LINER LTC1096IN8 Micropower sampling 8-bit serial i/o a/d converter Datasheet

LTC1096/LTC1096L
LTC1098/LTC1098L
Micropower Sampling
8-Bit Serial I/O A/D Converters
U
DESCRIPTIO
FEATURES
■
■
■
■
■
■
■
■
■
■
80µA Maximum Supply Current
1nA Typical Supply Current in Shutdown
8-Pin SO Plastic Package
5V Operation (LTC1096/LTC1098)
3V Operation (LTC1096L/LTC1098L)(2.65V Min)
Sample-and-Hold
16µs Conversion Time
33kHz Sample Rate
±0.5LSB Total Unadjusted Error Over Temp
Direct 3-Wire Interface to Most MPU Serial Ports and
All MPU Parallel I/O Ports
UO
APPLICATI
■
■
■
■
■
■
S
Battery-Operated Systems
Remote Data Acquisition
Battery Monitoring
Battery Gas Gauges
Temperature Measurement
Isolated Data Acquisition
, LTC and LT are registered trademarks of Linear Technology Corporation.
The LTC ®1096/LTC1096L/LTC1098/LTC1098L are
micropower, 8-bit A/D converters that draw only 80µA of
supply current when converting. They automatically power
down to 1nA typical supply current whenever they are not
performing conversions. They are packaged in 8-pin SO
packages and have both 3V (L) and 5V versions. These
8-bit, switched-capacitor, successive approximation ADCs
include sample-and-hold. The LTC1096/LTC1096L have a
single differential analog input. The LTC1098/LTC1098L
offer a software selectable 2-channel MUX.
On-chip serial ports allow efficient data transfer to a wide
range of microprocessors and microcontrollers over three
wires. This, coupled with micropower consumption, makes
remote location possible and facilitates transmitting data
through isolation barriers.
These circuits can be used in ratiometric applications or
with an external reference. The high impedance analog
inputs and the ability to operate with reduced spans
(below 1V full scale) allow direct connection to sensors
and transducers in many applications, eliminating the
need for gain stages.
UO
TYPICAL APPLICATI
10µW, S8 Package, 8-Bit A/D
Samples at 200Hz and Runs Off a 5V Battery
TA = 25°C
VCC = VREF = 5V
5V
MPU
(e.g., 8051)
ANALOG INPUT
0V TO 5V RANGE
CS/
VCC
SHUTDOWN
CLK
+IN
LTC1096
–IN
DOUT
GND
1000
P1.4
P1.3
P1.2
SUPPLY CURRENT, ICC (µA)
1µF
Supply Current vs Sample Rate
100
10
VREF
LTC1096/8 • TA01
1
0.1
1
10
SAMPLE FREQUENCY, fSMPL (kHz)
100
LTC1096/98 • TPC03
1
LTC1096/LTC1096L
LTC1098/LTC1098L
W W
W
AXI U
U
ABSOLUTE
RATI GS
(Notes 1 and 2)
Operating Temperature
LTC1096AC/LTC1096C/LTC1096LC/
LTC1098AC/LTC1098C/LTC1098LC ....... 0°C to 70°C
LTC1096AI/LTC1096I/LTC1096LI/
LTC1098AI/LTC1098I/LTC1098LI ..... – 40°C to 85°C
Lead Temperature (Soldering, 10 sec.)................ 300°C
Supply Voltage (VCC) to GND ................................... 12V
Voltage
Analog and Reference ................ –0.3V to VCC + 0.3V
Digital Inputs ......................................... –0.3V to 12V
Digital Outputs ........................... –0.3V to VCC + 0.3V
Power Dissipation .............................................. 500mW
Storage Temperature Range ................. – 65°C to 150°C
U
W
U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
CS/
1
SHUTDOWN
+IN 2
8
VCC
7
CLK
–IN 3
6
DOUT
GND 4
5
VREF
N8 PACKAGE
8-LEAD PLASTIC DIP
S8 PACKAGE
8-LEAD PLASTIC SOIC
TJMAX = 150°C, θJA = 130°C/W (N8)
TJMAX = 150°C, θJA = 175°C/W (S8)
S8 PART MARKING
1096
1096A
1096I
1096IA
1096L
1096LI
(Notes 3)
ORDER PART
NUMBER
ORDER PART
NUMBER
TOP VIEW
CS/
1
SHUTDOWN
CH0 2
LTC1096ACN8
LTC1096ACS8
LTC1096AIN8
LTC1096AIS8
LTC1096CN8
LTC1096CS8
LTC1096IN8
LTC1096IS8
LTC1096LCS8
LTC1096LIS8
8
VCC(VREF)
7
CLK
CH1 3
6
DOUT
GND 4
5
DIN
N8 PACKAGE
8-LEAD PLASTIC DIP
LTC1098ACN8
LTC1098ACS8
LTC1098AIN8
LTC1098AIS8
LTC1098CN8
LTC1098CS8
LTC1098IN8
LTC1098IS8
LTC1098LCS8
LTC1098LIS8
S8 PACKAGE
8-LEAD PLASTIC SOIC
TJMAX = 150°C, θJA = 130°C/W (N8)
TJMAX = 150°C, θJA = 175°C/W (S8)
S8 PART MARKING
1098
1098A
1098I
1098IA
1098L
1098LI
Consult factory for Military grade parts.
U
U
U
U WW
RECO
E DED OPERATI G CO DITIO S
LTC1096/LTC1098
SYMBOL
PARAMETER
CONDITIONS
MIN
VCC
Supply Voltage
LTC1096
LTC1098
3.0
3.0
TYP
MAX
9
6
500
UNITS
V
V
VCC = 5V Operation
f CLK
Clock Frequency
VCC = 5V
25
t CYC
Total Cycle Time
LTC1096, fCLK = 500kHz
LTC1098, fCLK = 500kHz
29
29
t hDI
Hold Time, DIN After CLK↑
VCC = 5V
150
ns
t suCS
Setup Time CS↓ Before First CLK↑ (See Operating Sequence)
VCC = 5V, LTC1096
VCC = 5V, LTC1098
500
500
ns
ns
t WAKEUP
Wake-Up Time CS↓ Before First CLK↓ After First CLK↑
(See Figure 1 LTC1096 Operating Sequence)
VCC = 5V, LTC1096
10
µs
Wake-Up Time CS↓ Before MSBF Bit CLK↓
(See Figure 2 LTC1098 Operating Sequence)
VCC = 5V, LTC1098
10
µs
t suDI
Setup Time, DIN Stable Before CLK↑
VCC = 5V
400
ns
t WHCLK
CLK High Time
VCC = 5V
0.8
µs
2
kHz
µs
µs
LTC1096/LTC1096L
LTC1098/LTC1098L
U
U
U
U WW
RECO
E DED OPERATI G CO DITIO S
LTC1096/LTC1098
SYMBOL
PARAMETER
CONDITIONS
MIN
t WLCLK
t WHCS
t WLCS
TYP
MAX
UNITS
CLK Low Time
VCC = 5V
0.8
µs
CS High Time Between Data Transfer Cycles
VCC = 5V
1
µs
CS Low Time During Data Transfer
LTC1096, fCLK = 500kHz
LTC1098, fCLK = 500kHz
28
28
µs
µs
VCC = 3V Operation
f CLK
Clock Frequency
VCC = 3V
25
t CYC
Total Cycle Time
LTC1096, fCLK = 250kHz
LTC1098, fCLK = 250kHz
58
58
250
kHz
µs
µs
t hDI
Hold Time, DIN After CLK↑
VCC = 3V
450
ns
tsuCS
Setup Time CS↓ Before First CLK↑ (See Operating Sequence)
VCC = 3V, LTC1096
VCC = 3V, LTC1098
1
1
µs
µs
t WAKEUP
Wake-Up Time CS↓ Before First CLK↓ After First CLK↑
(See Figure 1 LTC1096 Operating Sequence)
VCC = 3V, LTC1096
10
µs
Wake-Up Time CS↓ Before MSBF Bit CLK↓
(See Figure 2 LTC1098 Operating Sequence)
VCC = 3V, LTC1098
10
µs
t suDI
Setup Time, DIN Stable Before CLK↑
VCC = 3V
1
µs
t WHCLK
CLK High Time
VCC = 3V
1.6
µs
t WLCLK
CLK Low Time
VCC = 3V
1.6
µs
t WHCS
CS High Time Between Data Transfer Cycles
VCC = 3V
2
µs
t WLCS
CS Low Time During Data Transfer
LTC1096, fCLK = 250kHz
LTC1098, fCLK = 250kHz
56
56
µs
µs
LTC1096L/LTC1098L
SYMBOL
PARAMETER
VCC
Supply Voltage
f CLK
Clock Frequency
t CYC
Total Cycle Time
t hDI
CONDITIONS
MIN
TYP
MAX
UNITS
2.65
4.0
V
VCC = 2.65V
25
250
kHz
LTC1096L, fCLK = 250kHz
LTC1098L, fCLK = 250kHz
58
58
µs
µs
Hold Time, DIN After CLK↑
VCC = 2.65V
450
ns
t suCS
Setup Time CS↓ Before First CLK↑ (See Operating Sequence)
VCC = 2.65V, LTC1096L
VCC = 2.65V, LTC1098L
1
1
µs
µs
t WAKEUP
Wake-Up Time CS↓ Before First CLK↓ After First CLK↑
(See Figure 1, LTC1096L Operating Sequence)
VCC = 2.65V, LTC1096L
10
µs
Wake-Up Time CS↓ Before MSBF Bit CLK↓
(See Figure 2, LTC1098L Operating Sequence)
VCC = 2.65V, LTC1098L
10
µs
t suDI
Setup Time, DIN Stable Before CLK↑
VCC = 2.65V
1
µs
t WHCLK
CLK High Time
VCC = 2.65V
1.6
µs
t WLCLK
CLK Low Time
VCC = 2.65V
1.6
µs
t WHCS
CS High Time Between Data Transfer Cycles
VCC = 2.65V
2
µs
t WLCS
CS Low Time During Data Transfer
LTC1096L, fCLK = 250kHz
LTC1098L, fCLK = 250kHz
56
56
µs
µs
3
LTC1096/LTC1096L
LTC1098/LTC1098L
U
U W
CO VERTER A D ULTIPLEXER CHARACTERISTICS
LTC1096/LTC1098
VCC = 5V, VREF = 5V, fCLK = 500kHz, unless otherwise noted.
