4
LTC1285/LTC1288
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
t
SMPL
Analog Input Sample Time See Operating Sequence 1.5 CLK Cycles
f
SMPL(MAX)
Maximum Sampling Frequency LTC1285 ● 7.5 kHz
LTC1288 ● 6.6 kHz
t
CONV
Conversion Time See Operating Sequence 12 CLK Cycles
t
dDO
Delay Time, CLK↓ to D
OUT
Data Valid See Test Circuits ● 600 1500 ns
t
dis
Delay Time, CS↑ to D
OUT
Hi-Z See Test Circuits ● 220 660 ns
t
en
Delay Time, CLK↓ to D
OUT
Enable See Test Circuits ● 180 500 ns
t
hDO
Time Output Data Remains Valid After CLK↓ C
LOAD
= 100pF 520 ns
t
f
D
OUT
Fall Time See Test Circuits ● 60 180 ns
t
r
D
OUT
Rise Time See Test Circuits ● 80 180 ns
C
IN
Input Capacitance Analog Inputs, On Channel 20 pF
Analog Inputs, Off Channel 5 pF
Digital Input 5 pF
(Note 5)
AC CHARACTERISTICS
The ● denotes specifications which apply over the full 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: These devices are specified at 3V. For 5V specified devices, see
LTC1286 and LTC1298.
Note 4: Increased leakage currents at elevated temperatures cause the
sample-and-hold to droop, therefore it is recommended that f
CLK
≥ 75kHz
at 70° andf
CLK
≥ 1kHz at 25°C.
Note 5: V
CC
= 2.7V, V
REF
= 2.5V and CLK = 120kHz unless otherwise
specified.
Note 6: Linearity error is specified between the actual end points of the
A/D transfer curve.
Note 7: 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 V
CC
. This spec allows 50mV forward
bias of either diode for 2.7V ≤ V
CC
≤ 6V. This means that as long as the
reference or analog input does not exceed the supply voltage by more than
50mV the output code will be correct. To achieve an absolute 0V to 2.7V
input voltage range will therefore require a minimum supply voltage of
2.650V over initial tolerance, temperature variations and loading. For 2.7V
< V
CC
≤ 6V, reference and analog input range cannot exceed 6.05V. If
reference and analog input range are greater than 6.05V, the output code
will not be guaranteed to be correct.
Note 8: The supply voltage range for the LTC1285 and the LTC1288 is
from 2.7V to 6V.
Note 9: Recommended operating conditions
Note 10: Channel leakage current is measured after the channel selection.
SAMPLE RATE (kHz)
0.1
1
SUPPLY CURRENT (µA)
10
1000
100
110
LTC1285/88 • TPC01
LTC1288
LTC1285
T
A
= 25°C
V
CC
= 2.7V
V
REF
= 2.5V
f
CLK
= 120kHz
Supply Current vs Sample Rate
FREQUENCY (kHz)
1
0
SUPPLY CURRENT (µA)
1
2
3
4
5
6
20
40
60 80
LTC1285/88 • TPC03
100
7
8
9
0.002
120
T
A
= 25°C
V
CC
= 2.7V
V
REF
= 2.5V
CS = 0
(AFTER CONVERSION)
CS = V
CC
Shutdown Supply Current vs Clock
Rate with CS High and CS Low
TEMPERATURE (°C)
–55
SUPPLY CURRENT (µA)
150
200
250
105
LTC1285/88 • TPC02
100
50
0
–15
25
65
–35 125
5
45
85
V
CC
= 2.7V
V
REF
= 2.5V
f
CLK
= 120kHz
LTC1285
f
SMPL
= 7.5kHz
LTC1288
f
SMPL
= 6.6kHz
Supply Current vs Temperature
