LTC1099
High Speed 8-Bit A/D
Converter with Built-In
Sample-and-Hold
DESCRIPTIO
The LTC
®
1099 is a high speed microprocessor compatible
8-bit analog-to-digital converter (A/D). An internal sample-
and-hold (S/H) allows the A/D to convert inputs up to the
full Nyquist limit. With a conversion rate of 2.5µs, this
allows 156kHz 5V
P-P
input signals or slew rates as high as
2.5V/µs, to be digitized without the need for an external
S/H.
Two modes of operation, Read (RD) mode and Write-Read
(WR-RD) mode, allow easy interface with processors. All
timing is internal and edge sensitive which eliminates the
need for external pulse shaping circuits. The Stand-Alone
(SA) mode is convenient for those applications not involv-
ing a processor.
Data outputs are latched with three-state control to allow
easy interface to a processor data bus or I/O port. An
overflow output (OFL) is provided to allow cascading for
higher resolution.
FEATURES
s
s
s
s
s
s
s
s
s
s
s
Built-In Sample-and-Hold
No Missing Codes
No User Trims Required
All Timing Inputs Edge Sensitive for Easy Processor
Interface
Fast Conversion Time: 2.5µs
Latched Three-State Outputs
Single 5V Operation
No External Clock
Overflow Output Allows Cascading
T
C
Input Allows User Adjustable Conversion Time
0.3" Wide 20-Pin PDIP
KEY SPECIFICATIO S
s
s
s
s
s
Resolution: 8-Bits
Conversion Time: 2.5µs (RD Mode)
2.5µs (WR/RD Mode)
Slew Rate Limit (Internal S/H): 2.5V/µs
Low Power: 75mW Max
Total Unadjusted Error
LTC1099:
±1
LSB
LTC1099A:
±0.75
LSB
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
Infinite Hold Time Sample-and-Hold (T
ACQ
= 240ns)
5V
12
20
REF
+
V
CC
LTC1099
MODE
17
16
15
14
5
4
3
2
1
2
3
4
5
6
7
8
10k
14
REF +
B1
B2
B3
B4
B5
B6
B7
B8
REF
–
15
15V
SIGNAL-TO-NOISE RATIO, SNR (dB)
Signal-to-Noise Ratio (SNR) vs Input Frequency
– 36
– 38
– 40
– 42
– 44
– 46
– 48
– 50
– 52
1
10
INPUT FREQUENCY (kHz)
100
1099 G08
20
V
+
18
2
2.5k
V
IN
SAMPLE
HOLD
DB7
DB6
1
DB5
V
IN
DB4
6
WR/RDY DB3
DB2
8
DB1
RD
DB0
13
CS
GND
10
REF
–
11
7
I
O
AM6012
I
O
+
–
7
LT1022
6
V
OUT
3
19
4
10k
V
–
17
–15V
1099 TA01
U
U
U
T
A
= 25°C
T
C
= 2.5µs
1
LTC1099
ABSOLUTE
AXI U RATI GS
Supply Voltage (V
CC
) to GND Voltage ...................... 12V
Analog and Reference Inputs... – 0.3V to (V
CC
+ 0.3V)
Digital Inputs .........................................– 0.3V to 12V
Digital Outputs ........................ – 0.3V to (V
CC
+ 0.3V)
Power Dissipation .............................................. 500mW
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
IN
DB0
DB1
DB2
DB3
WR/RDY
MODE
RD
INT
1
2
3
4
5
6
7
8
9
20 V
CC
19 T
C
18 OFL
17 DB7
16 DB6
15 DB5
14 DB4
13 CS
12
REF
+
11 REF
–
N PACKAGE
20-LEAD PDIP
ORDER PART
NUMBER
LTC1099CN
LTC1099ACN
LTC1099AIN
GND 10
T
JMAX
= 150°C,
θ
JA
= 100°C/W
Consult factory for parts specified with wider operating temperature ranges.
CONVERTER CHARACTERISTICS
The
q
denotes the
+
specifications which apply over the full operating
–
PARAMETER
Accuracy
Total Unadjusted Error
LTC1099A
LTC1099
Minimum Resolution (No Missing Codes)
Reference Input
Input Resistance
REF
+
Input Voltage Range
REF
–
Input Voltage Range
Analog Input
Input Voltage Range
Input Leakage Current
Input Capacitance
Sample-and-Hold
Acquisition Time
Aperture Time
Tracking Rate
240
110
2.5
240
110
2.5
CS = V
CC
, V
IN
= V
CC
, GND
q
q
q
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V, REF = 5V, REF = 0V and T
A
= T
MIN
to T
MAX
unless otherwise
noted.