PARAMETER
LTC1096A/LTC1098A
MIN
TYP
MAX
CONDITIONS
LTC1096/LTC1098
MIN
TYP
MAX
Resolution (No Missing Code)
●
Offset Error
●
±0.5
±0.5
LSB
●
±0.5
±0.5
LSB
●
±0.5
±1.0
LSB
●
±0.5
±1.0
LSB
Linearity Error
(Note 4)
Full Scale Error
Total Unadjusted Error (Note 5)
VREF = 5.000V
Analog Input Range
(Notes 6, 7)
REF Input Range (Notes 6, 7)
4.5 ≤ VCC ≤ 6V
6V < VCC ≤ 9V, LTC1096
Analog Input Leakage Current
(Note 8)
8
8
UNITS
Bits
– 0.05V to VCC + 0.05V
– 0.05V to VCC + 0.05V
– 0.05V to 6V
V
V
V
±1.0
±1.0
µA
LTC1096A/LTC1098A
MIN
TYP
MAX
LTC1096/LTC1098
MIN
TYP
MAX
UNITS
●
LTC1096/LTC1098
VCC = 3V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted.
PARAMETER
CONDITIONS
Resolution (No Missing Code)
●
Offset Error
●
±0.75
±1.0
●
±0.5
±1.0
LSB
●
±1.0
±1.0
LSB
±1.0
±1.5
LSB
Linearity Error
(Notes 4, 9)
Full-Scale Error
Total Unadjusted Error (Notes 5, 9)
VREF = 2.500V
Analog Input Range
(Notes 6, 7)
REF Input Range (Notes 6, 7, 9)
3V ≤ VCC ≤ 6V
Analog Input Leakage Current
(Notes 8, 9)
8
8
●
Bits
– 0.05V to VCC + 0.05V
V
– 0.05V to VCC + 0.05V
±1.0
●
LSB
V
±1.0
µA
LTC1096L/LTC1098L
TYP
MAX
UNITS
LTC1096L/LTC1098L
VCC = 2.65V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted.
PARAMETER
CONDITIONS
Resolution (No Missing Code)
●
Offset Error
Linearity Error
(Note 4)
Full-Scale Error
Total Unadjusted Error (Notes 5)
VREF = 2.5V
Analog Input Range
(Notes 6, 7)
REF Input Range (Note 6)
2.65V ≤ VCC ≤ 4.0V
Analog Input Leakage Current
(Note 8)
4
MIN
8
Bits
●
±1.0
LSB
●
±1.0
LSB
●
±1.0
LSB
●
±1.5
LSB
– 0.05V to VCC + 0.05V
V
– 0.05V to VCC + 0.05V
●
V
±1.0
µA
LTC1096/LTC1096L
LTC1098/LTC1098L
U
DIGITAL AND DC ELECTRICAL CHARACTERISTICS
LTC1096/LTC1098
VCC = 5V, VREF = 5V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VIH
High Level Input Voltage
VCC = 5.25V
●
MIN
TYP
MAX
VIL
Low Level Input Voltage
VCC = 4.75V
●
IIH
High Level Input Current
VIN = VCC
IIL
Low Level Input Current
VIN = 0V
VOH
High Level Output Voltage
VCC = 4.75V, IO = 10µA
VCC = 4.75V, IO = 360µA
●
●
VOL
Low Level Output Voltage
VCC = 4.75V, IO = 1.6mA
●
0.4
V
IOZ
Hi-Z Output Leakage
CS ≥ VIH
●
±3.0
µA
ISOURCE
Output Source Current
VOUT = 0V
– 25
mA
ISINK
Output Sink Current
VOUT = VCC
45
mA
IREF
Reference Current
CS = VCC
tCYC ≥ 200µs, fCLK ≤ 50kHz
tCYC = 29µs, fCLK = 500kHz
●
●
●
0.001
3.500
35.000
2.5
7.5
50.0
µA
µA
µA
ICC
Supply Current
CS = VCC
●
0.001
3.0
µA
LTC1096, tCYC ≥ 200µs, fCLK ≤ 50kHz
LTC1096, tCYC = 29µs, fCLK = 500kHz
●
●
40
120
80
180
µA
µA
LTC1098, tCYC ≥ 200µs, fCLK ≤ 50kHz
LTC1098, tCYC = 29µs, fCLK = 500kHz
●
●
44
155
88
230
µA
µA
TYP
MAX
UNITS
2.0
UNITS
V
0.8
V
●
2.5
µA
●
– 2.5
µA
4.5
2.4
4.74
4.72
V
V
LTC1096/LTC1098
VCC = 3V, VREF = 2.5V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
VIH
High Level Input Voltage
VCC = 3.6V
●
VIL
Low Level Input Voltage
VCC = 3V
●
0.45
V
IIH
High Level Input Current (Note 9)
VIN = VCC
●
2.5
µA
IIL
Low Level Input Current (Note 9)
VIN = 0V
●
– 2.5
µA
VOH
High Level Output Voltage
VCC = 3V, IO = 10µA
VCC = 3V, IO = 360µA
●
●
VOL
Low Level Output Voltage
VCC = 3V, IO = 400µA
●
IOZ
Hi-Z Output Leakage (Note 9)
CS ≥ VIH
●
ISOURCE
Output Source Current (Note 9)
VOUT = 0V
– 10
mA
ISINK
Output Sink Current (Note 9)
VOUT = VCC
15
mA
IREF
Reference Current (Note 9)
CS = VCC
tCYC ≥ 200µs, fCLK ≤ 50kHz
tCYC = 58µs, fCLK = 250kHz
●
●
●
0.001
3.500
35.000
2.5
7.5
50.0
µA
µA
µA
ICC
Supply Current (Note 9)
CS = VCC
●
0.001
3.0
µA
LTC1096, tCYC ≥ 200µs, fCLK ≤ 50kHz
LTC1096, tCYC = 58µs, fCLK = 250kHz
●
●
40
120
80
180
µA
µA
LTC1098, tCYC ≥ 200µs, fCLK ≤ 50kHz
LTC1098, tCYC = 58µs, fCLK = 250kHz
●
●
44
155
88
230
µA
µA
1.9
2.3
2.1
V
2.69
2.64
V
V
0.3
±3.0
V
µA
5
LTC1096/LTC1096L
LTC1098/LTC1098L
U
DIGITAL AND DC ELECTRICAL CHARACTERISTICS
LTC1096L/LTC1098L
VCC = 2.65V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
VIH
High Level Input Voltage
VCC = 3.6V
●
VIL
Low Level Input Voltage
VCC = 2.65V
●
0.45
V
IIH
High Level Input Current
VIN = VCC
●
2.5
µA
IIL
Low Level Input Current
VIN = 0V
●
– 2.5
µA
VOH
High Level Output Voltage
VCC = 2.65V, IO = 10µA
VCC = 2.65V, IO = 360µA
●
●
VOL
Low Level Output Voltage
VCC = 2.65V, IO = 400µA
●
IOZ
Hi-Z Output Leakage
CS = High
●
ISOURCE
Output Source Current
VOUT = 0V
– 10
mA
ISINK
Output Sink Current
VOUT = VCC
15
mA
IREF
Reference Current
CS = VCC
tCYC ≥ 200µs, fCLK ≤ 50kHz
tCYC = 58µs, fCLK = 250kHz
●
●
●
0.001
3.500
35.000
2.5
7.5
50.0
ICC
Supply Current
CS = VCC
1.9
2.3
2.1
UNITS
V
2.64
2.50
V
V
0.3
±3.0
V
µA
µA
µA
µA
●
0.001
3.0
µA
tCYC ≥ 200µs, fCLK ≤ 50kHz
tCYC = 58µs, fCLK = 250kHz
●
●
40
120
80
180
µA
µA
LTC1098L, tCYC ≥ 200µs, fCLK ≤ 50kHz
LTC1098L, tCYC = 58µs, fCLK = 250kHz
●
●
44
155
88
230
µA
µA
TYP
MAX
LTC1096L,
LTC1096L,
AC CHARACTERISTICS
LTC1096/LTC1098
VCC = 5V, VREF = 5V, fCLK = 500kHz, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
tSMPL
Analog Input Sample Time
See Operating Sequence
fSMPL(MAX)
Maximum Sampling Frequency
tCONV
Conversion Time
See Operating Sequence
tdDO
Delay Time, CLK↓ to DOUT Data Valid
See Test Circuits
●
200
450
ns
tdis
Delay Time, CS↑ to DOUT Hi-Z
See Test Circuits
●
170
450
ns
ten
Delay Time, CLK↓ to DOUT Enable
See Test Circuits
●
60
250
thDO
Time Output Data Remains Valid After CLK↓
CLOAD = 100pF
tf
DOUT Fall Time
See Test Circuits
●
tr
DOUT Rise Time
See Test Circuits
●
CIN
Input Capacitance
Analog Inputs On Channel
Analog Inputs Off Channel
25
5
pF
pF
Digital Input
5
pF
6
MIN
1.5
●
UNITS
CLK Cycles
33
kHz
8
CLK Cycles
180
ns
ns
70
250
ns
25
100
ns
LTC1096/LTC1096L
LTC1098/LTC1098L
AC CHARACTERISTICS
LTC1096/LTC1098
VCC = 3V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
tSMPL
Analog Input Sample Time
See Operating Sequence
MIN
fSMPL(MAX) Maximum Sampling Frequency
TYP
MAX
1.5
●
UNITS
CLK Cycles
16.5
kHz
tCONV
Conversion Time
See Operating Sequence
tdDO
Delay Time, CLK↓ to DOUT Data Valid
See Test Circuits (Note 9)
●
500
8
1000
CLK Cycles
ns
tdis
Delay Time, CS↑ to DOUT Hi-Z
See Test Circuits (Note 9)
●
220
800
ns
ten
Delay Time, CLK↓ to DOUT Enable
See Test Circuits (Note 9)
●
160
480
ns
thDO
Time Output Data Remains Valid After CLK↓
CLOAD = 100pF
tf
DOUT Fall Time
See Test Circuits (Note 9)
●
tr
DOUT Rise Time
See Test Circuits (Note 9)
●
CIN
Input Capacitance
Analog Inputs On Channel
Analog Inputs Off Channel
25
5
pF
pF
Digital Input
5
pF
400
ns
70
250
50
150
ns
ns
LTC1096L/LTC1098L
VCC = 2.65V, VREF = 2.5V, fCLK = 250kHz, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
tSMPL
Analog Input Sample Time
See Operating Sequence
fSMPL(MAX) Maximum Sampling Frequency
TYP
MAX
1.5
●
See Operating Sequence
UNITS
CLK Cycles
16.5
kHz
tCONV
Conversion Time
tdDO
Delay Time, CLK↓ to DOUT Data Valid
See Test Circuits
●
500
1000
ns
tdis
Delay Time, CS↑ to DOUT Hi-Z
See Test Circuits
●
220
800
ns
ten
Delay Time, CLK↓ to DOUT Enable
See Test Circuits
●
160
480
ns
thDO
Time Output Data Remains Valid After CLK↓
CLOAD = 100pF
tf
DOUT Fall Time
See Test Circuits
●
70
250
ns
tr
DOUT Rise Time
See Test Circuits
●
50
200
ns
CIN
Input Capacitance
Analog Inputs On Channel
Analog Inputs Off Channel
25
5
pF
pF
Digital Input
5
pF
The ● denotes specifications which apply over the operating temperature
range.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: All voltage values are with respect to GND.
