT7202LA15
13
D8
Q8
19
D7
Q7
18
D6
Q6
17
D5
Q5
16
D4
Q4
12
D3
Q3
11
D2
Q2
10
D1
Q1
9
D0
Q0
15
WR
R
21
FF
EF
20
RS
HF
23
RT
GND
XI
7
14
8 × 1k
READ_LOW_FIFO
LOW_FIFO_EMPTY
LOW_FIFO_HALF_FULL
LOW BYTE_FIFO_RETRANSMIT
18523 TA03
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1410
12-Bit, 1.25Msps, ± 5V ADC
71.5dB SINAD at Nyquist, 150mW Dissipation
LTC1415
12-Bit, 1.25Msps, Single 5V ADC
55mW Power Dissipation, 72dB SINAD
LTC1418
14-Bit, 200ksps, Single 5V ADC
15mW, Serial/Parallel ±10V
LTC1419
Low Power 14-Bit, 800ksps ADC
True 14-Bit Linearity, 81.5dB SINAD, 150mW Dissipation
LTC1604
16-Bit, 333ksps, ±5V ADC
90dB SINAD, 220mW Power Dissipation, Pin Compatible with LTC1608
LTC1850/LTC1851
10-Bit/12, 8-Channel, 1.25Msps ADCs
Pin-Compatible, Programmable Multiplexer and Sequencer
18523fa
24 Linear Technology Corporation
LT 0108 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2001
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