CONDITIONS
(Note 3)
q
q
q
(Note 4)
(Note 4)
2
U
U
W
W W
U
W
(Notes 1, 2)
Operating Temperature Range
LTC1099C/LTC1099AC ............................ 0°C to 70°C
LTC1099I/LTC1099AI ..........................–40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
V
IN
1
DB0 2
DB1 3
DB2 4
DB3 5
WR/RDY 6
MODE 7
RD 8
INT 9
GND 10
SW PACKAGE
20-LEAD PLASTIC SO
20 V
CC
19 TC
18 OFL
17 DB7
16 DB6
15 DB5
14 DB4
13 CS
12 REF
+
11 REF
–
ORDER PART
NUMBER
LTC1099CSW
T
JMAX
= 150°C,
θ
JA
= 130°C/W
U
LTC1099AI/LTC1099I
MIN
TYP
MAX
LTC1099AC/LTC1099C
MIN
TYP
MAX
UNITS
±0.75
±1
8
1
REF
–
GND
GND
60
3.2
6
V
CC
REF
+
V
CC
±3
60
8
2
REF
–
GND
GND
3.2
±0.75
±1
LSB
LSB
Bits
4.5
V
CC
REF
+
V
CC
±3
kΩ
V
V
V
µA
pF
ns
ns
V/µs
q
q
LTC1099
DIGITAL AND DC ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
CC
= 5V, REF
+
= 5V, REF
–
= 0V and T
A
= T
MIN
to T
MAX
unless otherwise noted.
SYMBOL PARAMETER
V
IH
V
IL
I
IH
I
IL
V
OH
High Level Input Voltage
Low Level Input Voltage
High Level Input Current
Low Level Input Current
CONDITIONS
All Digital Inputs, V
CC
= 5.25V
All Digital Inputs, V
CC
= 4.75V
V
IH
= 5V; CS, RD, Mode
V
IH
= 5V; WR
V
IL
= 0V; All Digital Inputs
q
q
q
q
q
q
2.4
0.0001
0.0005
–0.0001
4.0
4.7
0.4
0.1
–0.1
–11
14
11
3
–3
–6
7
20
0.1
–0.1
–11
14
11
LTC1099AI/LTC1099I
MIN
TYP
MAX
2.0
0.8
1
3
–1
2.4
LTC1099AC/LTC1099C
MIN
TYP
MAX
2.0
0.0001
0.0005
–0.0001
4.0
4.7
0.4
3
–3
–7
9
15
0.8
1
3
–1
UNITS
V
V
µA
µA
µA
V
V
V
µA
µA
mA
mA
mA
High Level Output Voltage DB0-DB7, OFL, INT; V
CC
= 4.75V
I
OUT
= 360µA
I
OUT
=10µA
V
OL
I
OZ
I
SOURCE
I
SINK
I
CC
Low Level Output Voltage DB0-DB7, OFL, INT, RDY; V
CC
= 4.75V
q
I
OUT
=1.6mA
Hi-Z Output Leakage
Output Source Current
Output Sink Current
Supply Current
DB0-DB7, RDY; V
OUT
= 5V
DB0-DB7, RDY; V
OUT
= 0V
DB0-DB7, OFL, INT; V
OUT
= 0V
DB0-DB7, OFL, INT, RDY; V
OUT
= 5V
CS = WR = RD = V
CC
q
q
q
q
q
The
q
denotes the specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. V
CC
= 5V, REF
+
= 5V, REF
–
= 0V and T
A
= T
MIN
to T
MAX
unless otherwise noted.
SYMBOL PARAMETER
RD Mode (Figure 2) Pin 7 = GND
t
CRD
t
RDY
t
ACC0
t
INTH
t
1H
, t
0H
t
P
t
ACC2
t
CWR
t
ACC0
t
ACC2
t
INTH
t
IHWR
t
1H
, t
0H
t
P
t
WR
Conversion Time
Delay From CS↓ to RDY↓
Delay From RD↓ to Output Data Valid
Delay From RD↑ to INT↑
Delay From RD↑ to Hi-Z State on Outputs
Delay Time Between Conversions
Delay Time From RD↓ to Output Data Valid
Conversion Time
T
A
= 25°C
q
AC CHARACTERISTICS
WR/RD Mode (Figures 3 and 4) Pin 7 = V
CC
2.2
2.5
t
CWR
+ 40
70
70
240
70
700
55
2.8
5.0
2.2
2.5
t
CWR
+ 40
70
70
240
70
700
55
2.8
3.75
µs
µs
ns
ns
ns
ns
ns
ns
ns
Delay Time From WR↓ to Output Data Valid C
L
= 100pF
Delay From RD↓ to Output Data Valid
Delay From RD↑ to INT↑
Delay From WR↓ to INT↑
Delay From RD↑ to Hi-Z State on Outputs
Delay Time Between Conversions
Minimum WR Pulse Width
C
L
= 100pF
C
L
= 100pF
C
L
= 100pF
Test Circuit Figure 1
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All voltages are with respect to GND (Pin 10) unless otherwise
noted.