Note 3: For the 8-lead PDIP, consult the factory.
Note 4: Linearity error is specified between the actual and points of the
A/D transfer curve.
Note 5: Total unadjusted error includes offset, full scale, linearity,
multiplexer and hold step errors.
Note 6: Two on-chip diodes are tied to each reference and analog input
which will conduct for reference or analog input voltages one diode drop
below GND or one diode drop above VCC. This spec allows 50mV forward
bias of either diode. This means that as long as the reference or analog
8
CLK Cycles
400
ns
input does not exceed the supply voltage by more than 50mV, the output
code will be correct. To achieve an absolute 0V to 5V input voltage range
will therefore require a minimum supply voltage of 4.950V over initial
tolerance, temperature variations and loading. For 5.5V < VCC ≤ 9V,
reference and analog input range cannot exceed 5.55V. If reference and
analog input range are greater than 5.55V, the output code will not be
guaranteed to be correct.
Note 7: The supply voltage range for the LTC1096L/LTC1098L is from
2.65V to 4V. The supply voltage range for the LTC1096 is from 3V to 9V,
but the supply voltage range for the LTC1098 is only from 3V to 6V.
Note 8: Channel leakage current is measured after the channel selection.
Note 9: These specifications are either correlated from 5V specifications or
guaranteed by design.
7
LTC1096/LTC1096L
LTC1098/LTC1098L
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Clock Rate
for Active and Shutdown Modes
VCC = 9V
SUPPLY CURRENT, ICC (µA)
SUPPLY CURRENT, ICC (µA)
200
150
VCC = 5V
100
50
10
0.002
0
CS = VCC
TA = 25°C
VREF = 2.5V
TA = 25°C
VCC = VREF = 5V
80
60
“ACTIVE” MODE CS = 0
40
20
10
1
0
1000
100
“SHUTDOWN” MODE CS = VCC
0.001
10
100
FREQUENCY (kHz)
1
1000
100
TA = 25°C
CS = 0V
Supply Current vs Sample
Frequency LTC1096
SUPPLY CURRENT, ICC (µA)
250
Supply Current vs Supply Voltage
Active and Shutdown Modes
0
1
7
3
2
5
6
4
SUPPLY VOLTAGE,VCC (V)
8
0.1
9
1
10
SAMPLE FREQUENCY, fSMPL (kHz)
LTC1096/98 • TPC01
100
LTC1096/98 • TPC03
Change in Offset vs
Reference Voltage LTC1096
Change in Offset vs
Supply Voltage
0.50
0.50
0
–0.25
1
0
3
4
2
REFERENCE VOLTAGE (V)
0.4
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
1
2
3 4 5 6 7 8
SUPPLY VOLTAGE, VCC (V)
9
10
0.3
0.1
0
–0.1
–0.2
0.2
0.1
0
–0.1
–0.2
–0.3
–0.3
–0.4
–0.4
–0.5
0
1
2
3 4 5 6 7 8
SUPPLY VOLTAGE, VCC (V)
9
10
LTC1096/98 • TPC07
3
4
2
REFERENCE VOLTAGE (V)
5
0.50
TA = 25°C
VREF = 2.5V
FCLK = 100kHz
0.4
0.2
1
Change in Gain vs
Reference Voltage LTC1096
CHANGE IN GAIN (LSB)
0.3
0
LTC1096/98 • TPC06
0.5
TA = 25°C
VREF = 2.5V
FCLK = 100kHz
CHANGE IN GAIN (LSB)
CHANGE IN LINEARTY (LSB)
–0.25
Change in Gain vs Supply Voltage
0.5
8
0
LTC1096/98 • TPC05
Change in Linearity vs
Supply Voltage
–0.5
0.25
–O.50
0
LTC1096/98 • TPC04
0.4
TA = 25°C
VCC = 5V
FCLK = 500kHz
–0.4
–0.5
5
TA = 25°C
VREF = 2.5V
FCLK = 100kHz
CHANGE IN LINEARITY (LSB)
0.25
–0.50
Change in Linearity vs
Reference Voltage LTC1096
0.5
TA = 25°C
VCC = 5V
FCLK = 500kHz
MAGNITUDE OF OFFSET CHANGE (LSB)
MAGNITUDE OF OFFSET CHANGE (LSB = 1/256 × VREF)
LTC1096/98 • TPC02
TA = 25°C
VCC = 5V
FCLK = 500kHz
0.25
0
–0.25
0
1
2
3 4 5 6 7 8
SUPPLY VOLTAGE, VCC (V)
9
10
LTC1096/98 • TPC08
–O.50
0
1
3
4
2
VOLTAGE REFERENCE (V)
5
LTC1096/98 • TPC09
LTC1096/LTC1096L
LTC1098/LTC1098L
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Maximum Clock Frequency vs
Source Resistance
1.5
VIN
+ INPUT
– INPUT
0.75
RSOURCE–
0.50
0.25
5
TA = 25°C
VREF = 2.5V
1.25
TA = 25°C
4
LOGIC THRESH0LD (V)
TA = 25°C
VCC = VREF = 5V
MAXIMUM CLOCK FREQUENCY (MHz)
1.0
0.75
0.5
10
1
1
0.25
0
100
2
RSOURCE – (kΩ)
4
1000
MINIMUM WAKE-UP TIME (µs)
TA = 25°C
VREF = 5V
1
0
2
6
8
4
SUPPLY VOLTAGE, VCC (V)
VREF = 5V
VCC = 5V
100
7.5
5.0
RSOURCE+
VIN
2.5
+
10
1
ON CHANNEL
1
LTC1096/98 • TPC14
Minimum Clock Frequency for
0.1LSB Error† vs Temperature
LTC1096/98 • TPC15
FFT Plot
ENOBs vs Frequency
200
VREF = 5V
VCC = 5V
10
0
9
–10
8
–20
140
7
–30
ENOBs
120
6
5
80
4
60
3
40
2
20
1
0
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
AMPLITUDE (dB)
160
100
OFF CHANNEL
0.01
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
100
RSOURCE (kΩ)
LTC1096/98 • TPC13
10
0.1
–
0
10
10
Input Channel Leakage Current
vs Temperature
10
TA = 25°C
VREF = 2.5V
2
6
8
4
SUPPLY VOLTAGE, VCC (V)
LTC1096/98 • TPC12
Minimum Wake-Up Time
vs Source Resistance
3
2
0
LTC1096/98 • TPC11
Wake-Up Time vs Supply Voltage
WAKE-UP TIME (µs)
0
10
4
6
8
SUPPLY VOLTAGE (V)
LTC1096/98 • TPC10
MINIMUM CLOCK FREQUENCY (kHz)
2
0
0
180
3
LEAKAGE CURRENT (nA)
MAXIMUM CLOCK FREQUENCY* (MHz)
1
0
Digital Input Logic Threshold
vs Supply Voltage
Maximum Clock Frequency vs
Supply Voltage
TA = 25°C
VCC = VREF = 5V
fSMPL = 31.25kHz
10
FREQUENCY (kHz)
LTC1096/98 • TPC16
* Maximum CLK frequency represents the clock frequency at which a 0.1LSB shift in the error at any code
transition from its 0.75MHz value is first detected.
† As the CLK frequency is decreased from 500kHz, minimum CLK frequency (∆error ≤ 0.1LSB) represents
the frequency at which a 0.1LSB shift in any code transition from its 500kHz value is first detected.
