Datasheet

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SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
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4
ELECTRICAL CHARACTERISTICS
For the Total System
(1)
, −40°C ≤ T
A
≤ 85°C, V
DD
= 5 V, BUFIN = 2.5 V (using external reference), 2.5-MHz CCLK and 2.5-MHz SCLK (unless
otherwise noted).
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Digital Outputs
Data coding Binary 2s complement
Low-level output voltage, V
OL
I
SINK
= 5 mA 0.4
V
Logic levels
Low-level output voltage, V
OL
I
SINK
= 16 mA 0.8
V
Logic levels
High-level output voltage, V
OH
I
SOURCE
= 0.5 mA V
DD
− 0.4
V
High-level output voltage, V
OH
I
SOURCE
= 5 mA 4.6
V
Leakage current Hi-Z state, V
O
= 0 V to V
DD
1 µA
Output capacitance 5 pF
Voltage Reference
Bandgap voltage
V
REF
= 2.048 V, 2.5 V
Pin 26 used as output,
Use internal OSC or external
−0.25 ±0.05 0.25 %FSR
Bandgap voltage
reference
V
REF
= 1.15 V
Use internal OSC or external
CCLK as conversion clock
1.15 V
Output drive ±0.6 µA
Reference Buffer
Input voltage, BUFIN 0.9 V
DD
− 0.2 V
Input impedance, BUFIN At pin 27 1000||3 GΩ||pF
Input offset −10 ±1 10 mV
Output voltage accuracy vs temperature,
(2) (3)
Pin 28 used as output,
−0.25 ±0.05 0.25 %FSR
Output voltage accuracy vs temperature,
BUFOUT/REFIN
(2) (3)
Pin 28 used as output,
V
REF
= 2.048 V and 2.5 V
10 50 ppm/°C
Output drive, BUFOUT/REFIN 20 mA
Power Supply Requirements
Supply voltage 2.7 5.5 V
(2)
1-kHz Sample rate
REF and BUF on, Internal os-
cillator on
0.45 mA
Power supply current
(2)
50-kHz Sample rate
REF and BUF on, External
CCLK
1.2 1.7 mA
Power down
REF, BUF, Internal
oscillator off
1 µA
(2)
1-kHz Sample rate
REF and BUF on, Internal
oscillator on
2.25 mW
Power dissipation
(2)
50-kHz Sample rate
REF and BUF on, External
CCLK
6 8.5 mW
Power down REF and BUF off 5 µW
Temperature Range
Operating free-air −40 85 °C
Storage range −65 150 °C
Thermal resistance, Q
JA
65 °C/W
(1)
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.
(2)
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
DD
< 3 V, V
REF
= 2.5 V is not usable.