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SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
ELECTRICAL CHARACTERISTICS
(1)
For the Total System , −40°C ≤ T ≤ 85°C, V
= 5 V, BUFIN = 2.5 V (using external reference), 2.5-MHz CCLK and 2.5-MHz SCLK (unless
A
DD
otherwise noted).
PARAMETER
Digital Outputs
Data coding
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Binary 2s complement
I
I
I
I
= 5 mA
0.4
SINK
Low-level output voltage, V
OL
V
V
= 16 mA
0.8
4.6
5
SINK
Logic levels
= 0.5 mA
= 5 mA
V
DD
− 0.4
SOURCE
SOURCE
High-level output voltage, V
OH
Leakage current
Hi-Z state, V = 0 V to V
O
1
µA
DD
Output capacitance
Voltage Reference
pF
Pin 26 used as output,
Use internal OSC or external
CCLK as conversion clock
V
V
= 2.048 V, 2.5 V
= 1.15 V
−0.25
0.9
0.05
0.25 %FSR
REF
Bandgap voltage
reference
1.15
0.6
V
REF
Output drive
µA
Reference Buffer
Input voltage, BUFIN
Input impedance, BUFIN
Input offset
V
DD
− 0.2
10
V
At pin 27
1000||3
1
GΩ||pF
mV
−10
−0.25
0.05
10
0.25 %FSR
50 ppm/°C
mA
Output voltage accuracy vs temperature,
(2) (3)
Pin 28 used as output,
BUFOUT/REFIN
V
REF
= 2.048 V and 2.5 V
Output drive, BUFOUT/REFIN
Power Supply Requirements
Supply voltage
20
2.7
5.5
V
REF and BUF on, Internal os-
cillator on
1-kHz Sample rate
0.45
1.2
mA
REF and BUF on, External
CCLK
(2)
50-kHz Sample rate
Power down
1.7
1
mA
µA
Power supply current
REF, BUF, Internal
oscillator off
REF and BUF on, Internal
oscillator on
1-kHz Sample rate
2.25
6
mW
(2)
REF and BUF on, External
CCLK
Power dissipation
50-kHz Sample rate
Power down
8.5
5
mW
REF and BUF off
µW
Temperature Range
Operating free-air
Storage range
−40
−65
85
°C
°C
150
Thermal resistance, Q
65
°C/W
JA
(1)
(2)
The specifications for the total system are overall analog input to digital output specifications. The specifications for internal functions indicate
the performance of the individual functions in the ADS7870.
REF and BUF contribute 190 µA and 150 µA (950 µW and 750 µW) respectively. At initial power up the default condition for both REF and BUF
functions is power off. They can be turned on under software control by writing a 1 to D3 and D2 of register 7, REF/OSCILLATOR CONTROL
register.
(3)
For V
< 3 V, V = 2.5 V is not usable.
DD
REF
4
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