–40
–50
–60
–70
–80
–90
0
1
TA = 25°C
VCC = VREF = 5V
fSMPL = 31.25kHz
fIN = 5.8kHz
100
LTC1096/98 • TPC17
–100
0
2
4
10 12
6
8
FREQUENCY (kHz)
14
16
LTC1096/98 • TPC18
9
LTC1096/LTC1096L
LTC1098/LTC1098L
U
U
U
PI FU CTIO S
LTC1096/LTC1096L
LTC1098/LTC1098L
CS/SHDN (Pin 1): Chip Select Input. A logic low on this
input enables the LTC1096/LTC1096L. A logic high on this
input disables the LTC1096/LTC1096L and disconnects
the power to the LTC1096/LTC1096L.
CS/SHDN (Pin 1): Chip Select Input. A logic low on this
input enables the LTC1098/LTC1098L. A logic high on this
input disables the LTC1098/LTC1098L and disconnects
the power to the LTC1098/LTC1098L.
IN + (Pin 2): Analog Input. This input must be free of noise
with respect to GND.
CH0 (Pin 2): Analog Input. This input must be free of noise
with respect to GND.
IN – (Pin 3): Analog Input. This input must be free of noise
with respect to GND.
CH1 (Pin 3): Analog Input. This input must be free of noise
with respect to GND.
GND (Pin 4): Analog Ground. GND should be tied directly
to an analog ground plane.
GND (Pin 4): Analog Ground. GND should be tied directly
to an analog ground plane.
VREF (Pin 5): Reference Input. The reference input defines
the span of the A/D converter and must be kept free of
noise with respect to GND.
DIN (Pin 5): Digital Data Input. The multiplexer address is
shifted into this pin.
DOUT (Pin 6): Digital Data Output. The A/D conversion
result is shifted out of this output.
CLK (Pin 7): Shift Clock. This clock synchronizes the serial
data transfer.
VCC (Pin 8): Power Supply Voltage. This pin provides
power to the A/D converter. It must be free of noise and
ripple by bypassing directly to the analog ground plane.
W
BLOCK DIAGRA
DOUT (Pin 6): Digital Data Output. The A/D conversion
result is shifted out of this output.
CLK (Pin 7): Shift Clock. This clock synchronizes the serial
data transfer.
VCC (VREF)(Pin 8): Power Supply Voltage. This pin provides power and defines the span of the A/D converter. It
must be free of noise and ripple by bypassing directly to
the analog ground plane.
LTC1096/LTC1096L
VCC (VCC /VREF)
CS (DIN) CLK
BIAS AND
SHUTDOWN CIRCUIT
IN + (CH0)
CSAMPLE
IN – (CH1)
SERIAL PORT
DOUT
–
SAR
+
MICROPOWER
COMPARATOR
CAPACITIVE DAC
GND
10
VREF
PIN NAMES IN PARENTHESES
REFER TO THE LTC1098/LTC1098L
LTC1096/LTC1096L
LTC1098/LTC1098L
TEST CIRCUITS
On and Off Channel Leakage Current
Load Circuit for tdDO, tr and tf
5V
1.4V
ION
A
ON CHANNEL
3kΩ
IOFF
DOUT
A
TEST POINT
100pF
•
•
•
•
OFF
CHANNEL
LTC1096/98 • TC02
POLARITY
LTC1096/98 • TC1
Voltage Waveforms for DOUT Delay Time, tdDO
CLK
VIL
Voltage Waveforms for DOUT Rise and Fall Times, tr, tf
VOH
DOUT
VOL
tdDO
VOH
tr
DOUT
tf
LTC1096/98 • TC04
VOL
LTC1096/98 • TC03
Load Circuit for tdis and ten
Voltage Waveforms for tdis
TEST POINT
2.0V
CS
3k
5V tdis WAVEFORM 2, ten
DOUT
100pF
tdis WAVEFORM 1
DOUT
WAVEFORM 1
(SEE NOTE 1)
90%
tdis
LTC1096/98 • TC05
DOUT
WAVEFORM 2
(SEE NOTE 2)
10%
NOTE 1: WAVEFORM 1 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH
THAT THE OUTPUT IS HIGH UNLESS DISABLED BY THE OUTPUT CONTROL.
NOTE 2: WAVEFORM 2 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH
THAT THE OUTPUT IS LOW UNLESS DISABLED BY THE OUTPUT CONTROL.
LTC1096/98 • TC06
11
LTC1096/LTC1096L
LTC1098/LTC1098L
TEST CIRCUITS
Voltage Waveforms for ten
LTC1096/LTC1096L
CS
t WAKEUP
1
CLK
B7
DOUT
VOL
ten
LTC1098/LTC1098L
LTC1096/98 • TC07
CS
START
DIN
1
CLK
2
3
4
5
B7
DOUT
VOL
ten
U
W
U
UO
APPLICATI
S I FOR ATIO
OVERVIEW
The LTC1096/LTC1096L/LTC1098/LTC1098L are 8-bit
micropower, switched-capacitor A/D converters. These
sampling ADCs typically draw 120µA of supply current
when sampling up to 33kHz. Supply current drops linearly
as the sample rate is reduced (see Supply Current vs
Sample Rate on the first page of this data sheet). The ADCs
automatically power down when not performing conversion, drawing only leakage current. They are packaged in
8-pin SO packages. The LTC1096L/LTC1098L operate on
a single supply ranging from 2.65V to 4V. The LTC1096
operates on a single supply ranging from 3V to 9V while
the LTC1098 operates from 3V to 6V supplies.
The LTC1096/LTC1096L/LTC1098/LTC1098L comprise
an 8-bit, switched-capacitor ADC, a sample-and-hold and
12
LTC1096/98 • TC08
a serial port (see Block Diagram). Although they share the
same basic design, the LTC1096(L) and LTC1098(L) differ
in some respects. The LTC1096(L) has a differential input
and has an external reference input pin. It can measure
signals floating on a DC common mode voltage and can
operate with reduced spans down to 250mV. Reducing the
span allows it to achieve 1mV resolution. The LTC1098(L)
has a 2-channel input multiplexer and can convert either
channel with respect to ground or the difference between
the two.
SERIAL INTERFACE
The LTC1098(L) communicates with microprocessors
and other external circuitry via a synchronous, half duplex,
4-wire serial interface while the LTC1096(L) uses a 3-wire
interface (see Operating Sequence in Figures 1 and 2).
LTC1096/LTC1096L
LTC1098/LTC1098L
W
U
U
UO
APPLICATI
S I FOR ATIO
Power Down and Wake-Up Time
tWAKEUP
CS
The LTC1096(L)/LTC1098(L) draw power when the CS pin
is low and shut themselves down when that pin is high. In
order to have a correct conversion result, a 10µs wake-up
time must be provided from CS falling to the first falling
clock (CLK) after the first rising CLK for the LTC1096(L)
and from CS falling to the MSBF bit CLK falling for the
LTC1098(L) (see Operating Sequence). If the LTC1096(L)/
LTC1098(L) are running with clock frequency less than or
equal to 100kHz, the wake-up time is inherently provided.
tsu
CLK
DOUT
NULL BIT
B7
Case 1. Timing Diagram
tWAKEUP
CS
tsu
Example
10µs
CLK
Two cases are shown at right to illustrate the relationship
among wake-up time, setup time and CLK frequency for
the LT1096(L).
DOUT
LTC1096/98 • AI Ex.
Case 2. Timing Diagram
In Case 1 the clock frequency is 100kHz. One clock cycle
is 10µs which can be the wake-up time, while half of that
can be the setup time. In Case 2 the clock frequency is
50kHz, half of the clock cycle plus the setup time (=1µs)
can be the wake-up time. If the CLK frequency is higher
than 100kHz, Figure 1 shows the relationship between the
wake-up time and setup time.
The wake-up time is inherently provided for the LTC1098(L)
with setup time = 1µs (see Figure 2).
tCYC
CS
POWER
DOWN
CLK
tsuCS
tWAKEUP
DOUT
HI-Z
NULL
BIT
B7
B6
(MSB)
B5
B4
B3
B2
B1
Hi-Z
B0
tCONV
tCYC
CS
POWER
DOWN
CLK
tsuCS
tWAKEUP
DOUT
Hi-Z
NULL
BIT
B7
(MSB)
B6
B5
B4
B3
B2
B1
B0
B1
B2
B3
B4
B5
B6
B7*
tCONV
Hi-Z
LTC1096/98 F01
*AFTER COMPLETING THE DATA TRANSFER, IF FURTHER CLOCKS ARE APPLIED WITH CS LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY.
Figure 1. LTC1096(L) Operating Sequence
13
LTC1096/LTC1096L
LTC1098/LTC1098L
U
W
U
UO
APPLICATI
S I FOR ATIO
MSB-FIRST DATA (MSBF = 1)
tCYC
CS
POWER
DOWN
tWAKEUP
CLK
tsuCS
ODD/
SIGN
START
DIN
DON'T CARE
MSBF
SGL/
DIFF
DOUT
NULL
BIT B7
B6
(MSB)
HI-Z
tSMPL
B5
B4
B3
B2
Hi-Z
B0*
B1
tCONV
MSB-FIRST DATA (MSBF = 0)
tCYC
CS
POWER
DOWN
tWAKEUP
CLK
tsuCS
ODD/
SIGN
START
DIN
DON'T CARE
SGL/
DIFF
DOUT
HI-Z
tSMPL
MSBF
NULL
B6
BIT B7
(MSB)
B5
B4
B3
B2
B0
B1
B1
B2
B3
B4
B5
B6
B7*
tCONV
Hi-Z
LTC1096/98 F02
*AFTER COMPLETING THE DATA TRANSFER, IF FURTHER CLOCKS ARE APPLIED WITH CS LOW, THE ADC WILL OUTPUT ZEROS INDEFINITELY.