U
CONDITIONS
T
A
= 25°C
q
LTC1099AI/LTC1099I
MIN
TYP
MAX
2.2
2.5
70
t
CRD
+ 35
70
70
700
70
2.8
5.0
LTC1099AC/LTC1099C
MIN
TYP
MAX
2.2
2.5
70
t
CRD
+ 35
70
70
700
70
2.8
3.75
UNITS
µs
µs
C
L
= 100pF
C
L
= 100pF
C
L
= 100pF
Test Circuit Figure 1
ns
ns
ns
ns
ns
ns
Note 3:
Total unadjusted error includes offset, gain, linearity and hold step
errors.
Note 4:
Reference input voltage range is guaranteed but is not tested.
3
LTC1099
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Temperature
20
18
SUPPLY CURRENT, I
CC
(mA)
4
T
A
= 25°C
T
C
= 2.5µs
3
LINEARITY ERROR (LBS)
16
V
OS
ERROR (LSB)
14
12
10
8
6
4
2
0
– 50
25
– 25
0
50
75 100
AMBIENT TEMPERATURE, T
A
(°C)
125
Total Error vs Reference Voltage
4
T
A
= 25°C
T
C
= 2.5µs
TOTAL UNADJUSTED ERROR (LBS)
CONVERSION TIME (µs)
3
TOTAL ERROR (LSB)
2
1
0
0
4
1
3
2
REFERENCE VOLTAGE, V
REF
(V)
1099 G04
Conversion Time vs Temperature
CONVERSION TIME/CONVERSION TIME AT 25°C
1.8
1.6
1.4
1.2
1.0
0.8
0.6
50
100
–50 –25
25
75
0
AMBIENT TEMPERATURE, T
A
(°C)
4.5
4.0
CONVERSION TIME (µs)
3.5
3.0
2.5
2.0
1.5
125
SIGNAL-TO-NOISE RATIO, SNR (dB)
4
U W
1099 G01
V
OS
Error vs Reference Voltage
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
4
1
3
2
REFERENCE VOLTAGE, V
REF
(V)
5
1099 G02
Linearity Error vs Reference
Voltage
T
A
= 25°C
T
C
= 2.5µs
2
1
0
0
1
3
4
2
REFERENCE VOLTAGE, V
REF
(V)
5
1099 G03
Conversion Time vs R
EXT
100
T
A
= 25°C
1.0
Accuracy vs Conversion Time
T
A
= 25°C
0.8
10
RESISTOR BETWEEN
PIN 19 AND V
CC
0.6
1.0
RESISTOR BETWEEN
PIN 19 AND GND
0.4
0.2
0.1
5
10
100
RESISTANCE (kΩ)
1000
1099 G05
0
1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5
CONVERSION TIME (µs)
1099 G06
Signal-to-Noise Ratio (SNR) vs
Input Frequency
– 36
– 38
– 40
– 42
– 44
– 46
– 48
– 50
– 52
1
10
INPUT FREQUENCY (kHz)
100
1099 G08
T
A
= 25°C
T
C
= 2.5µs
1099 G07
LTC1099
PIN FUNCTIONS
V
IN
(Pin 1):
Analog Input.
DB0 to DB3 (Pins 2 to 5):
Data Outputs. DB0 = LSB.
WR/RDY (Pin 6):
WR/RDY is an input when M0DE = V
CC
.
Falling edge of WR switches internal S/H to hold then
starts conversion. WR/RDY is an open drain output (active
pull-down) when M0DE = GND. RDY goes low at start of
conversion and pull-down is turned off when conversion
is complete. Resistive pull-up is usually used in this mode.
MODE (Pin 7):
WR-RD when MODE = V
CC
. RD when
M0DE = GND. No internal pull-down.
RD (Pin 8):
A Low on RD with CS Low Activates Three-
State Outputs. With MODE = GND and CS low, the falling
edge of RD switches internal S/H to hold and starts
conversion.
INT (Pin 9):
Output that goes low when the conversion in
process is complete and goes high after data is read.
GND (Pin 10):
Ground Connection.
REF
–
(Pin 11):
Low Reference Potential (Analog Ground).
REF
+
(Pin 12):
High Reference Potential. V
REF
= Full Scale
= (REF
+
) – (REF
–
).
CS (Pin 13):
Chip Select. When high, data outputs are high
impedance and all inputs are ignored.
DB4 to DB7 (Pins 14 to 17):
Data Outputs. DB7 = MSB.
OFL (Pin 18):
Overflow Output. Goes low when V
IN
> V
REF
.
T
C
(Pin 19):
User Adjustable Conversion Time.
V
CC
(Pin 20):
Positive Supply. 4.75V
≤
V
CC
≤
5.25V.
TEST CIRCUITS
t
1H
t
r
= 20ns, C
L
= 10pF
t
r
V
CC
RD
GND
RD
CS
C
L
1k
DATA
OUT
DATA OUT
GND
V
0H
10%
t
1H
90%
V
CC
90%
50%
RD
CS
C
L
DATA
OUT
U
U
U
t
0H
t
r
= 20ns, C
L
= 10pF
t
r
V
CC
1k
RD
GND
10%
t
0H
V
CC
DATA OUT
V
0L
10%
1099 F01
V
CC
V
CC
90%
50%
Figure 1. Three-State Test Circuit
5
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