Figure 2. LTC1098(L) Operating Sequence Example: Differential Inputs (CH +, CH –)
Data Transfer
The CLK synchronizes the data transfer with each bit being
transmitted on the falling CLK edge and captured on the
rising CLK edge in both transmitting and receiving systems. The LTC1098(L) first receives input data and then
transmits back the A/D conversion result (half duplex).
Because of the half duplex operation, DIN and DOUT may be
tied together allowing transmission over just three wires:
CS, CLK and DATA (DIN/DOUT).
Data transfer is initiated by a falling chip select (CS) signal.
After CS falls the LTC1098(L) looks for a start bit. After the
start bit is received, the 3-bit input word is shifted into the
DIN input which configures the LTC1098(L) and starts the
conversion. After one null bit, the result of the conversion
14
CS
DIN 1
DIN 2
DOUT 1
DOUT 2
SHIFT MUX
ADDRESS IN
1 NULL BIT
SHIFT A/D CONVERSION
RESULT OUT
LTC1096/98 • AI01
is output on the DOUT line. At the end of the data exchange
CS should be brought high. This resets the LTC1098(L) in
preparation for the next data exchange.
The LTC1096(L) does not require a configuration input
word and has no DIN pin. A falling CS initiates data transfer
as shown in the LTC1096(L) operating sequence. After CS
falls, the first CLK pulse enables DOUT. After one null bit,
LTC1096/LTC1096L
LTC1098/LTC1098L
W
U
U
UO
APPLICATI
S I FOR ATIO
the A/D conversion result is output on the DOUT line.
Bringing CS high resets the LTC1096(L) for the next data
exchange.
Input Data Word
The LTC1096(L) requires no DIN word. It is permanently
configured to have a single differential input. The conversion result, in which output on the DOUT line is MSB-first
sequence, followed by LSB sequence providing easy interface to MSB- or LSB-first serial ports.
The LTC1098(L) clocks data into the DIN input on the rising
edge of the clock. The input data words are defined as
follows:
START
SGL/
DIFF
ODD/
MSBF
SIGN
MSB-First/LSB-First (MSBF)
The output data of the LTC1098(L) is programmed for
MSB-first or LSB-first sequence using the MSBF bit.
When the MSBF bit is a logical one, data will appear on
the DOUT line in MSB-first format. Logical zeros will be
filled in indefinitely following the last data bit. When the
MSBF bit is a logical zero, LSB-first data will follow the
normal MSB-first data on the DOUT line. (see Operating
Sequence)
Unipolar Transfer Curve
The LTC1096(L)/LTC1098(L) are permanently configured for unipolar only. The input span and code assignment for this conversion type are shown in the following figures for a 5V reference.
MUX MSB-FIRST/
ADDRESS LSB-FIRST
Unipolar Transfer Curve
LTC1096/8 • AI02
Start Bit
11111111
11111110
•
•
•
00000001
00000000
VIN
VREF
VREF–1LSB
VREF–2LSB
1LSB
0V
The first “logical one” clocked into the DIN input after CS
goes low is the start bit. The start bit initiates the data
transfer. The LTC1098(L) will ignore all leading zeros
which precede this logical one. After the start bit is
received, the remaining bits of the input word will be
clocked in. Further inputs on the DIN pin are then ignored
until the next CS cycle.
LTC1096/8 • AI04
Multiplexer (MUX) Address
Unipolar Output Code
The bits of the input word following the START bit assign
the MUX configuration for the requested conversion. For
a given channel selection, the converter will measure the
voltage between the two channels indicated by the “+” and
“–” signs in the selected row of the followintg tables. In
single-ended mode, all input channels are measured with
respect to GND.
SINGLE-ENDED MUX MODE
DIFFERENTIAL MUX MODE
INPUT VOLTAGE
INPUT VOLTAGE
(VREF = 5.000V)
11111111
11111110
•
•
•
00000001
00000000
VREF – 1LSB
VREF – 2LSB
•
•
•
1LSB
0V
4.9805V
4.9609V
•
•
•
0.0195V
0V
LTC1096/8 • AI05
Operation with DIN and DOUT Tied Together
LTC1098(L) Channel Selection
MUX ADDRESS
SGL/DIFF ODD/SIGN
1
0
1
1
0
0
0
1
OUTPUT CODE
CHANNEL #
0
1
+
+
+
–
–
+
GND
–
–
LTC1096/8 • AI03
The LTC1098(L) can be operated with DIN and DOUT tied
together. This eliminates one of the lines required to
communicate to the microprocessor (MPU). Data is transmitted in both directions on a single wire. The processor
pin connected to this data line should be configurable as
either an input or an output. The LTC1098(L) will take
control of the data line and drive it low on the 4th falling
15
LTC1096/LTC1096L
LTC1098/LTC1098L
W
U
U
UO
APPLICATI
S I FOR ATIO
MSBF BIT LATCHED
BY LTC1098(L)
CS
1
2
3
4
START
SGL/DIFF
ODD/SIGN
MSBF
CLK
DATA (DIN/DOUT)
B7
MPU CONTROLS DATA LINE AND SENDS
MUX ADDRESS TO LTC1098(L)
• • •
B6
LTC1098(L) CONTROLS DATA LINE AND SENDS
A/D RESULT BACK TO MPU
PROCESSOR MUST RELEASE
DATA LINE AFTER 4TH RISING CLK
AND BEFORE THE 4TH FALLING CLK
LTC1098(L) TAKES CONTROL OF
DATA LINE ON 4TH FALLING CLK
LTC1-96/8 • F03
Figure 3. LTC1098(L) Operation with DIN and DOUT Tied Together
CLK edge after the start bit is received (see Figure 3).
Therefore the processor port line must be switched to an
input before this happens, to avoid a conflict.
In the Typical Applications section, there is an example of
interfacing the LTC1098(L) with DIN and DOUT tied together to the Intel 8051 MPU.
normal operating power continuously. Figure 5 shows
that the typical current varies from 40µA at clock rates
below 50kHz to 100µA at 500kHz. Several things must
be taken into account to achieve such a low power
consumption.
ACTIVE AND SHUTDOWN MODES
140
120
With typical operating currents of 40µA and automatic
shutdown between conversions, the LTC1096/LTC1098
achieves extremely low power consumption over a wide
range of sample rates (see Figure 4). In systems that
convert continuously, the LTC1096/LTC1098 will draw its
SUPPLY CURRENT, ICC (µA)
ACHIEVING MICROPOWER PERFORMANCE
TA = 25°C
VCC = 5V
100
80
60
40
20
0.002
1000
0
100
SUPPLY CURRENT, ICC (µA)
TA = 25°C
VCC = VREF = 5V
ACTIVE (CS LOW)
SHUTDOWN (CS HIGH)
10k
100k
1k
CLOCK FREQUENCY (Hz)
1M
LTC1096/98 • F05
100
Figure 5. After a Conversion, When the Microprocessor
Drives CS High, the ADC Automatically Shuts Down Until the
Next Conversion. The Supply Current, Which Is Very Low
During cConversions, Drops to Zero in Shutdown
10
Shutdown
1
0.1
1
10
SAMPLE FREQUENCY, fSMPL (kHz)
100
LTC1096/98 • TPC03
Figure 4. Automatic Power Shutdown Between Conversions
Allows Power Consumption to Drop with Sample Rate
16
Figures 1 and 2 show the operating sequence of the
LTC1096/LTC1098. The converter draws power when the
CS pin is low and powers itself down when that pin is high.
If the CS pin is not taken to ground when it is low and not
taken to supply voltage when it is high, the input buffers of
LTC1096/LTC1096L
LTC1098/LTC1098L
U
W
U
UO
APPLICATI
S I FOR ATIO
the converter will draw current. This current may be larger
than the typical supply current. It is worthwhile to bring the
CS pin all the way to ground when it is low and all the way
to supply voltage when it is high to obtain the lowest
supply current.
When the CS pin is high (= supply voltage), the converter
is in shutdown mode and draws only leakage current. The
status of the DIN and CLK input have no effect on supply
current during this time. There is no need to stop DIN and
CLK with CS = high, except the MPU may benefit.
Minimize CS Low Time
In systems that have significant time between conversions, lowest power drain will occur with the minimum CS
low time. Bringing CS low, waiting 10µs for the wake-up
time, transferring data as quickly as possible, and then
bringing it back high will result in the lowest current drain.
This minimizes the amount of time the device draws
power. Even though the device draws more power at high
clock rates, the net power is less because the device is on
for a shorter time.
Wake-Up Time
A 10µs wake-up time must be provided for the ADCs to
convert correctly on a 5V supply. The wake-up time is
typically less than 3µs over the supply voltage range (see
typical curve of Wake-Up Time vs Supply Voltage). With
10µs wake-up time provided over the supply range, the
ADCs will have adequate time to wake up and acquire input
signals.
Input Logic Levels
The input logic levels of CS, CLK and DIN are made to meet
TTL on 5V supply. When the supply voltage varies, the
input logic levels also change. For the LTC1096/LTC1098
to sample and convert correctly, the digital inputs have to
meet logic low and high levels relative to the operating
supply voltage (see typical curve of Digital Input Logic
Threshold vs Supply Voltage). If achieving micropower
consumption is desirable, the digital inputs must go railto-rail between supply voltage and ground (see ACHIEVING MICROPOWER PERFORMANCE section).
Clock Frequency
DOUT Loading
Capacitive loading on the digital output can increase
power consumption. A 100pF capacitor on the DOUT pin
can more than double the 100µA supply current drain at a
500kHz clock frequency. An extra 100µA or so of current
goes into charging and discharging the load capacitor. The
same goes for digital lines driven at a high frequency by
any logic. The CxVxf currents must be evaluated and the
troublesome ones minimized.
Lower Supply Voltage
For lower supply voltages, LTC offers the LTC1096L/
LTC1098L. These pin compatible devices offer specified
performance to 2.65VMIN supply.
OPERATING ON OTHER THAN 5V SUPPLIES
The LTC1096 operates from 3V to 9V supplies and the
LTC1098 operates from 3V to 6V supplies. To operate the
LTC1096/LTC1098 on other than 5V supplies, a few things
must be kept in mind.
The maximum recommended clock frequency is 500kHz
for the LTC1096/LTC1098 running off a 5V supply. With
the supply voltage changing, the maximum clock frequency for the devices also changes (see the typical curve
of Maximum Clock Rate vs Supply Voltage). If the maximum clock frequency is used, care must be taken to
ensure that the device converts correctly.
Mixed Supplies
It is possible to have a microprocessor running off a 5V
supply and communicate with the LTC1096/LTC1098
operating on 3V or 9V supplies. The requirement to
achieve this is that the outputs of CS, CLK and DIN from the
MPU have to be able to trip the equivalent inputs of the
ADCs and the output of DOUT from the ADCs must be able
to toggle the equivalent input of the MPU (see typical curve
of Digital Input Logic Threshold vs Supply Voltage). With
the LTC1096 operating on a 9V supply, the output of DOUT
may go between 0V and 9V. The 9V output may damage
the MPU running off a 5V supply. The way to get around
this possibility is to have a resistor divider on DOUT
17
LTC1096/LTC1096L
LTC1098/LTC1098L
W
U
U
UO
APPLICATI
S I FOR ATIO
(Figure 6) and connect the center point to the MPU input.
It should be noted that to get full shutdown, the CS input
of the LTC1096/LTC1098 must be driven to the VCC
voltage. This would require adding a level shift circuit to
the CS signal in Figure 6.
9V
OPTIONAL
LEVEL SHIFT
The VCC pin should be bypassed to the ground plane with
a 1µF tantalum with leads as short as possible. If power
supply is clean, the LTC1096(L)/LTC1098(L) can also
operate with smaller 0.1µF surface mount or ceramic
bypass capacitors. All analog inputs should be referenced
directly to the single point ground. Digital inputs and
outputs should be shielded from and/or routed away from
the reference and analog circuitry.
9V 4.7µF
SAMPLE-AND-HOLD
MPU
(e.g. 8051)
CS
DIFFERENTIAL INPUTS
COMMON MODE RANGE
0V TO 6V
P1.4
VCC
+IN
CLK
–IN
DOUT
GND
VREF
5V
P1.3
50k
P1.2
6V
50k
LTC1096
LTC1096/98 • F06
Both the LTC1096(L) and the LTC1098(L) provide a builtin sample-and-hold (S&H) function to acquire signals.
The S&H of the LTC1096(L) acquires input signals from
“+” input relative to “–” input during the tWAKEUP time (see
Figure 1). However, the S&H of the LTC1098(L) can
sample input signals in the single-ended mode or in the
differential inputs during the tSMPL time (see Figure 7).
Figure 6. Interfacing a 9V Powered LTC1096 to a 5V System
Single-Ended Inputs
BOARD LAYOUT CONSIDERATIONS
Grounding and Bypassing
The LTC1096(L)/LTC1098(L) should be used with an analog ground plane and single point grounding techniques.
The GND pin should be tied directly to the ground plane.
The sample-and-hold of the LTC1098(L) allows conversion of rapidly varying signals. The input voltage is sampled
during the tSMPL time as shown in Figure 7. The sampling
interval begins as the bit preceding the MSBF bit is shifted
SAMPLE
HOLD
"+" INPUT MUST
SETTLE DURING
THIS TIME
CS
tSMPL
tCONV
CLK
DIN
START
SGL/DIFF
MSBF
DOUT
DON'T CARE
B7
1ST BIT TEST "–" INPUT MUST
SETTLE DURING THIS TIME
"+" INPUT
"–" INPUT
LTC1096/8 • F07
Figure 7. LTC1098(L) “+” and “–” Input Settling Windows
18
LTC1096/LTC1096L
LTC1098/LTC1098L
U
W
U
UO
APPLICATI
S I FOR ATIO
in and continues until the falling CLK edge after the MSBF
bit is received. On this falling edge, the S&H goes into hold
mode and the conversion begins.
Differential Inputs
With differential inputs, the ADC no longer converts just a
single voltage but rather the difference between two voltages. In this case, the voltage on the selected “+” input is
still sampled and held and therefore may be rapidly time
varying just as in single-ended mode. However, the voltage on the selected “–” input must remain constant and be
free of noise and ripple throughout the conversion time.
Otherwise, the differencing operation may not be performed accurately. The conversion time is 8 CLK cycles.
Therefore, a change in the “–” input voltage during this
interval can cause conversion errors. For a sinusoidal
voltage on the “–” input this error would be:
VERROR (MAX) = VPEAK • 2 • π • f(“–”) • 8/fCLK
Where f(“–”) is the frequency of the “–” input voltage,
VPEAK is its peak amplitude and fCLK is the frequency of the
CLK. In most cases VERROR will not be significant. For a
60Hz signal on the “–” input to generate a 1/4LSB error
(5mV) with the converter running at CLK = 500kHz, its
peak value would have to be 750mV.
ANALOG INPUTS
Because of the capacitive redistribution A/D conversion
techniques used, the analog inputs of the LTC1096(L)/
LTC1098(L )have capacitive switching input current spikes.
These current spikes settle quickly and do not cause a
problem. However, if large source resistances are used or
if slow settling op amps drive the inputs, care must be
taken to ensure that the transients caused by the current
spikes settle completely before the conversion begins.
t WAKEUP or tSMPL for the LTC1096(L) or the LTC1098(L)
respectively. Minimizing RSOURCE+ and C1 will improve
the input settling time. If a large “+” input source resistance must be used, the sample time can be increased by
using a slower CLK frequency.
“–” Input Settling
At the end of the tWAKEUP or tSMPL, the input capacitor
switches to the “–” input and conversion starts (see
Figures 1 and 7). During the conversion the “+” input
voltage is effectively “held” by the sample-and-hold and
will not affect the conversion result. However, it is critical
that the “–” input voltage settles completely during the
first CLK cycle of the conversion time and be free of noise.
Minimizing RSOURCE– and C2 will improve settling time. If
a large “–” input source resistance must be used, the time
allowed for settling can be extended by using a slower CLK
frequency.
Input Op Amps
When driving the analog inputs with an op amp it is
important that the op amp settle within the allowed time
(see Figure 7). Again, the “+” and “–” input sampling times
can be extended as described above to accommodate
slower op amps. Most op amps, including the LT1006 and
LT1413 single supply op amps, can be made to settle well
even with the minimum settling windows of 3µs (“+”
input) which occur at the maximum clock rate of 500kHz.
Source Resistance
The analog inputs of the LTC1096/LTC1098 look like a
25pF capacitor (CIN) in series with a 500Ω resistor (RON)
as shown in Figure 8. CIN gets switched between the
selected “+” and “–” inputs once during each conversion
“+” Input Settling
The input capacitor of the LTC1096(L) is switched onto
“+” input during the wake-up time (see Figure 1) and
samples the input signal within that time. However, the
input capacitor of the LTC1098(L) is switched onto “+”
input during the sample phase (tSMPL, see Figure 7). The
sample phase is 1.5 CLK cycles before conversion starts.
The voltage on the “+” input must settle completely within
RSOURCE +
“+”
INPUT
LTC1096
LTC1098
VIN +
C1
RSOURCE –
“–”
INPUT
RON = 500Ω
CIN = 25pF
VIN –
C2
LTC1096/8 • F8
Figure 8. Analog Input Equivalent Circuit
19
LTC1096/LTC1096L
LTC1098/LTC1098L
U
W
U
UO
APPLICATI
S I FOR ATIO
cycle. Large external source resistors and capacitances
will slow the settling of the inputs. It is important that the
overall RC time constants be short enough to allow the
analog inputs to completely settle within the allowed time.
RC Input Filtering
It is possible to filter the inputs with an RC network as
shown in Figure 9. For large values of CF (e.g., 1µF), the
capacitive input switching currents are averaged into a net
DC current. Therefore, a filter should be chosen with a
small resistor and large capacitor to prevent DC drops
across the resistor. The magnitude of the DC current is
approximately IDC = 25pF(VIN /tCYC) and is roughly proportional to VIN. When running at the minimum cycle time
of 29µs, the input current equals 4.3µA at VIN = 5V. In this
case, a filter resistor of 390Ω will cause 0.1LSB of fullscale error. If a larger filter resistor must be used, errors
can be eliminated by increasing the cycle time.
RFILTER
IDC
“+”
VIN
CFILTER
LTC1098
“–”
LTC1096/8 • F9
Figure 9. RC Input Filtering
Input Leakage Current
Input leakage currents can also create errors if the source
resistance gets too large. For instance, the maximum
input leakage specification of 1µA (at 125°C) flowing
through a source resistance of 3.9k will cause a voltage
drop of 3.9mV or 0.2LSB. This error will be much reduced
at lower temperatures because leakage drops rapidly (see
typical curve of Input Channel Leakage Current vs Temperature).
tive current spike will be generated on the reference pin by
the ADC. These current spikes settle quickly and do not
cause a problem.
Using a slower CLK will allow more time for the reference
to settle. Even at the maximum CLK rate of 500kHz most
references and op amps can be made to settle within the
2µs bit time.
REF+
5
ROUT
VREF
LTC1096
EVERY CLK CYCLE
RON
GND
4
5pF TO 30pF
LTC1096/8 • F10
Figure 10. Reference Input Equivalent Circuit
Reduced Reference Operation
The minimum reference voltage of the LTC1098 is limited
to 3V because the VCC supply and reference are internally
tied together. However, the LTC1096 can operate with
reference voltages below 1V.
The effective resolution of the LTC1096 can be increased
by reducing the input span of the converter. The LTC1096
exhibits good linearity and gain over a wide range of
reference voltages (see typical curves of Linearity and Full
Scale Error vs Reference Voltage). However, care must be
taken when operating at low values of VREF because of the
reduced LSB step size and the resulting higher accuracy
requirement placed on the converter. The following factors must be considered when operating at low VREF
values.
1. Offset
2. Noise
3. Conversion speed (CLK frequency)
Offset with Reduced VREF
REFERENCE INPUTS
The voltage on the reference input of the LTC1096 defines
the voltage span of the A/D converter. The reference input
transient capacitive switching currents due to the switchedcapacitor conversion technique (see Figure 10). During
each bit test of the conversion (every CLK cycle), a capaci-
20
The offset of the LTC1096 has a larger effect on the output
code when the ADC is operated with reduced reference
voltage. The offset (which is typically a fixed voltage)
becomes a larger fraction of an LSB as the size of the LSB
is reduced. The typical curve of Unadjusted Offset Error vs
Reference Voltage shows how offset in LSBs is related to
LTC1096/LTC1096L
LTC1098/LTC1098L
U
W
U
UO
S I FOR ATIO
reference voltage for a typical value of VOS. For example,
a VOS of 2mV which is 0.1LSB with a 5V reference becomes
0.5LSB with a 1V reference and 2.5LSBs with a 0.2V
reference. If this offset is unacceptable, it can be corrected
digitally by the receiving system or by offsetting the “–”
input of the LTC1096.
Noise with Reduced VREF
The total input referred noise of the LTC1096 can be
reduced to approximately 1mV peak-to-peak using a ground
plane, good bypassing, good layout techniques and minimizing noise on the reference inputs. This noise is insignificant with a 5V reference but will become a larger
fraction of an LSB as the size of the LSB is reduced.
For operation with a 5V reference, the 1mV noise is only
0.05LSB peak-to-peak. In this case, the LTC1096 noise
will contribute virtually no uncertainty to the output
code. However, for reduced references, the noise may
become a significant fraction of an LSB and cause
undesirable jitter in the output code. For example, with a
1V reference, this same 1mV noise is 0.25LSB peak-topeak. This will reduce the range of input voltages over
which a stable output code can be achieved by 1LSB. If
the reference is further reduced to 200mV, the 1mV
noise becomes equal to 1.25LSBs and a stable code may
be difficult to achieve. In this case averaging readings
may be necessary.
This noise data was taken in a very clean setup. Any setupinduced noise (noise or ripple on VCC, VREF or VIN) will add
to the internal noise. The lower the reference voltage to be
used, the more critical it becomes to have a clean, noise free
setup.
Conversion Speed with Reduced VREF
With reduced reference voltages the LSB step size is
reduced and the LTC1096 internal comparator overdrive is reduced. Therefore, it may be necessary to
reduce the maximum CLK frequency when low values
of VREF are used.
Input Divider
It is OK to use an input divider on the reference input of the
LTC1096 as long as the reference input can be made to
settle within the bit time at which the clock is running.
When using a larger value resistor divider on the reference
input the “–” input should be matched with an equivalent
resistance.
Bypassing Reference Input with Divider
Bypassing the reference input with a divider is also possible. However, care must be taken to make sure that the
DC voltage on the reference input will not drop too much
below the intended reference voltage.
AC PERFORMANCE
Two commonly used figures of merit for specifying the
dynamic performance of the ADCs in digital signal processing applications are the signal-to-noise ratio (SNR)
and the effective number of bits (ENOBs).
Signal-to-Noise Ratio
The signal-to-noise ratio (SNR) is the ratio between the
RMS amplitude of the fundamental input frequency to
the RMS amplitude of all other frequency components at
the A/D output. This includes distortion as well as noise
products and for this reason it is sometimes referred to
as signal-to-noise + distortion [S/(N + D)]. The output is
band limited to frequencies from DC to one half the
sampling frequency. Figure 11 shows spectral content
from DC to 15.625kHz which is 1/2 the 31.25kHz sampling rate.
0
–10
fSAMPLE = 31.25kHz
fIN = 11.8kHz
–20
AMPLITUDE (dB)
APPLICATI
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
2
4
8
10 12
6
FREQUENCY (kHz)
14
16
LTC1096/8 • F11
Figure 11. This Clean FFT of an 11.8kHz Input Shows
Remarkable Performance for an ADC That Draws Only 100µA
When Sampling at the 31.25kHz Rate
21
LTC1096/LTC1096L
LTC1098/LTC1098L
U
W
U
UO
APPLICATI
S I FOR ATIO
8
EFFECTIVE NUMBER OF BITS (ENOBs)
Effective Number of Bits
The effective number of bits (ENOBs) is a measurement of
the resolution of an A/D and is directly related to the
S/(N + D) by the equation:
ENOB = [S/(N + D) –1.76]/6.02
where S/(N + D) is expressed in dB. At the maximum
sampling rate of 33kHz the LTC1096 maintains 7.5 ENOBs
or better to 40kHz. Above 40kHz the ENOBs gradually
decline, as shown in Figure 12, due to increasing second
harmonic distortion. The noise floor remains approximately 70dB.
fSAMPLE = 31.25kHz
7
6
5
4
3
2
1
0
0
20
40
INPUT FREQUENCY (kHz)
LTC1096/8 • F12
Figure 12. Dynamic Accuracy Is Maintained Up to an Input
Frequency of 40kHz
UO
TYPICAL APPLICATI
S
MICROPROCESSOR INTERFACES
The LTC1096(L)/LTC1098(L) can interface directly (without external hardware to most popular microprocessor
(MPU) synchronous serial formats (see Table 1). If an
MPU without a dedicated serial port is used, then three or
four of the MPU’s parallel port lines can be programmed
to form the serial link to the LTC1096(L)/LTC1098(L).
Included here is one serial interface example and one
example showing a parallel port programmed to form the
serial interface.
Motorola SPI (MC68HC05C4,CM68HC11)
The MC68HC05C4 has been chosen as an example of
an MPU with a dedicated serial port. This MPU transfer
data MSB-first and in 8-bit increments. With two 8-bit
transfers, the A/D result is read into the MPU. The first
8-bit transfer sends the DIN word to the LTC1098(L)
and clocks into the processor. The second 8-bit transfer clocks the A/D conversion result, B7 through B0,
into the MPU.
ANDing the first MUP received byte with 00Hex clears the
first byte. Notice how the position of the start bit in the first
MPU transmit word is used to position the A/D result
right-justified in two memory locations.
Table 1. Microprocessor with Hardware Serial Interfaces
Compatible with the LTC1096(L)/LTC1098(L)
PART NUMBER
TYPE OF INTERFACE
Motorola
MC6805S2,S3
MC68HC11
MC68HC05
SPI
SPI
SPI
RCA
CDP68HC05
SPI
Hitachi
HD6305
HD63705
HD6301
HD63701
HD6303
HD64180
SCI Synchronous
SCI Synchronous
SCI Synchronous
SCI Synchronous
SCI Synchronous
CSI/O
National Semiconductor
COP400 Family
COP800 Family
NS8050U
HPC16000 Family
MICROWIRETM
MICROWIRE/PLUSTM
MICROWIRE/PLUS
MICROWIR/PLUS
Texas Instruments
TMS7002
TMS7042
TMS70C02
TMS70C42
TMS32011*
TMS32020
Serial Port
Serial Port
Serial Port
Serial Port
Serial Port
Serial Port
* Requires external hardware
MICROWIRE and MICROWIRE/PLUS are trademarks of
National Semiconductor Corp.
22
LTC1096/LTC1096L
LTC1098/LTC1098L
UO
TYPICAL APPLICATI
S
Data Exchange Between LTC1098(L) and MC68HC05C4
START
BIT
MPU TRANSMIT
WORD
0
0
0
1
BYTE 1
SGL/ ODD/
MSBF X
DIFF SIGN
BYTE 2 (DUMMY)
X
X
X
X
X
X
X
X
X = DON'T CARE
CS
START
SGL/ ODD/
DIFF SIGN MSBF
DIN
DON'T CARE
CLK
DOUT
MPU RECEIVED
WORD
?
?
?
?
?
?
?
0
B7
B6
B5
B4
B3
B2
B1
B0
B7
B6
B5
B4
B3
B2
B1
B0
1ST TRANSFER
2ND TRANSFER
Hardware and Software Interface to Motorola MC68HC05C4
C0
CS
ANALOG
INPUTS
SCK
MC68HC05C4
MISO
CLK
LTC1098
DIN
DOUT
MOSI
LABEL
MNEMONIC
START
BCLRn
LDA
STA
TST
BPL
LDA
LTC1096/8 • TA04
DOUT from LTC1098(L) Stored in MC68HC05C4
LOCATION A
0
0
0
0
0
0
0
0
BYTE 1
LSB
LOCATION A + 1
B7
B6
B5
B4
B3
B2
B1
B0
BYTE 2
STA
AND
STA
TST
BPL
BSETn
LDA
STA
LTC1096/8 • TA03
COMMENTS
Bit 0 Port C goes low (CS goes low)
Load LTC1098(L) DIN word into Acc.
Load LTC1098(L) D IN word into SPI from Acc.
Transfer begins.
Test status of SPIF
Loop to previous instruction if not done
with transfer
Load contents of SPI data register
into Acc. (DOUT MSBs)
Start next SPI cycle
Clear the first D OUT word
Store in memory location A (MSBs)
Test status of SPIF
Loop to previous instruction if not done
with transfer
Set B0 of Port C (CS goes high)
Load contents of SPI data register into
Acc. (D OUT LSBs)
Store in memory location A + 1 (LSBs)
LTC1096/8 • TA05
23
LTC1096/LTC1096L
LTC1098/LTC1098L
UO
TYPICAL APPLICATI
S
Interfacing to the Parallel Port of the
Intel 8051 Family
LABEL
The Intel 8051 has been chosen to demonstrate the
interface between the LTC1098(L) and parallel port microprocessors. Normally the CS, CLK and DIN signals would
be generated on three port lines and the DOUT signal read
on a fourth port line. This works very well. However, we
will demonstrate here an interface with the DIN and DOUT
of the LTC1098(L) tied together as described in the
SERIAL INTERFACE section. This saves one wire.
LOOP 1
LOOP
The 8051 first sends the start bit and MUX address to the
LTC1098(L) over the data line connected to P1.2. Then
P1.2 is reconfigured as an input (by writing to it a one) and
the 8051 reads back the 8-bit A/D result over the same
data line.
CS
LTC1098(L) CLK
DOUT
DIN
ANALOG
INPUTS
MNEMONIC
OPERAND
COMMENTS
MOV
SETB
CLR
MOV
RLC
CLR
MOV
SETB
DJNZ
MOV
CLR
MOV
MOV
RLC
SETB
CLR
DJNZ
MOV
SETB
A, #FFH
P1.4
P1.4
R4, #04
A
P1.3
P1.2, C
P1.3
R4, LOOP 1
P1, #04
P1.3
R4, #09
C, P1.2
A
P1.3
P1.3
R4, LOOP
R2, A
P1.4
DIN word for LTC1098(L)
Make sure CS is high
CS goes low
Load counter
Rotate DIN bit into Carry
CLK goes low
Output DIN bit to LTC1098(L)
CLK goes high
Next bit
Bit 2 becomes an input
CLK goes low
Load counter
Read data bit into Carry
Rotate data bit into Acc.
CLK goes high
CLK goes low
Next bit
Store MSBs in R2
CS goes high
DOUT from LTC1098(L) Stored in 8051 RAM
P1.4
P1.3
P1.2
8051
MSB
MUX ADDRESS
R2
A/D RESULT
B7
LSB
B6
B5
B4
B3
B2
B1
B0
LTC1096/8 • TA07
LTC1096/8 • TA06
MSBF BIT LATCHED
BY LTC1098(L)
CS
1
2
START
SGL/
DIFF
3
4
CLK
DATA (DIN/DOUT)
ODD/
SIGN
MSBF
8051 P1.2 OUTPUTS DATA
TO LTC1098(L)
8051 P1.2 RECONFIGURED
AS AN INPUT AFTER THE 4TH RISING
CLK AND BEFORE THE 4TH FALLING CLK
24
B7
B6
B5
B4
B3
B2
LTC1098(L) SENDS A/D RESULT
BACK TO 8051 P1.2
LTC1098(L) TAKES CONTROL OF DATA LINE
ON 4TH FALLING CLK
B1
B0
LTC1096/8 • TA08
LTC1096/LTC1096L
LTC1098/LTC1098L
UO
TYPICAL APPLICATI
S
A “Quick Look” Circuit for the LTC1096
CS
Users can get a quick look at the function and timing of the
LT1096 by using the following simple circuit (Figure 13).
VREF is tied to VCC. VIN is applied to the +IN input and the
– IN input is tied to the ground. CS is driven at 1/16 the
clock rate by the 74C161 and DOUT outputs the data. The
output data from the DOUT pin can be viewed on an
oscilloscope that is set up to trigger on the falling edge of
CS (Figure 14). Note the LSB data is partially clocked out
before CS goes high.
4.7µF
VIN
NULL
BIT
LSB
(B0)
MSB
(B7)
LSB DATA
(B1)
VERTICAL: 5V/DIV
HORIZONTAL: 10µs/DIV
CLR
VCC
CLK
RC
A
QA
B
QB
74C161
C
QC
D
QD
P
T
GND
LOAD
VCC
CH0
CLK
LTC1096
CH1
DOUT
GND
DOUT
5V
+
CS
CLK
VREF
5V
Figure 14. Scope Trace the LTC1096 “Quick Look” Circuit
Showing A/D Output 10101010 (AAHEX)
3V
0.1µF
LM134
75k
CLOCK IN 150kHz MAX
TO OSCILLOSCOPE
678Ω
VCC
LTC1096/8 • F13
CS
+IN
13.5k
Figure 13. “Quick Look” Circuit for the LTC1096
–IN LTC1096 CLK
DOUT
VREF
Figure 15 shows a temperature measurement system.
The LTC1096 is connected directly to the low cost silicon
temperature sensor. The voltage applied to the VREF pin
adjusts the full scale of the A/D to the output range of the
sensor. The zero point of the converter is matched to the
zero output voltage of the sensor by the voltage on the
LTC1096’s negative input.
TO µP
182k
GND
LT1004-1.2
0.01µF
0.01µF
63.4k
LTC1096/8 • F15
Figure 15. The LTC1096’s High Impedance Input Connects
Directly to This Temperature Sensor, Eliminating Signal
Conditioning Circuitry in This 0°C to 70°C Thermometer
25
LTC1096/LTC1096L
LTC1098/LTC1098L
UO
TYPICAL APPLICATI
S
Remote or Isolated Systems
Figure 16 shows a floating system that sends data to a
grounded host system. The floating circuitry is isolated by
two optoisolators and powered by a simple capacitor
diode charge pump. The system has very low power
requirements because the LTC1096 shuts down between
conversions and the optoisolators draw power only when
data is being transferred. The system consumes only
50µA at a sample rate of 10Hz (1ms on-time and 99ms offtime). This is easily within the current supplied by the
charge pump running at 5MHz. If a truly isolated system
is required, the system’s low power simplifies generating
an isolated supply or powering the system from a battery.
FLOATING SYSTEM
1N5817
+
0.001µF
2kV
2N3904
47µF
0.1µF
75k
1N5817
0.022µF
VCC
100k
LT1004-2.5
CS
5MHz
LTC1096
1N5817
300Ω
100k
CLK
VREF
20k
CLK
+IN
–IN
ANALOG
INPUT
DOUT
GND
1k
10k
DATA
500k
LTC1096/8 • F16
Figure 16. Power for This Floating A/D System Is Provided by a Simple Capacitor Diode Charge Pump. The Two Optoisolators
Draw No Current Between Samples, Turning On Only to Send the Clock and Receive Data
26
LTC1096/LTC1096L
LTC1098/LTC1098L
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters), unless otherwise noted.
N8 Package
8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
0.255 ± 0.015*
*THESE DIMENSIONS DO NOT INCLUDE (6.477 ± 0.381)
MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL
NOT EXCEED 0.010 INCH (0.254mm)
0.300 – 0.325
(7.620 – 8.255)
0.065
(1.651)
TYP
0.009 – 0.015
(0.229 – 0.381)
(
+0.635
–0.381
0.125
(3.175)
MIN
0.005
(0.127)
MIN
+0.025
0.325 –0.015
8.255
0.130 ± 0.005
(3.302 ± 0.127)
0.045 – 0.065
(1.143 – 1.651)
)
0.018 ± 0.003
(0.457 ± 0.076)
0.100 ± 0.010
(2.540 ± 0.254)
0.015
(0.380)
MIN
N8 0695
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
1
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
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.
SO8 0695
27
LTC1096/LTC1096L
LTC1098/LTC1098L
UO
TYPICAL APPLICATI
A/D Conversion for 3V Systems
The LTC1096/LTC1098 are ideal for 3V systems. Figure 17
shows a 3V to 6V battery current monitor that draws only
70µA from the battery it monitors. The battery current is
sensed with the 0.02Ω resistor and amplified by the
LT1178. The LTC1096 digitizes the amplifier output and
sends it to the microprocessor in serial format. The
LT1004 provides the full-scale reference for the ADC. The
other half of the LTC1178 is used to provide low battery
detection. The circuit’s 70µA supply current is dominated
by the op amps and the reference. The circuit can be
located near the battery and data transmitted serially to
the microprocessor.
0.1µF
0.1µF
3V TO 6V
73.2k
470k
750k
L
O
A
D
24.9k
0.02Ω FOR 2A FULL SCALE
0.2Ω FOR 0.2A FULL SCALE
+
1/2 LT1178
–
CS
VCC
CLK
LTC1096 D
OUT
VREF
GND
+
–
TO µP
20M
+
LO BATTERY
1/2 LT1178
LT1004-1.2
470k
–
LTC1096/8 • F17
Figure 17. This 0A to 2A Battery Current Monitor Draws Only 70µA from a 3V Battery
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1196/LTC1198
8-Pin SO, 1Msps, 8-Bit ADCs
Low Power, Small Size, Low Cost
LTC1286/LTC1298
8-Pin SO, 5V Micropower, 12-Bit ADCs
1- or 2-Channel, Auto Shutdown
LTC1285/LTC1298
8-Pin SO, 3V Micropower, 12-Bit ADCs
1- or 2-Channel, Auto Shutdown
LTC1400
5V High Speed,Serial 12-Bit ADC
400ksps, Complete with VREF, CLK, Sample-and-Hold
LTC1594/LTC1598
4- and 8-Channel, 5V Micropower, 12-Bit ADCs
Low Power, Small Size, Low Cost
LTC1594L/LTC1598L
4- and 8-Channel, 3V Micropower, 12-Bit ADCs
Low Power, Small Size, Low Cost
28
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417● (408) 432-1900
FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com
10968fb LT/TP 0397 5K REV B • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 1994
Similar pages